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Biosorption Potential of the Macrofungus Ganoderma carnosum for Removal of Lead(II) Ions from Aqueous Solutions

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Biosorption Potential of the Macrofungus Ganoderma carnosum for Removal of Lead(II) Ions from Aqueous Solutions
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   Journal of Environmental Science and Health Part A, 41:2587–2606, 2006 Copyright   C  Taylor & Francis Group, LLC  ISSN: 1093-4529 (Print); 1532-4117 (Online) DOI: 10.1080/10934520600927989 Biosorption Potential of theMacrofungus  Ganodermacarnosum  for Removal ofLead(II) Ions from AqueousSolutions Tamer Akar, 1 Ahmet Cabuk, 2 Sibel Tunali, 1 and Mustafa Yamac 2 1 Department of Chemistry, Faculty of Arts and Science, Eskis¸ehir Osmangazi Univer-sity, Eskis¸ehir, Turkey 2 Department of Biology, Faculty of Arts and Science, Eskis¸ehir Osmangazi University,Eskis¸ehir, TurkeyThis paper reports the utilization of a macro-fungus  Ganoderma carnosum  as a biosor-bent material for the removal of lead(II) ions from aqueous solutions. The biosorp-tion potential of   G. carnosum  was investigated by batch experiments. The influencesof physico-chemical parameters like pH, biosorbent dosage, contact time and initialmetal ion concentration were evaluated. The biosorption equilibrium was attained in10 minutes. Equilibrium biosorption data were analyzed by the Freundlich, Langmuirand Dubinin–Radushkevich (D–R) isotherm models. Maximum biosorption capacity of biosorbentwasfoundtobe22.79mgg  − 1 (1.10 × 10 − 4 molg  − 1 )atthepHvalueof5.0.Thebiosorbent was regenerated using 10 mM HCl solution, with up to 96% recovery, andreused four times in biosorption-desorption cycles successively. Biosorption efficiency of  G.carnosum wasalsoexaminedinarealeffluent.Themechanismofthebiosorptionwasinvestigated with FTIR, SEM and EDAX analysis and the findings suggested that thebiosorption process involved in ion exchange as dominant mechanism as well as com-plexation. The ion exchange mechanism was also confirmed by the mean free energyvalue obtained from D–R isotherm model.  Key Words:  Biosorption, Equilibrium,  Ganoderma carnosum , Ion-exchange, Isotherm.Received March 30, 2006. Address correspondence to Tamer Akar, Eskis¸ehir Osmangazi University, Faculty of  Arts and Science, Department of Chemistry, 26480, Eskis¸ehir, Turkey; E-mail: takar@ogu.edu.tr 2587  2588  Akar et al. INTRODUCTION Heavy metals are hazardous contaminants because they cannot be broken intosimpler, less toxic forms and they persist unchanged in the environment formany years. [1] The presence of heavy metal ions in the aquatic systems hasbeen of great concern because of their toxicity even at lower concentrations. [2] Toxic metals enter waterways from two main sources: industrial waste dis-charges and particulates in the atmosphere that settle and are carried inrunoff. [1] One of the significant toxic metal ions for human health is lead. It is themost widely distributed in the environment and the one that the average per-son is the most likely to encounter. The hazardous effects of lead are on centraland peripheral nervous systems, haematopoietic, renal, gastrointestinal, car-diovascular and reproductive systems. The other damaging effects of lead areanaemia, tenderness, loss of cognitive abilities, nausea [1 , 2] and suppression of the mental capacity of children. [3] Studies have shown that infants exposed tolead have IQ scores that are 5% lower by age 7 than the scores of unexposedchildren; the children are six times more likely to have reading disabilities andseven times more likely to drop out of school. [1] Therefore, there is significantinterest regarding lead removal from contaminated water systems.Biosorptiontechnologyhasemergedasapromisingalternativemethodoverconventional treatment methods with the advantages of low operating cost,minimization of the chemical and/or biological sludge volume, high efficiencyin detoxifying very dilute effluents, no nutrient requirements and regenerationof sorbent material and possibility of metal recovery. It is based on the propertyof microbial biomass to sequester heavy metals through interactions betweentoxicmetalionsandthemetalbindingfunctionalgroupspresentonthecellwallstructure of the microbial srcin sorbents composed mainly of polysaccharides,proteins and lipids. [4 , 5] The most of the earlier reports in the literature indicates the potentialuse of different types of biomass in heavy metal removal. Those include micro-fungi, [6 − 11] bacteria, [12 − 16] yeast [17 , 18] and algae [19 , 20] whereas there is still verylittle information about the use of the biomass of the macro-fungi [21 − 23] as abiosorbent for heavy metal removal.In the present study macro-fungi  Ganoderma carnosum , was identifiedas a promising biosorbent for the removal of lead(II) ions from aqueous so-lution. To our knowledge, it has not been used for the sorption of heavy metalsfrom aqueous solutions. The influence of initial pH, biosorbent dosage, contacttime, initial lead(II) ion concentration and co-ions on biosorption was studied.Biosorption-desorption cycles were performed to determine the reusability po-tential of biosorbent. The biosorption equilibrium data at 20 ◦ C were modelledbyusingtheLangmuir,FreundlichandDubinin–Radushkevich(D–R)isothermmodels. The mechanism of the process was investigated by Fourier transform  Ganoderma carnosum  as Biosorbent for Lead Removal   2589 infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX). MATERIALS AND METHODSPreparation of the Biosorbent Material The macro-fungus used in the present study was  G. carnosum , providedfrom fungi culture laboratory of Biology Department of Eskisehir OsmangaziUniversity. The fungal biomass was washed with deionised water for severaltimesinordertoremovedust,cutintosmallpiecesandthendriedinanovenat70 ◦ Cuntilconstantweight.Thebiomasswasthengroundedandsievedtoselectparticle size of less than 300  µ m and subsequently was used for biosorptionexperiments. Batch Biosorption Experiments Batch experiments were performed with a magnetic stirrer at 200 rpm and20 ◦ C using 100 mL beakers containing test solutions. The stock lead(II) ionsolution (1 g L − 1 ) was prepared by dissolving of Pb(NO 3 ) 2  of analytical grade indeionised water. Other concentrations were prepared by dilution of this stocksolution and fresh dilutions were used in each experiment.To study the effect of initial pH on lead(II) biosorption onto  G. carnosum biomass,50mLof100mgL − 1 lead(II)solutionwasusedandthentheinitialpHvalues of the contact solutions were adjusted to a value in the range of 1.0–5.0by adding 0.1 M HCl or 0.1 M NaOH. Then 0.1 g of biomass was added to eachbeaker and the biosorption mixtures were stirred for 1 h, which is sufficientlylong enough for biosorption equilibrium. The effect of biosorbent dosage wasstudied by using different dose of biomass (0.2–12 g L − 1 ). The optimum pH andbiosorbentconcentrationweredeterminedas5.0and4.0gL − 1 ,respectivelyandused throughout all biosorption experiments. The period of contact time wasvaried from 5 to 120 min by using the same sorption mixture described aboveto determine the optimum biosorption time. The effect of the initial lead(II)concentrationonthebiosorptionwasstudiedatoptimumconditionsdeterminedabove except that the concentration of lead(II) in the biosorption mixture wasvaried between 30 and 300 mg L − 1 . The co-ion effect on the biosorption of lead(II) was also investigated in multiple metal ion mixture containing Pb 2 + ,Ni 2 + , Cd 2 + and Mn 2 + ions. The medium containing 100 mg L − 1 of each metalion was incubated with 0.2 g of biosorbent at pH 5.0 for 10 min. After biosorption, the contents of the beakers were centrifuged at 4500 rpmfor 3 min and the biomass was successfully separated from aqueous solu-tion. The supernatants were analyzed for residual lead(II) concentration us-ing an atomic absorption spectrophotometer (Hitachi 180-70, Japan). The  2590  Akar et al. measurements were performed under the following conditions: air-acetyleneflame, 7.5 mA lamp current, 1.3 nm spectral slit width and 283.3 nm wave-length.The instrument calibration was checked using a known lead standard so-lution in every 10 readings. The biosorption capacity, ( q  e ), per g of biomass, wascalculated from the general mass-balance equation (Eq. 1) as follows: q  e  = [( C i − C  e )] · V  /  M   (1)where,  C i (mg L − 1 ) and  C  e (mg L − 1 ) are the initial and equilibrium lead(II) ionconcentrations of the solution; V: volume of the lead(II) solution (L); M: weightof the biomass added into reaction mixture (g). Reusability Tests of Biomass The recovery and reusability of biosorbent material are important param-eters related to the application potential of biosorption technology. [24] In thisworkconsecutivebiosorptionanddesorptioncycleswererepeatedforfourtimesusing the same biomass in order to determine the reusability potential of   G.carnosum. Followingthebatchbiosorptionprocess,lead(II)-loadedbiomasswasseparated by centrifugation and suspended into 50 mL of the eluent solution(10 mM HCl). Each biosorption and desorption cycles were allowed 10 min of contacttimeinthesolutionscontainingbiosorbent—lead(II)ionsorbiosorbent-desorbent agent for achieving sorption or desorption equilibrium. The concen-trations of the lead(II) ion released into eluent solutions were determined asdescribed above. The eluted biosorbent was thoroughly washed with deionisedwater and placed into metal solution for the next biosorption and desorptioncycles. Desorption efficiency was calculated by using the following equation.Desorption efficiency =  Amount of lead(II) desorbed Amount of lead(II) biosorbed  × 100 (2) Real Industrial Wastewater  The industrial wastewater was collected from the main drain of the casting unit of metal processing industry from Eskis¸ehir, Turkey. Wastewater samplewas placed into a sterile container and transferred to laboratory and stored at5 ◦ C. The various characteristics of wastewater were presented in Table 1. Fur-thermore, real wastewater sample was spiked with lead(II) and the proposedbiosorption method was applied to with and without spiked samples. Statistical Analysis Data presented are the mean values from three independent experiments.Standard deviation and error bars are indicated wherever necessary. All  Ganoderma carnosum  as Biosorbent for Lead Removal   2591 Table 1:  Chemical characteristics of wastewater sample. Parameters Effluent quality  pH 3 . 16Temperature ( ◦ C) 27Suspended solid (mg L − 1 ) 26Lead (mg L − 1 ) 1 . 9Copper (mg L − 1 ) 137 . 3Nickel (mg L − 1 ) 22 . 3Cadmium (mg L − 1 ) 5 . 8Sodium (mg L − 1 ) 66 . 2Potassium (mg L − 1 ) 7 . 0Calcium (mg L − 1 ) 243 . 0Magnesium (mg L − 1 ) 112 . 0 statistical analysis was done using SPSS 9.05 for Windows where it is pos-sible to evaluate whether the effect and the interaction among the investigatedfactors are significant with respect to the experimental error. FTIR Spectral Analysis Inanefforttofindoutthebindingfunctionalgroupsonthebiomasssurfacethatareresponsiblefromthelead(II)biosorption,infraredanalysisofunloadedand lead(II)-loaded biomass samples were carried out with a Bruker Tensor 27FTIR spectrophotometer within the range of 400–4000 cm − 1 . SEM and EDAX Analysis The porosity of biosorbent surface and possible metal-biosorbent interac-tions were examined with SEM and EDAX analysis. The morphological anal-ysis of unloaded and lead(II) loaded biomass were carried out by means of aCam Scan Oxford Link scanning electron microscope coupled with an energydispersive X-ray analyzer. RESULTS AND DISCUSSIONEffect of Initial pH The pH dependency of the biosorption of lead(II) ions was studied at apH range of 1.0–5.0 and the results are represented in Figure 1. It was ob-served that biosorption was negligible at the initial pH below 2.0. When theinitial pH values were increased from 3.0 to 5.0 the biosorption capacity of   G.carnosum  biomass was increased as much as about five fold (from 4.11 ± 0.75to 18.79  ±  1.19 mg g  − 1 ,  P  <  0 . 05). The higher pH values (pH  >  5.5) were notused due to precipitation of lead(II) ions. The low lead(II) biosorption at highly
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