The Synergistic Effect of Cu2+ Fe2+ Fe3+ Acidic System on the Oxidation Kinetics of Ag-Doped Pyrite

The impurities contained in the structure of natural pyrite have been reported to introduce variation in its semiconducting properties and oxidation behavior. However, there is no direct study about the effect of specific impurities on the pyrite electrodissolution process kinetics. Among the impurity elements, silver is of particular interest and is often found in natural pyrite. Silver is shown to be capable of catalysis of sulfide mineral dissolution in an acidic environment. In the present study, Ag-doped pyrite was fabricated by a hydrothermal method. X-ray powder diffraction and X-ray photoelectron spectroscopy analyses of the pyrite showed a homogeneous silver distribution in the pyrite. The electrochemical dissolution kinetics of the Ag-doped pyrite were studied in different sulfuric acid electrolytes, with or without the addition of Fe and Cu cations. A variety of electrochemical techniques, including linear sweep voltammetry, cyclic voltammetry, chronoamperometry, and impedance analysis were applied to evaluate the electrochemical response of the pyrite minerals. The experimental results showed a reduced pyrite electrochemical reactivity with increasing Ag content of the Ag-doped pyrites. The exchange current density of the pyrite electrodes in the sulfuric acid electrolytes decreased from 4.0 x 10(-6) to 1.0 X 10(-6) A/cm(2) by increasing the silver content of the pyrites from 138 to 3820 ppm. However, the anodic dissolution of the Ag-doped pyrite electrode showed a substantial increase in the Cu Fe-containing sulfuric acid solution. For instance, 4) of a pyrite electrode with 138 ppm Ag increased from 9.6 X 10(-6) A/cm(2) in the Fe-containing sulfuric acid solution to 2.3 X 10(-s) A/cm(2) in the Fe Cu-containing sulfuric acid solution. In the electrochemical impedance spectroscopy analysis, the Ag-doped pyrite with a higher concentration of Ag showed smaller charge -transfer resistances.

据报道，天然黄铁矿结构中所含的杂质会导致其半导体性质和氧化行为发生变化。然而，关于特定杂质对黄铁矿电溶解过程动力学的影响尚无直接研究。在杂质元素中，银特别引人关注，且经常在天然黄铁矿中被发现。研究表明银能够在酸性环境中催化硫化物矿物的溶解。在本研究中，通过水热法制备了掺银黄铁矿。对黄铁矿进行的X射线粉末衍射和X射线光电子能谱分析表明，银在黄铁矿中均匀分布。在添加或不添加铁和铜阳离子的不同硫酸电解质中研究了掺银黄铁矿的电化学溶解动力学。应用了多种电化学技术，包括线性扫描伏安法、循环伏安法、计时电流法和阻抗分析来评估黄铁矿矿物的电化学反应。实验结果表明，随着掺银黄铁矿中银含量的增加，黄铁矿的电化学反应性降低。在硫酸电解质中，黄铁矿电极的交换电流密度随着黄铁矿中银含量从138 ppm增加到3820 ppm，从4.0×10⁻⁶ A/cm²降低到1.0×10⁻⁶ A/cm²。然而，在含铜和铁的硫酸溶液中，掺银黄铁矿电极的阳极溶解显著增加。例如，含138 ppm银的黄铁矿电极的电流密度在含铁硫酸溶液中为9.6×10⁻⁶ A/cm²，在含铁和铜的硫酸溶液中增加到2.3×10⁻⁵ A/cm²。在电化学阻抗谱分析中，银浓度较高的掺银黄铁矿显示出较小的电荷转移电阻。