Biosorption of hexavalent chromium and malachite green from aqueous effluents, using Cladophora sp.

Biosorption potential of green macroalgae Cladophora sp., (GAC) for the removal of hexavalent chromium (Cr(VI)) and malachite green (MG) from aqueous medium was investigated. Optimal conditions for biosorption experiments were determined as a function of initial pH, GAC dosage, temperature and initial concentration of Cr(VI) and MG. The biosorption equilibrium data were fitted with the isotherm models of Langmuir, Freundlich, Kiselev, Frumkin and Jovanovic, while the experimental data were analysed using the kinetic models such as pseudo-first-order, pseudo-second-order, Ritchie's and intraparticle diffusion. The Langmuir maximum biosorption capacity was calculated as 100.00 mg/g (Cr(VI)) and 142.85 mg/g (MG). The biosorption kinetic data showed better agreement with the pseudo-second-order kinetic model. The thermodynamic parameters indicated spontaneous and endothermic nature of the biosorption process for Cr(VI) removal, whereas exothermic in the case of MG removal. Furthermore, the biosorption efficiencies of the GAC reusability were found significant up to five cycles and tested using 0.1, 0.5 and 1.0 M HCl, respectively. The results of the present study indicated that GAC is a suitable biosorbent for the sequestration of Cr(VI) and MG from aqueous solutions.