Kinetic, Equilibrium and thermodynamic studies on the biosorption of Cd(II) from aqueous solutions by the leaf biomass of <i>Calotropis procera</i> – ‘Sodom apple’

The kinetics, equilibrium and thermodynamics of the biosorption of Cd (II) from aqueous solution by the leaf biomass of Calotropis procera popularly known in western Nigeria as ‘bom bom’and genrally known as Sodom apple were investigated at different experimental conditions. Optimum conditions of pH, contact time, biomass dosage, initial metal ion concentration and temperature were determined to be 5, 60 minutes, 110 mg, 0.3 mM and 27°C respectively. The maximum biosorption capacity was found to be 8.91 mg/g. The kinetic studies indicated that the biosorption process of the metal ion followed the pseudo-second-order and intraparticle diffusion models with an R2 value of 0.998 and 0.985 respectively. Equilibrium studies showed that the biosorption of Cd (II) is well represented by both Freundlich and Langmuir isotherms but the Langmuir model gave a better fit with an R2 value of 0.979, Langmuir constant bm of 0.0080 and monolayer adsorption capacity, m of 123.46. The calculated thermodynamic parameters (ΔG° -4.846 kJmol-1, ΔH° 10.60 kJmol-1 and ΔS° 0.052 kJK-1mol1) showed that the biosorption of Cd (II) is feasible, spontaneous, endothermic and highly disordered in nature under the experimental conditions. These findings indicate that the leaf of Calotropis procera could be employed in the removal of Cd (II) from industrial effluents. @JASEM Keywords: Calotropis procera, Cadmium, Adsorption isotherm J. Appl. Sci. Environ. Manage. Dec, 2011, Vol. 15 (4) 607 - 61

Biosorption of Cr (III) from aqueous solution by the leaf biomass of <i>Calotropis procera – ‘Bom bom’</i>

The biosorption of Cr (III) onto the leaf biomass of Calotropis procera popularly known as ‘bom bom’ in western Nigeria, over a wide range of reaction conditions were studied. The batch experimentsshowed that the biosorption of Cr (III) onto Calotropis procera leaf biomass is a rapid process reaching equilibrium within 10 minutes at an optimum pH value of 5. Other reaction conditions such as biomass dosage, initial metal ion concentration and temperature were also found to influence the biosorption process. Both Langmuir and Freundlich isotherms were employed to describe the biosorption process and both proved to beapplicable. However, Langmuir gave a better fit with an R-Squared value of 0.967 (closer to unity than that of freundlich), Langmuir constant, KL of 0.0188 and monolayer adsorption capacity, qm of 32.26 whereas the Rsquared value for the freundlich plot was 0.948 with adsorption capacity Kf and adsorption intensity, n of 1.156 and 1.146 respectively. The biosorption process followed the pseudo-second order kinetic model evident by an Rsquared value of 0.999 and the pseudo second order rate constant, K2 of 0.3668 gmg-1min-1. Thermodynamic studies revealed negative value of change in free energy, G0 (- 4.046KJmol-1) as an indicator of feasibility and spontaneity of the Cr (III) biosorption process. A positive value of enthalpy, H0 (26.099 kJmol-1) was obtainedwhich indicated the endothermic nature of the biosorption process. FT-IR studies of the biosorbent before and after the biosorption process indicated that carboxylate, amino and nitro functional groups were involved in the sorption of Cr (III) onto Calotropis procera leaf biomass. These findings indicate that the leaf of biomass of Calotropisprocera could be employed in the removal of Cr (III) from aqueous solutions and industrial effluents