Redox Controlled Chalcopyrite Leaching as a New Method for Copper Production

低品位铜矿石的堆浸，结合溶剂萃取/电浸，由于其低资金和操作成本，操作简单，已成为重要的铜生产。然而，由于常见的铜源，黄铜矿（CuFeS_2）的浸出动力学极其缓慢，该工艺尚未完全成功。黄铜矿浸出是一个氧化还原过程，提出通过氧化剂铁离子与还原剂铁离子的浓度比来控制氧化还原电位以提高浸出率。本研究研究了硫酸溶液中黄铜矿浸出的氧化还原电位依赖性及影响浸出电位依赖性的因素，以建立氧化还原控制的黄铜矿浸出。浸出和阳极极化实验表明，铜和铁离子的共存激活了黄铜矿的阳极溶解，在电位低于一定值（临界电位）时，铜的萃取速度更快。黄铜矿电极的交流阻抗谱分析表明，在没有铜和/或亚铁离子的情况下，黄铜矿表面形成了一层高电阻的被动层，这些离子的共存导致了另一层产物的形成，并在低电位下抑制了被动层的生长。这些结果可以用假设黄铜矿还原生成中间Cu_2S和随后Cu_2S氧化的反应模型来解释。临界电位与Cu_2S形成的氧化还原电位相对应，预测值与实验结果相吻合，黄铜矿溶解的最佳氧化还原电位是铜和铁离子浓度的函数。并在此基础上解释了银离子、活性炭等催化剂对黄铜矿浸出的影响。

Heap leaching of low-grade copper ore, combined with solvent-extraction/electro-winning, has become important in copper production, because of its low capital and operation costs, operational simplicity However, the process has not been fully successful, due to the extremely slow leaching kinetics of a common copper source, chalcopyrite (CuFeS_2). Chalcopyrite leaching is a redox process and the control of the redox potential determined by the concentration ration of oxidant ferric ion to reductant ferrous ion has been proposed to improve the leaching rate. In this study, the redox potential dependence of chalcopyrite leaching in sulfuric acid solutions and the factors affecting the potential dependence of the leaching were investigated to establish the redox controlled chalcopyrite leaching. Leaching and anodic-polarization experiments showed that coexistence of cupric and ferrous ions activate anodic dissolution of chalcopyrite, causing faster copper extraction at the potentials below a certain value (critical potential). The analysis of the AC impedance spectra for chalcopyrite electrode indicated that a high-resistance passive layer grows on the chalcopyrite surface without cupric and/or ferrous ions, and that coexistence of these ions causes a formation of another product layer and inhibits the passive layer growth at low potentials. These results are explained by a reaction model assuming the formation of intermediate Cu_2S due to chalcopyrite reduction and the subsequent oxidation of the Cu_2S. The critical potential corresponds to the redox potential of the Cu_2S formation and the predicted values matched with the experimental results, and the optimum redox potential for chalcopyrite dissolution is a function of cupric and ferrous ion concentrations. Effects of catalysts like silver ions and activated carbon on chalcopyrite leaching were also explained based on the above model.