Dual-functional millisphere of anion-exchanger-supported nanoceria for synergistic As(III) removal with stoichiometric H2O2: Catalytic oxidation and sorption

Abstract

Aiming at efficient As(III) removal, a millimetric nanocomposite Ce-201, with dual functionalities of catalytic H2O2 oxidation and sorption, was synthesized by confined growth of hydrous nanoceria in macroporous anion-exchanger host D201. The removal of As(III) by Ce-201 was significantly enhanced by H2O2 at stoichiometric dosage (H2O2/As(III) molar ratio = 1–2), during which the catalytic oxidation of As(III) into As(V) played a vital role. The surface peroxide species formed on the surface of the embedded hydrous nanoceria induced by H2O2 were proved the predominant reactive species for As(III) oxidation, and the resultant As(V) was mostly sequestered by the quaternary ammonium groups of the D201 host. The removal of As(III) by Ce-201/H2O2 was favorable over wide pH range of 5–9, whilst the presence of chloride, carbonate (up to 10 mM), sulfate, silicate, nitrate (up to 1 mM), and humic acid (up to 30 mg DOC/L) posed negligible adverse effect on As(III) removal. The As-laden Ce-201 could be well regenerated by NaOH−NaCl binary solution for sustainable utilization without significant capacity loss. In fixed-bed mode, the working capacity of Ce-201 with H2O2 spiked into the influent at trace level (2.67 μM) for continuous As(III) removal (∼6500 BV) was over twenty times that of the classic nanocomposite HFO-201 or twice of Ce-201 without H2O2. Therefore, the Ce-201/H2O2 technique showed great potential for full scale application of highly efficient decontamination of As(III) from water.