Batch and column studies for Cadmium (II) removal using sawdust from Triplochiton Scleroxylon.

Transcription

1 Batch and column studies for Cadmium (II) removal using sawdust from Triplochiton Scleroxylon. L.C. Koffi Akissi 1, K. Adouby 1*, B.Yao 1 and D. Boa 2 1 Laboratory of Industrial Process, Synthesis, Environment and New Energy, National Polytechnic Institute Felix Houphouët-Boigny, BP 1093 Yamoussoukro, Côte d Ivoire 2 Laboratory of Thermodynamics and Physical Chemistry of the environment University of Abobo-Adjamé (UFR-SFA), 02 BP 801 Abidjan 02 Côte d Ivoire Abstract Batch and column sorption studies to removal Cd(II) from aqueous solution was investigated using sawdust from Triplochiton Scleroxylon. Langmuir and Freundlich isotherm models were applied to equilibrium data at four temperatures. The maximum sorption capacity (q o ) obtained from Langmuir isotherm models plots were found to be , , and mg.g 1 respectively at 30, 40, 50 and 60 C. Thermodynamic parameters ( G 0, H 0 and S 0 ) for sorption process were evaluated. The temperature variation study showed that the cadmium ions sorption is exothermic and spontaneous. Thomas model was used to analyze the experimental data and model parameters were obtained. The column was regenerated using 0.2mol.L -1 CaCl 2 solution. The sorption desorption tests for four cycles were also performed. Sorption of Cd(II) at specific binding sites on sawdust was identified by Fourier transform infrared spectroscopy (FTIR). Also, Sorption of Cd(II) is accompanied by releasing of Ca(II) and Mg(II) in the solution showing that the sorption mechanism of Cd(II) involved both ion exchange and complexation. Keywords: Sawdust, Isotherm, Fixed-bed column, Ion exchange, Sorption desorption 1. Introduction An expansion of several industrial sectors leads to an increasing demand for the usages of heavy metals. Cadmium makes its way to water bodies through wastewater from metal plating industries, industries of Cd Ni batteries, phosphate fertilizer, mining, pigments, stabilizers and alloys (Rao and Khan, 2009). Cadmium has been well recognized for its negative effect on the environment where it accumulates readily in living systems (Benguella and Benaissa, 2002). Various physicochemical techniques for removing metal ions from wastewaters were based on chemical precipitation, adsorption, ion exchange, extraction and membrane processes (Feng et al., 2011). Biosorption technology, utilizing natural materials or industrial and agricultural wastes to remove cadmium from aqueous solutions, offers an efficient and cost-effective alternative compared to traditional chemical and physical remediation and decontamination techniques. Lignocellulosic waste materials are suitable biosorbents for the removal of heavy metal ions from water or wastewater as they are cheap and the further treatment is simple and economic. Most of these materials contain functional groups associated with proteins, polysaccharide, lignin and cellulose as major constituents. The binding mechanisms of heavy metals by biosorption could be explained by the physical and chemical interactions between cell functional groups and adsorbates by ion exchange, complexation, and microprecipitation (López-García et al., 2010). Sawdust, a Lignocellulosic waste material is a cheap, widely available and abundant natural material. It has been reported to have ion exchange and complexation properties for heavy metals (Ahmad et al., 2007). Taty- Costodes et al. (2003) studied the removal of heavy metal ions (Cd(II) and Pb(II)) by Pinus sylvestris sawdust. Memon et al. (2007) studied the Sorption of cadmium on treated and non-treated Deodar Cedrus sawdust. Ahmad et al.(2007) utilized sissoo wood sawdust as an adsorbent for the removal of Cd(II) ions from aqueous solution. This work investigates the potential of Triplochiton Scleroxylon sawdust in the removal of Cd(II) from aqueous solutions. Batch studies were conducted using synthetic cadmium solution to assess sorption isotherm models. Fixed bed column tests were conducted to ascertain their practical applicability. In addition the metal-binding mechanisms of Cd(II) onto sawdust were investigated. ISSN : Vol. 5 No.01 January

2 2. Materials and method 2.1. sorbent Sawdust waste of Triplochiton Scleroxylon wood generated in local wood processing industries was collected from small sawmill. The Sawdust was dried in sunlight for 15 days until constant weight. It was ground to a fine powder and sieved for a particle size of 0.5 mm then directly used without any pretreatment, as a sorbent for the removal of cadmium (II) ions from aqueous solutions Sorbate All chemicals used in this study were analytical grade. Cadmium (II) solutions of desired concentration were prepared by dissolving the appropriate amount of its nitrate: Cd(NO 3 ) 2,4H 2 O (99.5% MERCK) in distilled water. Nitrate salt was selected as a possibly inhibiting anion because of its low tendency for complex formation with most metals. ph of solutions was adjusted by the addition of concentrated nitric acid: HNO 3 (67% Prolabo). The solutions are prepared at the experiment day Analytical method Batch sorption studies Sorption studies were carried out by batch process in 250mL conical flasks. The equilibrium isotherms were determined by contacting fixed cadmium initial concentration C 0 = 100mgL -1 with different mass of sawdust (2 to 25g). The Sawdust and cadmium solutions were agitated in a series of flasks with equal volumes of solution (100 ml) for a period of 45 minutes at desired temperature. The series of flasks was agitated at a constant speed of 300 rpm in a water bath at temperatures 30, 40, 50 and 60 C, respectively. Sawdust from the samples was separated by vacuum filtration using 45μm membrane filters to remove the particulates and the filtrate was analyzed using a Varian AA 20 Atomic Absorption Spectrophotometer Sorption desorption in fixed bed column reactor The column experiments were carried out in a glass column of 4 cm of internal diameter. Each bed of sorbent was underlain by 1cm of glass wool and 2cm of 3mm glass beads. The addition of glass wool and glass beads was made to improve the flow distribution. Metal solutions having an initial concentration of 100 mg.l -1 at ph 4 was pumped through the column at a desired flow rate (22mL.min -1 ) by a peristaltic pump (pp20-ex, Miclins). Samples were collected from the exit of the column at different time intervals and analyzed using an atomic absorption spectrometer for metal concentration. The experiment was carried out until the column became saturated with cadmium ions (when the effluent and influent concentrations were equal). After the column reached exhaustion, the loaded biomass with metal ions was regenerated using 0.2 M CaCl 2 solutions (flow rate is 22mL.min -1 ). After elution, 500mL of distilled water was used to wash the bed until the ph in the wash effluent stabilized near 7. Then, the column was fed again with metal solution and sorption studies were carried out. After bed exhaustion, elutant was fed into the column and regeneration studies were conducted. The sorption desorption tests for four cycles were performed. 3. Results and discussion 3.1. Batch sorption studies Modelling of biosorption equilibrium depending on temperature Langmuir (1916) developed a theoretical equilibrium isotherm relating the amount of gas adsorbed on a surface to the pressure of the gas. The Langmuir isotherm takes an assumption that the adsorption occurs at specific homogeneous sites within the adsorbent. The generalized Langmuir isotherm can be written in the form, q C (1) C where C e is the equilibrium concentration of metal ion in the solution (mgl 1 ), q e is the amount of the metal ion sorbed at equilibrium (mgg 1 ), and b (Lmg 1 ) is a constant related to the affinity of the binding sites. The empirical Freundlich equation based on a monolayer adsorption by the adsorbent with a heterogeneous energy distribution of active sites is given below by equation (2). q K F C (2) where K F and n are Freundlich constants The non-linearized Langmuir and Freundlich sorption isotherms of Cd(II) obtained at the temperatures of 30, 40, 50 and 60 C are given in Figures 1 and 2. The sorption isotherm constants were determined by using non-linear regression. The sorption isotherm constants (q 0, b K F, 1/n) with the correlation coefficients are presented in Table 1. ISSN : Vol. 5 No.01 January

3 High values of regression coefficients for both Langmuir and Freundlich models indicated the applicability of sawdust for Cd(II) removal in both monolayer sorption and heterogeneous surface conditions, but the values of R 2 for Langmuir sorption isotherms are greater than that of Freundlich isotherms showing its higher applicability. Langmuir sorption model constants values which express the surface properties and affinity of the sorbent, can be used to compare the sorptive capacity of sawdust for Cd(II). The value of q 0 obtained at 30 C (10.793mg.g -1 ) appears to be higher in comparison with the uptakes obtained at the other temperatures. The higher value of b obtained at 30 C also implied strong bonding of Cd(II) to sawdust at this temperature. The uptake of the cadmium ions decreased with an increase in temperature thereby indicating the process to be exothermic Thermodynamic parameters of sorption Thermodynamic considerations of a sorption process are necessary to conclude whether the process is spontaneous or not. The standard free energy change, G 0 is an indication of spontaneity of a chemical reaction. Also, both standard enthalpy change and standard entropy change factors must be considered in order to determine the standard free energy of the process. Reactions occur spontaneously at a given temperature if G 0 is negative. Value of G 0 can be determined from the following equation: G RTLnb 3 Where R is gas constant, J.mol -1.K -1, b (L mol 1 ) the Langmuir constant and T is absolute temperature. Relation between G 0, H 0 and S 0 can be expressed by the following equations: G H T S Equation (4) can be written as 5 where values of H 0 and H 0 can be determined from the slope and the intercept of the plot of lnb versus 1/T (Figure 3). The thermodynamic parameters ( G 0, H 0 and S 0 ) of sorption were shown in Table 2. The results show that G 0 is negative and decreases with increase in temperature indicating that sorption of Cd(II) by sawdust is spontaneous and spontaneity increases with the increase in temperature. The negative value of H 0 ( KJ.mol -1 ) show the exothermic nature of sorption. This is also supported by the decrease in value of uptake capacity of sorbent with the rise in temperature. Negative values of H 0 have also reported for the biosorption of cadmium by algal biomass (Gupta and Rastogi, 2008) and sawdust (Memon et al., 2007) The positive value of S 0 (38.01 J.mol -1.K -1 ) reflects the affinity of Cd(II) for sawdust. In addition, positive value of S 0 shows the increasing randomness at the solid/liquid interface during the sorption of Cd(II) on sawdust. Moreover, the positive values of S 0 point out some structural changes as a result of the interaction of Cd(II) ions with the active sites of sawdust compounds, especially hydroxyl groups in cellulose and lignin. (Acemioğlu and Alma, 2004) Desorption and reusability of the absorbent Regeneration of the biosorbent may be crucially important for keeping the process costs down and opening the possibility of recovering the metal ions extracted from the liquid phase (Vijayaraghavan et al., 2006). Four consecutive sorption desorption tests were performed in order to show the reusability of the sorbent after using dilute CaCl 2 solution as eluent. Table 3 gives the data on the desorption efficiency of the sawdust. The results indicate that the sawdust may repeatedly be used for Cd(II) ion sorption without significant losses in their sorption performance. The higher percentage of desorption (79%) indicated that ion exchange mechanism played significant role in the sorption process (Baral et al., 2009) sorption in fixed bed column Sorption and elution breakthrough curves The performance of a bed depth is obtained through the concept of breakthrough curve. The time or volume for breakthrough appearance and the shape of the breakthrough curve are important characteristics for determining the operation and dynamic response of sorption column. Again, successful design of a sorption column requires prediction of the concentration time or concentration volume profile from breakthrough curve for the effluent discharged from the column. When the sorption zone moves up and the upper edge of this zone reaches the top of the column, the effluent concentration starts to rise rapidly; this is called the breakthrough point. Figure 4 indicates the sorption and desorption curves for the sorption of Cd(II) by sawdust in a continuous liquid flow system. The breakthrough curve of the Cd(II) sorption represent commonly observed shape. The breakthrough volume for the first cycle occurs at 1550mL and the desired breakthrough point is determined to (4) ISSN : Vol. 5 No.01 January

4 0.02 C/C 0. After this point, the concentration of Cd (II) increases gradually and attains C 0 at around 2700 ml of treated volume. When the sorbent in the column is saturated with the Cd(II), it is important to regenerate it in order to recovered the metal ions as well as the use of the sorbent for further sorption. After each elution, the column is washed with distilled water in order to eliminate the rests of acid until ph values between 4 and 5 have obtained in the effluent solution. The column desorption studies were carried out by using a 0.2 M CaCl 2 solution. The desorption curves showed a very unsymmetrical shape, with a rapid metal concentration increase, followed by a flatter diminution. The regeneration of packed columns is necessary when the sorbent used is expensive or if it is not always available in large quantities. From an economical point of view, the sorbent can be considered effective if it can be easily regenerated and re-utilized as many times as possible without alteration of its performance. The cycle sorption-desorption-washing was repeated four times. The amount of Cd(II) sorbed after each sorptiondesorption process were almost the same. This indicates that the column can be considered to be recyclable Modeling of column study results: Thomas model Thomas model is one of the most general and widely used models in the column performance theory. Further, it is derived with the assumption that the rate driving force obeys 2 nd order reversible reaction kinetics (Suksabye et al., 2008). Thomas model also assumes a constant separation factor but is applicable to either favorable or unfavorable isotherm. The expression developed by Thomas (1944) calculates the maximum solid phase concentration of the solute on the sorbent and the adsorption rate constant for a continuous sorption process in column. The model has the following form C 1 C 1 Exp K 6 T Q q m C V where K Th is the Thomas rate constant (L.(min mg) -1 ) and Q is the volumetric flow rate (L.min -1 ). Non-linear regression analysis was used to determine the Thomas model parameters of q 0 (9.79mg.g -1 ) and K Th (0.88 ml.(min.mg) -1 ). The comparison of the experimental and predicted breakthrough curves obtained according to Thomas model is shown in Figure 5. The High value of regression coefficient (0.991) indicates that the simulation whole breakthrough curve was well predicted by the Thomas model Effect of co-ions The effect of Cu(II), and Pb(II) on the uptake of Cd(II) onto Triplochiton Scleroxylon sawdust was investigated (Figures 6). Thomas model capacity (q 0 ) determined for ternary system are compiled in Table 4 In the presence of other metals in a solution, chemical interactions between these ions as well as with the biomass take place resulting in a competition on the active sites of the sorbent. The amount of metal sorbed would also depend on the ionic size, stability of metal ion-sawdust bonding, nature of metal ion-sawdust interaction and the distribution of the reactive groups on the sawdust. It is postulated that the effective binding sites available for single metal are reduced in ternary system depending on the equilibrium between sorption competition from all the cations onto the sawdust surface (Pradhan and Rai 2001). In ternary solution, affinity sequence is Pb(II) > Cu(II) > Cd(II). The Cd(II) ions sorption was inhibited in ternary system. Preferential metal uptake in ternary systems did not match the atomic weight series. The variation in sorption order could be attributed to differences in their electronegativity. Electronegativity of Cadmium (1.69) is lower than that of Copper (1.90); therefore it will be less sorbed than the latter Sorption mechanism During the sorption in the fixed bed column, metals ions such as Ca(II) et Mg(II) were observed to be released significantly. Figure 7 shows released Ca(II) and Mg(II) in the column effluent during Cd (II) sorption in the fixed bed column. The Amounts of Ca(II) released were higher than those of Mg(II) during Cd(II) sorption as shown in a passed study in batch (Koffi et al., 2007). The releases of such ions suggested that ion exchange could play a significant role as a sorption mechanism as the heavy metals could replace Ca(II) and Mg(II) in sawdust structure. However, the amount of Cd(II) uptaken by the sawdust was found to be higher than that of total Ca(II) and Mg(II) released indicating that Cd(II) could be sorbed on some free binding sites in the sawdust by complexation (Apiratikul and Pavasant, 2008). In other words, the sorption mechanism of Cd(II) involved both ion exchange and complexation. In order to further investigate the existence of the complexation processes, results from the IR spectra of Triplochiton Scleroxylon sawdust before and after Cd(II) sorbed were used. IR spectra of the Triplochiton Scleroxylon sawdust sample was measured as potassium bromide pellets using a Perkin-Elmer 1600 series FTIR spectrometer. The FTIR spectra of the sawdust are shown in Figure 8. The broad and intense sorption peaks at 3412cm 1 correspond to the O H stretching vibrations of cellulose, pectin and lignin. The peaks observed at 2925cm 1 can be attributed to the C H stretching vibrations of methyl, methylene and methoxy groups. Peak observed at 1749cm 1 is the stretching vibration of C O bond due to nonionic carboxyl groups ( COOH, COOCH 3 ), and may be assigned to carboxylic acids or their esters. ISSN : Vol. 5 No.01 January

5 Asymmetric and symmetric stretching vibrations of ionic carboxylic groups ( COO ), respectively, appeared at 1647cm 1 (Khormaei et al., 2007). The bands at 1157 cm -1 were due to the C-O stretching of ether groups, while the C-O stretching of alcoholic groups was assigned at 1053 cm -1. It is well indicated from FTIR spectrum of Triplochiton Scleroxylon sawdust before binding Cd(II) that carboxyl and hydroxyl groups were present in abundance. These groups in biopolymers may function as proton donors; hence deprotonated hydroxyl and carboxyl groups may be involved in coordination with metal ions (Feng et al., 2011). The spectral analysis after metal binding indicated that carboxyl and hydroxyl groups (peaks observed at 3420 and 1647 cm 1 ) are involved in Cd(II) binding to the Triplochiton Scleroxylon sawdust. 4. Conclusion This work demonstrated the Cd(II) ions sorption, both in batch and column systems with Triplochiton Scleroxylon sawdust a agricultural by-product. The Langmuir and Freundlich sorption model were used for the mathematical description of the sorption of Cd(II) onto Triplochiton Scleroxylon sawdust and it was found that the sorption data fitted well to the Langmuir model and the batch sorption capacity was found as mg.g -1 at 30 C. The thermodynamic parameters such as G 0, H 0 and S 0 calculated show that process of Cd(II) sorption is spontaneous and exothermic. Column studies data have shown a good agreement with the predicted results obtained by application of Thomas model. Results on column regeneration for four cycles indicated that the reusability of Triplochiton Scleroxylon sawdust for Cd(II) removal is viable. Complexation in addition to ion-exchange mechanism must be involved in the sorption process of Cd(II). References [1] Acemioğlu, B. ; Alma, M. H. (2004). Sorption of copper (II) ions by pine sawdust. Holz Roh Werkst, 62, pp [2] Ahmad, A.; Rafatullah, M.; Danish, M. (2007). Sorption studies of Zn(II)- and Cd(II)ions from aqueous solution on treated sawdust of sissoo wood. Holz Roh Werkst 65, pp [3] Apiratikul, R.; Pavasant, P. (2008). Batch and column studies of biosorption of heavy metals by Caulerpa lentillifera. Bioresour Technol., 99, pp [4] Baral, S.S.; Das, N.; Ramulu, T.S.; Sahoo, S.K.; Das S.N.; Chaudhury,G. R. (2009). Removal of Cr(VI) by thermally activated weed Salvinia cucullata in a fixed-bed column. Journal of Hazardous Materials B, 161, pp [5] Benguella, B.; Benaissa, H. (2002). Cadmium removal from aqueous solutions by chitin: kinetic and equilibrium studies. Water Research, 36, pp [6] Feng, N.; Guo, X.; Liang, S. ; Zhu, Y.; Liu, J. (2011). Biosorption of heavy metals from aqueous solutions by chemically modified orange peel. Journal of Hazardous Materials B, 185, pp [7] Gupta, V.K.; Rastogi, A. (2008). Equilibrium and kinetic modelling of cadmium(ii) biosorption by nonliving algal biomass Oedogonium sp. from aqueous phase. Journal of Hazardous Materials B, 153, pp [8] Khormaei, M.; Nasernejad, B.; Edrisi, M.; Eslamzadeh, T. (2007). Copper biosorption from aqueous solutions by sour orange residue. Journal of Hazardous Materials B, 149, pp [9] Koffi, L. C. A.; Adouby, K.; Wandan, E. N.; Yao, B.; Kotchi, K. P. (2010). Sorption and desorption of Pb(II) from aqueous solution using Triplochiton scleroxylon sawdust as sorbent. Journal of applied sciences 10 (15), pp [10] Langmuir, I. (1916). The adsorption gasses on plane surface of glass, mica and platinum. J. Am. Chem. Soc., 40, pp [11] López-García, M. ; Lodeiro, P.; Barriada, J. L.; Herrero, R.; Sastre de Vicente, M. E. (2010). Reduction of Cr (VI) levels in solution using bracken fern biomass: Batch and column studies. Chemical Engineering Journal, 165, pp [12] Memon, S.Q.; Memon, N.; Shah, S.W.; Khuhawar, M.Y.; Bhanger M.I. (2007). Sawdust A green and economical sorbent for the removal of cadmium (II) ions. Journal of Hazardous Materials B, 139, pp [13] Pradhan, S; Rai, L.C. (2001). Biotechnological potential of Microcyistis sp in Cu, Zn, and Cd ions sorption from single and multimetallic system. BioMetals, 14, pp [14] Rao, R. A. K.; Khan M. A. (2009). Biosorption of bivalent metal ions from aqueous solution by an agricultural waste: Kinetics, thermodynamics and environmental effects. Colloids and Surfaces A: Physicochem. Eng. Aspects, 332, pp [15] Suksabye, P.; Thiravetyan, P.; Nakbanpote, W. (2008). Column study of chromium(vi) adsorption from electroplating industry by coconut coir pith. Journal of Hazardous Materials B, 160, pp [16] Taty-Costodes, V. C.; Fauduet, H.; Porte, C.; Delacroix, A. (2003). Removal of Cd(II) and Pb(II) ions, from aqueous solutions by adsorption onto sawdust of Pinus sylvestris. Journal of Hazardous Materials B, 105, pp [17] Thomas, H.C. (1944). Heterogeneous ion exchange in a flowing system. J. Am. Chem. Soc., 66, pp [18] Vijayaraghavan, K.; Palanivelu, K.; Velan, M. (2006). Biosorption of copper(ii) and cobalt(ii) from aqueous solutions by crab shell particles. Bioresource Technology, 97, pp Table 1: Langmuir and Freundlich sorption constants obtained from the sorption isotherms of Cd(II) onto sawdust at different temperatures. Temperatur e ( C) q o (mg.g -1 ) Langmuir model b (L.mg 1 ) R 2 K F (mg.g -1 ) Freundlich model /n R 2 ISSN : Vol. 5 No.01 January

6 Table 2: Thermodynamics parameters for for Cd(II) sorption onto sawdust. Temperature (K) b (L mol 1 ) Lnb G o (kj mol 1 ) H o (kj.mol -1 ) S o (J.(mol.K) -1 ) Table 3: Regeneration of sawdust on the sorption and desorption of Cd(II) N Cycle sorption Desorption (mg.g -1 ) (mg.g -1 ) (%) Table 4: Parameters predicted from the Thomas model for Triplochiton Scleroxylon sawdust from ternary solution. Ionic radius Electronegativity Ions (Ǻ) (Pauling) q o (mg.g -1 ) R 2 Cd(II) Cu(II) Pb(II) Figure captions Figure 1: Non-linearized Langmuir sorption isotherms of Cd(II) obtained at 30, 40, 50 and 60 C (initial ph 4;C 0 = 100 mgl -1, 2 to 25gL -1 of sawdust concentration). Figure 2: Non-linearized Freundlich sorption isotherms of Cd(II) obtained at 30, 40, 50 and 60 C (initial ph 4;C 0 = 100 mgl -1, 2 to 25gL -1 of sawdust concentration) Figure 3: Plot of Langmuir constant (Lnb) vs temperature (1/T. (initial ph 4 and 20 g.l -1 of sawdust concentration) Figure 4: Sorption and elution breakthrough curves for Cd(II) during regeneration cycles (C 0 = 100 mg.l -1, sawdust mass = 2 g, flow rate = 22mL.min -1, ph 4.) Figure 5: Simulation data for the breakthrough curve using Thomas model for the sorption of Cd(II) by sawdust. (C 0 = 100 mg.l -1, sawdust mass = 2 g, flow rate =22mL.min -1, ph 4.) Figure 6: Simulation data for the breakthrough curve using Thomas model for the sorption of Cd(II), Cu(II) and Pb(II) by Triplochiton Scleroxylon sawdust in ternary system. (ph = 4 ; C 0 = 100 mgl -1 ). Figure 7: Amounts of metal ions released during the column sorption experiment (Co =100mg.L -1, ph 4, flow rate = 22mL.min -1, sawdust mass = 2 g). Figure 8: FTIR spectra of Triplochiton Scleroxylon sawdust (α) before and (β) after Cd (II) sorption ISSN : Vol. 5 No.01 January

7 8 6 q e (mg.g -1 ) C e (mg.l -1 ) 30 C 40 C 50 C 60 C Figure q e (mg.g -1 ) C e (mg.l -1 ) 30 C 40 C 50 C 60 C Figure 2 ISSN : Vol. 5 No.01 January

8 8,75 8,70 8,65 8,60 Lnb 8,55 8,50 8,45 8,40 8,35 0, , , , , , , /T Figure Cadmium concentration (mg.l -1 ) Treated volume (ml) Figure 4 ISSN : Vol. 5 No.01 January

9 1,0 0,8 0,6 C/C 0 0,4 0,2 Experimental data Thomas model 0,0 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 Volume(L) Figure 5 1,0 0,8 0,6 C/C 0 0,4 0,2 0,0 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Treated Volume (L) Cd 2+ Cu 2+ Pb 2+ Thomas Model Figure 6 ISSN : Vol. 5 No.01 January

10 C (mg.l -1 ) Treated Volume (ml) Cd(II) Ca(II) Mg(II) Figure * Absorbance β α Wavenumber (cm -1 ) Figure 8 ISSN : Vol. 5 No.01 January