Journal of Hazardous Materials 166 (2009) 383388

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Journal of Hazardous Materials

journa l homepage: www.e lsev ier .com

Use of Cu(in indu

Crystian n VAntonioDepartamento , Braz

a r t i c l

Article history:Received 14 JuReceived in reAccepted 11 NAvailable onlin

Keywords:Rice strawBiosorbentAdsorptionHeavy metalsToxic metals

d outI) ionuenndlicII) > Core 1.re invof re

1. Introduction

The indunowadays,soil. This istrations of tof contaminsidered tha[1]

Heavy mfrom diverspainting, catural sourceused. Cu, Ztry that posresources. Hmulate in li[2-11]. For ehypertensio

The reduwhen toxiction and io

CorresponE-mail add

remove them. These methods explore the availability of differ-ent kinds of adsorbents associated with convenient procedures for

0304-3894/$ doi:10.1016/j.jstrial activities represent an important pollutant sourcemainly concerning the addition of heavy metals in thecontributing to a signicant increase on the concen-hose ions in waters, representing an important sourceation of the aquatic bodies, especially when it is con-

t such ions can be disseminated through the food chain

etal contamination exists in aqueous waste streamse industries such as metal plating, mining, tanneries,r radiator manufacturing, batteries, as well as agricul-s where fertilizers and fungicidal sprays are intensivelyn, Hg and Cd are harmful wastes produced by indus-e a risk of contaminating groundwater and other watereavy metals are not biodegradable and tend to accu-

ving organisms, causing various diseases and disordersxample, cadmiumcauses serious renal damage, anemia,n and itai-itai [2].ction of the pollutant to an acceptable level is necessarymetals are present in the aquatic system [12]. Adsorp-n exchange processes are the most useful methods to

ding author. Tel.: +55 43 33714811.ress: alfaya@uel.br (A.A.d.S. Alfaya).

obtaining high efciency [13,14]. A large number of different adsor-bent materials containing a variety of attached chemical functionalgroups have been reported for this purpose. For instance, activatedcarbon is the most popular material, however, its high cost restrictsits large-scale use [15,16].

In recent years, special attention has been focused on the useof natural adsorbents as an alternative to replace the conventionaladsorbents, based on both the environmental and the economicalpoints of view [15,16]. Natural materials that are available in largequantities, or certain waste products from industrial or agriculturaloperations,mayhavepotential as inexpensive sorbents.Due to theirlow cost, when these materials the end of their lifetime, they canbe disposed ofwithout expensive regeneration. The abundance andavailability of agricultural by-products make them good sources ofraw materials for natural sorbents.

In Brazil there are extensive plantations of rice in the southernarea of the country. The annual production of rice in Brazil is ofapproximately 11.1 million tons [17]. The rice straw, an agricultureresidue, represents 45 % of the volume of the production of rice andin Brazil this residue is used in processes of energy generation.

In this paper, rice straw was treated with NaOH solution toproduce a carbonaceous adsorbent. The capacity of the producedadsorbent to remove Cu(II), Zn(II), Cd(II) e Hg(II) from aqueoussolution was tested.

see front matter 2008 Elsevier B.V. All rights reserved.hazmat.2008.11.074rice straw as biosorbent for removal ofstrial efuents

Goncalves Rocha, Dimas Augusto Morozin Zaia, ReAlberto da Silva Alfaya

de Qumica, Universidade Estadual de Londrina, UEL, CP 6001, 86051-990, Londrina, PR

e i n f o

ly 2008vised form 26 October 2008ovember 2008e 30 November 2008

a b s t r a c t

Adsorption experiments were carrieadsorb Cu(II), Zn(II), Cd(II) and Hg(Ithe best adsorption conditions the inof adsorption were tted to the Freumodel, the adsorption order was Cd(process reached the equilibrium befaspects of the adsorption process wethe removal of ions Cu, Zn, Cd and Hgied./ locate / jhazmat

II), Zn(II), Cd(II) and Hg(II) ions

entura da Silva Alfaya,

il

using waste rice straw of several kinds as a biosorbent tos from aqueous solutions at room temperature. To achievece of pH and contact time were investigated. The isothermsh equation. Based on the experimental data and Freundlichu(II) > Zn(II) >Hg(II) on the rice straw. This quick adsorption5h, with maximum adsorptions at pH 5.0. Thermodynamicestigated. The biosorbent material was used in columns foral samples of industrial efuent and its efciency was stud-

2008 Elsevier B.V. All rights reserved.

384 C.G. Rocha et al. / Journal of Hazardous Materials 166 (2009) 383388

2. Materials and methods

2.1. Chemicals

All thetions of Cu(water usingcadmium cthe workingin miliQplusmiliQplus.

2.2. Biosorb

The riceversity of Lwater threerice straw wfraction witused in thinamed as R

10g of t1.0mol L1

material wof the excedispersed inunderagitawas ltereddried at 60

point ahead

2.3. Biosorb

2.3.1. SurfaN2 adso

apparatus adegassed atrial was obtvolume wa[19].

2.3.2. FT-IRThe infr

the equipmwith 4 cm

2.3.3. ScannThe SEM

on double-fsample wasmicroscope

2.3.4. ThermThe ther

an DuPontsamples wi

2.4. Adsorp

2.4.1. pH vaThemax

method atpension foradjusted wa typical ex50.0mL of t

and the mixtures were orbitally stirred at 251 C for 2h. At dif-ferent periods of time, aliquots of supernatant were withdrawn formetal analysis. The amount ofmetal adsorbedon the adsorbent sur-face (Nf) was calculated by applying the equation Nf = (Ni Ns)/m,

Ni and Ns are the initial and the amount (mmol) of the metalich remained in solution after adsorption procedure, respec-and m is the mass (g) of the solid in each ask. The metal ionsnalyzed by complexometric EDTA titration using an appro-indicator [20,21].

Batch adsorptionrice straw adsorption capacity for individual metals wasat the optimum pH 5.0 using the batch procedure. For

termination, about 300mg of the adsorbent was immersedmL of the metal solutions, whose concentrations varied

en 2.90103 and 30.70103 mol L1. The mixtures werely shaken in a thermostatedwater batchwith constant speed. After the prescribed contact time, the aliquots of super-withdrawn were analyzed as stated before.

atistical analysis

parisonsbetweenmeanswereperformedusingANOVAandt-Newman-Keuls test (S. N. K. test) at a signicance level of.

ults and discussion

arac

ricegnint SiO, byng wsurf

g1, 01 shtheH stlar a

ed tochemicals used were of analytical grade. Stock solu-II), Zn(II), Cd(II) and Hg(II) were prepared in miliQpluscupper chloride (CuCl22H2O), zinc chloride (ZnCl2),

hloride (CdCl2H2O) and mercury chloride (HgCl2). Allsolutions were prepared by diluting the stock solutionwater. The water used in all experiment has quality

ent preparation

straw was given kindly by School Farm of the State Uni-ondrina, UEL. The natural material was washed withtimes and it was dried to 60 C. Soon afterwards theas triturated and the particles were sieved to obtain ah particles size between 0.05 and 0.10mm which wass work. This material passes starting from here to beS.riturated RS was dispersed in 50mL of HNO3 solutionand left agitating for 1h at the room temperature. Theas ltered and washed with water until the removalss of acid in the material. After that, the material was

100mL of a NaOH solution 0.75mol L1 and was lefttion for1hat the roomtemperature. The rice strawagainand washed exhaustingly with water. The material wasC. Biosorbent obtained in this processwill be called thismodied rice straw, MRS.

ent analysis

ce area and average pore volumerption isotherms were determined on an ASAP 2010t liquid nitrogen temperature. Initially the sample was100 C for 48h. The specic surface area of the mate-ained using the MP method [18] and the average pores obtained using the Horvath-Kavazoe approximation

spectraared spectra were obtained as KBr pellets (1wt%) andentusedwas a ShimadzuFT-IR3300 spectrophotometer1 resolution, using 200 cumulative scans.

ing electron microscopy (SEM)images were obtained by the dispersion of the sampleaced conducting tape xed on a graphite support. Thecovered with a conductive lm of gold. The electronicused was a JEOL JSM T-300.

ogravimetry (TG)mogravimetric curves of the materials were obtained inmodel 9900 Thermoanalyzer equipment warming theth a speed of 10 Cmin1, under ow of argon gas.

tion studies

riationimumadsorption capacitywas determinedby the batchpH values varying between 2 and 6, shaking the sus-1.5h at a temperature of 251 C. The desired pH was

ith sodium hydroxide or hydrochloric acid solutions. Inperiment 300mg of the adsorbent were suspended inhe cation solution 2.88103 mol L1 at the desired pH

whereionwhtively,were apriate

2.4.2.The

studiedthis dein 50.0betweorbitalfor 1hnatant

2.5. St

ComStudenp

C.G. Rocha et al. / Journal of Hazardous Materials 166 (2009) 383388 385

the aliphatiare characteat 1080 andbending indpresents a1080 and 46This fact suedprolethe chemicaOH acids

ing in interdened freq

Fig. 2 shIt can be obsilica andnachemical trenot total, beon MRS. Ththe leachingexposed the

Thermogshown in Fipresent a lobetween 20in MRS duethem to theto the oxida500970 C500 up to 9were identi

ig. 3. Thermogravimetric curves of RS (curve A) and MRS (curve B).

termination of equilibrium time

adsorption data for metal uptake versus contact time foradsorbent amount are shown in the Fig. 4. The maximum

ty of adsorption of MRS for the Cu(II), Zn(II), Cd(II) andonsw 1

ing t60mol L

ionssolidF

3.2. De

Thea xedcapaciHg(II) iAccord20 and1.0mmconditat theFig. 2. Image SEM of RS (A) and MRS (B).

c nature [23]. The absorption bands at 18001300 cm1

ristics of C C in aromatics ring [24]. The absorptions460 cm1 are attributed to Si O stretching and Si Oicating of the silica presence [2528]. The spectra MRS

very similar prole to the RS while the absorptions at0 cm1 attributed of the silica, decreased considerably.ggests that a portion of silica was removed. The modi-of the absorption at 34003300 cm1 suggests that afterl treatment of RS, with removal of the silica, the groups

became more exposed in the material probably result-actions between them and water molecules with moreuencies.ows the image SEM of RS (A) and MRS (B) materials.served that the irregular supercial layer of protectivetural resinspresent inRSwere largely removedwith theatment inMRS. The removal of the supercial layerwascause it is possible to observe to several free fragmentse appearance of perforations in the material indicatesof structural substances that might have generated oractive sites in MRS.ravimetric curves of RS (curve A) and MRS (curve B) areg. 3. The TG curves show that the materials until 100 Css of 3wt% corresponding to the humidity. In the range0 and 500 C occurs a loss of 77wt% in RS and of 90wt%to two different processes, belonging probably one ofoxidation of the aliphatic organic matter and the othertion of the aromatic organic matter. In RS (curve A) ofa residue of 20wt% stays constant. In MRS (curve B) of70 C a residue of 7wt% stays constant. These residuesed as silica for FT-IR.

with 1.5h oequilibriummetals from

3.3. Effects

The extrdependent.the quantit

Fig. 4. Contacmercury () cere0.128, 0.132, 0.133and0.110mmol g , respectively.o these data, equilibrium is achieved at round 45, 15,in for Cu(II), Zn(II), Cd(II) and Hg(II) respectively, at

1 solutions. However, to be sure of the best adsorptionat higher concentration levels and to obtain equilibrium/liquid interface, all the experiments were carried outf contact time. This short time period required to attainsuggests an excellent afnity of the adsorbent for theseaqueous solution.

of pH

actability of the cations from the solution phase is pHThe effectiveness of the process can be expressed byy adsorbed (mmol g1) versus pH plot for the cationst time for 1.0103 mol L1 of copper (), zinc (), cadmium () andhloride adsorption from aqueous solution at 251 C.

386 C.G. Rocha et al. / Journal of Hazardous Materials 166 (2009) 383388

Fig. 5. Effect of pH on 1.0103 mol L1 of copper, zinc, cadmium and mercurychloride adsorption from aqueous solution at 251 C.

involved, as represented in Fig. 5 for divalent copper, zinc, cad-mium andan increaseing the madecrease oobserved. Thydrolysis,and Cd(OH)capacity, dulic ion. In thhydrolysedto preventor the precielectrostation the resurice straw is

As can bcellulose anof divalentgroups whithe rst stehydration wnon-solvateadsorptionthe divalent

Scheme 1. Re

carbonaceous CxOH are dissociated at various pH values dependingon their respective acidic dissociation constants and consequentlytake part in surface complexation/exchange of metal cations [30].

OH O +

COOH

CxOH

It shoul5 allows thremoval fro[31]. In thisby severalduring the

3.4. Adsorp

The isotsented by nunder optim

equn betliquid

ndli

KfC

re Cdivacorrse, Kgmu

=(n

re niummon

line) logthe amercury. From the corresponding data for each metal,in pH corresponds to an increase in adsorption, reach-ximum capacity at pH 5. On higher pH values a slightf adsorption for Cu(II), Zn(II), Cd(II) and Hg(II) washe metallic ions (Cu, Zn and Cd) could be sufferingstarting at pH higher than 5, forming Cu(OH)+, Zn(OH)++ species, which promotes a reduction of the adsorptione to the diminution of the formal charge of the metal-e case of Hg(II) in solution, these ions are extensivelyand the specie formed is HgO, and require acidicationthe formation of polynuclear hydroxo-bridged speciespitation of basic salts [29]. This specie does not presentc interaction with the active site of the rice straw. Basedlts a mechanism is proposed for metallic ion uptake bydepicted on the Scheme 1.

e seen, the brous rice straw containing cellulose, hemi-d lignin (phenol groups) loses two protons per eachmolcation (the brous materials contains several phenolch were withdrawn from the scheme for simplicity) atp. In the second step the hydrated metallic ion loses itsaters. In the third step the brous material uptakes thed metallic ion. At pH lower than 5, the rst step of theprocedure is hindered, diminishing the adsorption ofmetallic ions. The functional groups like OH and ber

Tworelatioin theare:

a) Freu

qe =

whebatethepha

b) Lan

Ceqe

whelibrthe

Theting (iwhichaction that takes place for divalent ion uptake by rice straw.

equation isparameter

RL =1

(1 + bwhere C

ableadsorpdescribe un

The expof Langmuitions coefshown in ththat the orthat there ametal morenally thedifferent stThe differen+H

COO +H+

CxO +H+

d be stressed that, the maximum metal uptake at pHis low-cost natural adsorbent be used for metallic ionm natural waters without requiring pH adjustmentsway the rice straw is a heterogeneous material formed

types of site capable to interact with the metallic ionsprocess of adsorption.

tion data

herms of adsorption for these divalent cations, repre-umber of moles per gram of the adsorbent at 251 C,um contact times and pH values, are shown in Fig. 7.ilibrium isotherm equations were used to nd out theween the equilibrium concentrations of the adsorbatephase and in the solid phase. These isotherms [32,33]

ch isotherm:

ne ,

e and qe are respectively the concentration of the adsor-lent cation at equilibrium in the liquid phase and qe is

esponding concentration of the adsorbate in the solidf and n being Freundlich coefcients.ir isotherm:

1qm)

+(

1qm

)Ce,

and qm are Langmuir coefcients representing the equi-constant for the adsorbate-adsorbent equilibrium andolayer capacity, respectively.

ar Freundlich and Langmuir plots are obtained by plot-qe vs. log Ce and (ii) Ce/qe vs. Ce, respectively, fromdsorption coefcients could be evaluated. The Langmuiralso used to obtain RL, the dimensionless equilibrium

or the separation factor [34,35] from the expression:

C0),

0 is the initial concentration of the adsorptive. For favor-tion, 0 1,RL = 1andRL = 0, respectively,favorable, linear and irreversible adsorption [3638].erimental data didnt adjust appropriately to the modelr and therefore only the values parameters and correla-cients of Freundlich equations of experimental data aree Table 1. For the analysis of the Kf values is revealed

der of adsorption was Cd>Cu>Zn>Hg. Table 1 showsre three different strips of adsorption on rice straw. Theadsorbed was Cd2+, following for Cu2+ and Zn2+ and

metal less adsorbed was Hg2+, and these values wereatistically amongst themselves (p

C.G. Rocha et al. / Journal of Hazardous Materials 166 (2009) 383388 387

Table 1The values of parameters and correlation coefcients of Freundlich equation.

Ion Freundlich

Kf/103 n R2

Cu2+ 2.7 0.2 4.1 0.4 0.9125Zn2+ 2.3 0.1 3.9 0.1 0.9214Cd2+ 4.2 0.1 7.4 0.1 0.9353Hg2+ 1.2 0.4 2.7 0.5 0.9218

Table 2Thermodynamic adsorption parameters.

Ion G (kJmol1) H (kJmol1) S (Jmol1 K1)

Cu2+ 8.9 0.1 7.9 0.1 56.5Zn2+ 8.3 0.4 33.5 0.2 140.0Cd2+ 9.8 0.9 5.4 0.6 51.2Hg2+ 7.1 0.3 9.7 0.3 56.7

can be explained by the strong interference of the size of the parti-cle of the material adsorbent used on the process of adsorption, asit can be observed by the data of the literature [39,40]. The loweradsorption value observed for Hg2+ it can also be presumably dueto the stronger interaction of Hg2+ with Cl species in solutionphase. Hg2+ can form stable species such as HgCl+ and HgCl2 insolution phase while for Cu2+, Cd2+ and Zn2+ this interaction is neg-ligible. As all of the ions present n>1 values one can suppose thatthe adsorption sites on surface of the rice straw are heterogeneousnature.

3.5. Effects

The vari15 and 45

tions selectparametersuated using

LnKd = S/

where Kd, kequal to (qethe slope a

Fig. 6. Effect of temperature on 1.0103 mol L1 of copper, zinc, cadmium andmercury chloride adsorption from aqueous solution at 251 C.

tively. These values could be used to compute G from the Gibbsrelation, G=H TS at constant temperature. All these rela-tions are valid when the enthalpy change remains constant in thetemperature range.

Of the th. 6 shawwly asof t

plicaent

veed wtive wn Tabcy to

Table 3AAS result of w

Sample

12.61 99.64.50 100.08.02 100.0

2 2.10 100.0

3

4

5

* nd=not deof temperature

ation of sorption with temperature was studied fromC for each toxic metal ion under the optimized condi-ed and the data are shown in Fig. 6. The thermodynamicfor the adsorption process, H, S and G, were eval-the equation [41,42]:

R H/RT,

nown as the distribution coefcient of the adsorbate, is/Ce). The plot of ln Kd vs. 1/T (with T in K) is linear withnd the intercept giving values of H and S, respec-

the Figrice strprobabsurface

3.6. Aptreatm

Theanalyzrespecgiven iefcien

astewater real samples before and after treatment with the biosorbent.

Metal ion Cinitial (mgL1) Cnal (mgL1)

Cu 2.54 nd*

Zn 2.62 0.01Cd 4.50 ndHg 8.02 nd

Cu 2.10 nd

Zn 1.83 ndCd 3.96 0.01Hg 6.00 nd

Cu 1.97 ndZn 2.38 0.01Cd 4.00 ndHg 7.07 nd

Cu 2.01 ndZn 1.98 0.01Cd 4.16 ndHg 5.80 nd

Cu 1.87 ndZn 2.25 0.01Cd 5.07 ndHg 6.78 nd

tected.ermodynamic point of view the data in Table 2 and ofows that the adsorption process of the metals ions onas exothermic and that occurs a decrease of the entropysociated to the organization of the metal adsorbed onhe adsorbent.

tion of the biosorbent studied for wastewater

real samples fromwastewater of a battery industrywereith atomic adsorption spectrophotometer (AAS) at theiravelength. The results before and after treatment are

le 3. It is seen that the biosorbent displays high removalwards Cu, Zn, Cd and Hg.

Adsorption amount (mgg1) Removal ratio (%)

2.54 100.01.83 100.03.95 99.76.00 100.0

1.97 100.02.37 99.64.00 100.07.07 100.0

2.01 100.01.97 99.54.16 100.05.80 100.0

1.87 100.02.24 99.65.07 100.06.78 100.0

388 C.G. Rocha et al. / Journal of Hazardous Materials 166 (2009) 383388

Fig. 7. Isother() chloride at

3.7. Elution

The coluthis study. Trate of 5.5mHCl solutiorate of 3.5mcurrent mooperation gume and incalculated brun by theated biosorone over f

4. Conclus

The riceCd(II) and HadsorptionpH values, bat 251 C0.132, 0.133respectively

The ricemetallic ioindividuallybiosorbentstrated highCu, Zn, Cd a

Of the ththe poisonodecrease ofadsorbed on

Acknowled

The auth(UEL), to Conolgico (C

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Use of rice straw as biosorbent for removal of Cu(II), Zn(II), Cd(II) and Hg(II) ions in industrial effluentsIntroductionMaterials and methodsChemicalsBiosorbent preparationBiosorbent analysisSurface area and average pore volumeFT-IR spectraScanning electron microscopy (SEM)Thermogravimetry (TG)

Adsorption studiespH variationBatch adsorption

Statistical analysis

Results and discussionCharacterization of the biosorbentDetermination of equilibrium timeEffects of pHAdsorption dataEffects of temperatureApplication of the biosorbent studied for wastewater treatmentElution and regeneration

ConclusionAcknowledgmentsReferences