Resource utilization of arsenic into As(0) by iodide/sulfite boosted photo-reduction and cloud point extraction

To mitigate the risk of secondary pollution from arsenic-containing residues generated by conventional treatment methods, this paper proposes a novel ultraviolet (UV) light-driven reduction strategy, enhanced by iodide and sulfite, that effectively reduces arsenic in wastewater to valuable elemental arsenic (As(0)). Coupled with cloud point extraction (CPE), this approach facilitates the efficient recovery of As(0). Under optimized conditions, concentrations of 10 mg/L of As(III) and As(V) can be completely reduced to As(0) with a purity exceeding 96 % within 70 min. Utilizing TX-114 as an extractant (0.1 %), over 95 % of the produced As(0) can be separated via CPE, eliminating the need for complex separation processes. Speciation and transformation analysis of arsenic, sulfur, and iodine during the reaction indicate that the highly reducing active hydrated electron (e(aq)(-)), generated by UV activation of iodide and sulfite, is primarily responsible for the reduction of arsenic into As(0). A synergistic effect between iodide and sulfite was confirmed that enhances the conversion of harmful reactive iodine species (RISs) and dithionate, significantly improving the generation and utilization efficiency of e(aq)(-). The system demonstrates a broad operational pH range (pH 4 similar to 10), minimal interference from coexisting ions and dissolved oxygen, and low operational costs (similar to$1.2 per m(3)). The successful application of this method in non-ferrous metal wastewater further highlights its potential for effective arsenic pollutant remediation and resource recovery.