Synergistic oxidation and adsorption of As(III) in water using biochar-mediated Fe(II)/nano-CaO2 system

Abstract

Due to its mobility and high toxicity, As(III) can easily migrate and accumulate through the food chain, endangering human health. The common treatment method for As(III) is a combination of oxidation and adsorption, in which the Fenton-like method exhibits a prominent removal performance. Based on our previous work, the Fe(II)/nano-CaO₂/biochar Fenton-like system with excellent oxidizing and adsorption capabilities was used to remove As(III) from water. Compared to the common oxidation systems, the Fe(II)/nano-CaO₂/RBC system showed an excellent As(III) removal through simultaneous oxidation and adsorption. The research findings demonstrated that under the cooperative effects of Fe(II) hydrolysis and RBC catalysis, As(III) in water could be efficiently removed in a broad initial 3.0–10.0 pH range, which solved the challenge of pH elevation that other metal peroxide systems encountered. In this system, most of the common co-existing cations and anions had no discernible impact on the As(III) elimination process, and some of the humic acid (HA) (< 60 mg L^− 1) was mineralized simultaneously. Quenching and characterization experiments confirmed that •OH dominated the oxidation of As(III), and •OH production was boosted by the addition of RBC. The purification of oxidized As(V) from water can be achieved by binding it with Fe and Ca through the synthetic action of electrostatic adsorption, surface complexation, and co-precipitation. Overall, this work presents an alternative approach for effectively eliminating As(III) from water.