Reductive Removal\nof Antimony from Wastewater by a\nUV/Sulfite Process: Targeted Recovery of Strategic Metalloid Antimony

The removal of antimony from wastewater using traditional\nmethods\nsuch as adsorption and membrane filtration generates large amounts\nof antimony-containing hazardous wastes, posing significant environmental\nthreats. This study proposed a new treatment strategy to reductively\nremove and recover antimony from wastewater using an advanced UV/sulfite\nreduction process in the form of valuable strategic metalloid antimony\n(Sb(0)), thus preventing hazardous waste generation. The results indicated\nthat more than 99.9% of Sb(V) and Sb(III) were removed from wastewater,\nreducing residual antimony concentration as low as 5 μg L<sup>–1</sup> and obtaining Sb(0) product with a high purity of\nover 99.9 wt %. Mechanistic investigations revealed the reductive\nH<sup>•</sup> radicals and hydrated electrons (e<sub>aq</sub><sup>–</sup>), along with oxidative SO<sub>3</sub><sup>•–</sup> radicals generated by the photolysis of sulfite, in which H<sup>•</sup> and e<sub>aq</sub><sup>–</sup> are responsible\nfor the reduction of Sb(V) and Sb(III) to Sb(0). Additionally, although\nSb(0) can be further reduced to stibine (SbH<sub>3</sub>) by H<sup>•</sup> and e<sub>aq</sub><sup>–</sup>, the formed\nSbH<sub>3</sub> rapidly decays and transforms back to Sb(0) through\nphotolysis and oxidation by SO<sub>3</sub><sup>•–</sup>. Thus, the proposed method can achieve the targeted reduction of\nSb(III) and Sb(V) to Sb(0) but not to SbH<sub>3</sub>. This study\nprovides a theoretical foundation for the recovery of antimony from\nwastewater.