Optimization of Conditions for Biosorption of Chromium and Cadmium by Shell of Anodontoides ferussacianus

The biosorption of chromium [Cr (VI)] and cadmium [Cd (II)] ions using dead biomass of bivalve mollusk shell, Anodontoides ferussacianus was studied. Effect of various physico-chemical parameters was determined. Optimum pH was 4, temperature was 30°C, biosorbent concentration was 15 g/L and sorbate-sorbent contact time was 90 min with equilibrium concentration (qeq) of 300 mg/g and 280 mg/g for Cr (VI) and Cd (II) respectively. Many models of adsorption isotherm were used like Temkin, Langmuir and Freundlich. Regression coeffient (R2) values of Cr (VI) and Cd (II) were 0.99 & 0.97 for Langmuir, 1 & 0.99 for Freundlich, 0.99 & 0.97 for Temkin respectively. Vaious parameters of these models were also determined for Cr (VI) and Cd (II) with Langmuir’s qmax= 12.6 and 14.4 mg/g respectively and Fruendlich’s KF= 1.6 and 1.18 respectively. This shows multilayer sorption by A. ferussacianus shell for Cr (VI) and Cd (II). Kinetic model of Pseudo-second order revealed the process of Kinetics [K2= 0.19 & 2.4 and R2=0.96 & 0.93 for Cr (VI) and Cd (II) respectively]. Additionally, shifts in FTIR (Fourier Transform Infra-red Spectroscopy) spectra indicated the binding sites of specific functional groups (–OH, -NH, C=O and S=O) for Cr (VI) and Cd (II) on biosorbent surface.