2020同步年報

070 ACTIVITY REPORT 2020 S b 2 S 3 is the most important and ubiquitous antimony ore; its exposure to weathering is considered as the dominant source of Sb in aqueous solutions. Environmental factors, such as light irradiation and mineral surfaces, play an important role in controlling the transformation and mobilization of Sb 2 S 3 . FeS 2 is the most common natural min- eral associated with Sb 2 S 3 , regulating diverse environmental processes such as reduction-oxidation and sequestration to control the geochemical cycling of Sb. Understanding the reactions at the Sb 2 S 3 -FeS 2 -water interfaces at a molecular level is hence of paramount importance to elucidate the weathering and environmental fate of mineral tailings. The dissolution and transformation of Sb 2 S 3 arise from reac- tive oxygen species (ROS) that are generated with electron transfer. That condition is exactly what Chuan-Yong Jing (Chinese Academy of Sciences, China) and his team imple- mented to investigate the oxidative dissolution and seques- tration of Sb 2 S 3 on FeS 2 . Collaborating with Ting-Shan Chan (NSRRC), Jing’s team recorded Sb K-edge X-ray-absorption near-edge structure (XANES) spectra at TLS 01C1 at cryo- genic temperature (77 K) in an ultrahigh vacuum condition, which could prevent damage to the sample from X-ray- induced Sb(III) oxidation on FeS 2 . Collectively, Fe K-edge and S K-edge XANES spectra were recorded at TLS 16A1 . Fig. 1 : XANES spectra of (a) Sb K-edge, (b) S K-edge, and (c) Fe K-edge of solid minerals after reaction. Linear-combination fitting is shown as lines. [Reproduced from Ref. 1] Mechanism of Oxidative Dissolution and Sequestration of Stibnite on Pyrite The dissolution and transformation of stibnite (Sb 2 S 3 ) on mineral surfaces are fundamental steps that control the fate of antimony (Sb) in the environment. X-ray absorption spectra show that the heterogeneous electron transfers from Sb 2 S 3 to pyrite (FeS 2 ) facilitate the generation of hydroxyl and superoxide radicals to oxidize Sb(III). Furthermore, oxidation and sequestration of Sb(III) on a FeS 2 surface coupled Fe 2+ /Fe 3+ cycling and inhibited FeS 2 dissolution. The insights gained from this study extend our understanding of the transformation and transport of Sb 2 S 3 at environmental mineral-water interfaces.