Biosorption of Hexavalent Chromium from Aqueous Medium withOpuntiaBiomass

Abstract

The biosorption of hexavalent chromium from aqueous solutions byOpuntiacladodes and ectodermis from cactus fruits was investigated. Both types of biomass are considered low-cost, natural, and ecofriendly biosorbents. Batch experiments were carried out to determine Cr(VI) biosorption capacity and the efficiency of the biosorption process under different pH, initial Cr(VI) concentration, and sorbent dosage. The biosorption of Cr(VI) byOpuntiabiomass was highly pH dependent, favoring higher metal uptake at low pH. The higher biosorption capacity was exhibited at pH 2. The optimal conditions were obtained at a sorbent dosage of 1 g L−1and initial metal concentration of 10 mg L−1. Biosorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The rate constant, the initial biosorption rate, and the equilibrium biosorption capacity were determined. The experimental equilibrium data obtained were analyzed using two-parameter isotherm models (Langmuir, Freundlich, and Temkin). The Langmuir maximum monolayer biosorption capacity (qmax) was 18.5 mg g−1for cladodes and 16.4 mg g−1for ectodermis. The results suggest thatOpuntiabiomass could be considered a promising low-cost biosorbent for the ecofriendly removal of Cr(VI) from aqueous systems.