Novel, bio-based, photoactive arsenic sorbent: TiO 2-impregnated chitosan bead

Abstract

A novel sorbent for arsenic, TiO 2-impregnated chitosan bead (TICB), has been synthesized and successfully tested. Kinetic plots, pH dependence, isotherm data, and bead morphology are reported. Equilibrium is achieved after 185 h in batch experiments with exposure to UV light. The TICB system performs similarly to the mass equivalent of neat TiO 2 nanopowder. The point of zero charge (pzc) for TICB was determined to be 7.25, and as with other TiO 2-based arsenic removal technologies, the optimal pH range for sorption is below this pH pzc. Without exposure to UV light, TICB removes 2198 μg As(III)/g TICB and 2050 μg As(V)/g TICB. With exposure to UV light, TICB achieves photo-oxidation of As(III) to As(V), the less toxic and more easily sequestered arsenic form. UV irradiation also results in enhanced arsenic removal, reaching sorption capacities of 6400 μg As/g TICB and 4925 μg As/g TICB, where arsenic is initially added as As(III) and As(V), respectively. Because the TICB system obviates filtration post-treatment, TICB is superior to TiO 2 nanopowder from the perspective of implementation for decentralized water treatment.