有菌和无菌体系下辉铜矿氧化电化学

运用循环伏安曲线、稳态极化曲线和Tafel曲线等电化学手段以及X射线光电能谱（XPS）法研究了辉铜矿在有菌和无菌体系下氧化过程的电化学行为.研究结果验证了辉铜矿在有菌体系和无菌体系下的两步氧化溶解机理，第一步氧化反应为辉铜矿不断氧化生成缺铜的中间产物Cu_xS（1≤x<2），直至生成CuS，在较低电位下即可进行；第二步反应为中间产物CuS的氧化，需要在较高电位下才可进行，反应速率较慢，是整个氧化反应的限制性步骤.循环伏安实验显示有菌体系电流密度明显大于无菌体系，表明细菌加快了辉铜矿的氧化速率.稳态极化实验显示辉铜矿点蚀电位较低，无菌体系第一段反应活化区电位范围小于有菌体系，表明辉铜矿氧化过程生成的中间产物硫膜具有钝化效应，细菌可以通过自身氧化作用破坏硫膜，减弱辉铜矿表面的钝化效果，加快辉铜矿的氧化溶解速率.X射线光电子能谱分析显示电极表面钝化层物质组成复杂，包含了CuS、多硫化物（S_n2-）、（S0）和含（SO₄2-）的氧化中间产物等多种物质，其中主要的钝化物为CuS，表明辉铜矿的氧化遵循多硫化物途径. 

Electrochemistry of oxidation of chalcocite in the presence and absence of microorganisms

The electrochemical behavior of the chalcocite oxidation process in the presence and absence of microorganisms was investigated using electrochemical techniques, including cyclic voltammetry, anodic polarization curves, Tafel curves, and X-ray photoelectron spectroscopy (XPS) analysis. The research results prove the stepwise dissolution mechanism of chalcocite in the presence and absence of microorganisms. The initial stage of oxidation is initiated at low redox potentials. During the initial stage, the intermediate products of Cu_xS (1 ≤ x < 2) are successively oxidized until CuS is formed. The later stage is the oxidation of the intermediate product CuS and this period requires initiation at high redox potentials owing to the formation of a passivation layer on the electrode surface, and the reaction rate of the later stage is extremely slow; in this case, it is the rate-limiting step of the whole reaction. The cyclic voltammograms show that the electric current density in the presence of microorganisms is higher than that in the absence of microorganisms, indicating that the microorganisms accelerates the dissolution rate of chalcocite. The anodic polarization curves show that the pitting potential of chalcocite is low; the potential range of the first active corrosion zone in the presence of microorganisms is much wider than that in the absence of microorganisms, indicating that the intermediate products of the sulfur film are passivating, and their effects could be reduced by the oxidation of microorganisms; in this manner, the dissolution rate of chalcocite is promoted. To identify the components of the passivation layer during the process of chalcocite dissolution in the presence and absence of microorganisms, the electrodes were detected via XPS. The XPS analysis results show that the components of the passivation layer on the electrode surface are complex, including CuS, polysulfide (S_n2-), elemental sulfur (S0) and intermediate oxidation products that contain sulfate (SO₄2-) and that CuS is the main passivating component; therefore, the oxidation of chalcocite follows the multisulfur method.