Arsenic Sorption on Chitosan-Based Sorbents: Comparison of the Effect of Molybdate and Tungstate Loading on As(Ⅴ) Sorption Properties

摘要

Modified chitosan gel beads, prepared by molybdate and tungstate coagulation methods, were tested for As(V) removal from solutions in the range of 5-200 mg As L-1. The sorbent is efficient at removing As(V) from acid solutions (optimum pH close to 3), the sorption capacities for As uptake in molybdate- and tungstate-loaded beads are 75 and 44 mg As g(-1) of dry mass, respectively. The mechanism of As(V) sorption is related to the ability of molybdate and tungstate ions to complex As(V) ions in acid solutions. As(V) sorption process is mainly influenced by the presence of phosphate ions, but there is no influence of co-ions as nitrate and chloride. Arsenic desorption can be performed using phosphoric acid solutions. Arsenic adsorption proceeds in acidic solutions with a partial release of molybdate and tungstate and with residual concentrations of arsenic above the regulations for drinking water. For that reason, this material is a candidate for the treatment of industrial effluents.[GRAPHICS].