研究生知识库

方铅矿是地球内部原生铅矿资源的主要矿石矿物，地球内部绝大多数原生方铅矿床的形成则是高温高压水流体-方铅矿相互作用的产物。基本的电化学原理告诉我们，电子导电性固体物质与水流体间的相互作用，其机制完全不同于非电子导电性固体物质，前者是一种复杂的腐蚀电化学过程，后者则是一种简单的化学反应过程。方铅矿是选冶工业上提炼金属铅的主要载体矿物，其在水流体中尤其是在高压水热流体中的电化学腐蚀行为是湿法冶铅和选矿工艺条件的决定性因素。目前，已经有大量的文献报道了方铅矿在常温常压下的电化学腐蚀行为。然而，由于实验技术条件的限制，迄今为止有关高温高压水流体中方铅矿的腐蚀电化学实验研究极少报道，从而严重阻碍人们对地球内部原生铅矿床成因的认识。本文通过原位电化学技术较为系统研究了高温高压氯化钠水热体系中方铅矿的电化学腐蚀行为。主要研究工作包括：（1）基于所在实验室拥有的六面顶大腔体压力机，成功地发明了一种在高温高压条件下烧结高纯致密大块体方铅矿的新工艺，并对制备的样品用多种分析测试方法进行表征。由该工艺制得的大块体材料经特殊的磨削机加工后可很好地满足下一步该材料的高压水热腐蚀电化学实验需要。（2）研究了温度为360℃压力为20 MPa时，氯化钠溶液浓度对方铅矿电化学腐蚀行为的影响。结果表明：在高温高压纯水和氯化钠溶液中，方铅矿都表现出氧化溶解的特征，且氧化溶解的控制步骤为电化学极化。氯化钠对方铅矿的腐蚀溶解具有一定的促进作用。随着溶液浓度的增大，方铅矿的开路电位下降。溶液浓度的提高使方铅矿的腐蚀电位下降而腐蚀电流密度上升。氯化钠浓度对方铅矿电化学腐蚀的影响在阻抗谱上表现在全频率范围上。氯化钠的存在会破坏方铅矿电极表面的阻挡性腐蚀产物膜层。（3）研究了压力为20 MPa时，0.10 M氯化钠溶液中温度对方铅矿电化学腐蚀行为的影响。结果表明：在研究的温度范围内，方铅矿都表现出氧化溶解的特征，且氧化溶解的控制步骤为电化学极化。随着溶液温度的增大，方铅矿的开路电位下降。溶液温度的提高使方铅矿的腐蚀电位下降而腐蚀电流密度上升。氯化钠温度对方铅矿电化学腐蚀的影响在阻抗谱上表现在全频率范围上。温度的升高不仅会加速电化学反应而且会破坏方铅矿电极表面的阻挡性腐蚀产物膜层。（4）研究了温度为25℃时，0.10 M氯化钠溶液中压力对方铅矿电化学腐蚀行为的影响。结果表明：在研究的压力范围内，方铅矿都表现出氧化溶解的特征，且氧化溶解的控制步骤为电化学极化。随着溶液压力的增大，方铅矿的开路电位下降，说明方铅矿的腐蚀倾向变大。溶液压力的提高使方铅矿的腐蚀电位下降而腐蚀电流密度略微上升。氯化钠压力对方铅矿电化学腐蚀的影响在阻抗谱上主要表现在低频率范围上，而对高频区的影响不大。压力的升高不会破坏方铅矿电极表面的阻挡性腐蚀产物膜层。（5）研究了温度为300℃时，0.10 M氯化钠溶液中压力对方铅矿电化学腐蚀行为的影响。结果表明：在研究的压力范围内，方铅矿都表现出氧化溶解的特征且氧化溶解的控制步骤为电化学极化。随着溶液压力的增大，方铅矿的开路电位下降，说明方铅矿的腐蚀倾向变大。随着溶液压力的提高，方铅矿的腐蚀电位下降而腐蚀电流密度上升。氯化钠溶液压力对方铅矿电化学腐蚀的影响在阻抗谱上主要表现在低频率范围上，而对高频区的影响不大。压力的升高不会破坏方铅矿电极表面的阻挡性腐蚀产物膜层。

Galena is the main mineral of primary lead ore resources in the earth's interior. The formation of most primary galena deposits in the earth is the product of interaction between high temperature and high pressure aqueous fluids and galena. The basic electrochemical principle tells us that the interaction mechanism between electronic conductive solid materials and aqueous fluids is completely different from that of non-electroconductive solid materials. The former is a complex electrochemical corrosion process, while the latter is a simple chemical reaction process. Galena is the main mineral for the extraction of metal lead in metallurgical industry. Its electrochemical corrosion behavior in aqueous fluids, especially in high pressure hydrothermal fluids, is the decisive factor for hydrometallurgy of lead and mineral processing conditions. At present, a large number of literatures have reported the electrochemical corrosion behavior of galena at room temperature and pressure. However, due to the limitations of experimental technical conditions, up to now, the corrosion electrochemical experiments on galena in high temperature and high pressure fluids have been rarely reported, which seriously hinders people's understanding of the genesis of primary lead deposits of the earth's interior. In this paper, the electrochemical corrosion behavior of galena in high temperature and high pressure sodium chloride hydrothermal system was systematically studied by in situ electrochemical technique.The main research work includes:(1) Based on the six anvil large-volume press apparatus owned by the laboratory, a new process for sintering high-purity and compact massive galena under high temperature and pressure was successfully invented, and the prepared samples were characterized by various analytical methods. The bulk material prepared by this process can be processed by a special grinding machine, which satisfies the need of high pressure hydrothermal corrosion electrochemical experiment.(2) The effect of concentration of NaCl solution on the electrochemical corrosion behavior of galena was studied at 360℃ and 20 MPa. The results were shown as following: Galena exhibits the characteristics of oxidation dissolution in high temperature and high pressure pure water and sodium chloride solution, and the control step of oxidation dissolution is electrochemical polarization. Sodium chloride can promote the corrosion dissolution of galena. With the increase of solution concentration, the open circuit potential of galena decreases. The corrosion potential of galena decreases and the corrosion current density increases with the increase of solution concentration. The effect of sodium chloride concentration on electrochemical corrosion of galena is shown in the whole frequency range of impedance spectroscopy. The presence of sodium chloride destroys the corrosion product film on galena electrode surface.(3) The effect of temperature on the electrochemical corrosion behavior of galena in 0.10 M sodium chloride solution at 20 MPa was studied. The results were shown as following: Galena shows the characteristics of oxidation dissolution in the temperature range studied, and the control step of oxidation dissolution is electrochemical polarization. With the increase of solution temperature, the open circuit potential of galena decreases. The corrosion potential of galena decreases and the corrosion current density increases with the increase of solution temperature. The effect of temperature on electrochemical corrosion of galena is shown in the whole frequency range in impedance spectroscopy. The increase of temperature not only accelerates the electrochemical reaction but also destroys the corrosion product film on the electrode surface of galena.(4) The effect of pressure on the electrochemical corrosion behavior of galena in 0.10 M sodium chloride solution at 25℃ was studied. The results were shown as following: Within the pressure range studied, galena shows the characteristics of oxidation dissolution, and the controlling step of oxidative dissolution is electrochemical polarization. With the increase of solution pressure, the open circuit potential of galena decreases, which indicates that galena has a greater corrosion tendency. The corrosion potential of galena decreases and the corrosion current density increases slightly with the increase of solution pressure. The effect of pressure on electrochemical corrosion of galena is mainly in the low frequency range of impedance spectroscopy, but not in the high frequency range. The increase in pressure does not destroy the corrosion product film on the galena electrode surface.(5) The effect of pressure on the electrochemical corrosion behavior of galena in 0.10 M sodium chloride solution at 300℃ was studied. The results were shown as following: Galena exhibits the characteristics of oxidation dissolution within the pressure range studied and the control step of oxidation dissolution is electrochemical polarization. As the solution pressure increases, the open circuit potential of galena decreases, indicating that the corrosion tendency of galena increases. With the increase of solution pressure, the corrosion potential of galena decreases while the corrosion current density increases. The effect of pressure on galena electrochemical corrosion is mainly in the low frequency range, but not in the high frequency range. The increase of pressure will not destroy the corrosion product film on galena electrode surface.