Enhanced arsenic removal using mixed metal oxide impregnated chitosan beads

Mixed metal oxide impregnated chitosan beads (MICB) containing nanocrystalline Al2O3 and nanocrystalline TiO2 were successfully developed. This adsorbent exploits the high capacity of Al2O3 for arsenate and the photocatalytic activity of TiO2 to oxidize arsenite to arsenate, resulting in a removal capacity higher than that of either metal oxide alone. The composition of the beads was optimized for maximum arsenite removal in the presence of UV light. The mechanism of removal was investigated and a mode of action was proposed wherein TiO2 oxidizes arsenite to arsenate which is then removed from solution by Al2O3. Pseudo-second order kinetics were used to validate the proposed mechanism. MICB is a more efficient and effective adsorbent for arsenic than TiO2-impregnated chitosan beads (TICB), previously reported on, yet maintains a desirable life cycle, free of complex synthesis processes, toxic materials, and energy inputs.

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► Nanocrystalline Al2O3 and TiO2 in chitosan yields a sustainable arsenic sorbent.
► This mixed sorbent is more efficient and effective than either metal oxide alone.
► Al2O3 demonstrates an enhanced sorptive capacity for arsenate as compared to TiO2.
►  Proposed mechanism for arsenic removal is oxidation by TiO2 and sorption by Al2O3.
► Pseudo-second order kinetic models were used to validate this proposed mechanism.