Facile fabrication of nanostructured cerium-manganese binary oxide for enhanced arsenite removal from water

Abstract

Arsenite [As(III)] is more toxic and more difficult to remove from water than arsenate [As(V)]. For enhanced As(III) removal from water, a new nanostructured Ce-Mn binary oxide with a Ce/Mn molar ratio of 3:1 was fabricated via a facile one-step oxidation-coprecipitation method at ambient temperature. The synthetic Ce-Mn binary oxide is amorphous with a high surface area of 157 m2/g. Cerium (Ce) and manganese (Mn) in this oxide exist mainly in the oxidation state of Ce(IV) and Mn(IV), respectively. It can effectively oxidize As(III) to As(V) and efficently adsorb the formed As(V). Moreover, this sorbent exhibits an obviously synergistic effect. The maximal sorption capacity of As(III) is 97.7 mg/g, which is competitive with most of reported sorbents. The As(III) uptake is rapid and slightly affected by tested solution pH, ionic strength, dissolved organic matters and coexisting anions except for phosphate, indicating the high selectivity toward arsenic. The arsenic-loaded Ce-Mn binary oxide could be readily regenerated and repeatedly used. Both Mn and Ce oxides in sorbent are responsible for As(III) oxidation, and the Ce oxide is dominant for adsorbing formed As(V) during As(III) removal. The oxide could be used as an attractive sorbent for As(III) removal from contaminated water, because of its facile and low-cost synthesis process, good As(III) sorption performance, and reusability.