Simultaneous Biosorption of Chromium (III) and Chromium (VI): Application of Multiple Response Optimizations

This work aims, optimization of simultaneous biosorption of Cr(III) and Cr(VI) onto Gelidilla acerosa, a marine macro algae using multiple response optimization combined with central composite design of design of experiments. The three important physicochemical parameters of biosorption such as initial pH, initial concentration of metal solution and biosorbent dosage were optimized. The most favorable condition for simultaneous removal of Cr(III) and Cr(VI) were: pH 2.8, initial concentration 20 mg l-1 and biosorbent dosage 0.05g with maximum overall desirability of 1.0. Surface morphological features of biosorbent were studied using FTIR. The nature of biosorption was analyzed by fitting the equilibrium data to various adsorption isotherms and found that both Langmuir and Freundlich model were best fitted with R2: 0.99 for both chromium species. The maximum biosorption capacities predicted from Langmuir model were 285.71 mg g-1 for Cr(III) and 270.27 mg g-1 for Cr(VI). The pseudo-second order kinetic model was found to be proper approach to demonstrate biosorption kinetics indicating chemisorption with film diffusion as the rate controlling mechanism. The results demonstrated that multiple response optimization combined with central composite design using desirability function was best approach for optimization of simultaneous biosorption of Cr(III) and Cr(VI) from aqueous medium.