Bifunctional mesoporous g-C3N4/Fe3O4 composites were prepared and used for the simultaneous visible-light catalysis and adsorption of arsenic from aqueous solution. The as-prepared composites were characterized by wide-angle X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, a vibrating sample magnetometer, and Brunauer–Emmett–Teller surface analysis. Experimental results showed that meso-g-C3N4/Fe3O4 composites could oxidize As­(III) to As­(V), which was in turn effectively removed by the composites. The photocatalytic activity was significantly enhanced by the synergistic effect between g-C3N4 and Fe3O4. In addition, a reasonable visible-light catalytic oxidation mechanism of As­(III) was investigated.

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A highly selective polymeric ligand exchanger was developed for the removal of trace As(V) from aqueous solution. This adsorbent was prepared by loading Fe(III) onto porous amidoximated polyacrynitrile (AN)/itaconic acid (IA) copolymers (Fe(III)-AO AN/IA). Negligible ferric ion dissolution was observed from Fe(III)-AO AN/IA in solution of acidic pHs up to 2. As(V) adsorption by Fe(III)-AO AN/IA is a pH-dependent process with maximum capacity of 1.32 mg/g at pH 2–3. The adsorption process was found to be governed by pseudo-second-order kinetics, and could be described by the Freundlich model. Fe(III)-AO AN/IA had higher adsorption selectivity for As(V) than other anions in a simulated groundwater body such as Cl−, SO42−, PO43−, SiO32−. Fixed-bed adsorption indicated that As(V) in simulated groundwater could be effectively captured from 400 μg/L to <10 μg/L within 190 bed volumes (BV). The As(V) adsorbed on Fe(III)-AO AN/IA could be efficiently eluted with 10 BV of 5% NaCl solution (at pH = 9.0).