Novel, bio-based, photoactive arsenic sorbent: TiO2-impregnated chitosan bead

A novel sorbent for arsenic, TiO2-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 TiO2 nanopowder. The point of zero charge (pzc) for TICB was determined to be 7.25, and as with other TiO2-based arsenic removal technologies, the optimal pH range for sorption is below this pHpzc. 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 TiO2 nanopowder from the perspective of implementation for decentralized water treatment.