Habilitation thesis - doctorat.tuiasi.ro de... · îndepărtarea poluanţilor de natură organică din apele uzate ... la epurarea apei prin fotocataliză pe ... realizării studiilor

Habilitation thesis

Contributions to

Nanotechnology Application

in wastewater treatment field

Assoc. Professor PhD. Eng. Cristina-Ileana COVALIU

University POLITEHNICA of Bucharest

2017

Cristina Ileana COVALIU Habilitation thesis

1

SUMMARY

REZUMAT…………………………………………………………………………… 4

ABSTRACT…………………………………………………………………………. 7

Chapter 1. SCIENTIFIC, PROFESSIONAL AND ACADEMIC

ACHIEVEMENTS……………………………………………………………………. 10

1.1. Scientific research activity……………………………………………......... 10

1.2. Academic activity………………………………………………………...... 16

1.3. Results dissemination………………………………………………………. 18

Chapter 2. CONTRIBUTION TO NANOTECHNOLOGY APPLICATION IN

WASTEWATER TREATMENT…………………………………………………… 23

2.1. Contribution to nitrates ions efficient removal from water using

nanoadsorbents………………………………………………………………….. 26

2.1.1. General considerations…………………………………………………….. 26

2.1.2. The investigation nitrates removal from water using Pd-Sn/γ-Al2O3,

NiTiO3 and NiFe2O4 ……………………………………………………………… 29

2.1.3. The investigation of CuTiO3 and CuFe2O4 for nitrates removal from

water………………………………………………………………………………. 36

2.2. Contribution to the removal of Cd (II) ions from wastewater using

maghemite and poly-DL-alanine based core-shell magnetic nanohybrids 44


2.2.2. The investigation of Cd (II) ions removal from wastewater using

multifunctional maghemite and poly-DL-alanine based core-shell magnetic

nanohybrids……………………………………………………………………… 46

2.3. Contribution to the removal of Cu (II) ions removal from industrial

wastewater using environmental friendly nanomaterials…………………… 62


2.3.2. The investigation of copper (Cu2+) ions removal from industrial

wastewater using maghemite, γ-Fe2O3 and its corresponding hybrid, γ-Fe2O3-

poly-DL-alanine ………………………………………………………………… 67


2

2.4. Contribution to the removal of Cr (II), Cd (II), Cu (II), Zn (II) and Ni

(II) using magnetite (Fe3O4) and Fe3O4-PAA nanomaterials…………………. 70

2.4.1. General consideration……………………………………………………… 70

2.4.2. The investigation of Cr (II), Cd(II), Cu(II), Zn(II) and Ni(II) removal from

wastewater using magnetite (Fe3O4) and Fe3O4-PAA……………………………. 71

2.5. Contribution to Pb(II) and Cd(II) ions removal from wastewater using

as magnetic adsorbant nanomaterials: Fe3O4, Fe3O4-PEG and Fe3O4-PVP… 82

2.5.1. General consideration………………………………………………………. 82

2.5.2. The investigation of Pb(II) and Cd(II) ions removal from wastewater using

iron-based magnetic hybrid nanoparticles: Fe3O4, Fe3O4-PEG and Fe3O4-PVP ... 83

2.6. Contribution to Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) removal

from wastewater using Fe3O4 and Fe3O4-PVP magnetic nanomaterials ........ 86

2.6.1. General consideration…………………………………………………….. 86

2.6.2. The investigation of Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) ions

removal from wastewater using Fe3O4 and Fe3O4-PVP nanomaterials………….. 89

2.7. Study of zeolites nanomaterial as a multifunctional environmental

engineering solution……………………………………………………………... 91

2.8. Contribution to organic (C6H6 and C6H5-CH3) and inorganic (Pb+2 and

Zn+2) pollutants removal from for wastewater using powdered activated

carbon …………………………………………………………………………… 94


2.8.2. The investigation of removal organic (C6H6 and C6H5-CH3) and inorganic

(Pb+2 and Zn+2) pollutants for wastewater using activated carbon ……………… 97

2.9. Contribution to wastewater treatment by using photocatalysis based

titanium dioxide…………………………………………………………………. 107


2.9.2. The investigation of removal methylene blue and diclofenac from

wastewater by photocatalysis based titanium dioxide……………………………. 110

Chapter 3. PLAN OF SCIENTIFIC, PROFESSIONAL AND ACADEMIC 113


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DEVELOPMENT IN THE FUTURE…………………………..............................

Bibliography …………………………………………………………………………… 117


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REZUMAT

Prezenta teză de abilitare cu titlul “Contribuţii la aplicarea nanotehnologiei în domeniul

epurării apelor” prezintă o parte a rezultatelor activităţii de cercetare a candidatei după susținerea

tezei de doctorat la Universitatea Politehnica din Bucureşti. “Nanotehnologia aplicată în

domeniul epurării apelor”, ce reprezintă domeniul meu de cercetare, este una dintre cele mai

mari descoperiri din timpurile noastre. Nanotechnologia (prin utilizarea nanomaterialelor) oferă

oportunitatea apariţiei şi dezvoltării noii generaţii de tehnologii, foarte eficiente, de epurare a

apelor.

Activitatea de cercetare ştiintifică, ulterioară susţinerii tezei de doctorat, am desfăşurat-o

în mod continuu în cadrul Universitatii Politehnica din Bucureşti, abordând teme cu caracter

multidisciplinar, care au putut fi realizate în colaborare cu cercetători din cadrul universităţii la

care lucrez, dar şi de la Institutul National de Fizica Materialelor (INFIM), Institutul Naţional de

Cercetare – Dezvoltare pentru Chimie şi Petrochimie (ICECHIM), Universitatea din Belgrad,

Institutul Național de Mașini Agricole (INMA),etc.

În Capitolul 1 al tezei de abilitare este descrisă evoluţia carierei profestionale până în

prezent, menționând cele mai importante realizări ştiinţifice şi academice. Sunt prezentate

succinct direcţiile de cercetare abordate, între care mentionez: 1) Îndepartarea eficientă a

nitraţilor din apă utilizând nanoadsorbanţi şi nanocatalizatori; 2) Îndepartarea toluenului din apă

prin oxidare, utilizând diferiţi oxizi micşti. ca de exemplu: MTiO3 (M=Cu,Ni), NiTiO3 şi

NiFe2O4; 3) Îndepărtarea metalelor grele din apa uzată utilizând nanomateriale magnetice

oxidice: maghemita (ɤ-Fe2O3), ferrite (Fe3O4, CuFe2O4), etc; 4) ) Îndepartarea metalelor grele din

apa uzată utilizând nanomateriale magnetice hibride (Fe3O4-PAA, Fe3O4-PEG şi Fe3O4-PVP, ɤ-

Fe2O3-poly-DL-alanine); 5) Îndepartarea poluanţilor organici şi a metalelor grele din apă

utilizând nanomateriale zeolitice- ZSM-5; 6) Îndepărtarea poluanţilor organici din apa uzată

printr-un tratament ce are la bază nanomaterialul fotocatalizator TiO2.

Începând din anul 2015, am adăugat în sfera preocupărilor ştiinţifice, cercetarea privind

îndepărtarea poluanţilor de natură organică din apele uzate (ex: grăsimi) prin procedeul de

flotaţie eficientizat de prezenţa nanomaterialelor. Cercetările aferente acestui subiect constituie

tema unui proiect de cercetare de tip PTE (transfer la operatorul economic) din cadrul


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programului P2- Creşterea competitivităţii economiei româneşti prin cercetare, dezvoltare şi

inovare, finanţat pe doi ani (2016-2018), la care sunt responsabilă din partea Universităţii

Politehnica din Bucureşti.

Celelalte direcţii de cercetare ştiinţifică sunt dezvoltate în cadrul Bursei de Excelență pe

tema “Aplicaţiile bionanotehnologiei în scopul epurării apelor industriale”, câştigată prin

competiţie şi finanţată din bugetul Universităţii Politehnica din Bucureşti în perioada 2016-2017.

Tot în cadrul acestui capitol este prezentat prestigiul profesional naţional şi internațional

care este susținut de numărul mare de articole publicate în jurnale de prestigiu, de numărul mare

de citări ale articolelor publicate, de numărul mare de conferinţe internaționale la care candidata

a participat, inclusiv având calitatea de membru în comitetul ştiinţific, moderator al unor secțiuni

sau referent pentru lucrări.

Activitatea de cercetare ştiinţifică desfăşurată până în prezent a stat la baza coordonării

a trei proiecte în calitate de director sau responsabil, a publicării a 31 de articole cu factor de

impact având valori cuprinse între 0.3-3.21, citate de 200 de ori în reviste de prestigiu precum:

Nano Research (F.I.-6.963), Advances in Colloid and Interface Science (F.I. - 8,636), Journal of

the American Chemical Society (F.I.-12,113). Până în prezent, candidata are o activitate

ştiinţifică pe plan international cuantificată prin valoarea indicelui Hirsch de 8.

Capitolul 2 intitulat „Contribuţii la aplicarea nanotehnologiei în epurarea apei" este

compus din nouă subcapitole. În primul subcapitol sunt prezentate contribuţiile personale cu

privire la îndepărtarea eficientă a nitraţilor din apă utilizând nanoadsorbanţi de tipul: Pd-Sn/γ-

Al2O3, NiTiO3, NiFe2O4 CuTiO3 ; CuFe2O4. În subcapitolele doi şi trei sunt prezentate

contribuţiile autoarei cu privire la îndepărtarea ionilor de Cd (II) and Cu (II) din apa uzată

utilizând nanomaterialele maghemită (γ-Fe2O3) şi hibridul magnetic "miez-carapace" γ-Fe2O3 -

poli-DL-alanină. În cel de-al patrulea subcapitol sunt prezentate contribuţiile autoarei cu privire

la îndepărtarea ionilor de Cu (II), Zn (II), Cr (II), Cd (II) şi Ni (II) din apa uzată utilizând

nanoametrialele Fe3O4 şi Fe3O4-PAA. Apoi, în subcapitolul al cincilea, sunt prezentate

contribuţiile privind îndepărtarea ionilor de Pb (II) şi Cd (II) din apa uzată utilizând ca adsorbanţi

următoarele nanomateriale magnetice: Fe3O4, Fe3O4-PEG şi Fe3O4-PVP. În subcapitolul al

şaselea sunt evidenţiate contribuţiile autoarei cu privire la îndepărtarea ionilor de Cu (II), Zn (II),


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Cr (II), Cd (II) and Ni (II) din apa uzată folosind nanomaterialele magnetice: Fe3O4 şi Fe3O4-

PVP. În cel de-al şaptelea subcapitolul se prezintă contribuţiile autoarei legate de

nanomaterialele zeolitice care pot reprezenta o soluţie inginerească, multifuncţională a

problemelor de mediu. În cel de-al optulea subcapitol este descris un studiu complex al

îndepărtării poluanţilor organici (C6H6 and C6H5-CH3) şi anorganici (Pb+2 and Zn+2) din apa

uzată folosind cărbune activ. În cel de-al nouălea subcapitol sunt prezentate contribuţiile autoarei

la epurarea apei prin fotocataliză pe bază de dioxid de titan.

În capitolul 3 este descris planul de dezvoltare ştiinţifică, profesională şi academică

viitoare, din care reiese dorinţa de sporire a prestigiului pe plan naţional şi internaţional, de a

coordona şi studenţi străini în scopul realizării studiilor de doctorat, de a câştiga proiecte

internaţionale şi de a transfera cunoştinţele generaţiilor viitoare de doctori în ingineria mediului.

Teza se încheie cu partea de "Bibliografie" în care se regăsesc enumerate materialele

care au stat la baza realizării studiilor ştiinţifice aferente articolelor publicate şi prezentate în

capitolul 2.


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ABSTRACT

The present thesis entitled “Contributions to nanotechnology application in wastewater

treatment field” shows a part of the research results of the candidate after sustaining the PhD

thesis at University Politehnica of Bucharest. “Nanotechnology applied in wastewater treatment”

representing my field of research is one of the greatest scientific discoveries of recent times.

Nanotechnology (and thus nanomaterials) provides the opportunity of appearance and

development of the next generation of wastewater treatment technologies having very high

efficiency.

After obtaining the PhD title, I continuously conducted my research activity at the

University Politehnica of Bucharest, addressing multidisciplinary topics that have been

developed in collaboration with researchers from other universities and institutes, such as:

National Institute of Materials Physics (INFIM), National Institute of Research and Development

for Chemistry and Petrochemistry (ICECHIM), University of Belgrade, National Institute of

Agricultural Machines (INMA), etc.

In chapter 1 of the habilitation thesis is described the evolution of the professional

carrier until the present, specifying the most important scientific and academic achievements.

There are highlighted the approached research directions, including: 1) Nitrates ions efficient

removal from water using different nanoadsorbents and nanocatalysts; 2) Toluene removal from

water by oxidation using different mixed oxides as nanocatalysts, such as: MTiO3 (M=Cu, Ni),

NiTiO3 and NiFe2O4; 3) Heavy metals removal from wastewater using magnetic oxides

nanomaterials: maghemite (ɤ-Fe2O3), ferrite (Fe3O4, CuFe2O4), etc; 4) Heavy metals removal

from wastewater using magnetic hybrid nanomaterials having inorganic core and polymeric shell

Fe3O4-PAA, Fe3O4-PEG and Fe3O4-PVP, ɤ-Fe2O3-poly-DL-alanine); 5) Heavy metals removal

from wastewater using zeolites nanomaterials- ZSM-5; 6) Heavy metals and organic pollutants

removal from wastewater using activated carbon nanomaterial; 6) Organic pollutants removal

from wastewater using a treatment based on TiO2 photocatalytic nanomaterial.

Since 2016, I have added to scientific concerns sphere, the research on removing

organic type pollutants from wastewater (eg fats) by flotation process having an increased

efficiency conferred by using the nanomaterials. The research on this topic is the subject of a


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PTE (transfer to the economic operator) type research project within the program P2- Increase

the competitiveness of Romanian economy through research, development and innovation,

funded over two years (2016-2018), at which I am the responsible from the University

Politehnica of Bucharest.

The other directions of the scientific research are developed within the Excellence

fellowship on "Bionanotechnology applications in industrial wastewater treatment", won

by competition and financed from the budget of the University Politehnica of Bucharest during

2016-2017.

Also, in this section is presented the national and international professional prestige

given by the large number of articles published in journals having high impact factor, the high

number of citations of the published articles, the large number of international conferences

attended by the candidate, including as being member of the Scientific Committee, moderator of

certain sections or referent for scientific articles.

The scientific research carried out so far led to the coordination of the three projects as

director or responsible, the publication of 31 articles having impact factor values between 0.3-

3.21), cited 200 times in prestigious journals such as: Nano Research (F.I.-6963), Advances in

Colloid and Interface Science (F.I. - 8636), Journal of the American Chemical Society (F.I.-

12.113).

So far, the impact of international and national scientific activity of the candidate

measured by the index Hirsch is 8.

Chapter 2 entitled “Contribution to nanotechnology application in wastewater

treatment” consists of nine subchapters. In the first subchapter are presented the contributions to

nitrates ions efficient removal from water using the following nanoadsorbents: Pd-Sn/γ-Al2O3,

NiTiO3, NiFe2O4, CuTiO3 and CuFe2O4. The second and third subchapters present the author

contributions to the removal of Cd (II) and Cu (II) ions from wastewater using γ-Fe2O3

(maghemite) and γ-Fe2O3 -poly-dl-alanine based core-shell magnetic hybrids nanomaterials. In

the fourth subchapter are presented the authors’s contribution to Cu (II), Zn (II), Cr (II), Cd (II)

and Ni (II) removal from wastewater using Fe3O4 and Fe3O4-PAA magnetic nanomaterials.

Then, in the fifth subchapter are presented the contributions to Pb(II) and Cd(II) ions removal


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from wastewater using as adsorbants the following magnetic nanomaterials: Fe3O4, Fe3O4-PEG

and Fe3O4-PVP. In the sixth subchapter are presented the author contributions to Cu (II), Zn (II),

Cr (II), Cd (II) and Ni (II) removal from wastewater using Fe3O4 and Fe3O4-PVP magnetic

nanomaterials. The seventh subchapter shows the author contributions related to research on

zeolites nanomaterials as a multifunctional environmental engineering solution. In the eighth

subchapter is presented a complex study regarding the removal of organic (C6H6 and C6H5-CH3)

and inorganic (Pb+2 and Zn+2) pollutants from wastewater using powdered activated carbon. The

ninth subchapter describes the author contributions to wastewater treatment by using

photocatalysis based titanium dioxide.

In chapter 3 is presented the plan of future scientific, professional and academic

development, based which results the desire to increase the national and international prestige, to

coordinate foreign students for doctoral thesis, to win national and international projects and to

transfer the scientific knowledge to future generation of PhD students in environment

engineering field.

The thesis ends with "References" where are listed the scientific materials used to

develop the studies related to the published articles presented in Chapter 2.


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Chapter 1.

SCIENTIFIC, PROFESSIONAL AND ACADEMIC ACHIEVEMENTS

1.1. Scientific research activity

Nanotechnology (and thus nanomaterials) is one of the greatest technology discoveries of

recent times.

The nanotechnology (and thus nanomaterials) market has a huge potential of application in

environmental engineering field.

My own scientific achievements in the field of environmental engineering, regarding the

application of nanotechnology in water treatment field, have focused on the fundamental and applied

research activities regarding the synthesis, characterization and testing of nanomaterials having

special properties suitable for removing various inorganic and organic pollutants from water.

My own scientific activity on fundamental and applied research in the environment

engineering field began in 2003, during the research conducted on "Polyphosphazene materials

applied for treatment of industrial wastewater polluted with 3d type metal ions", aiming to obtain a

new polymer with high efficiency for removing 3d metal ions (Cu2+, Ni2+, Cr3+) from the wastewater

resulted from industrial processes. During this study I investigated the influence of the following

factors such as: pH, contact time, the concentration of metal ions from wastewater upon the degree of

treatment efficiency of the tested material.

The results of the experimental research obtained in the nanotechnology field during

Master, PhD and Postdoctoral studies and the discovery of the special properties of the

nanomaterials conferred by their dimensions in the nanometer range encouraged me to expand the

study of their application in the field of environmental engineering.

Among these special properties of nanomaterials, the adsorption capacity given by the

“nano” dimension is remarkable, because offer them the capacity of retaining various types of

chemical pollutants from water. Thus, I have studied in the last years the adsorption capacity of

various nanomaterials, such as: metallic oxides, composites and hybrids composed by metallic

oxides and biopolymers.

Regarding my personal activities developed in the field of nanotechnology applied in

environmental engineering field, contributions are related to:

http://nanoportal.gc.ca/default.asp?lang=Fr&n=C139F81E-1


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- New methods for synthesis of nanomaterials applied in environmental engineering field, by

controlling the influencing factors such as: temperature, pH, surfactant concentration;

- Study of the advanced characterization techniques of nanomaterials applied in environmental

engineering field expressing accurately the information obtained by comparing various

characterization and analysis methods such as: transmission electron microscopy (TEM), scanning

electron microscopy (SEM), X-ray diffraction (XRD), atomic absorption analysis (AAS), etc.;

- Investigation of inorganic and organic type pollutants removal from wastewater using

nanomaterials, studying the following issues:

the optimum quantity of nanomaterial suitable to be used for removing a certain value

of pollutant concentration found in water;

the maximum quantity of nanomaterials used for obtaining the highest yield of

wastewater treatment;

the type of nanomaterials used for removing different types of pollutants found in

water, etc.

The research directions representing my own contribution to the environmental engineering

field are the following:

1) Nitrates ions efficient removal from water using different nanoadsorbents and

nanocatalysts, such as: Pd-Sn/γ-Al2O3, NiTiO3 and NiFe2O4;

2) Toluene removal from water by oxidation using different mixed oxides as nanocatalysts

such as: MTiO3 (M=Cu2+, Ni2+), NiTiO3 and NiFe2O4;

3) Heavy metals removal from wastewater using magnetic oxides nanomaterials: maghemite

(ɤ-Fe2O3), ferrite (Fe3O4, CuFe2O4), etc;

4) Heavy metals removal from wastewater using magnetic hybrid nanomaterials having

inorganic core and polymeric shell Fe3O4-PAA, Fe3O4-PEG and Fe3O4-PVP, ɤ-Fe2O3-poly-DL-

alanine);

5) Heavy metals removal from wastewater using zeolites nanomaterial- ZSM-5 zeolites;

6) Heavy metals and organic pollutants removal from wastewater using activated carbon

nanomaterial;

7) Organic pollutants removal wastewater from using a treatment based on TiO2

photocatalyst nanomaterial;

All these results were disseminated by publishing of books, articles, manuals.


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Till the present, the scientific activity was materialized in publishing: 5 books, 1 Laboratory

guide, 27 ISI quoted articles listed on the ISI Web of Science, 28 BDI. I have one national patent

application pending. The published articles were cited 200 times times in prestigious journals such

as: Nano Research (F.I.-6963), Advances in Colloid and Interface Science (F.I. - 8636), Journal of

the American Chemical Society (F.I.-12.113).

According to Scopus Scientific database, my personal Hirsch index is 8, whereas according

to Web of science database Hirsch index is 7. One of publication had the privilege to be published

on the SAO/NASA Astrophysics Data System (ADS) which is a Digital Library portal for

researchers in Astronomy and Physics, operated by the Harvard University and Smithsonian

Astrophysical Observatory (SAO) under a NASA grant:

http://adsabs.harvard.edu/abs/2013ApSS..285...86C.

My ability to coordinate research teams is sustained till the present by: submission of eight

grant applications as project director or responsible, coordination of collective work teams in two

conference organization: "International Symposium ISB-INMA TEH - Agricultural And Mechanical

Engineering" and "International Conference on Thermal Equipment, Renewable Energy and Rural

Development – TE-RE-RD", coordination of students and groups of students in research work for

participation at some scientific national and international competitions:

Annual Session of Scientific Communications for Students organized by University

Politehnica of Bucharest, some example are:

- in 2013, papers presented at Session of Scientific Communications for Students

organized by University Politehnica of Bucharest:

- Priority environmental issues regarding wastewater resulted from hospital,

student: Nicoleta Ghiţeanu;

-Treatment of wastewater containing heavy metals (Cd(II)) using

nanostructured hybrids, student: Iuliana Tudose;

- Study of heavy metals (Pb(II) si Cd (II)) adsorption capacity using oxides

having nanometric size, student: Cristina Popa;

-Unconventional method of wastewater treatment,

student: Raluca Micu;

- in 2014, papers presented at Session of Scientific Communications for Students

organized by University Politehnica of Bucharest and also at International Session

http://adsabs.harvard.edu/abs/2013ApSS..285...86C


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of Scientific Communications for Students organized by Maritime University from

Constanţa;

- Orange peels used in wastewater treatment, Turcan Monica Oana, Grama

Silviu Nicolae, premium III at both competitions.

- Innovative method for removing chromium ions from wastewater,

Dumitrache Robert;

- Method for removal lead ions from wasteswater, Burcea Georgeta;

- Versatile system with potential applications in cooper ions removal from

industrial watewater, Stanescu Raluca.

- Strategy of retaining copper from wastewater, Stanescu Raluca, I premium,

at Session of Scientific Communications for Students organized by University

Politehnica of Bucharest;

- Unconventional method for treatment of wastewater polluted with lead,

Burcea Georgeta, I premium, at Session of scientific communications for students

organized by University Politehnica of Bucharest;

- Study of vegetable waste utilization as adsorbants for wastewater treatment,

Turcan Monica Oana, Grama Silviu, III premium, at Session of Scientific

Communications for Students organized by University Politehnica of Bucharest;

- in 2015 papers presented at International Session of Scientific Communications

for Students organized by Maritime University from Constanţa:

- Chromium ions removal from wastewater using carbon nanotubes, Miclescu

Alexandra-Maria;

- Phytoremediation of wastewater polluted with chromium ions, Gheorghian

Alexandra, Cotoara Nicoleta Emanuela;

- Copper ions removal from wastewater using bulrush (Typhaangustifolia),

Oana Stoian, Raluca Damian;

- Versatile system for the removal of copper from industrial wastewater,

Gheorghe Catalin Nicolae.

- in 2015 papers presented at ”XX International Session of Scientific

Communications for Students SECOSAFT 2015” organized by Academia of

terrestrial forces Nicolae Balcescu:

- Wastewater treatment using orange peels, Gritsco Iulian, Munteanu Tatiana;


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-Ecological depollution of wastewater using plants (Typha latifolia), Stoian

Oana, Damian Raluca;

-Unconventional method for wastewater treatment, Cristescu Andreea

Catalina, Pascu Lucian Eduard;

-Innovative method for treatment of wastewater containing chromium,

Hoaghe Dan, Burlacu Cristina;

- from 2015 papers presented at the Session of Scientific Communications for

Students organized by University Politehnica of Bucharest:

- Innovative method for depollution of wastewater containing chromium ions,

Hoaghe Dan, Burlacu Cristina;

- Versatile system for treatment of industrial wastewater containing copper

ions, Gheorghe Cătălin;

- Unconventional method for Pb (II) removal from industrial wastewater,

Cristescu Andreea Cătălina;

- Wastewater treatment method using ecological nanomaterials, Damian

Raluca;

- Treatment of wastewater from tannery industry, TAMEȘ Ana Maria;

- Ecological nanosystems for treatment of wastewater polluted with chromium

ions, Miclescu Alexandra Maria, Badan Daniela Nicoleta;

- Fitoremediation of wastewater polluted with chromium ions, Stoian Oana;

The Management competences were developed as director or responsible within the

following three research projects:

1) Technology for treatment by flotation of water highly loaded with pollutants, PN III,

PTE nr.25/2016. The project aim is to obtain a wastewater treatment plant which uses the flotation

process for depollution. The flotation process applied for wastewater depollution will use different

types of nanoparticles for increasing its efficiency. Till the present the team of University Politehnica

of Bucharest coordinated by me as responsible had obtained the following results disseminated as

follows:

- Participation with the paper: M. Matache, C.Covaliu, G. Petrescu “Improved

treatment technology through the floatation of heavily loaded waters“, at International Symposium

ISB-INMA TEH’ 2016 Symposium, 27 – 29 October 2016, Bucharest, Romania;

- Participation with the paper: I.C. Moga, C.I.Covaliu, M.G. Matache, “Improved


15

dissolved air flotation technology for highly polluted wastewaters”, at 5th International Conference

on Advanced material Engineering & Technology (ICAMET 2016), 8 – 9 December 2016, Taiwan.

- Participation with the paper: G. Petrescu, M.G. Matache, C.I. Covaliu, I. Voicea,

G. Paraschiv, A.D. Diaconu, B.D. Nasarimba-Grecescu, I. C. Moga, “Improved Flotation treatment

technology for heavily loaded wastewater” presented at International Salon of Inventions –

Kaohsiung International Invention and Design EXPO (KIDE) 2016, 9 – 11 December 2016, Taiwan,

where it was awarded with Diploma of Excellence.

2) Bionanotechnology application in wastewater treatment, No.44/26.09.2016, an

Excellence Fellowship, coordinated by me, within University Politehnica of Bucharest, The project

aim is to obtain various types of nanomaterials as used as photocalaysts or adsorbants for removal of

pollutants from wastewater. Till the present the team of UPB together with me as responsible had

obtained the following results disseminated as follows:

- Participation with the paper: C.I. Covaliu, M. Ionescu, G. Paraschiv, S.St. Biris, C.

Matei, L. Toma, M.G. Matache, New trend in the application of nanotechnology in wastewater

treatment - CeO2 photocatalyst, Internațional Symposium– ISB-INMA TEH’ 2016 International

Symposium, 27 – 29 octombrie 2016, Bucharest, România,

- C. I.Covaliu, G.Paraschiv, S.St.Biris, C.Matei, M.Ionescu, Nanotechnology applied

in wastewater treatment. Photocatalysis based titanium dioxide, 16th International Multidisciplinary

scientific geoconference SGEM 2016, 2 –5 noiembrie 2016, Vienna, Austria. At this conference I

was awarded with the Best oral presentation.

Strictly related with scientific activity is the fact that from 2012 I am the resposible of the

Laboratory “Environment Quality Analysis”, within the Faculty of Biotechnical Systems

Engineering, University Politehnica of Bucharest, which has the infrastructure suitable for doing

analyses of pollutants from wastewater and obtaining nanomaterials used for water depollution.

Also, I am member of the scientific comity of two annual international conferences:

"International Conference on Thermal Equipment, Renewable Energy and Rural Development – TE-

RE-RD" and "International Symposium ISB-INMA TEH - Agricultural And Mechanical

Engineering".

From 2013 till the present I had the honor to win four awards given by UEFISCDI for

scientific research publication in prestigious journals.

Regarding the scientific activity I had the honor to win prizes for the best oral presentation

at international conferences, some of them are:


16

1. I.C. Covaliu, G. Paraschiv, S.St Biris., C. Matei, M. Ionescu, Nanotechnology applied in

wastewater treatment. Photocatalysis based titanium dioxide, 16th International Multidisciplinary

scientific geoconference SGEM 2016, Vienna, 2 –5 noiembrie 2016.

2. C. Covaliu, G. Paraschiv, S. Ş. Biriş, I. Filip, M. Ionescu, Nanotechnology for wastewater

treatment, TE-RE-RD conference, 2-4 June 2016, Golden Sands, Bulgaria.

3. G. Petrescu, M.G. Matache, C.I. Covaliu, I. Voicea, G. Paraschiv, A.D. Diaconu, B.D.

Nasarimba-Grecescu, I. C. Moga, “Improved Flotation treatment technology for heavily loaded

wastewater”, Diploma of Excellence, at International Salon of Inventions – Kaohsiung International

Invention and Design EXPO (KIDE) 2016, 9 – 11 December 2016, Taiwan.

4. C. Covaliu, I.R. Bunghez, S.Şt. Biriş, G. Paraschiv, Research on copper ions removal from

industrial wastewater using environmental friendly nanomaterials, ISB-INMA THE’2014, 30- 31

octombrie 2014.

I am member in various professional international associations, such as: Romanian Society

of Chemistry, Romanian Society of Biomaterials Romanian Society of Magnetic Materials and

Society of Mechanical Engineers from Romania –SIMAR.

1.2. Academic activity

The didactic activity was initiated in 2007 as a collaborator professor at Faculty of Applied

Chemistry and Materials Science within University Politehnica of Bucharest.

Since 2012, I was employed as lector at Faculty of Biotechnical Systems Engineering, from

University Politehnica of Bucharest, being titular at the disciplines: „Ecology and environment

protection”, „Biochemical processes in environmental engineering”, “Ecology fundaments”,

“Analyses techniques of the environment quality”, etc.

In the present time, I am titular at the disciplines: „Ecology and environmen protection”,

„Ecology fundaments”, „Biochemical processes in environmental engineering”, “Analyses

techniques of the environment quality”, “Processes and equipments for separation and purification”.

Currently, I am associate professor at Faculty of Biotechnical Systems Engineering, from

University Politehnica of Bucharest.

In the present time, within the Faculty of Biotechnical Systems Engineering from University

Politehnica of Bucharest I am the president of the commission of diploma thesis evaluation at the

specialization "Biotechnical and Ecological Systems Engineering" and I am member of the


17

dissertation thesis commission of the "Engineering and Management in Environmental Protection”

specialization.

One of my goals as regarding academic activity is continuously transfer of the scientific

researches knowledge to didactic activity in field of environmental engineering.

Currently, within University Politechnica of Bucharest I coordinate both diploma projects

for the field of specialization "Biotechnical and Ecological Systems Engineering" and dissertation

projects for two specializations “Engineering and Management of Biotechnical Systems" and

"Engineering and Management in environmental protection”.

I work closely with the professors from Faculty of Environmental Protection and Land

Improvement from University of Agriculture Science And Veterinary Medicine, where I am

collaborator professor, teaching “Biotechnologies and sustainable industries” discipline within the

“Management of Investments in Ecosystems” master. Moreover, at this master I coordinate

dissertation projects and I am member of dissertation commission.

Some examples of the research topics in the field of environmental engineering which were

studied within the diploma projects and dissertation thesis coordinated by me are the following:

1) System for treatment of leachates from waste disposal landfills;

2) Versatile system for industrial water treatment;

3) Treatment system of wastewater from leather industry;

4) Wastewater treatment using photocatalytic processes;

5) Study of unconventional water treatment technologies;

6) Innovative procedure of removing heavy metals from industrial wastewater;

7) Removal process of chromium ions from industrial wastewater;

8) Treatment of wastewater polluted with cooper ions;

9) Unconventional methods for treatment of wastewater polluted with lead ions;

10) Versatile system for removal of copper from industrial wastewater;

11) Nanomaterials used as adsorbents for heavy metals removal from industrial

wastewater;

12) Application of TiO2 nanomaterial as photocatalyst for methylorange pollutant removal

from wastewater;

13) Application of TiO2 nanomaterial as photocatalyst for methyleneblue pollutant removal

from wastewater, etc.


18

In close connection with the ability to coordinate PhD students, I am member of two

doctoral guidance commissions, as follows:

1) Oxidative photocatalysts with applications in depollution of the environment, PhD

student: Arsenescu Daniela, pHd Coordinator: Prof.Phd.Chem. Ioana Jitaru, from Faculty of

Applied Chemistry and Materials Science, University Politehnica of Bucharest;

2) Contributions to wastewater treatment by decantation and aeration / flotation, PhD

student: Zabava (Dragoiu) Bianca, pHd Coordinator: Prof.Phd.Eng. Gheorghe Voicu, from

Faculty of Biotechnical Systems Engineering, University Politehnica of Bucharest.

1.3. Results dissemination

Till the present I am reviewer at the many journals, some examples are:

1. Journal of Nanaoparticle Research (F.I.-2,184);

2. Scientific Bulettin of University Politehnica of Bucharest;

3. Powder Technology (F.I.-2,349),;

4. Journal of Sol-Gel Science and Technology (F.I.-1,532);

5. Arabian Journal of Chemistry (F.I.-3,725),

6. Journal of American Chemical Society (F.I.- 12.113).

Books and Manuals

I have published 5 books, from which in the field of the habilitation thesis are the following:

1. C. Covaliu, E.Matei, G. Paraschiv, Ecology and Environment Protection, Publisher

Printech, 2014, ISBN 978-606-23-0336-5, 200 pages,

2. C. Covaliu, G. Paraschiv, Biochemichal Processes in environment engineering, Publisher

Printech, 2014, ISBN 606- 23- 0337-2, 150 pages.

3. C. Covaliu, E. Matei, A. Predescu, G. Paraschiv, Analysis Methods of water quality,

Publisher Printech, 2014, ISBN 978-606-23-0329-7, 108 pages.

4. I. Jitaru, C. I.Covaliu, Inorganic Chemistry. Representative elements, Publisher Printech,

2011, ISBN 978-606-521-718-8, 365 pages;


19

The habilitation thesis has been elaborated based on some papers published in journals or

proceedings.

The most relevant articles in the research field of the habilitation thesis:

1. C.I. Covaliu, E. Matei , G. Georgescu, T. Malaeru, SS. Biris, Evaluation of powdered

activated carbon performance for wastewater treatment containing organic (C6H6 and C6H5-CH3)

and inorganic (Pb+2 and Zn+2) pollutants, Environmental Engineering and Management Journal, 15,

Issue: 5, 1003-1008, 2016, F.I=1.008.

2. C.I. Covaliu, M. Ionescu, G. Paraschiv, S.St. Biris, C. Matei, L. Toma, M.G. Matache,

New trend in the application of nanotechnology in wastewater treatment - CeO2 photocatalyst,

Internațional Symposium– ISB-INMA TEH’ 2016 International Symposium, 27 – 29 octombrie

2016, pp. 567-570, Bucharest, România, ISSN 2344 – 4118.

3. C. Covaliu, G. Paraschiv, S. Șt. Biriş, I. Filip, M. Ionescu, Nanotechnology for

wastewater treatment, Proceedings 5th International Conference of Thermal Equipment, Renewable

Energy and Rural Development, TE-RE-RD 2016, pp.205-209, ISSN 2359-7941, ISSN-L 2359-

7941, Golden Sands – Bulgaria.

4. C.I. Covaliu, G. Paraschiv, S.St. Biris, C. Matei, M. Ionescu, Nanotechnology applied in

wastewater treatment. Photocatalysis based titanium dioxide, Proceedings 16th International

Multidisciplinary scientific geoconference SGEM 2016, pp. 99-104, Viena, 2 –5 noiembrie 2016.

5. C. Covaliu, I.R. Bunghez, S.Şt. Biriş, G. Paraschiv, Research on copper ions removal

from industrial wastewater using environmental friendly nanomaterials, International symposium

Isb-Inma teh agricultural and mechanical engineering, 2014, pp.119-124, Bucuresti, Romania, ISSN

2344 – 4118.

6. C.I. Covaliu, G. Paraschiv, S.S. Biris, I. Jitaru, E. Vasile, L. Diamandescu, T.C.

Velickovic, M. Krstic, V. Ionita, H Iovu, E. Matei, Maghemite and poly-DL-alanine based core-shell

multifunctional nanohybrids for environmental protection and biomedicine applications, Applied

Surface Science, 285, 86-95, Part: A, 2013, ISSN: 0169-4332, F.I=2.538.

7. E. Matei, A. M. Predescu, C. Predescu, M.G. Sohaciu, A. Berbecaru, C. I. Covaliu,

Characterization and application results of two magnetic nanomaterials, Journal of Environmental

Quality, 42 (1), pp. 129-136, 2013 ISSN: 0047-2425.

8. G.A. Traistaru, C. I. Covaliu, G. Gallios, D. Cursaru, I. Jitaru, Removal of nitrate from

water by two types of catalysts: Characterization and sorption studies, Revista de Chimie, 63 (3),

pp.268-271, 2012, (corresponding author);


20

9. C.I. Covaliu, S.Şt. Biriş, G. Paraschiv, Fodorean, C. Ghitescu, E. Matei, A. Constantinescu,

Arsenescu D., Jitaru I., TiO2 photocatalyst for wastewater treatment applications – review,

International symposium isb-inma teh agricultural and mechanical engineering, pp.241-244, 2015,

ISSN 2344 – 4118.

10. G.A. Trăistaru, C.I. Covaliu, G. Paraschiv, G. Gallios, V.Vlăduț, D. Manea, C. Sorică,

Nitrates ions efficient removal from water using three nanoadsorbents, ANNALS of Faculty

Engineering Hunedoara – International Journal of Engineering, Tome XII, Fascicule 4, 235-328,

2014, ISSN: 1584‐ 2673.

11. C.I. Covaliu, G. Paraschiv, S.Șt. Biriș, E. Matei, I. Filip, M. Ionescu, Heavy metals

removal from wastewater using magnetic nanomaterials based adsortion strategies, Conference

Proceedings of “3nd International Conference on Thermal Equipment, Renewable Energy and Rural

Development”, TE-RE-RD 2014, p.205-208, ISSN 2359-7941.

12. C.I. Covaliu, S.Şt. Biriş, G. Paraschiv, G. Voicu, Iron-based magnetic hybrid

nanoparticles for high efficient removal of heavy metals from wastewater, Conference Proceedings

of “2nd International Conference of Thermal Equipment, Renewable Energy and Rural Development

TE-RE-RD 2013, p. 139-140, 2013, ISSN 1843 – 3359.

Awards

Till now I had some ISI articles awarded by UEFISCDI contest, some of them are:

1) F.Ilie, C. I. Covaliu, G. Chisiu, Tribological Study of Ecological Lubricants Containing Titanium

Dioxide Nanoparticles, Applied Mechanics and Materials, 658, 323-328, 2014, PN-II-RU-PRECISI-

2014-8-6840;

2) C.I. Covaliu, G. Paraschiv, S.S. Biris, I. Jitaru, E. Vasile, L. Diamandescu, T.C. Velickovic, M.

Krstic, V. Ionita, H Iovu, E. Matei, Maghemite and poly-DL-alanine based core–shell

multifunctional nanohybrids for environmental protection and biomedicine applications, PN-II-RU-

PRECISI-2013-7-4198;

3) E. Matei, A.M. Predescu, C. Predescu, M.G. Sohaciu, A. Berbecaru, C.I. Covaliu,

Characterization and Application Results of Two Magnetic Nanomaterials, PN-II-RU-PRECISI-

2013-7-3050;

4) C.I. Covaliu, I. Jitaru, G.Paraschiv, E. Vasile, S.Ş. Biriş, L. Diamandescu, V. Ionita, H. Iovu,

Core–shell hybrid nanomaterials based on CoFe2O4 particles coated with PVP or PEG biopolymers

for applications in biomedicine, PN-II-RU-PRECISI-2013-7-4193;


21

Some of the articles in the field of environment engineering presented at conferences are

the following:

1. C.I. Covaliu, G. Paraschiv, S.St. Biris, C. Matei, M. Ionescu, Nanotechnology applied in

wastewater treatment. Photocatalysis based titanium dioxide, 16th International Multidisciplinary

scientific geoconference SGEM 2016, Vienna, 2 –5 noiembrie 2016.

2. C. Covaliu, G. Paraschiv, S. Ş. Biriş., I. Filip, M. Ionescu, Nanotechnology for

wastewater treatment, TE-RE-RD conference, 2-4 June 2016, Golden Sands, Bulgaria.

3. C.I. Covaliu, S.Şt. Biriş, G. Paraschiv, Fodorean, C. Ghitescu, E. Matei, A

Constantinescu., D. Arsenescu, I. Jitaru, TiO2 photocatalyst for wastewater treatment applications –

review, International symposium isb-inma teh agricultural and mechanical engineering, pp.241-244,

2015, ISSN 2344 – 4118.

4. C.I. Covaliu, G. Paraschiv, S.Ş. Biriş, Cr. Cîrtoaje, I. Filip, E. Petrescu Chromium

removal from wastewater using carbon nanotubes, 4th International Conference of Thermal

Equipment, Renewable Energy and Rural Development TE-RE-RD 2015, pp.199-204, 2015, ISSN

2457 – 3302.

5. C.I. Covaliu, G. Paraschiv, S.St. Biris, E. Matei, I. Filip, M. Ionescu, Heavy Metals

Removal from Wastewater Using Magnetic Nanomaterials Based Adsortion Strategies, 3rd Internat.

Conf. on Thermal Equipment, Renewable Energy and Rural Development, 2014, ISSN2359-7941.

6. C.I.Covaliu, E. Matei, G.Paraschiv, M.A. Predescu, Depollution of Wasterwater

Containing Cr (Vi) Ions, Using a Polymer-Magnetite, Analytical and Nanoanalytical Methods for

Biomedical and Environmental Sciences, 2014, ISSN: 2360-3461.

7. C.I.Covaliu, G. Paraschiv, S.St. Biris, D. Stoica, E. Matei, Heavy Metals Removal from

Wastewater usingMagnetic Nanomaterials, Book of Abstracts, 2nd International Conference on

Analytical Chemistry, Romania –Targoviste, September, 2014, ISBN 978-973-712-902-4.

Requested Criteria according to Annex 4 (Annex 18 for 6.560/2012 Order) Annex 18 –

Environmental Engineering

2. Minimum criteria (Ai)

No.

Category

Activity Field Requested Profesor

Conditions Accomplished


22

1 Teaching and training (A1) 210 216,4

2 Research (A2) 500 1539,72

3 Recognition and activity impact (A3) 90 600

TOTAL Minim 800 puncte 2356,12

No. Criteria Minimum requested Accomplished

1 Books and chapters in specialized

books (with ISBN) minim 4 6

2 Articles in ISI Thomson Reuters

journals Punctaj ≥ 400, n ≥ 11 Punctaj≥ 1201,72, n = 29

3 Articles in journals and volumes

of scientificevents indexed in

international databases, ISI

Proceedings

Minim 16 29

4 In competition won grants Minim 2 2

5 Citations in ISI Thomson Reuters

and BDI

Minim 30 200

Research Support Acknowledgements

As author of this thesis I recognize the interdisciplinary team support: CS1. Lucian

Diamandescu from Institute of Physic and Engineering of Materials Magurele, Prof. Horia Iovu,

Prof. Ioana Jitaru, Prof. Ecaterina Matei and CS1 Eugeniu Vasile from University Politehnica of

Bucharest and Prof. Tanja Circovich Velikovichi from University of Belgrade.


23

Chapter 2. CONTRIBUTIONS TO NANOTECHNOLOGY APPLICATION IN

WASTEWATER TREATMENT

Nanotechnology is one of the greatest technology discoveries of recent times. As

presented in Fig.2.1. the global market for nanotechnologies is still developing, being pegged at

approximately $16 billion in 2010, $27 billion in 2015 and expected to reach a value of $76

billion by 2020 [1]. This evolution is generally related, in large part, with the growth of the

interest for research and multiple applications of the “new” materials called nanomaterials and

also with the requirements of environment legislation, the development of industry and

increasing the life quality.

Fig. 2.1. Global nanotechnology market, 2010-2020; p – projections [1].

The nanotechnology (and thus nanomaterials) market has a huge potential of application

in environmental engineering field. The environment applications market was 1.1 billion $ in

2008, 26 billion $ in 2015 and estimated to be 42 billion $ by 2020 as is presented in Fig.2.2.

Nanotechnology provides opportunities to develop next generation of wastewater

treatment technologies.

Nanomaterials are defined as materials with dimension smaller than 100 nm. At this

scale, materials often have novel size-dependent properties different from their large

counterparts, many of which have been explored for applications in water and wastewater

treatment. The scalable size-dependent properties used by these applications are: high specific

surface area, high reactivity, strong capacity of adsorption. Other applications take advantage of

http://nanoportal.gc.ca/default.asp?lang=Fr&n=C139F81E-1


24

their discontinuous properties, such as superparamagnetism. Most of their applications are still in

the stage of laboratory research.

Fig.2.2. Global market for nanotechnology applied in environmental field applications, 2008-

2012 p – projections [1].

In the environmental field, nanomaterials sustain and enhance the development of

innovative processes pursuing to eliminate the risks associated with pollution from various

industrial activities by providing effective solutions for example in the wastewater treatment

direction. Owing to their physic and chemical characteristics, nanomaterials have a great

capacity to adsorb or decompose pollutants from water.

The scientific importance of this research direction is given by recent discoveries in the

field of nanotechnology which offers the possibility of solving the problem of environmental

pollution with industrial wastewater, containing highly toxic pollutants, having inorganic (e.g.

heavy metals) or organic (e.g. colorants, pesticides) nature, by applying new methods of

treatment more efficient compared with the conventional ones presenting countless

disadvantages of which are worth mentioning: inefficiency for removal low concentrations of

pollutants existing in wastewater, high cost because it involves high reagent consumption,

generation of hazardous wastes from the treatment process that are harmful to the environment

and require additional treatment costs.

For instance, in the case of heavy metals is well known the extremely high toxicity,

even at low concentrations, tending to bioaccumulate in the food chain, the ability to attack the


25

cells of the human body, leading ultimately to default malformations and cancer. The action of

the organic nature pollutants (e.g. pesticides) on the human body leads to abnormal growth, low

fertility, weakening immunity, reduced intellectual capacity and increased morbidity from

cancer. Particularly serious are the consequences of the action of these organic pollutants on the

embryo, fetus and young children.

Therefore, finding the most effective ways of removing inorganic or organic pollutants

from industrial wastewater is a crucial problem that can be solved by making new discoveries in

the field of nanotechnology, involving synthesis of new materials, nontoxic, nano- sized (called

nanomaterials) with special properties, used as adsorbents or catalysts.

The limitations of current approaches by analyzing the current state of knowledge

related to the habilitation thesis theme are the following:

regarding the inorganic pollutants (eg metals heavy) from industrial wastewater-

although can be used various treatments such as chemical precipitation, coagulation

and flocculation, flotation, ion exchange and membrane filtration but they have their

inherent disadvantages such as low efficiency for decreased concentration of

pollutants existing in water and limitation in application.

regarding the elimination of pollutants of organic nature from industrial waters,

the existing techniques such as wastewater treatment with activated sludge, biofilters

or oxidation lakes have the following disadvantages: involve high costs and

generates wastes which are harmful to the environment if are not well treated or

processed.

These limitations led to the research of unconventional methods such as those in area of

nanotechnology that can overcome the disadvantages and inherent limitations of conventional

methods of wastewater treatment.

This research direction, “Nanotechnology applied in wastewater treatment field”, is

distinguished by a lack of scientific data because is relatively new and the transition from

laboratory results to the application in a wastewater treatment plant cannot be done without

significant efforts made to elucidate all aspects still unknown.


26

2.1. Contribution to nitrates ions efficient removal from water using nanoadsorbents

2.1.1. General considerations

Generally, nitrate ions are present in soil and water, but high levels of nitrates are

considered pollutants for ground and surface waters.

In recent years, it was observed an increase of nitrate concentration in groundwater in

many parts of the world due to increased usage of nitrogenous fertilizers in agriculture practice

and discharge of domestic and industrial wastewater Fig.2.3 and Table 2.1. [2].

Table 2.1. Groundwater nitrate concentration classes (mg NO3/L) and proportion of

groundwater monitoring stations in each class per country (%), 2009, EU-27, EFTA, candidate

and potential candidate countries Source: European Environment Agency [2].

Country Groundwater nitrate concentration classes (mg \NO3/l) and number of groundwater

monitoring stations in each concentration class per country

≤10 10< ... ≤ 25 25< ... ≤ 50 50< Total

Belgium 1024 381 534 835 2774

Bulgaria 52 21 24 15 112

Czech Republic 385 85 70 73 613

Denmark 308 107 119 88 622

France 679 394 431 152 1656

Netherlands 244 16 16 27 303

Romania 476 86 51 46 659

Poland 80 10 14 8 112

United Kingdom 2012 441 99 31 2583

Norway 50 7 1 0 58

Albania 10 1 0 0 11

Generally, the concentration of nitrates in the water from unpolluted areas is less than 1

mg/L. A compromised water is characterized by higher level of nitrates [3-5]. In the human body

nitrate anion is potentially harmful because it can be transformed into nitrite.

Many environmental regulatory agencies including the U.S. Environmental Protection

Agency (U.S. EPA) have set a maximum pollutant level (MCL) of 10 mg/L of NO3- in drinking


27

water [6].

In case of children, the presence of nitrate levels above the EPA maximum contaminant

level of 10 mg/L N- NO3 or 45 mg/L NO3- is responsible for the appearance of the disease called

methemoglobinemia, also known as blue baby syndrome [7-13].

High concentration of nitrate ions in drinking water is responsible for impairing blood

to carry oxygen throughout the body causing multiple health problems, such as: cancer,

disruption of thyroid function, birth defects and other health risks. As nitrate has no taste, odor or

color, its determination can be done only by laboratory analyses [14-16].

Fig.2.3. Annual average river nitrate concentration averaged by National River Basin Districts

(mg N/L), (2009), EU-27 and EFTA Source: European Environment Agency [2]

Nitrates are water soluble, crossing freely through most soils reaching to groundwater

and surface water (through groundwater connections). Nitrogen based fertilizers (such as

ammonium sulfate, ammonium chloride, ammonium nitrate, urea etc.) within the agriculture


28

practice are applied on land surface for the growth of plants. Ammonia (NH4+) contained by

fertilizer can leach into the ground below the root zone, reaching into the groundwater and rivers

being transformed to nitrates (NO3-) (see Fig.2.4) according to the following potential reactions:

NH4+ + 1.5 O2 → 2H+ + H2O + NO2 (2.1)

NO2- +0.5 O2 → NO3

- (2.2)

Nitrate ions concentrations from surface water coming from agriculture are especially

from groundwater connections and other subsurface flows. Another important source of nitrate

water pollution from agriculture practice is using as fertilizers the animal manure.

Fig. 2.4. Schematic presentation of leaching ammonia from fertilizer to groundwater as

nitrates [17].

Although there are many sources of nitrogen (natural and anthropogenic) that could

potentially lead to the pollution of the groundwater with nitrates, the anthropogenic sources are

the ones that generally cause the rising of concentration of nitrate to a dangerous level. Many

local sources of potential nitrate pollution of groundwater are: the "sites” used for disposal of

human and animal sewage, industrial wastes related to food processing, munitions, and some

polyresin facilities, septic tanks.

As regarding the industrial pollution with nitrates it worth mentioning industrially-

relevant nitrate esters such as nitroglycerin (1,2,3-trinitroxypropane, NG) or ethylene glycol

dinitrate (EGDN) which have received much scientific attention [18, 19]. These substances are


29

used for the production of explosives and exist as co-pollutants in nitrate polluted wastewater

originating from manufacturing activities. During the washing steps from the production process

of explosives factories the wastewater is generated in very large volumes (often more than 240

m3/day) [20]. The difficulty of applying a treatment for this type of wastewater is given by its

specific composition, having a high concentration of nitrates (up to 7,500 mg N/L), sulphates and

a low pH value (usually between 1.0 and 1.5). For such industrial wastewater the conventional

physicochemical methods of wastewater treatment are limited in terms of efficiency or

completely inappropriate. For example, the removal of high nitrate concentration could not been

done using ion exchange-based methods. The application of membranes treatment for

nitroglycerin removal has the risk of explosions. Exist few physicochemical methods which can

be applied, such as microwave-assisted degradation [19] and reductive transformation by pyrite

and magnetite [21], but there are inefficient by the economic point of view due to the high

energy consumption, the need to specific chemical reagents, which make the process

economically inefficient.

My own contribution in this research direction was the removal of nitrates from

wastewater by adsorption on various nanomaterials synthesized and characterized before testing.

2.1.2. The investigation of Pd-Sn/γ-Al2O3, NiTiO3 and NiFe2O4 for nitrates removal from

water

This subchapter describes an efficient way of nitrate ions removal from water by using

the following adsorbants: Pd-Sn/γ-Al2O3, NiTiO3 and NiFe2O4. All three adsorbants were

synthesized and characterized prior their testing for depollution of water containing nitrates. The

Pd-Sn/γ-Al2O3 and NiTiO3 were successfully prepared by sol-gel method and NiFe2O4 by co-

precipitation method. The study presented in this subchapter has been published in the scientific

literature [17].

The Pd-Sn/γ-Al2O3 nanomaterial was obtained in two steps:

➢ γ-Al2O3 was prepared by sol-gel method using as template agent lauric acid. The

molar ratio between Al(OC3H7)3: C12H24O2: C4H9OH was 1: 0,15: 30. The molar ratio

between aluminum precursor and water was 1: 1.9. The reaction mixture was kept at


30

800C for 100 h, until was formed a white precipitate, which was washed with alcohol

several times, filtered, dried in air and finally calcined at 6000C for two hours.

➢ the Pd-Sn bimetallic material was prepared by sol-gel method using as precursor

salts PdCl2 and SnCl2, in a solution of ethylene glycol brought to pH 11 using NH3. The

Pd-Sn/γ-Al2O3 material contained 1 wt% noble metal (Pd) and 1 wt% Sn. The reaction

mixture was homogenized for 12 h, under reflux and then ammonia and ethylene glycol

were removed by washing with alcohol. After drying at 900C, the material was thermal

treated at 2000C for 1h.

➢ the material finally obtained was characterized by scanning electron microscopy

(TEM), X-ray diffraction (XRD) and BET analysis.

The synthesis and characterization of NiFe2O4 and NiTiO3 was published elsewhere [22].

Characterization of prepared adsorbant material

The X-ray diffraction (XRD) analysis shows the distortioned spinel structure of γ-Al2O3

(Fig. 2.5.). The characteristic diffraction peaks for bimetallic particles Pd-Sn are: 2θ =38.50,

43.0. The average crystallite size identified using Scherrer formula was 40 nm.

Fig. 2.5. XRD of Pd-Sn/Al2O3 adsorbant.


31

The textural characteristics are presented in Figs. 2.6 and 2.7. The specific surface area of

the nanomaterial Pd-Sn/ γ -Al2O3 is 275m2/g and the value of pores diameter is between 2 and 10

nm.

The morphology characterization done by transmission electron microscopy (TEM)

investigation presented Fig. 2.8 reveal that the Pd-Sn/ γ -Al2O3 mean particle size is of 100 nm.

Fig. 2.6. The adsorption-desorption isotherm of the Pd-Sn/g-Al2O3 adsorbant.

For the other two tested nanomaterials nickel titanated and nickel ferrites the

morphological characterization was done by scanning electron microscopy (SEM). The SEM

image of nickel titanate sample obtained by calcination at 6000C/4h show that the particles are

spherical, having an average particle size of 1µm (Fig.2.9).

The nickel ferrite calcined at 5000C/2h presents spherical shape, with a tendency to

form agglomerates. The average particle size is 90 nm and the average agglomerate is 150 nm

(Fig.2.10).


32

Fig. 2.7. Pores size distribution of the material Pd-Sn/ γ -Al2O3.

Fig. 2.8. TEM image of Pd-Sn/ γ -Al2O3


33

Fig.2.9. SEM image for NiTiO3 obtained by

precursor calcination at 6000C/4h

Fig.2.10. SEM image for NiFe2O4 obtained

by precursor calcination at 5000C/2h

Nitrate ions adsorption study on the three adsorbants: Pd-Sn/ γ -Al2O3, NiTiO3 and

NiFe2O4

The analysis of nitrates from wastewater was determined using SR ISO 7890/3-1998

standard method applied for drinking water, surface water and wastewater. The method provides

a rapid determination of nitrate from water.

Adsorption experiments were carried out in Erlenmeyer flasks using a temperature

controlled orbital shaker (stirring speed of 200 rpm) for 36 h. Am amount of 20 mg of the

adsorbent was contacted with 50 mL of nitrate solution solutions (concentration was 5 mg/L)

representing the synthetic polluted wastewater at 20 ±2◦C.

The nitrates ions adsorption capacity of the three prepared materials was calculated with

the formula:

m

CeCiVUptake

)( (2.3.)

where:

Uptake - adsorption capacity at time t, the concentration of nitrates retained per unit mass

of adsorbent materials, (mg/L);

V - volume of solution containing nitrate ions, (mL);

Ci - initial concentration of the nitrate ions, (mg/L);

Ce - equilibrium concentration, (mg/L);


34

m - adsorbant weight, (mg).

In order to investigate the effect of pH on nitrate adsorption, the experiments were

conducted in 2-10 pH range.

The pH of the water solution was adjusted using 0.1M HCl or 0.1M KOH.

In figure 2.11 is presented the plot adsorption of nitrate ions on Pd-Sn/ γ-Al2O3, nickel

ferrite and nickel titanate adsorbant nanomaterials. The maximum adsorption capacity of nitrate

was obtained at pH 3.5.

The maximum adsorption capacity values were 3.598 mg/L for Pd-Sn/g-Al2O3, 3.176

mg/L for nickel titanate and 3.051 mg/L for nickel ferrite.

Fig.2.11. Adsorption plot for retaining nitrate anions on Pd-Sn/ γ-Al2O3, NiTiO3 and NiFe2O4

adsorbants.

SIPS isotherm model

The SIPS isotherm model considers that the adsorption efficiency is limited at high

concentration of ions in solution. The model is similar to the Langmuir isotherm, with the

exception of a parameter representing heterogeneous system.


35

The SIPS model reduces to Langmuir's model when γ= 1.

)(1

)(max

eS

eS

CK

CKQQe

(2.4)

where:

eQ – the total adsorption capacity at equilibrium, (mg/L);

maxQ – the maximum adsorption capacity of the adsorbent material, (mg/L);

eC – the equilibrium concentration, (mg/L);

SK - the adsorption constant (dissociation parameter);

n – the number of variable parameters (3).

Fig. 2.12. SIPS linear model representation for nitrate ions adsorption of onto

Pd-Sn/ γ -Al2O3, NiTiO3 and NiFe2O4.

The regression factors obtained were 0.9987 for Pd-Sn/γ-Al2O3, 0.9984 for NiTiO3 and

0.9982 for NiFe2O4 (Fig.2.12). The regression factors show that the best results regarding nitrate

ions adsorption were obtained for Pd-Sn/γ-Al2O3 nanomaterial. This fact could be explained and

correlated with the specific surface area values of the three adsorbant nanomaterials: 275m2/g for

Pd-Sn/ γ-Al2O3, 32,6 m2/g for NiTiO3 and 10,1 m2/g for NiFe2O4 [22].


36

2.1.3. The investigation of CuTiO3 and CuFe2O4 for nitrates removal from water

In this subchapter is presented the evaluation of the adsorption capacity of CuFe2O4 or

CuTiO3 adsorbents for removing nitrate ions from water.

The metal titanates are known as inorganic functional materials with wide applications in

environment protection [22].

The research results presented in this subchapter were already published in scientific

literature [5].

Prior to describe the tests for removing the nitrates from water, is presented the synthesis

of the two nanomaterials in laboratory:

a) CuTiO3 was synthesized by sol-gel method as follows: as starting precursors

solutions were used 0.5 mmol Cu(CH3COO)2.4H2O in 50 mL ethanol and 0.5 mmol

Ti[OCH(CH3)2]4 in 50 mL of isopropanol (Cu: Ti = 1:1 molar ratio). The solution obtained was

heated under reflux at 800C, 4 hours, until a gel was formed. Then the gel was separated, filtered

and dried at 1500C. The solid precursor was thermal treated at 700oC for 5 hours.

b) CuFe2O4 was synthesized by coprecipitation method as follows: as starting raw

materials were used Fe(NO3)3 . 9H2O and Cu(NO3)2

. 2H2O in a 2:1 molar ratio at pH = 12

obtained by adding NH3 25% as precipitation agent. The reaction mixture was maintained under

reflux at 700C for 3h, until a black precipitate was formed. After the purification process which

implies washing ten times with water and ethanol (10:1), the precursor was calcined at 4000C for

3h in order to obtain a single phase CuFe2O4 powder.

Copper titanate and copper ferrite powders obtained by calcination at 7000C for 5h and

5000C for 2h respectively, were structural, morphological and textural characterized by scanning

electron microscopy (SEM), specific surface area BET and X-ray diffraction (XRD analysis).

The specific surface areas of the two synthesized compounds were measured with ASAP 2020

V3.04 H apparatus by using Brunauer-Emmet-Teller (BET) method using nitrogen at 77K.

Finally copper titanate and copper ferrite were tested for adsorption of nitrate ions from

water. The concentration of nitrate in solutions was determined by UV-VIS spectroscopy.

pH studies

In order to investigate the effect of pH on nitrate adsorption, the pH of the nitrate


37

solutions was adjusted from 4 to 6. The initial pH of the solution was adjusted by using 0.1M

HCl or 0.1M NaOH. Each of the two adsorbants was added in the nitrate polluted water

solutions. The objective was to determine which of the pH value conduct to the maximum nitrate

removal from water knowing that the adsorption pH is one of the factors that have been found to

have a important effect upon the adsorption. Maximum nitrate removal occurred at pH of 4,

because the predominant form of nitrate is at this pH.

For conducting the nitrate adsorption study was used a stock nitrate solution. The

required concentration of the nitrate solution was prepared by serial dilution of the stock

solution. Were used different concentrations of nitrate in the range 0 to 300 mg/L, to observe the

capacity of adsorption of the two nanomaterials at different concentration. A fixed amount of the

adsorbent was added to 50 mL nitrate solution into in Erlenmeyer flask, placed on a orbital

control shaker. The solutions were stirred continuously at constant temperature to achieve

equilibrium. After equilibrium, the two nanomaterial powders were separated by centrifugation.

The adsorbent was removed by centrifugation (6000 rpm) and the concentration of the

corresponding anion remaining in the supernatant was determined spectrophotometrically at

λ=220 nm.

X-ray diffraction

The XRD of copper titanate obtained has cubic structure with monoclinic symmetry

(Fig.2.13 and 2.14). The average crystallites size value calculated based on Scherrer formula is

30 nm. The XRD pattern presented in figure 2.14 is characteristic to CuFe2O4 having spinel

structure and cubic symmetry. The average crystallites size was estimated at 40 nm, with

Scherrer formula.

SEM investigation

The morphologies of CuTiO3 and CuFe2O4 powders, calcined at 7000C/5h and 5000C/2h

respectively, were investigated by scanning electron microscopy (SEM) and are shown in Figs.

2.15 and 2.16.


38

CuFe2O4 presents a higher tendency of the particles to form agglomerates (Fig.2.16).

Both samples have spherical shape particles. The average particles size is 70 nm for CuTiO3 and

90 nm for CuFe2O4 and the average agglomerates size is 100 nm for CuTiO3 and 150 nm for

CuFe2O4.

Fig.2.13. XRD patern of CuTiO3, calcined at 7000C for 5h.

Fig.2.14. XRD pattern of CuFe2O4, calcined at 5000C for 2h.


39

Fig. 2.15. SEM image for CuTiO3.

Fig.2.16. SEM image for CuFe2O4.

Textural characterization

For CuTiO3 nanomaterial the BET surface area is 15.95m2/g (Fig.2.17). The BJH

adsorption cumulative surface area of pores is 20.07m2/g and BJH desorption cumulative surface

area of pores is 21.21m2/g (Fig.2.19) The BJH is the method of Barret, Joyner and Halenda for

the pores distribution. The single point adsorption total volume of pores is less than 271.22 nm

diameter at p/p° = 0.99 is 0.10cm3/g.


40

Fig.2.17. Adsorption isotherm for CuTiO3.

Fig.2.18. Adsorption isotherm for CuFe2O4.

Fig.2.19. BJH adsorption dV/Dd pore volume for CuTiO3.


41

Fig.2.20. BJH adsorption dV/Dd pore volume for CuFe2O4

For CuFe2O4 the BET surface area for the CuFe2O4 is 9.15 m 2/ (Fig.2.18). The BJH

adsorption cumulative surface area of pores is 10.0 m2/g and BJH desorption cumulative surface

area of pores is 9.91 m2/g (Fig.2.20). Single point adsorption for total pores volume is less than

443.5148 nm and diameter at p/p° of 0.99 is 0.02 cm3/g.

Adsorption isotherms

Experiments were carried out in Erlenmeyer flasks placed in a temperature controlled

orbital shaker (stirring speed of 150 min-1) for 24 h. 15mg of the adsorbant were introduced in 30

mL of nitrate solution at 22 ± 2oC. Before starting the experiments both adsorbents were dried at

1000C for 3 h.

Batch adsorptions studies were performed as a function of contact time, initial nitrate

concentration, pH and influence of other interfering anion.

In figures 2.21a and 2.21.b were presented the plots of adsorption for copper titanate

and copper ferrite used as adsorbant nanomaterials. Good adsorbtion results were obtained both

in the absence of electrolyte and also in the presence of electrolyte.

The maximum adsorption capacity of nitrate was obtained at pH 4, at which is the

predominant form of the anion. In the case of copper titanate the maximum adsorption capacity

was 2.069 mg/L and in the case of copper ferrite was 0.951 mg/L. The adsorption equilibrium


42

was obtained at pH = 4.

The influence of sulphate (SO42-) anion on nitrate removal from water in the case of the

studied adsorbents was investigated at for nitrate concentration of 200 mg.L-1. The concentration

of sulphate anion was 0,1M. It was observed that nitrate adsorption was mainly influenced by the

presence of sulphate anion. At ionic strength 0.1M, the concentration of nitrate decreased.

Fig.2.21. a) Plot sorption of NO3-, versus equilibrium concentration for CuTiO3

adsorbant.

Fig.2.21 b) Plot sorption of NO3-, versus equilibrium concentration for

CuFe2O4 adsorbant.


43

Langmuir isotherm characteristic equation is:

(2.4)

where: a - adsorption capacity at equilibrium, mg/g;

1 - maximum adsorption capacity for a given set of conditions to balance the entire

monomolecular layer is occupied, mg/g;

Ce - concentration of solute in the system at equilibrium, mg/L;

b - equilibrium constant that depends on the nature of the adsorption system.

Langmuir equation can be written as:

(2.5)

The characteristic equation for experimental data is:

(2.6)

R2 - 0.9960 regression coefficient.

The Langmuir equation fits well the experimental data for nitrate ions adsorption. Since

R2 has values over 0.95 is considered that Langmuir equation is appropriate for nitrate anion

adsorption using the tested adsorbant nanomaterials.

Fig.2.22. Langmuir equation representation for CuTiO3.


44

In conclusion, the preliminary result of this study presents the capacities of copper

titanate and copper ferrite for nitrate removal from aqueous solutions. The results show that the

adsorption effectiveness of copper titanate for nitrate was higher in comparison with copper

ferrite when the concentration of nitrate was in the range of 0–300mg/L. It was observed that the

particle dimension, the specific surface area and the pH have influenced the adsorption capacity.

The maximum adsorption capacity was at pH of 4 for copper titanate (2.069 mg/L). The pH

affects the adsorption process, when the pH increased, the adsorption capacity decreased. Better

results for nitrate adsorption were obtained when the experiments were carried out in the absence

of an electrolyte (SO42-). The Langmuir equation characterized very well the adsorption for

nitrate anions.

2.2. Contribution to the removal of Cd (II) ions from wastewater using maghemite and

poly-DL-alanine based core-shell magnetic nanohybrids


In this subchapter is presented the application of nanotechnology for the Cd (II) ions

removal from wastewater via core-shell nanohybrids composed by inorganic and organic

components.

Industrial wastewaters are considered the largest source of pollution of the environment

because they contain toxic compounds. Industrial wastewater polluted with heavy metals (Pb2+,

Cd2+, Zn2+, Ni2+, Hg2+, Cr6+, Co2+, Cu2+) has as sources many industrial activities such as:

mining, metallurgy, dyes manufacture, pesticides manufacture, tanning, manufacture of

explosives , electroplating, petrochemical, etc.

This category of pollutants has a multitude of adverse effects on the environment and

humans.

As regarding the sources of cadmium in the environment can be considered the

following: iron and steel industry, waste incineration and disposal, zinc production, mining, ore

dressing, smelting of nonferrous metals, battery manufacturing industry, coal combustion,

phosphate fertilizer manufacture and use, etc. The largest cadmium input to aquatic systems is


45

considered the manufacture of cadmium- containing articles, followed by phosphate fertilizer

and zinc manufacture.

Effects of cadmium ions upon human’s health are presented in Fig. 2.23.

Fig.2.23. Effects of cadmium ions upon human’s health.

The core-shell nanohybrids which are the subject of current study are very interesting

because they possess several important properties and are attractive because of their potential to

be used in wastewater treatment. They are formed from a core and a shell between which can

exist chemical interaction Magnetic nanohybrids have special magnetic properties, such as

superparamagnetism, facilitating their removal from the technological system after the

wastewater treatment is ended.

Using biopolymers for coating of the magnetic oxide nanoparticles brings multiple

advantages such as:

a) it prevents the agglomeration by providing a steric barrier;

b) provides a lack of any king of toxicity of the core to the environment.

Poly-DL-alanine is a biodegradable polyaminoacid used as coat for maghemite

nanoparticle and is used in a wide range of applications: as release agents in agriculture, in water


46

treatments, as paint additives, in cosmetics composition, as metal adsorbents and as surfactants.

Also, polyaminoacids have clinical applications being used as components for diagnostics,

dialysis membrane, artificial skin, orthopedic implants, drug delivery systems and carriers for

therapeutic protein conjugates.

Until the publication of this research field, poly-DL-alanine polymer has not been used

for inorganic nanoparticles biocompatibilization (Fig.2.24).

N

O

n

H

CH3

Fig. 2.24 Structural formula of poly-DL-alanine

The study presented in this subchapter was already published [23].

2.2.2. Cd (II) ions removal from wastewater using multifunctional maghemite and poly-DL-

alanine based core-shell magnetic nanohybrids

This subchapter describes the synthesis of two core-shell nanohybrid materials based on

maghemite (γ- Fe2O3) and poly-DL-alanine and their testing on Cd (II) ions removal from

wastewater.

The synthesis method is a two-step procedure, which consists in the following:

1. Preparation of maghemite nanoparticles by microemulsion method - starting from the

following raw materials: ferric chloride (FeCl2.6H2O), sodium dodecyl sulfate (SDS), n-butanol,

ammonia solution (NH3) 25 %. Into the transparent mixture obtained by mixing the SDS, water

and n-butanol in a molar ratio of 1:2:5 was added the FeCl2.6H2O 0.5M solution and then NH3

solution to achieve the pH value of 10. After 2 h the precipitate obtained was separated by

centrifugation and washed several times with water and ethanol.

2. Coating of maghemite nanoparticles with poly-DL-alanine. The two nanohybrids

were obtained starting from two molar ratios (1:5 or 1:15) between maghemite nanopowder and


47

poly-DL-alanine biopolymer. The maghemite powder was added to 15 mL of poly-DL-alanine

0.5 M solution to obtain 1:5 nanohybrid (H1-5) or to 50 mL of poly-DL-alanine 0.5 M solution

for preparing 1:15 nanohybrid (H1-15) and stirred for 6 h at room temperature. The hybrid

particles were separated by centrifugation and dried at 900C for 2h [23].

In order to evaluate the adsorption properties of the γ- Fe2O3 and its corresponding

polymeric hybrids H1-5 and H1-15 the investigation was done for the removal of Cd (II) ions

from wastewater.

Cd (II) ions removal from wastewater

The synthetic wastewater containing cadmium ions was prepared from Merck reagent-

grade solutions by dissolving into ultrapure water. The stock solution had an initial concentration

of 1000 mg/L and pH value was adjusted by adding NaOH (0.1 mol/L) in order to obtain a

proper value similar to that of industrial wastewater, of pH 5.6. The adsorption studies were

carried out by measuring of the initial and final concentration of the metal by flame atomic

absorption spectrometry (FAAS).

The adsorbed metal amount at equilibrium is calculated by ratio between adsorbed

metal (mg) onto adsorbent mass (g) expressed as qe, according to the Eq. (1):

m

VCCq e

e

0 (2.7)

where:

C0 – initial concentration, mg/L;

Ce – equilibrium concentration, mg/L;

V – volume of solution, L;

m – adsorbent quantity, g.

Adsorption studies were performed by mixing of 0.1 g from each nanomaterial

adsorbents (γ-Fe2O3, H1-5 and H1-15) with 100 mL solution consists of 10, 20, 50, 80 and 100

mg/L of Cd(II) at room temperature (21.5°C).

For adsorption kinetic studies, the wastewater solutions prepared were kept into contact

with each type of adsorbent nanoparticles from 10 to 120 minutes. The adsorbent samples were

recovered by magnetic separation. In order to establish the quantity of adsorbed cadmium onto


48

nanomaterials was used FAAS with a GBC 932 AB Plus spectrometer with spectral domain

between 185 and 900 nm.

The adsorption isotherm for Cd (II) onto 0.1 g γ-Fe2O3, H1-5 and H1-15, respectively,

were fitted to the Langmuir model expressed as Eq. (2):

bqC

qq

C

m

e

me

e

11 (2.8)

where:

Ce –aqueous concentration at equilibrium, mg/L;

qe – adsorbed amount at equilibrium, mg/g;

qm and b – constants related to the adsorption capacity and the affinity coefficient.

For adsorption studies only 0.1 g of γ-Fe2O3 was added to 100mL of each mentioned

concentration of Cd (II). The procedure was similarly applied to the other two nanomaterials H1-

5 and H1-15.

Prior to test the water treatment properties, after the synthesis, all three nanomaterials

were characterized by: X-ray diffraction, X-ray photoemission spectroscopy, Mössbauer

spectroscopy, Fourier transform infrared spectroscopy, Transmission electron microscopy, High

resolution transmission electron microscopy with selected area electron diffraction and Atomic

absorption spectroscopy. Some of these analyses are further presented.

X-ray diffraction (XRD)

The XRD data show that uncoated oxide powder is mono-phase and has the crystalline

structure of maghemite (γ-Fe2O3), with cubic symmetry (Fig. 2.25 a). The average crystallite size

calculated by Scherrer formula is 21 nm. The XRD spectra of nanohybrids H1-5 and H1-15,

present beside characteristic peaks of the maghemite crystalline structure, peaks assigned to

poly-DL-alanine (Fig 2.25 b and d).

Atomic Absorption Analysis (AAS)

The content of maghemite from the two prepared nanohybrids determined by Atomic

absorption analysis was 40% for H1-5 and 18% for H1-15 hybrids.


49

Mössbauer spectroscopy

Maghemite has the composition of hematite but it exhibits the structure of magnetite

(Fe3O4). In the cubic structure of both maghemite 1/3 of the interstices are tetrahedral

coordinated with oxygen and 2/3 are octahedral coordinated. In maghemite, only 5/6 of the total

available positions are filled by Fe3+, the rest are vacant (□): Fe2.67□0.33O4. Maghemite may have

different structures depending on the degree of ordering of the vacancies. A total ordered

maghemite has a tetragonal symmetry.

Fig. 2.25. XRD patterns of γ-Fe2O3 powder (a), H1-15 hybrid (b), poly-DL-alanine (c) and H1-5

hybrid (d)

The maghemite lattice has 8 Fe3+ in tetrahedral sites and 13.33 Fe3+ ions in octahedral

sites. The magnetic field values are 488 KOe for the tetrahedral sites and 499 KOe for the

octahedral ones. The room temperature Mössbauer spectra of the initial maghemite and the

corresponding nanohybrids (H1-5 and H1-15) are displayed together with the computer fit

(continuous lines) in Fig. 2.26 a, b and c. All spectra contain six line magnetic hyperfine pattern

and a very small central doublet.


50

(a)

(b)

(c)

Fig. 2.26. Mössbauer spectra of the uncoated maghemite (a) together with the spectra of

maghemite based nanohybrids with poly-DL-alanine in different molar ratio: H1-5 (b) and H1-

15 (c)


51

The central doublet with a quadrupole splitting of ~ 0.45 mm/s and isomer shift of ~ 0.15

mm/s is assigned to a very small amount of Fe in the Beryllium detector windows; this is

observed only at very high statistics on the recorded spectra, as it is the case of our spectra. The

magnetic patterns were deconvoluted in two sextets corresponding to Fe3+ in A and respectively

B site of maghemite. The magnetic hyperfine fields are similar with the standard values of

maghemite values of 484 KOe for A sites and 495 KOe for the B sites, respectively. No

significant differences were observed between the Mössbauer spectra of the maghemite sample

and those of the two hybrids.

FTIR spectroscopy

For knowing if exist any kind of interaction between γ-Fe2O3 and poly-DL-alanine was

done FTIR analysis. The γ-Fe2O3 is a deficient magnetite having inverse spinel structure and is

represented as Fe3+[ Fe3+X]O3, where X is the vacancy site from the lattice, Fe3+ inside the square

bracket represents tetrahedral position and Fe3+outside the square bracket represents the

octahedral position.

By comparing the spectra of maghemite and poly-DL-alanine with those of the hybrids

were observed the following:

a) the shift of Fe-O vibration bands placed in octahedral and tetrahedral sites frequencies

located at 467 cm-1 and 615 cm-1 in maghemite spectrum to higher vibration frequencies for H1-

5 (478 cm-1 and 640 cm-1) and H1-15 (487 cm-1 and 637 cm-1) nanohybrids spectra;

b) the shift of vibration bands assigned to amino (N-H) and carbonyl (C=O) groups

located at 3210 cm-1 and 1637 cm-1 in poly-DL-alanine spectrum to higher wavenumbers for H1-

5 (3225 cm-1 and 1661 cm-1) and H1-15 (3227 cm-1 and 1661 cm-1) hybrids spectra (Fig.2.27).

The binding sites of the poly-DL-alanine biopolymer are the amino and carbonyl groups

which interact with Fe3+ ions from the maghemite like in Fig. 2.27 a and b.

XPS analysis

XPS spectroscopy was also used for the investigation of the existence of the

interactions between the poly-DL-alanine biopolymer and maghemite nanomaterials.


52

The principal signals in XPS spectra at 712.8 and 727 eV correspond to Fe 2p3/2 and Fe

2p1/2 both being contain in maghemite and nanohybrids spectra.

Fig.2.27. FTIR spectra of H1-5 hybrid (a), poly – DL-alanine (b), H1-15 (c), γ-Fe2O3 (d)

The binding energies assigned to the species presented in the spectra of maghemite,

poly-DL-alanine and nanohybrids are presented in Table 2.2.

Table 2.2. Binding Energy (eV) of γ-Fe2O3, poly-DL-alanine, H1-5 and H1-15 nanohybrids,[23].

Samples Nanopowder

γ-Fe2O3

Nanohybrid

H1-5

Nanohybrid

H1-15

Poly-DL-alanine

Fe 2p3/2 712.81 714.74 714 -

Fe 2p1/2 727 725 726 -

O1s 531.33 533.62 531.14 530.8

C1s - 290.89 286.3 285.47

N1s - 403.32 401.18 400.35


53

As regarding the peak of C1s was observed a significant shift of the corresponding

binding energy from 285.4 eV in the poly-DL-alanine to 286.3 eV and 290.8 eV in the

nanohybrids which is a strong argument for the interactions between Fe3+ and oxygen atoms

from the poly-DL-alanine (Fig. 2.28).

Fe3+

Fe3+

N

O

nCH3

N

O

n

H

CH3

(a)

(b)

Fig. 2.28 Expected interactions between Fe3+ ions of maghemite nanoparticles and poly-DL-

alanine molecules in amino group (a) and carbonyl group (b) [23].

Knowing that for the two hybrids the poly-DL-alanine shell thickness is less than 2 nm

(Figs. 2.28a and 2.28b) and the X-ray photoemission depth of surface examination is 3-5 nm, the

purpose of doing XPS analysis was to show the existence of the polymeric layer around the

maghemite nanoparticles and the interactions that exist between the two components of the H1-5

and H1-15 hybrid, not the well-defined poly-DL-alanine shell around the maghemite core.


54

Morphological characterization

TEM and high resolution transmission electron microscopy (HRTEM) investigation

show the core-shell nanostructure of the γ-Fe2O3 –poly-DL-alanine hybrids nanoparticles.

SAED investigation of uncoated maghemite and corresponding nanohybrids show the

Miller indices of crystalline structures first identified by XRD (insets of Figs. 2.29 d, 2.30 b, 2.31

c).

Fig. 2.29 a and b present the well defined nanostructure of H1-5 composed of 21 nm

maghemite core and a poly-DL-alanine shell of 1.5 nm.

An H1-5 hybrid nanoparticles have polyhedral shape. More information sustaining the

structure of H1-5 hybrid nanoparticles was revealed through the detailed analysis of HRTEM

which show the interplanar distances of 2.52 Å and 2.10Å assigned to crystallographic planes of

Miller indices (311) and (400) characteristic to cubic γ-Fe2O3 structure (Fig. 2.29 b and c).

For the H1-5 nanohybrid was calculated from the size distribution of 150 particles an

average particle size of 22 nm (Fig.2.30 b).

HRTEM investigation of maghemite nanoparticles present 2.52 Å and 2.95 Å

interplanar distances assigned to crystallographic planes of Miller index (311) and (220),

respectively (Fig. 2.30). In the absence of the polymeric coat, the agglomeration tendency of

maghemite nanoparticles is higher because of the magnetic interaction and the absence of a steric

barrier. The average particle size of uncoated maghemite determined by counting 150 particles is

21 nm (Fig.2.31 a) and their shape is polyhedral (Fig. 2.30 b). HRTEM image of H1-15 hybrid

shows a 2.52 Å interplanar distance assigned to crystallographic plane of Miller index (311) (Fig.

2.32 b).

Three different HRTEM images of H1-15 show that the core is smaller (9 nm and 11nm

Fig. 2.32 a with inset) or equal (21 nm Fig. 2.32 b) in comparison to H1-5, but the poly-DL-

alanine shell thickness is higher (1.7 nm in Fig. 2.29ba and 2 nm in Fig. 2.29 b) indicating that

when it was used an increased amount of polymer for maghemite coating an increased amount of

poly-DL-alanine is was retained on maghemite nanoparticles and, also an increase of the average

particle size of the hybrid was observed (23 nm, Fig. 2.32 c).


55

(a) (b)

(c) (d)

Fig.2.29. HRTEM images at different magnitudes (a), (b) and (c); TEM inset SAED (d) of H1-5

nanohybrid, beam direction: B=[ 001] [23]


56

(a)

(b)

Fig. 2.30. HRTEM (a) and TEM inset SAED (b) images of γ-Fe2O3 nanopowder, beam direction:

B=[112 ] [23].

By comparing Fig. 2.29 d with Fig. 2.32 c was observed that a higher value of the

polymeric coat thickness of the maghemite nanoparticles conducted to a decrease of the

agglomeration tendency of the hybrid nanoparticles [23] by two mechanisms:

creating a steric barrier;

avoiding the agglomeration of the magnetic particles.

Although exists an agglomeration tendency of maghemite nanoparticles due to their

magnetic properties, the polymeric shell represents a uniform coat and is preserved for each

individual hybrid particle (Figs. 2.29 a and 2.32 a).

The shell of poly-DL-alanine is composed by three-four polymeric layers (observed on

the central particles from Figs. 2.29 a, b and 2.32 b) also observed in XRD pattern at 2θ equal to

20.

TEM investigation revealed that maghemite and hybrid particle samples are nearly

monodispersed (Figs. 2.29 d, 2.30 b and 2.32 c).


57

15 20 250

5

10

15

20

25

30

35

40

D= 22 nm

Nan

op

art

icle

s c

ou

nts

Size (nm)

(a)

15 20 250

5

10

15

20

25

30

35

40

D= 22 nm

Nan

op

art

icle

s c

ou

nts

Size (nm)

(b)

15 20 250

5

10

15

20

25

30

35

40

D= 23 nmN

an

op

art

icle

s c

ou

nts

Size (nm)

(c)

Fig. 2.31 Size distribution for γ-Fe2O3 (a), H1-5 nanohybrid (b) and H1-15 nanohybrid (c)

For all the investigated samples the main magnetic parameters are presented in Table

2.3.

Both maghemite and hybrid nanoparticles present superparamagnetic behavior with

very narrow hysteresis cycles, which confirm the reduced size of particles that allows the

presence of a single magnetic domain. Because the density of the nanohybrid materials is

unknown, the comparison is done using the specific (mass) magnetization.

The two nanohybrids exhibit different superparamagnetic behavior, but the saturation

magnetization is diminished for the hybrid containing an increased amount of polymer, due to

the following:

the reduced composition of magnetic component;

the superparamagnetic property.


58

(a) (b)

(c)

Fig. 2.32. HRTEM images (a) and (b) at different magnitudes, TEM inset SAED (c) of H1-15,

beam direction: B=[130 ].

The diameter of hybrid particle can be computed as an average size corresponding to an

average susceptibility (e.g. for a half of the maximum susceptibility or it can be detailed for each

measured value). The magnetizations at small magnetic fields correspond to the large

nanoparticles, when the domain wall motion is possible; the smaller particles (monodomain) act

different at high fields. The exact values of the magnetic susceptibility could be known only if

the measured magnitudes can be corrected taking into account the demagnetization phenomenon


59

inside the sample, but this correction is possible for bulk materials. The samples as nanoparticles

need special techniques of numerical homogenization. The diameter D can be estimated from

(2.9):

32

0

18

sM

KTD

(2.9)

where χ is the magnetic susceptibility.

Based on (2.9), the calculated particle diameter was in the range of 5-10 nm for all the

investigated samples. These values explain the superparamagnetic behavior of the samples, but

are lower than those obtained from other measurements (e.g. TEM), which give the size range of

21-23 nm. This difference can be explained by the fact that the magnetic field is diminished

inside the sample by the demagnetization field; the real magnetic susceptibility χ is higher than

the measured one and the computed diameter will be higher.

The magnetic properties of the maghemite give the magnetic behavior of the two hybrid

materials. This investigation reveal that the experimental magnetization curves could be used for

the entire characterization of tested magnetic nanoparticles even for coated ones like in

nanohybrid materials. The superparamagnetism of nanoparticles is considering a benefit for

wastewater treatment application and this property requires particle sizes in the range of

nanometers.

Fig. 2.33. Hysteresis loops of - Fe2O3 (a), H1-5 nanohybrid (b), H1-15 nanohybrid.


60

Table 2.3. Magnetic properties of the γ-Fe2O3 and corresponding H1-5 and H1-15 hybrids

Material Coercivity

[kA/m]

Remanence

[Am2/kg]

Saturation

[Am2/kg]

- Fe2O3 12.4 17.4 69.8

H1-5 11.8 8.1 38.2

H1-15 7.8 1.32 7.95

Cd (II) ions removal efficiency tests

The removal efficiency of Cd (II) ions after 10 min for all investigated nanomaterials is

presented in Fig. 2.33. After this period of time, the removal efficiency of Cd (II) ions remained

almost unchanged.

During the investigation of the tree nanomaterials as adsorbants for removal Cd (II)

ions form wastewater were observed the following:

the wastewater treatment efficiency obtained for H1-5 was over 50% after 10

min;

the wastewater treatment efficiency of H1-5 was higher than that of - Fe2O3;

a high removal rate for Cd ions was obtained using the nanohybrid H1-15, almost

70% after 10 min;

the rate of removal efficiency of Cd (II) from wastewater decrease in the

following order: H1-15 > H1-5 > - Fe2O3. This can be explained by the

adsorption capacity of the poly-DL- alanine polymer used.

the removal efficiency of Cd (II) from wastewater was 30% for uncoated -

Fe2O3;

the removal efficiency of Cd (II) from wastewater was 70% for H1-15, after 10

min and it remains almost the same after 120 min. The same tendency it was

observed for other concentrations of Cd (II) ions tested: 20, 50, 80 and 100

mg/L;


61

regarding the tendency of retaining Cd (II) ions onto the three adsorbents, as

comparison, for concentrations between 10 and 100 mg/L of Cd (II) ions, the

most efficient adsorbent is H1:15 nanohybrid, as it can be seen into Fig. 2.34.

Fig.2.34. Efficiency of removing Cd (II) (%) from wastewater using the three nanomaterials

(H1-15, H1-5, - Fe2O3)

Langmuir model parameters for adsorption of Cd (II) onto 0.1 g adsorbents can be

observed into Fig. 2.35. There were observed the following findings:

the adsorption parameters, regarding the maximum adsorbed quantity (qe, mg/g)

and regression coefficient R2 (almost 0.99) are fitted well with the Langmuir

requirements;

the highest value of R2 was observed for H1-15 hybrid nanomaterial;

the R2 value for - Fe2O3 indicate also a good adsorption but the model can be

improved.

In conclusion the novel nanostructures have the potential to be used as low cost and

efficient adsorbants for removal of cadmium ions for wastewater. The adsorption tests showed a

good correlation between Cd (II) concentrations and adsorbent quantity at pH 5.6. The


62

adsorption data fitted well with Langmuir isotherm model. Between the three tested

nanomaterials type adsorbants, the H1-15 nanohybrid presented the highest efficiency for Cd (II)

removal from wastewater.

Fig.2.35. Langmuir parameters for Cd (II) ions adsorption onto H1-15, H1-5, - Fe2O3 .

2.3. Contribution to the removal of Cu (II) ions removal from industrial wastewater using

environmental friendly nanomaterials


The larger source of water pollution with heavy metals is considered industrial

wastewater. The fast industry development has lead to generation of huge volumes of wastewater

containing heavy metals which were discharged into rivers and lakes causing serious problems to

the ecosystems and humans health.

The principal sources of pollution with heavy metals are presented in Fig.2.36.


63

Fig.2.36. The main sources of pollution with heavy metals [24].

The improper treatment applied to these wastewaters has lead to the pollution of surface

or underground water with various heavy metals such as: cadmium, copper, mercury, zinc,

nickel, lead, etc.

Copper is used for manufacture of alloys and wires in various industries such as:

electrical, electrotechniques, etc. According to statistics, electronics and electrical engineering

industries use approximately 60% of the total quantity of copper processed in industry. The

distribution of copper production at global level is presented in Fig.2.37.

Some examples of various industries from which result effluents polluted with copper

ions are: mining and metallurgy, explosives manufacturing, pesticides manufacturing,

petrochemistry, dyes manufacturing, etc. Other sources of copper pollution are: effluents from

wastewater treatment plants, from tailing and flotation cells, disposal of municipal and industrial

waste, bled electrolyte from electro-refining plant, acid spillage from sulphuric acid plant, and

mine tailing disposal of fly ash, etc. [24,25].


64

Fig.2.37 The distribution of copper production in the world [24].

Sources of heavy metals and their cycling in the ecosystem are presented in Fig.2.38.

Fig.2.38. The cyle of heavy metals into the the ecosystem components including soil-water-

air.


65

The content of heavy metals generally builds up from up to bottom, indicating the

vulnerability of humans to heavy metal toxicity from all ecosystems. It is imperative finding

efficient, economic and innovative ways of wastewater treatment knowing the major concern

regarding heavy metals toxicity and carcinogenicity and the stringent requirements for removal

of heavy metals from industrial wastewater.

In recent years the adsorption process has become more interesting for the wastewater

treatment owing to its efficiency of removing very stable and non-biodegradable pollutants found

in water and impossible to be decomposed by biological methods. Adsorption process is

considered better in comparison with other technologies for wastewater treatment because of

simplicity of design, convenience and easy operation.

Some general existing procedures for removal of copper ions from wastewater are

presented in Table 2.4.

Table 2.4. General procedures for copper ions removal from wastewater [24]

Procedures Description

1. Precipitation

-Is based on the effectively removal from aqueous solution of copper ions

with lime as hydroxides according to the following reaction:

Cu2+

+ 2(OH)- → M(OH)2

-The reaction is influenced by the concentration of the copper ions and

the pH of the solution.

-The precipitation takes place over a range of pH values with the

formation of hydrate oxides.

-This technique is often use in industry for removal of copper ions from

solution [26,27].

-Moreover for the precipitation of copper ions could be used several

organic compounds [28].

2. Ion exchange -It is used for removal of copper ions from wastewater.

-It is economical only for recovery of copper and recycling of water in

the electroplating processes. Otherwise, it is expensive because involves

the regeneration of the resin and the disposal and depollution of large


66

Procedures Description

2. Ion exchange volumes of the solution used for regeneration.

3.

Electrochemical

reduction

(Cementation)

-The recovery of copper ions from solution by transformation to its

elemental metallic state through electrochemical reduction [29].

-An example which describes this procedure is the reaction of copper

ions with iron: Cu2+

+ Fe0 → Cu

0 + Fe

2+

4. Flotation -One of the most important things in flotation is the choosing of suitable

surfactants.

-The suitable surfactants have distinct advantages when dealing with

large volume of highly polluted wastes that are quite dilute in the copper

ions [27].

5. Solvent

extraction

-When a substance is transferred from one liquid into another liquid

phase form a process is called solvent extraction. The liquid-liquid

partition of this process is form in the equilibrium stage.

-A substance with solvent properties used in a solution of a suitable

diluent is named extractant.

-A substance that is used to dissolve the extractant and improve its

physical properties is named diluent. The solvent is formed by the mixing

of extractant and diluent together. In usually systems an aqueous solution is

mixed with an organic solvent capable of dissolving the substance of the

interest.

6. Adsorption -The adsorption process occurs at the interface of an adsorbate (the

substance being adsorbed) and an adsorbant or adsorbent (adsorbing

material) [30].

-The list of adsorbant materials is very wide and contains activated

carbon, clay, flyash etc.

-For copper removal from water some of the adsorbants used are:

polyvinyl benzene trimethyl ammonium chloride [31], kaoline and

montmorillonite [32] etc.


67

As a result of the researchers over the world in the wastewater treatment domain, have

been developed many technologies with varying degrees of success, but recently studies have as

principal objective the removal of heavy metals from wastewater using nanomaterials.

2.3.2. The investigation of copper (Cu2+

) ions removal from industrial wastewater using

maghemite, γ-Fe2O3 and its corresponding hybrid, γ-Fe2O3- poly-DL-alanine

In this study were investigated two environmental friendly nanomaterials in order to

demonstrate their efficiency as adsorbants for removal of copper ions from wastewater.

The adsorbants used for testing of copper ions removal from wastewater were

maghemite, γ-Fe2O3 and its corresponding hybrid, γ-Fe2O3- poli-DL-alanine. Their synthesis and

characterization were published elsewhere [23].

The standard used for the testing of the copper ions removal from synthetic wastewater

was SR EN ISO 11885-2009 - "Water Quality. Determination of selected elements by optical

emission spectrometry with inductively coupled plasma (ICP-AES).

The adsorption capacity evaluation of the two samples was done by measuring the

evolution of copper ions concentrations during 140 min.

For both investigated adsorbants, the values of Cu2+

concentration measured during the

experiments show a linear evolution, having R2

values of 0.975 and 0.989, respectively

(Fig.2.39).

The Cu2+

ions removal efficiency from wastewater using the two studied nanomaterials

was calculated using the formula:

Ei =[ (Ci – Cf,t)/ Ci] x100 (2.10)

where:

Ei – Cu2+

ions removal efficiency from wastewater, (%);

Ci – initial concentration of Cu2+

in wastewater, (mg/L);

Cf,t – final concentration of Cu2+

measure at time t, (mg/L)


68

Fig.2.39 and Fig.2.40 show that the higher efficiency of removal of copper ions from

wastewater was obtained for γ -Fe2O3- -poly-DL-alanine hybrid nanomaterial. This fact is

explained by the presence of poly-DL-alanine polymer component in hybrid nanomaterial

composition which has a suplimentar contribution to the retention of the of copper (Cu2+

) from

wastewater by its functional groups.

(a)

(b)

Fig. 2.39 Variation of Cu2+

concentration values vs. time for γ-Fe2O3 (a) and γ-Fe2O3- poly-DL-

alanine (b), [24]


69

The efficiency of copper removal from wastewater was 85% for experiments when

maghemite (γ-Fe2O3) was used as adsorbant and 89% for those when was used as adsorbant γ-Fe2O3-

poly-DL-alanine.

In conclusion whithin this study was investigated a new route for removing toxic copper

ions from wastewater that is effective, and involve reusable and ecofriendly adsorbants.

(a)

(b)

Fig.2.40. Variations of copper (II) removal efficiency (%) vs. time for γ-Fe2O3 (a) and γ-

Fe2O3- poli-DL-alanine (b), [24].


70

The experimental results obtained for these two adsorbant nanomaterials offers

promising perspectives regarding the wastewater treatment implying the application of

nanotechnology.

In the future the studies for testing of the potential of applying these nanoadsorbants

for the depollution of wastewater containing other heavy metals will be done.

2.4. Removal of some toxic metals Cr, Cd, Cu, Zn and Ni using two magnetic

nanomaterials- magnetite (Fe3O4) and Fe3O4-PAA composite

2.4.1. General consideration

Because of the existence of toxic heavy metals in surface waters and underground water

is a huge environmental and public health problem, the effluents discharged from different

industrial activities having high concentrations of these metals have to be very well treated for

reducing their concentrations according to the legislative standards [33].

Adsorption represents one of the most efficient technologies for reducing the

concentration of heavy metals from industrial wastewater by using different types of adsorbents,

activated C being one of the most commonly used adsorbents [34].

The discovery of nanotechnologies led to the development of nanomaterials for

wastewater treatment [33]. Recently, in scientific literature has been presented Fe oxides type

nanomaterials used for the remove of toxic heavy metal and organic pollutants from water [35].

This is type of nanomaterial possess not only strong adsorption capacities but also the capacity of

being easily separated and collected by an external magnetic field [36, 37, 38]. Capacity of being

adsorbant for many heavy metal ions of magnetite nanoparticles has been reported in the

scientific literature [39, 40, 41]. The capacity of adsorption of Cr(VI) from wastewater onto

magnetite nanoparticles has also been reported [40, 42, 43]. As regarding the magnetite

nanoparticles recent studies have reported favorable results regarding adsorption capacity of

several toxic metal ions (e.g., Cu2+

, Ni2+

, Zn2+

, Cd2+

and Cr6+

) and its catalytic degradation

capacity of some organic pollutants [44]. Ions such as Ni2+

, Cu2+

and Cr6+

from multicomponent

wastewater were adsorbed with good results onto magnetite nanoparticles under acidic or basic

conditions [45].


71

Moreover, another study presented zero -valent Fe nanoparticles synthesized in a water–

oil microemulsion followed by homogenization with a cellulose acetate–acetone solution and

finally being formed into a porous membrane by phase inversion supported on cellulose acetate.

The magnetic nanomaterial finally obtained was tested for the dechlorination of trichloroethylene

in water highlighted [46].

In this subchapter is presented a research containing the investigation of two

nanomaterials: magnetite (Fe3O4) and its corresponding composite (magnetite covered with

sodium alginate, noted as Fe3O4–PAA). These two nanomaterials were used as adsorbents for

Cu, Cr, Zn, Cd and Ni from aqueous solutions. The dissolution capacity of Fe from uncoated

Fe3O4 nanoparticles (average size of 7 nm) under acidic conditions has been reported, showing

that 40% of the Fe was dissolved [43,47].

Sodium alginate is a polysaccharide type polymer known as a flocculation additive with

a high potential for removal of pollutants such as: Zn (II), Cd (II), Cu (II) and Pb (II) from

wastewater [48].

The combination between magnetite and sodium alginate to obtain a nanocomposite,

may lead to removal of heavy metals under acidic conditions without or with a lower tendency of

Fe to dissolve from Fe3O4–PAA nanocomposite in comparison with uncoated Fe3O4.

For obtaining the similar conditions of acidic wastewater released from the iron and

steel industries and from acid mine drainage the adsorption experiments were conducted at pH of

2.5. The experimental results obtained from the evaluation of the adsorption capacity of the two

magnetic adsorbents tested were correlated to the Langmuir adsorption model.

The research presented in this subchapter was published in scientific literature [49].

2.4.2. Cr (II), Cd(II), Cu(II), Zn(II) and Ni(II) using two magnetic nanomaterials

magnetite (Fe3O4) and Fe3O4-PAA

Prior to investigate the Cr (II), Cd(II), Cu(II), Zn(II) and Ni(II) removal from wastewater,

the two magnetite nanomaterials Fe3O4 and Fe3O4-PAA were synthesized and characterised.

Magnetite was prepared by coprecipitation method starting from the following compounds:

Fe(NO3)3.9H2O 0.4 M and FeCl2

.9H2O 0.4 M, NaOH 0.5 M, at room temperature. The reaction


72

mixture pH was kept at 10 for 3 hours. The molar ratio between the ferrous and ferric ions was

1:2. The precipitate obtained was separated by centrifugation and washed with distillated water

several times. The Fe3O4-PAA composite nanomaterial was obtained from of magnetite powder

and 5% sodium alginate solution (50%wt).

After the synthesis the nanomaterials used as adsorbents, Fe3O4 and Fe3O4 - PAA were

characterized by the following analyses:

X-ray diffraction (XRD) - using the Panalytical X`Pert PRO MPD X-ray

diffractometer with high-intensity Cu Kα radiation (λ = 1.54065 Å) with the 2θ

range from 10o to 90

o;

Transmission electron microscopy (TEM) and selected area electron diffraction

(SAED) - using TECNAI F30 G2STWIN high resolution transmission electron

microscope with 1Å line resolution;

Scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry

(EDS) – using the Quanta INSPECT F scanning electron microscope (SEM)

equipped with field emission gun (FEG) with a resolution of 1.2 nm and an

energy dispersive X -ray spectrometer (EDXS) with the resolution for MnKα of

133 eV.

After structural and morphological characterization the two magnetic nanomaterials

were tested as adsorbant following the following procedure:

All stock standard solutions (wastewater) of nickel, zinc, and cadmium, copper

were obtained from Merck reagent by dissolving into ultrapure water;

The solution containing chromium was prepared by dissolving of potassium

chromate (K2CrO4) p.a. into ultrapure water.

Each stock solution had an initial concentration of 1000 mg/L and pH value was

adjusted by adding HCl (0.1 mol/L) in order to obtain a value similar to that of

the industrial effluents.

The adsorption tests were conducted by measuring the initial and final

concentration of the metal using flame atomic absorption spectrometry (FAAS)


73

method- using the GBC 932 AB Plus spectrometer with spectral domain

between 185 and 900 nm in order to establish the quantity of adsorbed metal.

An amount of Fe3O4 and Fe3O4-PAA respectively were homogenized with 100

mL solution of 20 mg/L from each metal studied: Cd (II), Zn (II), Cr (VI), Cu(II)

and Ni(II), in a glass vial at room temperature (21.5°C). The Fe3O4 and Fe3O4-

PAA quantities used for tests were 0.05 g, 0.1 g and 0.2 g from each compound.

For adsorption kinetic studies, synthetic wastewater samples prepared were kept

into contact with each type of adsorbent nanoparticles from 10 to 100 minutes.

The pH value of each synthetic wastewater was 2.5 obtained by using HCl (0.1

mol/L) for pH adjustment.

At the end of each experiment the adsorbents were recovered by magnetic

separation.

For each magnetic nanomaterial was calculated the adsorbed metal amount at

equilibrium using the following by ratio between adsorbed metal (mg) onto adsorbent mass (g)

expressed as qe, according to Eq. (2.11):

m

VCCq e

e

0 (2.11)

where:



V – volume of solution, L;


The XRD spectrum of Fe3O4 is presented in Fig.2.41 showing the crystalline structure

of the powder, having a face centered cubic structure, according to 75-1610 ICDD, with the

diffraction peak with maximum intensity at 35.44° for 2θ.

The same crystalline peaks were observed for Fe3O4-PAA nanocomposite as it can be

seen in the Fig. 2.41 (b). This indicated the preservation of stability of Fe3O4 crystalline phase


74

during polymer coating. The influence of the sodium alginate polymer on diffraction line can be

identified as a characteristic increasing of background between 10 and 50°, as being an

amorphous phase. The TEMBF (transmission electron microscopy bright field) image of Fe3O4

nanoparticles from Fig.2.42 (a) showed nanoparticles with sizes between 40 and 100 nm, with an

average size of 80 nm. A few nanoparticles had dimensions up to 250 nm.

(a) (b)

Fig.2.41. XRD images (CuKα radiation) for Fe3O4 (a) and Fe3O4 – PAA (b).

Fig. 2.42. TEM (bright field) with inset SAED images of Fe3O4 nanoparticles.

.


75

The SAED image confirmed the crystalline structure of Fe3O4. The SEM analysis of

Fe3O4-PAA showed the spherical shape of the magnetite particles wrapped into polymer, the

mean particle dimension being about 200 nm. Another SEM image is presented in Fig. 2.43.

Fig. 2.43. Scanning electron microscopy (SEM) - secondary electron image for Fe3O4 – PAA,

[49].

Fig. 2.44 presents the energy dispersive X-ray spectrum which reveals the existence of

sodium, oxygen and iron elements from the Fe3O4 – PAA nanocomposite. Also, it is obviously

that the sodium and oxygen are uniform distributed, these two elements covering the areas where

the iron is concentrated which correspond with agglomerated nanoparticles of magnetite as it can

be seen from the left up-corner image (Fig.2.44(a)) [49].

The adsorption isotherms for Zn (II), Cu(II), Cr (II), Cd (II), and Ni (II) onto 0.05, 0.1

and 0.2 g of Fe3O4 and Fe3O4-PAA, respectively, were fitted to the Langmuir model expressed as

Eq. (2.12.):

bqC

qq

C

m

e

me

e

11 (2.12)

where:

Ce –aqueous concentration at equilibrium, mg/L;

qe – adsorbed amount at equilibrium, mg/g;

qm and b – constants related to the adsorption capacity and the affinity coefficient.


76

(a) (b)

Fig. 2.44 Mapping of the elements (a) and energy dispersive X-ray spectra (b) for Fe3O4 – PAA,

[49].

All samples were analyzed at specific time intervals from 10 to 100 minutes (21.5°C).

For evaluation of the quantity of the adsorbed metal the supernatant layer from all tested

samples was analyzed by AAS.

Also, was evaluated the effect of contact time for the adsorption of metals onto Fe3O4

and Fe3O4-PAA. The removal efficiency is shown in Fig. 2.45 for Fe3O4 and Fig. 2.46. for

Fe3O4-PAA.

The efficiency of removal for Zn (II), Cd(II), Cu(II), Cr(VI) and Ni(II) was initially

very high using Fe3O4 nanomaterial being between 70 and 80% after 10 minutes but remaining

almost the same after 100 minutes.

The highest removal efficiency was obtained in the case of chromium removal and the

smallest for nickel ions removal.

For all the metal ions tested, the adsorption equilibrium was achieved within 10

minutes. In case of using Fe3O4-PAA as adsorbent, the removal efficiency was between 70 and

80% after 10 minutes. Moreover, the efficiency was higher than that obtained for Fe3O4 in case

of the other metals: Zn (II), Cu (II), Cd (II). This can be explained by the adsorption capacity of


77

the sodium alginate polymer. The quantities used were the same as in the case of Fe3O4, but

percentage of Fe contained by Fe3O4-PAA was about 45% in the mass of the nanocomposite.

In case of Fe3O4-PAA as adsorbent it can be assumed that the adsorbtion process takes

place on the polymer surface. Also, the removal efficiency was higher and remained the same

after 100 minutes.

Increasing the quantity of the adsorbent from 0.05 g to 0.2 g did not lead to a significant

increase of the adsorption efficiency as can be seen in the Fig. 2.45. Also was observed that the

high adsorption efficiency was obtained for chromium and the lowest efficiency was obtained for

nickel, under acidic conditions [49].

The adsorption affinity was ordered as follows: Cr > Cd > Cu > Zn > Ni. This affinity

can be explained by zero point of charge pHpzc of Fe3O4 which is 6.5, according to [50]. Below

this value, the adsorbent surface is positively charged and the anions are adsorbed by

electrostatic attraction. Above this value of pHpzc, the adsorbent surface is negative charged and

the metal ions are adsorbed on the magnetite.

The retained of Cr (VI) ions will decrease with the increase of pH, because in the

aqueous phase the surface of the metal oxides is covered with hydroxyl groups that varies at

different pH values [49, 51, 52]. The species of hexavalent chromium from solution are

chromates (CrO42-

), dichromates (Cr2O72-

) and bichromates (HCrO4-). In case of the negative

charge of the adsorption surface, the electrostatic repulsions will increase between negatively

charged Cr (VI) species and negatively charged nanoparticles, leading to the removal of some

adsorbed species such as bichromates (HCrO4-) or chromates (CrO4

2-) [49]. The used quantities

do not have a major influence on adsorbed quantity of metal.

It can be seen for both adsorbents that the optimum quantity used in the experiments is

0.05 g, because in this case the amount adsorbed is higher in comparison with others common

adsorbent such as activated carbon or diatomite, according to the results from literature, namely:

11.5 mg/g for diatomite and 15.47 mg/g for activated carbon, respectively [51,53]. Langmuir

model parameters for adsorption of all metals onto 0.05, 0.1 and 0.2 g Fe3O4 and Fe3O4-PAA,

respectively, are given in the table 2.5.


78

(a)

Fig.2.45 Effect of contact time for metal removal onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-

PAA (b) nanoparticles at pH 2.5, [49].


79

(b)

Fig.2.46 Effect of contact time for metal removal onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-

PAA (b) nanoparticles at pH 2.5, [49].


80

Fig. 2.47. Metal amount quantity adsorbed onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-

PAA (b) adsorbents, [49].

Fig. 2.48. Metal amount quantity adsorbed onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-PAA

(b) adsorbents, [49].

(a)

(b)


81

Both type of magnetic nanoparticles exhibited a strong affinity for the metal ions found

in water. From the data listed in the table 2.5, the qe values indicate a weaker affinity of Fe3O4 in

comparison with Fe3O4-PAA [49].

Also, the optimum quantity for adsorption process was 0.05 g nanoparticles. It can be

observed that data are fitted well Langmuir monolayer adsorption isotherm [49].

Table 1.5 Langmuir parameters for adsorbed metals onto Fe3O4 and Fe3O4-PAA [49]

Metal

Quantity

of

adsorbe

nt

Langmuir parameters

Fe3O4 Fe3O4-PAA

qe (mg/g)* R2

qe

(mg/g)* R

2

Zn 0.05 29.80 0.9973 30.12 0.9998

0.1 14.84 0.9976 15.33 0.9989

0.2 7.99 0.9995 7.95 0.9980

Cd 0.05 31.00 0.9994 30.80 0.9975

0.1 15.57 0.9967 17.00 0.9975

0.2 7.94 0.9983 7.87 0.9977

Cu 0.05 30.97 0.9991 30.06 0.9987

0.1 15.50 0.9984 15.32 0.9986

0.2 7.50 0.9986 7.71 0.9982

Cr 0.05 31.99 0.9971 29.50 0.9972

0.1 16.36 0.9983 15.24 0.9981

0.2 7.82 0.9976 7.56 0.9985

Ni 0.05 29.97 0.9988 29.03 0.9981

0.1 15.13 0.9978 14.73 0.9976

0.2 7.57 0.9986 7.33 0.9987

* time- 10 minutes

The conclusions of this study were the following [49]:


82

the adsorption studies indicated a good correlation between metal ions concentration and

adsorbent quantity at pH 2.5. At pH 8.5 the most quantity of metals was precipitated (almost

100% for Cd and Cu) by adding NaOH;

under basic conditions two phenomena can appear: precipitation and adsorption.

between the two used adsorbent, the composite (Fe3O4-PAA) formed by magnetite

wrapped into sodium-alginate had a good protection from acid leaching, the leached Fe

content being smaller than magnetite (Fe3O4), after 24 hours.

2.5. Contribution to Pb(II) and Cd(II) ions removal from wastewater using as magnetic

adsorbant nanomaterials: Fe3O4, Fe3O4-PEG and Fe3O4-PVP


Pb(II) and Cd(II) ions were chosen as the metal adsorbates because they commonly

exist in the effluents from plating factories, electrolytic refining plants and acid mining

industries.

Source of Cd (II) pollution are the following activities:

Zn production which constitutes the larger source of Cadmium pollution: Zn refining

in which Zn ores could contain 5% Cd;

metal electroplating;

production of stabilizer or pigments in plastics (PVC) ;

fabrication of nickel-cadmium batteries;

production of alloys.

fabrication of anticorrosive agent;

a neutron-absorber in nuclear power plants;

fabrication of phosphate fertilizers also show a big cadmium load.

dumping and incinerating cadmium-polluted waste.

Source of Pb (II) pollution are the following industrial activities:

petroleum;

mining;


83

smelting;

lead-acid battery manufacturing,;

waste incineration.

The effects of cadmium pollution on human health are the following:

Kidney damage;

Gastrointestinal problems;

Bone damage and the Itai-Itai-disease (a disease under witch patients show a wide

range of symptoms such as: low grade of bone mineralization, high rate of fractures,

increased rate of osteoporosis, and intense bone associated pain);

Cancer.

Some of the effects of lead pollution on human health are the following:

damages of internal organs;

damages of the brain and nervous system;

reproductive disorders and/or osteoporosis.

The using of iron based magnetic hybrid nanoparticles as novel adsorbants is expected

to be an attractive and inexpensive option for the removal of heavy metals taking into

considerations the following: simple obtaining method, high surface area value, special magnetic

properties.

2.5.2. The investigation of Pb(II) and Cd(II) ions removal from wastewater using iron-

based magnetic hybrid nanoparticles: Fe3O4, Fe3O4-PEG and Fe3O4-PVP

Thus, the purpose of this study was to assess the performances of magnetite

nanoparticles and its polymeric nanohybrids for the removal of Cd (II) and Pb (II) ions from

synthetic wastewater. The research presented in this subchapter was already published in

scientific literature [54].

In this subchapter the tested magnetite nanomaterial was synthesized using sol–gel

method starting from cheap and environmentally friendly iron salts in the presence of a soft

template. The obtained magnetite nanoparticles were coated with polyethylene glycol (PEG) and

polyvinylpyrrolidinone (PVP) polymer, for obtaining the two magnetic nanohybrids: Fe3O4-PEG


84

and Fe3O4-PVP (Fig.2.49). After the synthesis, the magnetite nanomaterial was tested for the

selective removal and recovery from industrial wastewater of toxic heavy metals such as: Pb(II)

and Cd(II) ions (Fig.2.49).

Fig.2.49. The scheme of nanostructured hybrids proposed for Pb(II) and Cd(II) heavy metals

removal from wastewater, [54].

For performing the adsorption studies an amount of Fe3O4, Fe3O4-PEG and Fe3O4-PVP

respectively were mixed with 100 mL mixed solution of Pb(II) and Cd(II), at room temperature

(21.5°C), stirred speed of 400 rpm.

The adsorbent samples were recovered by magnetic separation and were analyzed by

atomic absortion analysis (AAS) using GBC 932 AB Plus spectrometer with spectral domain

between 185 and 900 nm.

The influence of contact time on the efficiency of metal ions adsorption onto Fe3O4,

Fe3O4-PEG and Fe3O4-PVP is presented in Fig. 2.50.

Between the two magnetic hybrid nanomaterials, Fe3O4-PVP had a higher efficiency for

adsorption of Pb (II) ions from wastewater. Regarding the Cd (II) ions the removal efficiency


85

was higher for Fe3O4 (almost 90%) and less than 50% for the two magnetic hybrid

nanomaterials.

0.00

20.00

40.00

60.00

80.00

100.00E

ffic

ien

cy, %

Fe3O4-PEG, Pb 90.30 90.16 89.92 83.00

Fe3O4-PVP, Pb 90.34 90.32 89.86 82.60

Fe3O4-PEG, Cd 49.13 46.33 47.95 49.75

Fe3O4-PVP, Cd 48.51 47.45 47.97 47.70

Fe3O4, Pb 89.68 89.97 91.94 89.82

Fe3O4, Cd 91.15 93.62 91.33 91.47

15 min. 30 min. 60 min. 24 hours

Fig.2.50. The removal efficiency vs. time for Pb (II) and Cd (II) using the magnetic

nanomaterials: Fe3O4, Fe3O4-PEG and Fe3O4-PVP, [54].


86

2.6. Contribution to Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) removal from wastewater

using Fe3O4 and Fe3O4-PVP magnetic nanomaterials


The study present in this subchapter was already published [55]. The following metal

ions: Cu2+

, Zn2+

, Cr2+

, Cd2+

and Ni2+

are part of “heavy metals” class which refers to metallic

elements with atomic density value higher than 4 g/cm3 or five times or more higher than water

and are toxic even at low concentration.

In Tabel 2.6. are presented some natural and atrophic sources of drinking water

pollution with heavy metals and their corresponding concentration related by U.S.

Environmental Protection Agency. There are multiple neurotoxic, carcinogenic, mutagenic or

teratogenic effects associated with the presence of cadmium, lead, arsenic, mercury, zinc, and

copper poisoning in human body.

Tabel 2.6. List of heavy metals pollutants found in drinking water, [55, 56].

Pollutant

substance

Concentration

(mg/L) 2

Sources of Pollutant in Drinking Water

Cadmium

Zinc

0.005

7

Erosion of natural deposits, anticorrosion coating,

electroplating, alloying activity in solders, stabilizer in

plastics (organic cadmium), pigments, drying of zinc

concentrates and roasting, smelting, refining of ores

corrosion of galvanized pipes, discharge from metal

refineries, runoff from waste batteries

Protecting steel against corrosion, brass and other alloys,

automotive equipment, household appliances, fittings, tools,

toys, building and construction, pharmaceuticals, medical

equipment, cosmetics, tyres and rubber goods, fertilizers,

animal feed.

Chromium 0.1 Erosion of natural deposits, discharge from steel and pulp

mills.

http://www.pollutionissues.com/knowledge/Erosion.html


87

Pollutant

substance

Concentration

(mg/L) 2

Sources of Pollutant in Drinking Water

Copper 1.3 Erosion of natural deposits, industrial operations such as

smelters, foundries, power stations, incinerators, various

combustion sources, corrosion of household plumbing

systems.

Lead 0.015 Erosion of natural deposits, corrosion of household

plumbing systems, industries such as the petroleum, mining,

smelting, lead-acid battery manufacturing, waste

incinerating, mining industries.

Mercury 0.002 Erosion of natural deposits, discharge from refineries and

factories, runoff from landfills and croplands, medicinal

industry, cosmetics industry, waste incineration, coal

combustion, base metal smelting, chlor-alkali industry.

Some of the effect of heavy metals associated with their presence in human body are:

-tremor;

- ataxia;

- paralysis;

- vomiting;

-convulsion when volatile vapors are inhaled;

- the gastrointestinal disorders;

- stomatitis;

- hemoglobinuria causing a rust–red color to stool;

- depression.

The directly discharging into natural waters of wastewaters containing heavy metals

without any treatment, will lead to risks for the aquatic ecosystem and public health.

The direct discharge of wastewaters containing heavy metals into the sewerage system

may result in malfunctioning of the conventional wastewater treatment [57].


88

The conventional physico-chemical processes for heavy metals removal such as: ion-

exchange, precipitation, and so one are considered inefficient in treating wastewater having low

heavy metals concentration and expensive.

In the present, one of the most efficient technologies for reducing or removal the heavy

metal from wastewater is through adsorption using various adsorbents.

Due to development of nanotechnologies, nanomaterials have been developed for

wastewater treatment. In Fig. 2.51 is presented the scheme of drinking water production plant

which uses as adsorbants nanostructured zeolites [58].

Recently, many researchers found that using of the magnetic iron oxides nanoparticles

for removal of heavy metal ions from wastewater [59] presents multiple advantages because their

huge adsorption potential and the benefits of being easily separated and recovered by using an

external magnetic field [60].

Fig.2.51 Scheme of drinking water production plant (A) and pilot plant “filter guards” (B) using

nanostructured adsorbants (NZ-, MNZ-CRO natural and modified zeolite from Croatia; NZ-,

MNZ-SRB natural and modified zeolite from Serbia), [56, 58].


89

2.6.2. The investigation of Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) ions removal

from wastewater using Fe3O4 and Fe3O4-PVP nanomaterials

The present subchapter presents the utilization of two magnetic nanomaterials Fe3O4

and Fe3O4-PVP adsorbents for the removal of heavy metal ions such as Cu2+

, Zn2+

, Cr2+

, Cd2+

and Ni2+

from synthetic acidic wastewater.

The wastewater treatment performance of the two magnetic nanomaterials (Fe3O4,

Fe3O4-PVP) was investigated by atomic absorption spectroscopy.

The experimental results of the adsorption studies are presented in Tabel 2.7, [55].

The available and active sites for nanoparticles are mostly present on the surface and

based on this assumption a higher surface area will provide more sites for adsorption.

The conclusions that can be drawn from fulfilling the investigation are the following:

the maximum efficiency was up to 80% for Cr(VI) and between 74 – 76% for the other

heavy metals ions tested. It is expected to decrease the Cr (VI) uptake with increasing of

pH, because in the aqueous phase the metal oxides surface is covered with hydroxyl

groups that vary at different pH values.

for uncoated Fe3O4 nanoparticles, the percentage of removal efficiency decreased in the

order: Cr(VI) > Cu(II) > Zn(II) > Ni(II) > Cd(II).

adsorption can be explained by the zero point of net charge pHpnzc of Fe3O4 which is 6.5.

Below pH of 6.5, the magnetite surface is more positively charged and anions are

adsorbed by electrostatic attraction. Above this value of pHpnzc, the magnetite surface is

more negatively charged and the metal ions are adsorbed on its surface.

with respect to the Fe3O4-PVP hybrid nanomaterial the adsorption phenomena varies as

follows: Cr(VI) > Cd(II) > Cu(II) ~ Zn(II) > Ni(II). Its adsorption capacity could be

explained taking into considerations the contribution of nitrogen or oxygen from PVP

polymer composition to bind the heavy metal ions found in wastewater.

The experimental results indicate that Fe3O4-PVP had the removal efficiency for metal

ions at approximately the same values as for the uncoated Fe3O4.


90

the hybrid nanomaterial Fe3O4-PVP could be used as adsorbent with the same

performance as uncoated Fe3O4 having the supplementary advantage of its stability in real

conditions when the industrial wastewaters have a low pH value.

Table 2.7. Wastewater treatment efficiency (η %) of two nanomaterials studied on metal

ions (Cr, Cu, Zn, Ni, Cd), [55].

Metal ion Co,

mg/L

Fe3O4, η % Fe3O4-PVP, η %

0.05 g 0.1 g 0.2 g 0.05 g 0.1 g 0.2 g

Cr (VI) 20 80 79 78 82 80 80

50 78 77 76 78 71 72

100 79 75 70 75 69 68

Cu (II) 20 76 76 72 75 72 70

50 75 74 70 72 70 67

100 75 73 68 70 66 65

Zn (II) 20 76 74 71 75 72 69

50 75 72 70 72 70 68

100 74 71 67 70 66 64

Ni (II) 20 74 70 69 70 68 65

50 72 68 67 68 66 64

100 69 65 64 67 65 64

Cd (II) 20 70 68 65 76 75 73

50 67 65 61 74 73 72

100 65 63 60 74 72 70


91

2.7. Study of zeolites nanomaterials as a multifunctional environmental engineering

solution

Natural zeolites are environmentally friendly aluminosilicates minerals which have an

open crystal structure containing cations, such as: Na+, K

+, Ca

2+, Mg

2+ and H2O molecules

having various morphologies such as those presented Fig.2.52 [61].

By ionic exchange and reversible rehydration the ions and water molecules from zeolite

structure can readily be exchanged within the large cavities.

Zeolites have some particularities:

display unique physical and chemical features;

the large system of three-dimensional cavities and channels of molecular size

crystal structure confers a huge storage space.

have a variety of industrial and agricultural applications Fig.2.53.

their features are useful for solving many environmental problems including

offensive odors and heavy metal pollution.

(a) (b) (c)

Fig.2.52. The image of (a) Scolecite on stilbite CaAl2Si3O10.3H2O-NaCa4[Al9Si27O72]

.30

H2O; (b) Scolecite - CaAl2Si3O10.3H2O; (c) analcime Na16[Al16Si32O96]

. 16 H2O, [62,63].

.

have the ability of turning waste into valuable fertilizer explained by their strong

affinity for ammonia ions (NH4+) and store it up instead of allowing it to


92

volatilize. The ammonium ion NH4+ is attracted to the negative charge of the

zeolite crystal.

due to their high cation exchange capacity have the ability, to absorb nutrients

needed by plants and improve fertilizer efficiency.

plant nutrient cations e.g. potassium (K+) and zinc (Zn

2+) can be also stored in

the zeolite crystal structure.

could be used to eliminate or to reduce, many longstanding environmental,

agricultural and industrial pollution problems.

In scientific literature is found that zeolites, have strong affinity for heavy metal ions

[64]. The mechanism of retaining heavy metals was found to be ion-exchange. In their three

dimensional structure exist large channels containing negatively charged sites resulting from

Al3+

replacement of Si4+

in the O tetrahedral–linked by sharing oxygen atoms in rings and cages-

cavities occupied by cations which are weakly kept in the crystal structure for compensation of

the charge imbalance [63]. The negative charges of the anions are balanced by cations that are

placed in the channels and can be replaced with heavy metal ions [63].

Zeolites are considered low-cost adsorbants.

It was reported that zeolites are materials that can be used for mercury removal from

flue gases and solutions [63].

Magnetic zeolite composites nanomaterial suited for environmental applications

obtained by condensation of silica film on magnetite (Fe3O4) particles having nanometer size,

had an adsorption capacity for Hg retaining at room temperature of 95%, whereas at 120 0C was

obtained a complete adsorption.

The zeolite can adsorb mercury by physical adsorption/condensation.

Another study, [65] the zeolite containing 70% clinoptilolite, 9% silica and clays, 5%

mica, 15% of zeolite water was tested on the effluent resulted from copper smelter and refinery

for obtaining electrolytic copper- cathodes. The low values of sorption capacity were explained

by the low concentration of mercury ions and competition of other cations that also undergo

sorption (Table 2.8).


93

Fig.2.53. The industrial and agricultural applications of zeolites, [63]

Table 2.8. Mercury removal from industrial effluents with zeolite, [63,65]

Sorbent

concentration

(g/l)

Hg concentration in

effluent Sewage

(mg/kg)

Sorption

capacity

(mg/g)

Hg concentration in

effluent

industrial and

domestic (mg/kg)

Sorption

capacity

(mg/g)

0 0.0109 0.0246

0.35 0.0080 0.0083 0.0174 0.021

0.70 0.0062 0.0067 0.0143 0.015

2.10 0.0028 0.0039 0.0117 0.006


94

2.8. Contribution to organic (C6H6 and C6H5-CH3) and inorganic (Pb+2

and Zn+2

) pollutants

removal from for wastewater using powdered activated carbon


Wastewaters treatment resulted from various industries such as: chemical factories,

coke plant, pharmaceutical, textile, food, storage installations, munitions factories, herbicides

manufacturing, pesticides manufacturing, petroleum refineries installations, organic pigments

and dyes, mineral processing plants, insecticides, pesticides, resins, detergents, explosives and

dyes [66,67]

One of the most efficient adsorbant for removing various organic pollutants from water

is represented by activated carbon. In Table 2.9 are some examples of chemical pollutants with

high, very high, moderate and low probability of being adsorbed by activated carbon [68].

The structure of pores of activated carbon sustains its application in wastewater

treatment being suitable for retaining small, medium or large pollutant molecules (Fig. 2.54).

Fig. 2.54. Scheme of retaining small, medium or large molecules of pollutants by one of the

pores of activated carbon, [68].

Large or medium molecules are considered organic compounds, whereas heavy metals

are considered small molecules.

Some characteristics regarding toluene (methyl benzene) and benzene representig two

of the pollutants studied in this subchapter are the following:

are colorless, flammable liquids;


95

are contained by petroleum crude oil and can reach in the environment during

manufacture or use of these substances or products containined by them;

in United States, large quantities of the toluene recovered from crude oil is

utilise for benzene production or in the composition of adhesives, printing ink,

paint strippers, antifreeze, aerosol spray paints, perfumes, cosmetics, lacquers,

wall paints, spot removers, etc.

the benzene pollution sources are: combustion processes, industries producing or

using it such as production of dyes, plastics, fibers, detergents, coatings

pesticides, lubricants, adhesives and dry cleaning agents

(http://www.epa.gov/chemfact/f_toluen.txt).

Table 2.9. Chemical pollutants with high, very high, moderate and low probability of being

adsorbed by activated carbon, [68].

Chemical compounds

with high probability

of being adsorbed by

activated carbon

Chemical compounds

with very high

probability of being

adsorbed by activated

carbon

Chemicals with

moderate

probability of

being adsorbed

by activated

carbon

Chemical compounds

for which adsorption

with activated carbon

is low and it is viable

method for

low wastewater flow

or concentration

Aniline

Aldrin

Acetic acid

Methyl chloride

Benzene

Anthracene

Acrylamide

Acetone


96

Table 2.9. Chemical pollutants with high, very high, moderate and low probability of being

adsorbed by activated carbon, [68].

Chemical compounds

with high probability

of being adsorbed by

activated carbon

Chemical compounds

with very high

probability of being

adsorbed by activated

carbon

Chemicals with

moderate

probability of

being adsorbed

by activated

carbon

Chemical compounds

for which adsorption

with activated carbon

is low and it is viable

method for

low wastewater flow

or concentration

Benzyl alcohol

Atrazine

Chloroethane

Acetonitrile

Benzoic acid

Azinphos-ethyl

Chloroform

Acrylonitrile

Bis(2-chloroethyl)

ether

Bentazone

1,1-

Dichloroethane

Dimethylformaldehyde

To the aquatic organisms both benzene and toluene are considered harmful

(http://www.epa.gov/chemfact/f_toluen.txt).


97

The human health and environment effects of toluene are influenced by some factors

such as: the length of time and frequency of exposure, concentration, health of the person

exposed, the environment conditions when exposure occurs [69]. Unfortunately, it was already

proved that benzene is carcinogen.

This subchapter presents the study of activated carbon for the removal of two types of

toxic pollutants that can exist in wastewater: organic and inorganic nature. The research from the

scientific literature is focused on testing activated carbon for the removing from wastewater of

the organic nature pollutants.

Consequently, in this study was approached a new research direction, by testing the

adsorption capacity of powdered activated carbon for treatment of synthetic wastewater

containing, inorganic pollutants such as Pb(II) and Zn(II) ions and as organic pollutants toluene

(C6H5-CH3) and benzene (C6H6).

2.8.2. The investigation of removal organic (C6H6 and C6H5-CH3) and inorganic (Pb+2

and

Zn+2

) pollutants for wastewater using activated carbon

The experimental procedures consisted in the following, [68]:

were used different heavy metals (Pb and Zn) concentrations (20, 40, 60, 80 mg/L

for each pollutant) together with organic compounds consisting of 0.5% C6H6 and

0.5% C6H5CH3;

organic compounds initial concentration was 100 mg/L expressed as chemical

oxygen demand (COD);

wastewater solutions were put together with 1 g of activated carbon;

activated carbon powder was purchased from Sigma-Aldrich, with the following

characteristics: vapor pressure < 0.1 mm Hg (20°C), resistivity 1375 μΩ-cm at

20°C, size dimension 37 – 149 μm;

the measurements of Pb(II) and Zn(II) concentrations were done by atomic

absorption spectrometry using the use of Deuterium lamp as background correction

and air/oxidized acetylene flame. The specific wavelength for Pb was 217 nm and


98

for Zn was 213.9 nm. The equipment used was 932 GBC Avanta Plus atomic

absorption spectrometer with flame;

For the measurements of concentration of organic compounds as COD, before and

after adsorption tests, was applied the following procedure: 100 mL of sample was

poured into an Erlenmeyer flask together with 5 mL H2SO4 1:3 and 10 mL

potassium permanganate accurately measured were added to the samples. All

mixtures were boiled on a hotplate for 10 minutes. Into the hot mixture were added

10 mL oxalic acid precisely measured. Titration operation was made with

potassium permanganate until a persistent pink color appeared.

Chemical oxygen consumption was calculated using the Eq. (2.12):

3

21

4V

10000.316VfVV/LmgKMnO

(2.12)

where:

V - volume of potassium permanganate initially added in the sample, mL;

V1 - volume of 0.01 N potassium permanganate used for sample titration, mL;

V2 - volume of oxalic acid added to the sample before titration, mL;

f - the factor of the potassium permanganate solution;

0.316 - equivalent expressed in mg of KMnO4 of 1 mL of 0.01 KMnO4 0.01 N;

V3 - volume of wastewater analyzed, in mL.

For adsorption capacity tests the experimental procedure consisted in the following:

two synthetic wastewater: 100 mL of sample with different concentrations of Zn(II) and

Pb(II) and 100 mg/L benzene and toluene solution were added into contact with 1 g of

activated carbon.

the samples were analyzed during the experiments after 10 minutes, 1 hour, 2 hours and

24 hours.

the time interval of measurements was chosen according to the previous researches

regarding the adsorption tests [70] in which was observed that the adsorption appears

after 10-15 minutes and the same results are observed after 2 hours.


99

in order to evaluate tendency of pollutants desorption a sample was analyzed after 24

hours.

the analysis of Zn(II) and Pb(II) were done according to the SR ISO 8288/2001 standard

for heavy metals.

pH value of wastewater samples tested was 3.17.

The removal efficiency of Zn(II) and Pb(II) pollutants was calculated according to the

Eq. (2.13):

%C

CC

i

ei 100

(2.13)

where:

- removal efficiency, %;

Ci – initial concentration, mg/L;

Ce - concentration at equilibrium, mg/L.

The adsorption process can be described based on the Langmuir equation, as monolayer

process where adsorbent surface has a specific number of sites available for reaction and linking

of retained molecules. Adsorption process is ended when all sites are occupied [71].

Langmuir model for adsorption [70] is given by the Eq. (2.14):

qe = Qmax.KL.Ce (1+KLCe) (2.14)

where:

qe - adsorbed quantity at equilibrium, mg/g;

Ce - concentration at equilibrium, mg/L;

Qmax - maximum quantity adsorbed, mg/g;

KL - Langmuir constant, L/mg.

Also, the adsorbed quantity at equilibrium, qe, was calculated with Eq. (2.15):

m

VCCq e

e

0

(2.15)


100

where:

qe - adsorbed quantity at equilibrium, mg/g;



V – volume, L;


In order to evaluate the profile of the Langmuir isotherm the separation factor (RL),

defined by the Eq. (2.16), can be used as dimensionless constant [71, 72]:

(2.16)

The profile of the isotherm could be according to RL values as follows: favorable

(0<RL<1), unfavorable (RL>1), linear (RL=1) or irreversible (RL=0).

The Freundlich model was applied for a better description of adsorption process [70],

given in the Eq. (2.17):

log qe = log KF + 1/n log Ce (2.17)

where:

Ce - the equilibrium liquid phase ion concentration, mg/L;

qe - the equilibrium solid phase ion concentration, mg/L;

n - empirical constant Freundlich;

KF - Freundlich constant.

Freundlich model sustains the possibility of adsorption on a heterogeneous surface,

[73]. The values of n indicate degree of nonlinearity between solution concentration and

adsorption as follows: n=1 for linear adsorption; n < 1 for chemical process; n > 1 for physical

process.

The tested activated carbon was morphological characterized by scanning electron

microscoy by using a Quanta Inspect F scanning microscope, with a field emission gun (FEG)

equipped with an EDAX spectrometer with a resolution at MnK of 133Ev.

The morphology of tested active carbon was investigated by SEM analysis Fig. 2.55.


101

The results obtained after the experiments of investigation of adsorption capacity of

activated carbon were expressed as the average of five measurements.

The efficiency removal values of activated carbon regarding Pb(II), Zn(II) and COD as

indicator for organic compounds, during the experimental procedure measured in time (10

minutes and 24 hours) are presented in Fig. 2.56 (a). Initial concentration of lead and zinc was 80

mg/L and 100 mg/L for organic compounds.

Fig.2.55. SEM image of the activated carbon used as adsorbant.

The equilibrium quantity (qe) for Pb (II), Zn (II) and COD adsorbed at different time

intervals is showed in Fig. 2.56(b).

The efficiency for organic compounds (COD) removal is higher than 90% in

comparison with lead (almost 70%) and zinc (higher than 15%), [68] Fig. 2.56 (a).

Moreover, results seem to be keeping the same tendency of removal from 10 minutes to

24 hours, [68]. This is the reason for which, the experiments were continued until 2 hours. After

24 was made only an analysis for checking of the results.

Results regarding the equilibrium quantity adsorbed (qe) onto activated carbon are

presented in Fig. 2.57 (b) where is observed of retaining by a possible adsorption for organic

compounds (as COD), [68].

The time interval and the quantity were kept at the same values as in the case of

efficiency removal evaluation.


102

Moreover, it can be observed the same tendency of Pb adsorption higher than Zn.

(a)

(b)

Fig. 2.56. (a) Efficiency removal (%) for Pb, Zn and COD at different period of time and (b)

Equilibrium quantity (qe) for Pb, Zn and COD adsorbed at different time intervals, [68].

Taking into account these observations was applied Langmuir model for single layer

adsorption. Results are presented in Fig. 2.57.


103

Considering Langmuir isotherm, correlation factors for COD were 0.91 and for Pb (II)

was 0.92 in comparison with Zn (II) (0.81), [68]. These values show a good correlation between

experimental data and Langmuir model for COD and Pb.

It is possible that the adsorption takes place at upper layer of solid material. In

accordance with RL values this process could be favorable one. RL are between 0 and 1, thus:

COD: 0.004, Pb: 0.09, Zn: 0.43, [68].

Fig.2. 57 Langmuir model for Pb, Zn and COD adsorbed onto activated carbon

Freundlich isotherm indicates possibility of a chemical process for Pb (II) and COD and

physical process for Zn (II), according to the n values, [68]. The obtained experimental results

are presented in Fig. 2.58.

According to the correlation factors for COD (0.9857), Pb (II) (0.8236) and Zn (II)

(0.7649), obtained experimental data are fitted with Freundlich model in case of COD.

Values of n that indicate the degree of nonlinearity between wastewater concentration

and adsorption are 0.676 for COD, 0.815 for Pb (II) and 1.245 for Zn (II), [68].

In these conditions, Freundlich isotherm indicates a chemical process for Pb and COD

(n < 1) and a physical process for Zn (n > 1).


104

Fig.2.58 Freundlich model for Pb, Zn and COD adsorbed onto activated carbon.

Moreover, KF values of 0.97 for Pb (II), 1.44 for COD and 0.88 for Zn (II) indicate a

higher adsorption capacity for COD and Pb (II) in comparison with Zn (II).

For a global view in Fig. 2.59 are presented the results for Pb(II) removal from

wastewater samples for a contact time between 10 minutes and 24 hours in presence of organic

compounds (Pb1) and organic compounds and zinc (Pb2), [68].

The process became important in the first 10 minutes and the results for different

concentration of Pb, Zn and COD were in accordance with two adsorption models, Langmuir and

Freundlich, [68].

The maximum adsorbed quantity of lead ions by the tested activated carbon is presented

in Fig. 2.60.

The results for Zn(II) removal from wastewater samples for a contact time between 10

minutes and 24 hours in presence of organic compounds (Zn1) and organic compounds and lead

(Zn2) are showed in Fig. 2.61.

Zn (II) removal efficiency after 10 min was 15.96% and increases to 23.42% during 24h

of investigation. After 24h, the removal efficiency of zinc was slightly lower in case of Pb (II)


105

presence. The maximum quantity of zinc adsorbed in presence of organic compunds (Zn1) and

organic compunds and lead (Zn2) is showed in Fig. 2.62.

Fig.2.59. The activated carbon wastewater treatment efficiency for Pb(II) removal during the

experiments.

Fig.2.60. Maximum quantity of lead adsorbed by the activated carbon.


106

Fig.2.61. The activated carbon wastewater treatment efficiency for Pb(II) removal during the

experiments.

Fig. 2.62. Maximum quantity of zinc adsorbed by the activated carbon.


107

Chemical oxygen demand (COD) represents an important parameter regarding organic

compounds content for wastewater.

As a conclusion the tendency of organic compounds removal was higher than for Zn(II)

about 6 times and almost 1.28 times in comparison with Pb(II), [68].

The highest efficiency removals decrease in the following order: COD (as benzene,

toluene) > Pb >Zn, [68].

Based on the experimental results we sustain the utilization of the powdered carbon as

adsorbants for removal of lead, zinc, benzene and toluene from wastewater.

2.9. Contribution to wastewater treatment by using photocatalysis based titanium dioxide


Nanotechnology provides through utilization of semiconductor nanomaterials used in

photocatalysis process an alternative way for eliminating of organic pollutants from wastewater

being able to replace the traditional wastewater technologies having the advantage of pollutants

decomposition instead of their transformation in other potential pollutants.

In the present time, the semiconductor nanomaterials are in various stages of research

and development, each having unique properties and functionalities which could be useful for

example in the depollution of industrial wastewater, surface water or groundwater.

Photocatalysis as one of AOPs (advanced oxidation process) represents a relatively new,

and “green” application of nanotechnology, which have a vast potential in the near future [74].

During the photocatalysis the organic compounds are mineralized up to CO2 and H2O, under the

action of photon energy equal to or greater than the band gap of the semiconductor nanomaterial.

The degradation of the organic pollutants take place through oxidation/reduction

reactions initiated by the dissolved oxygen from aqueous solution, which generates superoxide

ion (O2.-) or hydroperoxyl radicals (HO2

.).

Moreover photocatalysis has shown a great potential of being a sustainable wastewater

treatment technology because of it's low-cost, non-toxicity to the environment use and because

of these aspects is being a sustainable wastewater treatment technology [75].


108

TiO2 represents the most used photocatalytic nanomaterial used for the removal of

organic pollutants under the action of UV light.

Some of the advantages which sustain the titanium dioxide as the most popular

photocatalyst are the following: low cost, non-toxicity and high photocatalytic activity. Its main

disadvantage is the limited photocatalytic activity in the visible region. Overcoming this

limitation may be carried out by doping TiO2 with metals and non metallic elements [76].

Various types of organic pollutants can be removed by using photocatalysis from

wastewaters, such as: herbicides, pesticides, and others. In Fig.2.63 is showed the decomposition

of phenol during photocatalysis process [74, 78].

The principle of photocatalysis with TiO2 is represented in the Fig. 2.64 [77].

Fig.2.63 The decomposition of phenol during photocatalysis.

When TiO2 absorb the light with energy equal or greater than the band gap energy, the

electrons (having negative charge) existing in the valence band move to the conduction band,

leaving in the conduction band positively holes (h+) Fig. 2.65 and thus resulting the formation of

electron-hole pairs. These charge carriers reduce and oxidize the pollutants adsorbed on the

surface of photocatalyst [75].

The titanium dioxide is the most studied material for photocatalytic applications [77].

In the present times exist some passing attempts from the laboratory scale to the next

level. One example is a cylindrical reactor for photodegradation of some VOCs (i.e. acetone,


109

acetaldehyde, ethanol and toluene) tested for 0.05 g of photocatalyst Fig.2.65. The diameter

reactor is of 200 mm and the effective volume of 5 L [78]. Another example is a photocatalytic

membrane reactor which has two configurations: a) with separated membrane filtration unit and

b) with submerged membrane in the reactor Fig.2.65 [79]

Fig. 2.64 Schematic representation of TiO2 photocatalyst [74,75].


110

Fig. 2.65. VOC photodegradation—set-up [74,78].

Fig.2.66. Photocatalytic membrane reactor: (a) slurry reactor followed by a membrane filtration

unit; (b) submerged membrane in a slurry reactor [74,79].

An ideal photocatalyst should present the following properties:

stable in photocatalytic reactions;

chemically and biologically inert;

easy to produce and use;

not expensive;

efficient under sun irradiation;

not dangerous for humans and environment

2.9.2. The investigation of removal methylene blue and diclofenac from wastewater by

photocatalysis based titanium dioxide

In this study presented in this subchapter the experimental part is about testing the TiO2

nanomaterial in photocatalysis for depollution of wasterwater containing diclofenac and

methylene blue (Fig.2.67).

Methylene blue is a widely used dye in textile industry (Fig.2.67.b).

Diclofenac is a common anti-inflammatory drug used as analgesic, antiarthritic and

antirheumatic which shows the highest concentrations detected in effluents (Fig.2.67.1a) [80].


111

The measurements of the titanium dioxide efficiency for wastewater treatment were

carried out using UV-Vis spectrophotometer. The experiments were carried out in a

photocatalytic reactor.

The preliminary experimental results obtained are presented in Fig.2.67 a and b. The

highest removal efficiency was obtained for the removal of diclofenac from wasterwater.

In the case of the diclofenac removal from water by photocatalysis the efficiency was

(98%) whereas the metyleneblue removal from water (83%). Moreover the removal of

diclofenac from water was done in a shorter time (less than 160 min) than in the case of

methylene blue (aprox. 400 min), [74].

In the case of diclofenac removal investigation from water using TiO2 after 400 min still

was observed a slight increase of depollution efficiency (η) up to 700 min of measurement after

which it remained constant. After only 20 minutes of investigation, 97 % of diclofenac was

removed from the water.

As a conclusion, the utilization of TiO2 nanomaterial in photocatalysis had a high

efficiency of removing both tested pollutants, but the highest (97%) one was obtained in case of

diclofenac investigation. Moreover, there was a significant difference regarding the time required

for each pollutant removal from water meaning that while diclofenac was immediately removed

by photocatalysis using titanium dioxide nanomaterial, in the case of methyleneblue, it took

more time to achieve a high effective removal.

a)

b)

Fig. 2.67. The structural formula of a) diclofenac and methylene blue b).


112

0

10

20

30

40

50

60

70

80

90

0 200 400 600 800 1000 1200

T[min]

η[%

]

a)

b)

Fig. 2.68 The variation of removal efficiency in time for a) diclofenac and b) methylen

blue during the photocatalysis process, [74].


113

Chapter 3. PLAN OF SCIENTIFIC, PROFESSIONAL AND ACADEMIC

DEVELOPMENT IN THE FUTURE

After a scientific activity, uninterrupted, for 11 years, I shall continue the research on

the application of nanotechnology in environmental engineering field, both in order to find the

best adsorbents from nanomaterials class, as well as the best catalysts to degrade and remove the

pollutants found in wastewater. Also, I will start the research on other scientific themes that are

currently at the beginning, such as: levigates treatment, wastewater treatment using plants, etc.

In the future, I will establish the research topics depending on their social importance,

considering the evolution of scientific research over time.

The basis of the future research activities is represented by the experience developed for

publishing ISI articles or within various projects, as responsible or member of the research team

represents.

The scientific results that will be obtained in the future will be published in ISI quoted

journals, books and will sustain the winning of international and national research projects.

Till the present the scientific studies were possible with the help of multidisciplinary

research team, from many research institutes and universities. In the future I intend to continue

the existing collaborations and also to build many others, because only by collaborations can

result research innovations at a high scientific level.

The existence of the Laboratory of Environment Quality Analysis from Faculty of

Biotechnical Systems Engineering of University Politehnica of Bucharest coordinated by me

having an infrastructure suitable for doing doctoral studies, together with my professional

competences and abilities acquired so far, allowed me to create a suitable frame for sharing the

scientific experience and coordinating the students for sustaining their PhD thesis. This

represents the principal motivation for which I appreciate that I have capacity and competence

for coordination doctoral activities.

Regarding the scientific development plan I intend to work within international

programs such as Erasmus with foreign students from universities having the similar research

field for developing a good international collaboration that can sustain the gaining of


114

international research projects. Also, I will use my international prestige to attract foreign

doctoral students for doctoral theses in co- tutelage.

I will continue to participate to national and international competitions for research

grants and I will enhance the connections with partners from the country and abroad with whom

I worked before. I will conduct a constant activity of attracting extra budgetary funds through

research funded by economic agents and also from European funds projects by implication in

high-level scientific research.

I will try to contribute to the development of a pole of excellence in environmental

engineering in which will be involved reference persons in the field, from the country and

abroad, young students, master and PhD students.

Regarding the scientific objective in the future, I will continue to work in

nanotechnology field, obtaining and studying new nanomaterials having special properties

suitable for applying in environmental engineering field for replacing old and inefficient

environment technologies with new and efficient ones. Also, my future scientific research will

have a positive effect on improving life quality by preventing reaching in the environment and in

human body of hazardous substances (such as heavy metals). Another future scientific objective

will be industrial transfer of the new developed nanomaterials and technologies.

Some of my future research directions, according to the scientific domain that require a

sustained development with respect to international trends and may represent subjects of PhD

theses are the following:

Wastewater treatment using nanotechology: through nanotechnology by

synthesis and application of new nanomaterials with high potential for pollutants removal.

Nanotechnology exhibits potential to improve and develop new wastewater treatment

technologies, both through direct applications of nanomaterials for preventing reaching into

environment and/or removing pollutants.

The nanotechnology application benefits derived from the nanomaterials characteristics:

enhanced reactivity, huge surface area, non-toxicity, reusability, regenerability etc.

In this context, nanomaterials with magnetic properties will continue to be one of the

attracted nanomaterials, together with zeolites, titanium dioxide, etc.


115

This research goal mach very well with stringent wastewater discharge standards which

require the necessity to improved wastewater treatment performance.

Also, I will continue the research regarding the new and promising technology of water

treatment technology named photocatalysys based on “Advanced Oxidation Processes (AOPs)”

which consist of in situ generation of highly reactive species (i.e. H2O2,OH*, O2*-, O3) for

mineralization of pollutant organic compounds, water pathogens by using semiconductor

nanomaterials as catalysts (TiO2, ZnO2, CeO2).

Wastewater treatment using phytoremediation: by utilization of some plants

which have the ability to degrade, transform or absorb and store toxic substances found in water.

By approaching such a research subject, some mechanisms of heavy metals intake into plants

could be develop by using new experimental methods and so one.

Waste reuse by identification, characterization and processing of some valuable

by-products in order to synthesize nanomaterials with valuable properties (adsorption, ionic

exchange or oxidative properties). Some of the advantages of this research direction are:

decreasing pressure on natural resources, a good waste management. For example, scrap metals

can be recovered from ash, thereby avoiding mining and the consumption of primary metals,

while the mineral fraction can be utilized within the construction industry, substituting natural

aggregates and other natural materials.

Leachate treatment: is a major environmental concern associated of landfills and

the generation and eventual discharge of leachate into the environment. The objectives are:

finding relevant measures to reduce the production of leachate and methods to treat leachate

which include new nanomaterials for pre-treatment and/or methods to enhance the rate of

stabilisation/mineralisation.

All above mentioned research topics are in accordance with international level in the

field of environmental engineering. Thus, specialized publications will consist in scientific

articles, targeted educational journals and especially high impact factor journals.

The academic work will be based on the desire to transfer the knowledge gained till

now to future generations, targeting in the same time, the correlation with the labor market.


116

The results of research activities and permanent professional training will have to be

found as elements of added value in courses, seminars and laboratory activities with the students.

Consistently, I will pursue the improvement and perfecting courses from didactical

norm, paying attention to scientific content and the modern educational methods and tools used

in teaching activities.

During the development of didactical career I will considered: the students development

in order to increase their independent thinking, their intellectual and practical spirit of initiative,

creativity and originality.

Academic career development on medium and long-term will be supported by:

ensuring international visibility of the didactic career;

achieving national and international collaborations;

involvement in projects and programs dedicated to academics;

conducting academic exchanges with foreign universities involving students,

graduates, PhD students and professors.

guiding the students through coordination of diploma and dissertation thesis;

utilization of a student’s evaluation system more objective;

contributions to curriculum development by proposing new courses and practical

applications;

diversification of knowledge cumulated till now by attending new training

courses.

All future proposed objectives will be fulfilled if we take into account my professional

activity carried out until now.

In parallel with the academic work I intend to carry out further scientific work through

which I can contribute to the improvement of the infrastructure of laboratory (Analysis of

environment quality) coordinated by me within the Department of Biotechnical Systems, Faculty

of Biotechnical Engineering.

I will focus even more on publishing articles in ISI journals in ISI Thomosn Reuters, in

order to increase the visibility of own research results in the international scientific community.


117

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