Fast and efficient removal of As(III) from water by CuFeO with peroxymonosulfate: Effects of oxidation and adsorption.

Although oxidation of As(III) to As(V) is deemed necessary to promote arsenic removal, the oxidation process usually involves toxic byproducts, well-defined conditions, energy input or sludge generation. Moreover, extra operations are required to remove the resulting As(V). A heterogeneous catalytic process of CuFeO with peroxymonosulfate (PMS) is established for As(III) oxidation and adsorption. The PMS can be activated by CuFeO to generate radical species for As(III) oxidation. The CuFeO/PMS has a stronger affinity for arsenic than CuFeO alone. Oxidation and adsorption promote each other. As a result, the heterogeneous catalytic process is more efficient for As(III) removal than a preoxidation of As(III) followed by adsorption. The adsorption capacity for As on CuFeO/PMS reached up to 63.9 mg/g, which is much higher than that of As(III) (36.9 mg/g) or As(V) (45.4 mg/g) on CuFeO alone. The process can work effectively over a wide range of pH values (3-9) and temperatures (10-40 °C). Coexisting ions such as sulfate, carbonate, silicate and humic acid have an insignificant effect on As(III) removal. The As(III) (1415 μg/L) can be completely oxidized to As(V) and rapidly removed to below 10 μg/L (less than 15 min) using CuFeO(0.2 g/L)/PMS(100 μM). Moreover, the As(III) (50 μg/L) can be completely oxidized and removed within 1 min. The proposed process is easily applicable for the remediation of As(III)-contaminated water under ambient conditions.