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黄铁矿的溶解过程受表面化学反应控制,表面性质的变化是影响溶解动力学的关键因素。X射线光电子能谱技术(XPS)是研究矿物溶解过程先进的表面分析技术,可分析矿物表面5 nm范围内化学组成的变化,为解释矿物溶解机制和动力学提供可靠的数据指导。本文采用XPS分析了常温下黄铁矿生物浸出过程中矿物表面的变化,黄铁矿表面主要由含Fe和含S的两种化合物组成。其中,含Fe化合物主要为FeS_2、针铁矿、硫酸盐、高铁络合物;含S化合物主要为FeS_2、硫酸盐、半胱氨酸、多硫化合物。研究表明,黄铁矿的溶解与表面硫的氧化密切相关(从S_2~(2-)氧化至SO_4~(2-)),黄铁矿溶解过程首先是Fe-S键断裂,在细菌、溶氧等氧化剂的作用下,Fe~(2+)和S_2~(2-)迅速被氧化,化学反应界面逐步内扩至黄铁矿本体,最后铁氧化物或氢氧化物型氧化产物稳定存在于未反应的黄铁矿表面。黄铁矿的生物浸出遵循硫代硫酸盐机制,间接浸出和直接浸出机制同时存在,浸出过程中形成稳定的铁氧化物或氢氧化物型氧化产物,在一定程度上加快了表面电子传递速率,促进了黄铁矿电化学氧化溶解。
The pyrite dissolution process is controlled by the surface chemical reaction, and the change of the surface properties is the key factor affecting the dissolution kinetics. X-ray photoelectron spectroscopy (XPS) is an advanced surface analysis technique for studying the process of mineral dissolution. It can analyze chemical composition changes within 5 nm of the mineral surface and provide reliable data guidance for explaining dissolution mechanism and kinetics of minerals. In this paper, XPS was used to analyze the change of mineral surface during pyrite biological leaching at room temperature. The pyrite surface mainly consists of two compounds containing Fe and S. Among them, the Fe-containing compounds are mainly FeS 2, goethite, sulfate and high-iron complex; the S-containing compounds are mainly FeS 2, sulfate, cysteine and polysulfide compounds. The results show that the dissolution of pyrite is closely related to the oxidation of surface sulfur (from S_2 ~ (2-) to SO_4 ~ (2-)). The pyrite dissolution process is firstly broken by Fe-S bond, Oxygen and other oxidants, Fe 2+ and S 2 2- are quickly oxidized and the chemical reaction interface gradually expands to the pyrite body. Finally, the oxidation products of iron oxide or hydroxide are stably present in Unreacted pyrite surface. Pyrite biological leaching follow the thiosulfate mechanism, indirect leaching and direct leaching mechanism exist simultaneously, the leaching process to form a stable iron oxide or hydroxide oxidation products, to a certain extent, accelerate the surface electron transfer rate, Promote pyrite electrochemical oxidation and dissolution.