Influence of Surface Compositions on the Reactivity of Pyrite toward Aqueous U(VI)
Influence of Surface Compositions on the Reactivity of Pyrite toward Aqueous U(VI)
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表面成分对黄铁矿对 U(VI) 水溶液反应活性的影响
DOI：
10.1021/acs.est.0c01854
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发表时间：
2020
影响因子：
11.4
通讯作者：
Charlet Laurent
中科院分区：
文献类型：
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作者：
Ma Bin;Fern;ez-Martinez Alej;ro;Kang Mingliang;Wang Kaifeng;Lewis Aled R.;Maffeis Thierry G. G.;Findling Nathaniel;Salas-Colera Eduardo;Tisser;Delphine;Bureau Sarah;Charlet Laurent
黄铁矿在厌氧环境中通过矿水界面发生的氧化还原过程控制有毒铀的流动性方面起着重要作用，但影响反应动力学的因素仍然知之甚少。在这项研究中，天然黄铁矿与不同的杂质（铅，砷，硅）和不同的表面预处理，用于与水溶液U（VI）从pH值为3.0至9.5。水相和固相结果均表明，新粉碎的黄铁矿具有更多的表面Fe（S）-S键断裂产生的Fe 2 +/Fe 3+和S2-位，比酸洗处理的黄铁矿表现出更强的反应活性。此外，U（VI）还原，其中包括可能的中间体U（V）和超化学计量的UO 2 +x（s）的形成被发现优先发生在铅和砷富集点的黄铁矿表面上，这表明掺入的杂质可以作为反应位点，因为产生的晶格缺陷和方铅矿和毒砂样的本地配置。这些反应性的表面位点可以通过酸洗去除，使黄铁矿表面对水U（VI）几乎呈惰性。因此，黄铁矿对U（VI）的反应性在很大程度上取决于其表面组成，这提供了一个洞察黄铁矿和铀在不同环境中的化学行为。
Pyrite plays a significant role in governing the mobility of toxic uranium in an anaerobic environment via an oxidation–reduction process occurring at the mineral–water interface, but the factors influencing the reaction kinetics remain poorly understood. In this study, natural pyrites with different impurities (Pb, As, and Si) and different surface pretreatments were used to react with aqueous U(VI) from pH ∼3.0 to ∼9.5. Both aqueous and solid results indicated that freshly crushed pyrites, which do have more surface Fe2+/Fe3+and S2–sites that were generated from breakage of Fe(S)–S bonds during ball milling, exhibited a much stronger reactivity than those treated with acid washing. Besides, U(VI) reduction which involves the possible intermediate U(V) and the formation of hyperstoichiometric UO2+x(s) was found to preferentially occur at Pb- and As-rich spots on the pyrite surface, suggesting that the incorporated impurities could act as reactive sites because of the generation of lattice defects and galena- and arsenopyrite-like local configurations. These reactive surface sites can be removed by acid washing, leaving a pyrite surface nearly inert toward aqueous U(VI). Thus, reactivity of pyrite toward U(VI) is largely governed by its surface compositions, which provides an insight into the chemical behavior of both pyrite and uranium in various environments.