Enhanced Recovery of Strategic Metal Antimony from Wastewater via a Synergistic UV/Iodide/Sulfite Process

Abstract

Antimony-bearing wastewater poses substantial environmental risks, while conventional treatment technologies mainly transfer dissolved antimony into secondary hazardous wastes. Here, we developed a synergistic UV/iodide/sulfite process for the rapid reductive recovery of Sb(V) and Sb(III) from wastewater as high-purity elemental antimony (Sb(0)). This system achieved removal efficiencies of 99.91 ± 0.02% for both Sb(V) and Sb(III) within 60 min at substantially reduced chemical input, reducing residual antimony concentrations below 10 μg L–1. The recovered product was highly crystalline Sb(0) with a purity of up to 99.92 wt %. Mechanistic investigations demonstrated that hydrated electrons (eaq–) dominated antimony reduction. Iodide photolysis efficiently generated eaq– together with reactive iodine species (RIS), whereas sulfite rapidly quenched RIS and regenerated iodide, thereby suppressing electron scavenging and antimony reoxidation. This synergy prolonged the eaq– lifetime by 4.3-fold, maintained a higher steady-state reductive capacity, and thereby accelerated the reduction of Sb(V) and Sb(III) at lower chemical input. Validation with real wastewater further demonstrated the efficiency and practical applicability of the process. This work provides an efficient, low-chemical-input strategy for coupling antimony detoxification with resource recovery and offers useful insight into designing photochemical redox strategies for other redox-sensitive metal(loid)s in complex industrial wastewaters.