8
Cadmium (II) and nickel (II) biosorption by Bacillus laterosporus (MTCC 1628) Rajeswari.M. Kulkarni a,b, *, K. Vidya Shetty a , G. Srinikethan a a Department of Chemical Engineering, National Institute of Technology, Karnataka, Surathkal, India b Department of Chemical Engineering, M.S Ramaiah Institute of Technology, Bangalore, India 1. Introduction The presence of toxic heavy metals in aqueous streams, arising from the discharge of untreated metal containing effluent into water bodies, is one of the most important environmental issues [1]. The non-biodegradable nature and long biological half-life of most metals lead to potential accumulation and human exposure via water or food [2]. Cadmium (Cd (II)) enters into the aquatic systems from the effluents of electroplating, smelting, alloy manufacturing, pigments, plastic, cadmium–nickel batteries, fertilizers, pesticides, mining, pigments and dyes, textile operations and refining [3,4]. Toxic effects of Cd (II) on humans include both chronic and acute disorders like testicular atrophy, hyper tension, damage to kidneys and bones, anemia, itai-itai, etc. [5]. Nickel (Ni (II)) is widely used in electroplating, batteries manufacturing, mining, metal finishing, porcelain enameling and paint formulations [5,6]. The higher concentrations of Ni (II) in ingested water may cause severe damage to lungs, kidneys, gastrointestinal distress (nausea, vomiting and diarrhea), pulmonary fibrosis, renal edema and skin dermatitis [7]. According to Central Pollution Control Board (India), the permissible discharge level of Cd (II) and Ni (II) with industrial effluents into inland water is 2 mg/l and 3 mg/l respectively (CPCB) [8]. Conventional technologies that have been utilized for the treatment of these heavy metals are inefficient and/or very expensive when used to treat heavy metal ions to very low concentrations [9]. In the past few decades, biosorption using microbial biomass as the adsorbent has emerged as a potential alternative technique to the existing methods for metal removal. Biosorption process utilizes the inexpensive dead biomass like bacteria, algae, fungi and yeast which can easily remove toxic heavy metals from industrial effluents [10,11]. Heavy metal adsorption using Gram positive bacteria appear to be stronger compared to Gram negative bacteria [12]. The present study investigates the potential of dead biomass of Bacillus laterosporus (MTCC 1628) in cadmium (II) and nickel (II) metal ion removal. The results from the study could contribute in understanding the process, mechanism and characteristics of Gram positive bacteria B. laterosporus as a potential biosorbent for cat-ion removal. 2. Materials and methods 2.1. Preparation of biosorbent Brevibacillus laterosporus (MTCC1628), Gram positive bacteria was obtained from MTCC, Chandigarh, India. The bacteria were Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx A R T I C L E I N F O Article history: Received 2 October 2013 Received in revised form 13 November 2013 Accepted 17 November 2013 Available online xxx Keywords: Biosorption Bacillus laterosporus Cadmium and nickel ions Adsorption kinetics Isotherms A B S T R A C T Biosorption of heavy metals is a promising technology that involves removal of toxic metals from industrial waste streams and natural waters. The study describes the sorption of cadmium (II) [Cd (II)] and nickel (II) [Ni (II)] by dead biomass of Bacillus laterosporus, MTCC 1628. The biosorption conditions for the removal of Cd (II) and Ni (II) were examined by studying the effect of pH, contact time, biosorbent dosage and initial metal ion concentration. Shake flask studies yielded adsorption equilibrium in almost 120 min, for both the metals. It was found from Langmuir model that the maximum adsorption capacity for Cd (II) and Ni (II) ions was 85.47 mg/g and 44.44 mg/g respectively. Kinetic evaluation of the experimental data showed that the biosorption process followed pseudo-second order kinetics. Thermodynamic analysis showed that biosorption is an endothermic process with DH8 of 5.45 kJ/mol for Cd (II) biosorption and 24.33 kJ/mol for Ni (II) biosorption. The surface characteristics of B. laterosporus biomass before and after metal biosorption were analyzed by using scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDAX) to study the changes in surface morphology and elemental constitution of the adsorbent. B. laterosporus exhibited a higher and better potential biosorbent for the removal of Cd (II) as compared to Ni (II) from aqueous solution. ß 2013 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. * Corresponding author at: Department of Chemical Engineering, M.S Ramaiah Institute of Technology, Bangalore, India. Tel.: +91 8023600822. E-mail address: [email protected] (Rajeswari.M. Kulkarni). G Model JTICE-793; No. of Pages 8 Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) and nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J Taiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013.11.006 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers jou r nal h o mep age: w ww.els evier .co m/lo c ate/jtic e 1876-1070/$ see front matter ß 2013 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jtice.2013.11.006

Cadmium (II) and nickel (II) biosorption by Bacillus laterosporus (MTCC 1628)

  • Upload
    g

  • View
    214

  • Download
    1

Embed Size (px)

Citation preview

Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx

G Model

JTICE-793; No. of Pages 8

Cadmium (II) and nickel (II) biosorption by Bacillus laterosporus(MTCC 1628)

Rajeswari.M. Kulkarni a,b,*, K. Vidya Shetty a, G. Srinikethan a

a Department of Chemical Engineering, National Institute of Technology, Karnataka, Surathkal, Indiab Department of Chemical Engineering, M.S Ramaiah Institute of Technology, Bangalore, India

A R T I C L E I N F O

Article history:

Received 2 October 2013

Received in revised form 13 November 2013

Accepted 17 November 2013

Available online xxx

Keywords:

Biosorption

Bacillus laterosporus

Cadmium and nickel ions

Adsorption kinetics

Isotherms

A B S T R A C T

Biosorption of heavy metals is a promising technology that involves removal of toxic metals from

industrial waste streams and natural waters. The study describes the sorption of cadmium (II) [Cd (II)]

and nickel (II) [Ni (II)] by dead biomass of Bacillus laterosporus, MTCC 1628. The biosorption conditions

for the removal of Cd (II) and Ni (II) were examined by studying the effect of pH, contact time, biosorbent

dosage and initial metal ion concentration. Shake flask studies yielded adsorption equilibrium in almost

120 min, for both the metals. It was found from Langmuir model that the maximum adsorption capacity

for Cd (II) and Ni (II) ions was 85.47 mg/g and 44.44 mg/g respectively. Kinetic evaluation of the

experimental data showed that the biosorption process followed pseudo-second order kinetics.

Thermodynamic analysis showed that biosorption is an endothermic process with DH8 of 5.45 kJ/mol for

Cd (II) biosorption and 24.33 kJ/mol for Ni (II) biosorption. The surface characteristics of B. laterosporus

biomass before and after metal biosorption were analyzed by using scanning electron microscope (SEM)

with energy dispersive X-ray spectroscopy (EDAX) to study the changes in surface morphology and

elemental constitution of the adsorbent. B. laterosporus exhibited a higher and better potential

biosorbent for the removal of Cd (II) as compared to Ni (II) from aqueous solution.

� 2013 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Contents lists available at ScienceDirect

Journal of the Taiwan Institute of Chemical Engineers

jou r nal h o mep age: w ww.els evier . co m/lo c ate / j t i c e

1. Introduction

The presence of toxic heavy metals in aqueous streams, arisingfrom the discharge of untreated metal containing effluent into waterbodies, is one of the most important environmental issues [1]. Thenon-biodegradable nature and long biological half-life of mostmetals lead to potential accumulation and human exposure viawater or food [2]. Cadmium (Cd (II)) enters into the aquatic systemsfrom the effluents of electroplating, smelting, alloy manufacturing,pigments, plastic, cadmium–nickel batteries, fertilizers, pesticides,mining, pigments and dyes, textile operations and refining [3,4].Toxic effects of Cd (II) on humans include both chronic and acutedisorders like testicular atrophy, hyper tension, damage to kidneysand bones, anemia, itai-itai, etc. [5]. Nickel (Ni (II)) is widely used inelectroplating, batteries manufacturing, mining, metal finishing,porcelain enameling and paint formulations [5,6]. The higherconcentrations of Ni (II) in ingested water may cause severe damageto lungs, kidneys, gastrointestinal distress (nausea, vomiting anddiarrhea), pulmonary fibrosis, renal edema and skin dermatitis [7].According to Central Pollution Control Board (India), the permissible

* Corresponding author at: Department of Chemical Engineering, M.S Ramaiah

Institute of Technology, Bangalore, India. Tel.: +91 8023600822.

E-mail address: [email protected] (Rajeswari.M. Kulkarni).

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

1876-1070/$ – see front matter � 2013 Taiwan Institute of Chemical Engineers. Publis

http://dx.doi.org/10.1016/j.jtice.2013.11.006

discharge level of Cd (II) and Ni (II) with industrial effluents intoinland water is 2 mg/l and 3 mg/l respectively (CPCB) [8].

Conventional technologies that have been utilized for thetreatment of these heavy metals are inefficient and/or very expensivewhen used to treat heavy metal ions to very low concentrations [9].In the past few decades, biosorption using microbial biomass as theadsorbent has emerged as a potential alternative technique to theexisting methods for metal removal. Biosorption process utilizesthe inexpensive dead biomass like bacteria, algae, fungi and yeastwhich can easily remove toxic heavy metals from industrial effluents[10,11]. Heavy metal adsorption using Gram positive bacteria appearto be stronger compared to Gram negative bacteria [12].

The present study investigates the potential of dead biomass ofBacillus laterosporus (MTCC 1628) in cadmium (II) and nickel (II)metal ion removal. The results from the study could contribute inunderstanding the process, mechanism and characteristics ofGram positive bacteria B. laterosporus as a potential biosorbent forcat-ion removal.

2. Materials and methods

2.1. Preparation of biosorbent

Brevibacillus laterosporus (MTCC1628), Gram positive bacteriawas obtained from MTCC, Chandigarh, India. The bacteria were

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

hed by Elsevier B.V. All rights reserved.

Fig. 1. Effect of pH on % adsorption of Cd (II) and Ni (II) at temperature 30 � 2 8C, 24 h

contact time, 4 g/l biosorbent dosage, 50 mg/l initial metal ion concentration.

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx2

G Model

JTICE-793; No. of Pages 8

cultured at 30 8C in agitated and aerated liquid media for two daysin shake flasks. Two different growth media were used separately,to examine their effects on biomass production viz. (i) Luria Bertanibroth (LB) containing Hiveg hydrolysate 10 g/l, yeast extract 5 g/land NaCl 10 g/l (ii) Nutrient broth (NB) containing Peptic digest ofanimal tissue 5 g/l, NaCl 5 g/l, Beef extract 1.5 g/l and yeast extract1.5 g/l. The pH values of the growth media were adjusted to pH 7.0with 0.1 N H2SO4 or NaOH. When stationary phase of growth wasattained, B. laterosporus cells were separated by centrifugation at4 8C and 8000 rpm for 2 min. The biomass was washed withdistilled water to remove the growth medium and then dried at60 8C for 24 h. The powder was stored in a desiccator and used forbiosorption studies.

2.2. Preparation of metal ion solutions

The aqueous solution of each of the metal ions used in thepresent investigation was prepared by using analytical gradechemicals. Aqueous solutions of Cd (II) and Ni (II) ions wereprepared by dissolving the required quantities of Cadmium NitrateCd (NO3)2�4H2O and Nickel Sulphate NiSO4�6H2O salts in distilledwater. The pH of the metal solution was adjusted with diluteSodium hydroxide or Sulphuric acid solution.

2.3. Analysis of cadmium (II) and nickel (II)

The concentration of residual cadmium (II) and nickel (II) in thebiosorption medium was determined by atomic absorptionspectrometer (GBC 932 plus) at the wavelength of 351.5 nm forNi (II) and 326.1 nm for Cd (II).

2.4. Batch experiments

The batch experiments were performed in 250 ml Erlenmeyerflasks with a working volume of 50 ml in an orbital shaker at150 rpm. All the experiments were conducted twice and meanvalues were used in the result analysis. The effect of pH on thesorption capacity of B. laterosporus for Cd (II) and Ni (II) wasevaluated in the pH range of 3–9. The initial pH of metal solutionwas adjusted by using dilute sodium hydroxide or sulphuric acidsolution. Then 0.2 g of dried biosorbent was added to the 50 mg/lmetal ion solution and the reaction mixture was shaken on anorbital shaker at 150 rpm for 24 h at ambient temperature30 � 2 8C. Similarly, experiments were performed to find the effectof contact time (0–180 min), biosorbent dosage (2–40 g/l), initialmetal ion concentration (10–50 mg/l) and temperature (20–40 8C) onthe metal species sorption. In the biosorption experiments, unlessotherwise stated, the biosorbent dose, temperature and initial metalion concentration were 4 g/l, 30 8C and 50 mg/l, respectively. After thebiosorption, the samples were centrifuged, filtered to analyze themetal ion concentrations.

The amount of adsorbed Cd (II) and Ni (II) per unit mass of deadcells (metal uptake) was calculated according to Eq. (1).

q ¼ vðCi � CÞm

(1)

where q is the metal uptake (mg metal/gram of the biosorbent), v isthe working volume of the reactor (1), Ci is the initial concentrationof the metal in the solution (mg/l), C is the concentration of metalin the solution (mg/l) at any time and m is the amount of the addedbiosorbent on the dry basis (g).

Percentage removal of metal ions (% adsorption) at any timewere calculated by using Eq. (2)

% adsorption ¼ ðCi � CÞCi

� 100 (2)

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

2.4.1. Characterization of biomass

The surface characteristics of B. laterosporus biomass before andafter metal biosorption were analyzed by using scanning electronmicroscope (SEM) with energy dispersive X-ray spectroscopy(EDAX). To identify the functional groups responsible for Cd (II)and Ni (II) biosorption, IR analysis was performed with a Fouriertransform-infrared spectrometer.

3. Results and discussion

3.1. Effect of different culture media on biomass production

The biomass production with LB broth as growth medium wasfound to be higher than that of Nutrient broth. The biomassproduced after 48 h of growth in LB broth was 1.3 g/l as comparedto 0.8 g/l obtained with Nutrient broth. Hence in the production ofbiomass for its use as biosorbent for all the biosorption studies, theorganism was cultured in LB broth.

3.2. Effect of initial pH

Solution initial pH is a critical parameter for biosorptionprocess. Preliminary experiments were performed to find out theoptimum pH for maximizing the metal removal using B.

laterosporus biomass, before investigating the kinetic and isothermaspects of biosorption. The biosorption of Cd (II) and Ni (II)increased with pH and was found to be maximum at pH 7.0 forboth the metals (Fig. 1). The percentage of adsorption for Cd (II) ionwas found as increased from 53.22% to 76%, when the pH wasincreased from 3.0 to 7.0. Similarly, in case of Ni (II) ion, thepercentage of adsorption was found as increased from 5.28% to19.21%, for the same pH range. These results suggest that ionicinteraction is the main mechanism contributing to biosorption ofmetals on the biosorbent. At low pH, hydrogen ions compete withmetal ions resulting in protonation of active sites. But as the pHincreased, more negatively charged surfaces will be availableresulting in high metal removal. Another reason for increasedsorption with increasing pH is that hydrolyzed species have alower degree of hydration; it requires less energy for removal orreorientation of the hydrated water molecules upon binding[13,14]. However at pH 9.0 (alkaline condition), heavy metalprecipitation occurred due to low solubility of both ions at high pH.The pH of metal solution above 7.0 results in the formation ofhydroxylated complexes of the metals, such as nickel hydroxideand cadmium hydroxide, which compete with the active sites.Hence, working initial pH was chosen as 7.0 for this study.

3.3. Time course of metal biosorption

Contact time plays an important role in the efficient removal ofheavy metals using B. laterosporus as biosorbent. The influence of

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

Fig. 2. Percentage metal removal vs. time during Cd (II) and Ni (II) biosorption.Fig. 3. Effect of biomass dosage on % adsorption of Cd (II) and Ni (II) at pH 7.0,

temperature 30 � 2 8C, 2 h contact time, 50 mg/l initial metal ion concentration.

Fig. 4. Effect of initial metal ion concentration on % adsorption of Cd (II) and Ni (II) at

pH 7.0, temperature 30 � 2 8C, 2 h contact time, 4 g/l biosorbent dosage.

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx 3

G Model

JTICE-793; No. of Pages 8

contact time on percentage metal ion removal efficiency of thebiosorbent is shown in Fig. 2. It can be observed from concentra-tion–time profile (see supplementary data Fig. S1) that the initialrate of adsorption upto 10 min is very high for both the metals.These results show that the metal ion binding to the biomass is arapid phenomenon. However, the rate slows down eventually andthe concentration approaches the limiting value. It is moreapparent that biosorption of Ni (II) and Cd (II) on dead cellsconsisted of two phases: a primary rapid phase and a second slowphase of biosorption. The main part of total metal biosorption wascontributed by a rapid phase which lasted for 10 min at pH 7.0.Initial higher rate of metal uptake may be attributed to (a) the highconcentration gradient which exists during the initial period (b)availability of a large number of active sites on adsorbent.Secondary phase of slower rate may be (i) due to reduction innumber of successful collisions of the ions on the surface, due to avery few active sites being available and/or (ii) due to reduction inconcentration gradient.

As the adsorption process proceeds, the sorbed solute tends todesorb back into the solution. Eventually the rates of adsorptionand desorption will attain an equilibrium state. When the systemreaches the sorption equilibrium, no further net adsorption occurs[2]. The time at which the adsorption equilibrium is attained undergiven set of agitating conditions was determined as 120 min, asrevealed in Fig. S1, by the constancy of metal ion concentrations.Therefore in all the equilibrium studies, agitation time of 2 h wasprovided, for attainment of equilibrium. The quick biosorptionbehavior is characterized by no energy exchange reaction. Thegoverning factor for metal removal is a physico-chemicalinteraction between the biosorbent and metal ion in solution[15]. Maximum metal removal in a short period of biosorption wasreported by earlier researchers El-Naas et al. [16] and Hawari et al.[14].

Fig. 2 shows that the adsorption efficiency of the dead biomassof B. laterosporus is higher for Cd (II) ion than Ni (II) ion, as indicatedby higher rate of Cd (II) removal. These results show thatbiosorbent possesses a high affinity for Cd (II) as compared tothat for Ni (II).

3.4. Effect of biosorbent dosage

Effect of biosorbent dosage was evaluated with experimentsconducted at initial metal concentrations of 50 mg/l, pH 7.0,temperature 28 � 2 8C and contact time of 2 h. It is seen from Fig. 3that the removal efficiency i.e. % adsorption of both Cd (II) and Ni (II)increases with increase in adsorbent dosage. As biomass dosageincreases from 2 g/l to 40 g/l, the percentage biosorption was found tobe increasing from 15.34% to 58.05% for Ni (II) and 62.57% to 83.02%for Cd (II). 58% adsorption of Ni (II) was achieved when the biomassdosage was 40 g/l. However, 83% adsorption of Cd (II) was achieved

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

with the same biomass dosage. These data also show that thebiosorbent has higher affinity toward Cd (II) than Ni (II). Increase inbiosorption yield with increase in biosorbent dosage can be attributedto an increase in the biosorbent surface area and availability of morebiosorption sites [17]. Similar results were obtained by Gupta andRastogi [18] and Bermudez et al. [19].

3.5. Effect of initial metal ion concentration

The initial metal ion concentration provides an importantdriving force to overcome all mass transfer resistances of the metalbetween aqueous and solid phase. Fig. 4 indicates the effect ofinitial metal ion concentration on the removal of Ni (II) and Cd (II)ion on dead biomass of B. laterosporus. The removal efficiency hasdecreased from 20.19% to 19.21% with increase in Ni (II) ionconcentration from 10 to 50 mg/l. Similar trend was observed withCd (II) ion biosorption where the removal efficiency has decreasedfrom 78.7% to 76% with increase in Cd (II) ion concentration. Atlower concentrations, all metal ions in the solutions could interactwith the binding sites on the biosorbent and thus percentageremoval of metal ion was high in the beginning. The decrease inpercentage metal removal with increase in initial concentrationwas due to the exhaustion of the sorption sites available on thebiomass, for a given biomass dosage [20]. This is due to the increasein the number of ions, competing for available binding sites in thebiomass.

The sorption capacity of biomass toward the selected metal ionsfollow the order of Cd (II) > Ni (II). The atomic weight of Cd (II) is112.4 and ionic radius is 0.98 A. The atomic weight of Ni (II) is58.69 and ionic radius is 0.69 A [5]. The selectivity of the metal ionfollows the order of increased atomic mass and ionic radius.Similar conclusions were drawn by Prasher et al. [21] and Floutyet al. [22]. Prasher et al. [21] found the order of metal ion selectivityon biosorbent red algae Palmaria palmate as Pb (II) > Cd (II) > Cu

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

Table 1Comparison of pseudo first order and pseudo second order kinetic models for Cd (II) and Ni (II) biosorption.

Metal ion Experimental qe (mg/g) First order kineticslogðqe � qÞ ¼ log qe �K1

2:303

� �t Second order kinetics t

q ¼ 1hþ

tqe� � � , h = k2qe

2

qe (mg/g) k1 R2 qe (mg/g) k2 R2

Cadmium 9.5 7.033 0.0792 0.9275 9.661 0.0375 0.9999

Nickel 2.4 3.431 0.0619 0.9469 2.59 0.0317 0.9989

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx4

G Model

JTICE-793; No. of Pages 8

(II) > Ni (II). Flouty et al. [22] investigated the order of affinity ofmetal ion through biosorption study on removal of copper and leadby algae Chlamydomonas reinhardtii. The algal cells exhibited astronger physical affinity for Pb (II) ions than for Cu (II) ions as ionicradius of lead is higher than copper.

3.6. Adsorption kinetics

Adsorption kinetics is expressed as the solute removal rate thatcontrols the residence time of the sorbate in the solid–solutioninterface. In the current study, pseudo first order and pseudosecond order rate equations were tested with the experimentaldata (concentration–time profile) for kinetic modeling of Cd (II)and Ni (II) biosorption [23,24]. The applicability of both kineticmodels were tested using linearized plot of log (qe � q) versus t andt/q against t and specific rate constants are represented in Table 1.

The experimental data fit well with pseudo second order kineticmodel with the coefficients of determination (R2) values of 0.9999for Cd (II) and 0.9989 for Ni (II). In comparison with first order model,the calculated value of qe from pseudo second order kinetic modelwas found closer to the experimental data and high coefficients ofdetermination for both metal biosorption. The results suggest thatpseudo second order sorption kinetics explain the chemisorption ofCd (II) and Ni (II) by B. laterosporus biomass. In most of the publishedresults [25–27], pseudo second order kinetic model fit well with thekinetic data over the entire contact time range.

3.7. Adsorption isotherms

Adsorption isotherm describes a functional relationship be-tween qe, the amount of solute adsorbed per unit weight ofadsorbent and Ce, the residual equilibrium concentration. Sorptionisotherms were experimentally determined by varying the initialmetal ion concentration. In the present study, Langmuir andFreundlich models were used to describe the equilibrium data[28,29].

The essential characteristics of the Langmuir isotherm can beexpressed using Hall separation factor RL (dimensionless) which isdefined by Eq. (3).

RL ¼1

1 þ bC0(3)

where C0 is the highest initial metal ion concentration (mg/l) and b

is the Langmuir constant (l/mg). RL values can be used forinterpretation of the sorption type as given below:

Table 2Adsorption isotherm constants for Cd (II) and Ni (II) biosorption.

Metal ion Temperature (8C) Langmuir isotherm 1qe¼ 1

qmaxbCeþ 1

qmax

qmax (mg/g) b (l/mg)

Cadmium 20 84.03 10.34 � 10�3

30 85.47 11.09 � 10�3

40 86.20 11.93 � 10�3

Nickel 20 44.05 1.19 � 10�3

30 44.44 1.44 � 10�3

40 46.72 2.26 � 10�3

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

RL > 1: unfavorable; RL < 0: unfavorable; RL = 1: favorable(linear); 0 < RL < 1: favorable; RL = 0: irreversible.

The Langmuir and Freundlich isotherm parameters determinedfrom the slope and intercept of the isotherm plot at differenttemperatures (see supplementary data Figs. S2 and S3) along withtheir coefficients of determination are given in Table 2.

The values of qmax and b obtained from the Langmuir model forbiosorption of Cd (II) have been found to be higher than that for Ni(II). The RL values obtained from this study were less than oneindicating that the process of adsorption of both the metals on B.

laterosporus is favorable.The ‘‘n’’ values for Cd (II) and Ni (II) from Freundlich model

(n � 1) indicates the linear biosorption leading to identicaladsorption energies for all sites [1]. The ‘‘K’’ values show thatthe affinity of the biosorbent leans toward the adsorbate ion in thefollowing sequence Cd (II) > Ni (II). The adsorption order of thebiosorbent for metal adsorbate may be related to the properties ofthe metal adsorbate (ionic radius, electro-negativity). The reasonsfor affinity of biosorbent toward Cd (II) are

� the ionic radius of Cd (II) is 0.98 A, while that of Ni (II) is 0.69 A.The smaller the ionic radius, the greater is tendency to behydrolyzed, leading to reduced biosorption,� the electronegativity of Cd (II) (1.69 Pauling) is lower value than

that of Ni (II) (1.91 Pauling).

The sequence of selectivity followed the order of decreasingelectronegativity and increasing ionic radius. A similar observationwas reported on biosorption of Cd (II) and Ni (II) onto Chlorella

vulgaris [5].

3.8. Thermodynamic analysis

It is important to know the heat effect on the biosorptionprocess. The temperature affects the equilibrium capacity of thebiomass depending on exothermic or endothermic nature ofbiosorption process. The effect of temperature (20–40 8C) onbiosorption using dead cells of B. laterosporus was studied for bothmetals at different initial metal ion concentration. Increasing thetemperature will increase the rate of movement of metal ions toreach the surface of biosorbent.

The important thermodynamic parameters such as Gibbs freeenergy change (DG8), enthalpy change (DH8) and entropy change(DS8) were estimated using equilibrium constant. The Langmuirisotherm constant ‘‘b’’ obtained at different temperature (20–40 8C)

Freundlich isotherm ln qe ¼ 1n ln Ce þ ln K

RL R2 K n R2

0.65 0.9991 0.924 1.085 0.9955

0.64 0.9991 1.003 1.086 0.9954

0.62 0.9993 1.079 1.084 0.9961

0.94 0.9999 0.055 1.032 0.9993

0.93 0.9999 0.068 1.034 0.9994

0.89 0.9998 0.115 1.049 0.9987

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

Table 3Thermodynamic parameters for biosorption of Cd (II) and Ni (II) using dead cells of Bacillus laterosporus.

Metal ion Temperature (K) DG8 = �RT ln b ln b ¼ DS�R � DH�

RT

DG8 (kJ/mol) DH8 (kJ/mol) DS8 (J mol/K)

Cadmium 293 �17.193 5.45 77.27

303 �17.956

313 �18.739

Nickel 293 �10.343 24.33 117.9

303 �11.177

313 �12.719

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx 5

G Model

JTICE-793; No. of Pages 8

from Table 2 was used to calculate the thermodynamic parametersof biosorption of Cd (II) and Ni (II). The equilibrium constant wasreplaced with Langmuir isotherm constant b (l/mol). The standardenthalpy and entropy change of biosorption of Cd (II) and Ni (II) werecalculated from the slope and intercept of plot of ln b vs. 1/T.

The values of thermodynamic parameters are summarized inTable 3. The negative values of DG8 confirm the feasibility andspontaneous nature of biosorption. The decrease in Gibb’s freeenergy values with increase in temperature for biosorption of Cd(II) and Ni (II) indicates the biosorption process is more favorable athigh temperature. The mobility of adsorbate metal ions in thesolution increased with increase in temperature and the affinity ofboth metal ions on the adsorbent was higher at high temperatures[30,31]. The positive values of DH8 indicate the endothermicnature of the biosorption process. The positive values of DS8suggested the increased randomness at the biosorbent metalsolution interface with some structural changes in biosorbentduring biosorption process. The affinity of the biosorbent towardthe metal ion species was reflected by the positive values of DS8and indicates ion replacement reactions could have occurredduring biosorption.

3.9. Comparison of Bacillus laterosporus (MTCC 1628) biomass with

the other bacterial biomass

Table 4 presents the comparison of different bacterialbiosorbents used for Cd (II) and Ni (II) biosorption. It can beobserved that B. laterosporus (MTCC 1628) shows high uptake of Cd(II) as compared to many other bacterial biomass. Though thenickel uptake is lesser than cadmium uptake, the affinity of B.

laterosporus (MTCC 1628) for nickel adsorption is found to behigher than the other bacterial biomass reported in literature. Itshows that B. laterosporus (MTCC 1628) is a potent strain for theremoval of Cd (II) and Ni (II) from industrial wastewaters throughbiosorption.

Table 4Comparison of different bacterial biosorbents for Cd (II) and Ni (II) removal.

Metal Biomass type

Cd (II) Aeromonascaviae

Enterobacter sp.

Pseudomonas putida

Streptomyces pimprina

Streptomyces rimosus

Bacillus laterosporus (isolated from metal polluted soil)

Bacillus licheniformis (isolated from metal polluted soil)

Bacillus laterosporus (MTCC 1628)

Ni (II) Bacillus licheniformis

Bacillus subtillis

Manganese-oxidising bacteria MK-2

Bacillus thuringiensis

Streptomyces rimosus

Bacillus laterosporus (MTCC 1628)

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

3.10. Characterization of biomass

The scanning electron microscopy (SEM) equipped with EDAXwas used to analyze the components and morphology ofbiosorbent surface. Fig. 5(a)–(c) shows the SEM images withEDAX of the biosorbent samples before metal adsorption, aftercadmium adsorption and after nickel adsorption respectively. Afterbiosorption, considerable changes in surface morphology of B.

laterosporus were apparent. After metal biosorption, the surfaces ofbiomass seemed rougher. Through EDAX analysis of the biomasssample after cadmium biosorption, peaks of cadmium metal ionwere observed along with all the other components identified inbiomass. Similar observation was made with respect to biomassafter Nickel biosorption. Presence of metal ions on cell surface afterbiosorption as seen from EDAX images proved the biosorption ofthese metal ions by the dead biomass of B. laterosporus.

3.11. Fourier transform infrared (FTIR) analysis

In order to identify the functional groups responsible forbiosorption, FTIR analysis was carried out. FTIR spectrum of deaddried biosorbent and metal loaded biosorbents were compared.The vibrancy signals before and after biosorption of metals weredifferent. The broad adsorption band in the range of 3700–3200 cm�1 indicated the presence of amine groups and the –OH ofthe carboxyl groups. The peaks at 2923 cm�1 are due to C–Hstretching vibrations of –CH, –CH2, and –CH3 groups. In addition,the adsorption peaks were shifted at 1724, 1625, 1387, 1276 and1045 cm�1 which indicated that the carboxylic groups of cell wallwere responsible for metal sequestering. The adsorption peaksaround 1625 (N–H bending band) and 1537 cm�1 (H–N–Cstretching) indicated the existence of amine groups. The bandshift from 546 (before biosorption) to 567 cm�1 (Ni (II) biosorp-tion) and 552 cm�1 (Cd (II) biosorption) is due to complexformation of metals with –C–S– groups. Spectral analysis before

Metal uptake (mg/g) Ref.

155.3 [32]

46.2 [33]

8.0 [34]

30.4 [35]

64.9 [36]

159.5 [4]

142.7 [4]

85.47 Present study

29 [37]

6 [37]

16 [38]

45.9 [39]

32.6 [40]

44.44 Present study

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

Fig. 5. SEM (6000�) and EDAX image of dead biomass of Bacillus laterosporus (a) before biosorption, (b) after Cd (II) biosorption and (c) after Ni (II) biosorption.

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx6

G Model

JTICE-793; No. of Pages 8

and after metal binding indicated that many functional groupswere involved in the Cd(II) and Ni(II) biosorption process.

3.12. Desorption, regeneration and reuse studies

Biosorption–desorption experiments are useful to assess theregeneration capacity of the biosorbent to reuse in economicalway. Three desorption agents [HCl, HNO3 and H2SO4] ofconcentration 0.1 N were tested for desorbing Cd (II) and Ni (II)metal ion from the metal loaded dead biomass of B. laterosporus.The desorption efficiency was calculated from the ratio of amountof metal ion desorbed to amount of metal ion biosorbed.Desorption efficiency of elutants for effective removal of Cd (II)and Ni (II) ion followed order of HCl > HNO3 > H2SO4. HCl wasfound as efficient elutant in desorbing both metal ions.

The reusability of metal loaded biomass was assessed bycarrying out three cycles of sorption–desorption and regeneration

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

in a batch system. In each cycle, biosorption of Ni (II) and Cd (II) bydead biomass of B. laterosporus was carried out with biosorbentdosage 4 g/l in 50 ml of 50 mg/l initial metal ion concentration atpH 7.0 and temperature 30 8C. After biosorption, metal loadedbiomass of concentration 4 g/l added to 50 ml of 0.1 N HClsolutions and agitated for 24 h. The metal ion concentration elutedin HCl solution was measured using atomic absorption spectrom-eter and the data was used for finding the desorption efficiency ofthe selected elutant. The biomass was filtered, washed withdistilled water to remove the residual H+ ion and dried. Theregenerated biosorbent was reused in the next biosorption cycle. Itwas observed in all the cycles more than 85% of metal wasdesorbed using HCl as elutant. The study shows that 19.53%decrease in sorption of Ni (II) and 4.43% decrease in sorption of Cd(II) by the biomass in three biosorption–desorption cycles. Theregeneration of biomass indicates that biosorption–desorptionprocess is a reversible process. B. laterosporus biomass can be

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx 7

G Model

JTICE-793; No. of Pages 8

reused for effective removal of metal ions. The result showed thatbiosorbent B. laterosporus was restored close to the originalcondition.

4. Conclusions

In the present study, the dead biomass of B. laterosporus (MTCC1628) was used as a biosorbent for the removal of Cd (II) and Ni (II)ions from aqueous solution. Based upon the experimental resultscarried out in this work, the following conclusions are drawn.

� Luria Bertani broth media provides better production of B.

laterosporus (MTCC 1628) biomass as compared to nutrientbroth.� The dead biomass of B. laterosporus shows higher adsorption

capability for the removal of cadmium as compared to nickel.� The removal efficiency increases with increase in contact time

with the high rates of adsorption at the initial period of 10 minunder conditions of study.� The removal efficiency increases with increase in biomass

dosage.� The Langmuir model was able to describe the sorption

equilibrium better for biosorption of cadmium and nickel ion.� The kinetic data for both cadmium and nickel ion removal are

represented by pseudo-second order kinetic model indicatingchemisorption as rate controlling step.� The SEM and FTIR analysis confirmed the interaction between

metal and biosorbent.� Desorption studies revealed that the biomass can be effectively

regenerated using 0.1 N HCl.� B. laterosporus (MTCC 1628) showed better potential adsorbent

for the biosorption of heavy metals like Cd (II) and Ni (II), ascompared to many other bacterial biomasses reported inliterature. The maximum uptake values for biosorption of Cd(II) and Ni (II) on B. laterosporus was found to be 85.47 mg/g and44.44 mg/g, respectively. Presence of many functional groups onthe cell surface is responsible for biosorption of metal ionsleading to high metal uptake. Ion exchange, adsorption andcomplexation are the main mechanisms involved in biosorptionof selected cations on B. laterosporus. Owing to its high metaluptake potential, high biosorption rate and reusability potential,it can find its way toward the large scale wastewater treatmentfacilities, which necessitate further detailed studies on continu-ous biosorption. It can be concluded that B. laterosporus (MTCC1628) is a promising biosorbent for removal of Cd (II) and Ni (II)from aqueous solutions.

Acknowledgements

Authors thank the Department of Biotechnology, M.S. RamaiahInstitute of Technology, Bangalore and Department of ChemicalEngineering, NITK, Surathkal for providing the laboratory facilitiesto carry out this research work.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, in

the online version, at http://dx.doi.org/10.1016/j.jtice.2013.11.006.

References

[1] Febrianto J, Kosasih AN, Sunarso J, Yi-Hsu-Ju, Indraswati N, Ismadji S.Equilibrium and kinetic studies in adsorption of heavy metals using bio-sorbent: a summary of recent studies. Journal of Hazardous Materials2009;162:616–45.

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

[2] Volesky B. Detoxification of metal-bearing effluents: biosorption for the nextcentury. Hydrometallurgy 2001;59:203–16.

[3] Kefala MI, Zouboulis AI, Matis KA. Biosorption of cadmium ions by actinomy-cetes and separation by flotation. Environmental Pollution 1999;104:283–93.

[4] Zouboulis AI, Loukidou MX, Matis KA. Biosorption of toxic metals fromaqueous solutions by bacteria strains isolated from metal-polluted soils.Process Biochemistry 2004;39:909–16.

[5] Aksu Z, Donmez G. Binary biosorption of cadmium (II) and nickel (II) onto driedChlorella vulgaris: co-ion effect on mono-component isotherm parameters.Process Biochemistry 2006;41:860–8.

[6] Padmavathy V, Vasudevan P, Dhingra SC. Biosorption of nickel (II) ions onbaker’s yeast. Process Biochemistry 2003;38:1389–95.

[7] Akhtar N, Iqbal J, Iqbal M. Removal and recovery of nickel (II) from aqueoussolution by loofa sponge-immobilized biomass of Chlorella sorokiniana:characterization studies. Journal of Hazardous Materials 2004;B108:85–94.

[8] CPCB. http://www.cpcb.nic.in.[9] Abideen AI, Kareem SO, Durosanya JB, Balogun ES. Kinetics and Equilibrium

parameters of Biosorption and Bioaccumulation of lead ions from aqueoussolutions by TrichodermaLongibrachiatum. Journal of Microbiology Biotech-nology and Food sciences 2012;1:34–1221.

[10] Vijayaraghavan K, Yun YS. Bacterial biosorbents and biosorption. Biotechnol-ogy Advances 2008;26:266–91.

[11] Wang JL, Chen C. Biosorbents for heavy metals removal and their future: areview. Biotechnology Advances 2009;27:195–226.

[12] Rho J, Kim J. Heavy metal biosorption and its significance to metal tolerance ofstreptomycetes. Journal of Microbiology 2002;40:51–4.

[13] Volesky B, Holan ZR. Biosorption of heavy metals. Biotechnology Progress1995;11:235–50.

[14] Hawari AH, Mulligan CN. Biosorption of lead(II), cadmium(II), copper(II) andnickel(II) by anaerobic granular biomass. Bioresource Technology2006;97:692–700.

[15] Cruz CCV, Costa ACA, Henriques C, Luna AS. Kinetic modeling and equilibriumstudies during cadmium biosorption by dead Sargassum sp. biomass. Biore-source Technology 2004;91:249–57.

[16] El-Naas MH, Abu Al-Rub F, Ashour I, Al Marzouqi M. Effect of competitiveinterference on the biosorption of lead(II) by Chlorella vulgaris. ChemicalEngineering and Processing 2007;46:99–1391.

[17] Akar T, Kaynak Z, Ulusoy S, Yuvaci D, Ozsari G, Akar ST. Enhanced biosorptionof nickel (II) ions by silica-gel-immobilized waste biomass: biosorption char-acteristics in batch and dynamic flow mode. Journal of Hazardous Materials2009;163:41–1134.

[18] Gupta VK, Rastogi A. Equilibrium and kinetic modelling of cadmium (II)biosorption by nonliving algal biomass Oedogonium sp. from aqueous phase.Journal of Hazardous Materials 2008;153:759–66.

[19] Bermudez YG, Ivan LRR, Bermudez OG, Guibal E. Nickel biosorption usingGracilaria caudate and Sargassum muticum. Chemical Engineering Journal2011;166:122–31.

[20] Muhamad H, Doan H, Lohi A. Batch and continuous fixed-bed column biosorp-tion of Cd2+ and Cu2+. Chemical Engineering Journal 2010;158:369–77.

[21] Prasher SO, Beaugeard M, Hawari J, Bera P, Patel RM, Kim SH. Biosorption ofheavy metals by red algae (Palmaria palmata). Environment Technology2004;10:106–1097.

[22] Flouty R, Estephane G. Bioaccumulation and biosorption of copper and lead bya unicellular algae Chmydomonas reinhardtii in single and binary metal sys-tems: a comparative study. Journal of Environmental Management2012;111:106–14.

[23] Ho YS, McKay G. Pseudo-second order model for sorption processes. ProcessBiochemistry 1999;34:451–65.

[24] Ho YS. Review of second-order models for adsorption systems. Journal ofHazardous Materials 2006;136:681–9.

[25] Viraraghavan T, Yan G. Heavy metal removal from aqueous solution by fungusMucor rouxii. Water Research 2003;37:96–4486.

[26] Hameed BH, Mahmoud DK, Ahmad AL. Equilibrium modeling and kineticstudies on the adsorption of basic dye by a low cost adsorbent: coconut (Cocosnucifera) bunch waste. Journal of Hazardous Materials 2008;158:65–72.

[27] Padmavathy V. Biosorption of nickel (II) ions by baker’s yeast: kinetic, ther-modynamic and desorption studies. Bioresource Technology 2008;99:09–3100.

[28] Langmuir I. The adsorption of gases on plane surfaces of glass, mica andplatinum. Journal of the American Chemical Society 1918;403–1361.

[29] Freundlich H. Adsorption in solutions. Zeitschrift fur Physikalische Chemie(Germany) 1906;57:385–470.

[30] Papita Saha, Shamik Chowdhury. Insight into adsorption thermodynamics. In:Mizutani Tadashi, editor. Thermodynamics. InTech; 2011978-953-307-544-0.

[31] Fan T, Liu Y, Feng B, Zeng G, Yang C, Zhou M, et al. Biosorption of cadmium (II),zinc (II), and lead (II) by Pencillium simplicissimum: isotherms, kinetics andthermodynamics,. Journal of Hazardous Materials 2008;160:655–61.

[32] Loukidou MX, Karapantsios TD, Zouboulis AI, Matis KA. Diffusion kinetic studyof cadmium(II) biosorption by Aeromonas caviae. Journal of Chemical Tech-nology and Biotechnology 2004;79:711–9.

[33] Lu WB, Shi JJ, Wang CH, Chang JS. Biosorption of lead, copper and cadmium byan indigenous isolate Enterobacter sp J1 possessing high heavy-metal resis-tance. Journal of Hazardous Materials 2006;134:80–6.

[34] Pardo R, Herguedas M, Barrado E, Vega M. Biosorption of cadmium, copper,lead and zinc by inactive biomass of Pseudomonas putida. Analytical andBioanalytical Chemistry 2003;376:26–32.

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006

R.M. Kulkarni et al. / Journal of the Taiwan Institute of Chemical Engineers xxx (2013) xxx–xxx8

G Model

JTICE-793; No. of Pages 8

[35] Puranik PR, Chabukswar NS, Paknikar KM. Cadmium biosorption by Strepto-myces pimprina waste biomass. Applied Microbiology and Biotechnology1995;43:21–1118.

[36] Selatnia A, Bakhti MZ, Madani A, Kertous L, Mansouri Y. Biosorption of Cd2+

from aqueous solution by a NaOH-treated bacterial dead Streptomyces rimosusbiomass. Hydrometallurgy 2004;75:11–24.

[37] Beveridge TJ. The immobilization of soluble metals by bacterial walls. J. WileyInterscience; 1986. p. 127–40.

Please cite this article in press as: Kulkarni RM, et al. Cadmium (II) aTaiwan Inst Chem Eng (2013), http://dx.doi.org/10.1016/j.jtice.2013

[38] Stuetz RM, Madgwick JC, Gee AR. Immobilization of biosorbed metal ions. In:Torma AE, Apel ML, Brierley CL, editors. Biohydrometallurgical Technologies.Warrendale, PA: The Minerals, Metals & Materials Society; 1993. p. 85–94.

[39] Ozturk A. Removal of nickel from aqueous solution by the bacteriumBacillus thuringiensis. Journal of Hazardous Materials 2007;147:518–23.

[40] Selatnia A, Bakhti MZ, Madani A, Kertous L, Mansouri Y, Yous R. Biosorption ofNi2+ from aqueous solution by a NaOH-treated bacterial dead Streptomycesrimosus biomass. Minerals Engineering 2004;17:903–11.

nd nickel (II) biosorption by Bacillus laterosporus (MTCC 1628). J.11.006