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The overlooked mechanism of chalcopyrite passivation
Acta Materialia ( IF 9.4 ) Pub Date : 2022-06-22 , DOI: 10.1016/j.actamat.2022.118111
Zihe Ren , Chihwei Chao , Prashanth Krishnamoorthy , Edouard Asselin , David G. Dixon , Nelson Mora

Chalcopyrite (CuFeS₂) is the world's main source of copper. Electrification of the global economy will rely on economically viable Cu dissolution from low grade chalcopyrite ores, but this process is particularly slow. The reason for this slow reaction has been in dispute for over 50 years. In this study, electrochemical analysis showed that n-type chalcopyrite is in an accumulation state when immersed in electrolyte, not in a depletion state as is commonly assumed. A leaching test and surface analysis confirmed the formation of a Cu-rich surface layer during oxidative leaching. In addition, a similar leaching test on covellite (CuS) showed leaching kinetics that were as slow as chalcopyrite. Ex-situ current-voltage analysis showed that the Cu-rich (covellite-like) product layer on the surface of chalcopyrite was a p-type semiconductor. Therefore, as leaching progresses, chalcopyrite transitions from a resistor to a diode. Three mechanisms for slow dissolution of chalcopyrite in acidic ferric media are proposed based on these tests: 1. The dielectric breakdown potential of chalcopyrite (0.7 V vs Ag/AgCl) is higher than what the ferric/ferrous redox couple can provide (0.5 V). 2. A chemically stable covellite-like surface layer prevents further Cu dissolution. 3. Rapid formation of a p-n junction on the leached chalcopyrite surface hinders the electrochemical process. We hypothesize that all three mechanisms together prevent the full dissolution of chalcopyrite under oxidative conditions at ambient temperature.



中文翻译:

被忽视的黄铜矿钝化机理

黄铜矿 (CuFeS₂) 是世界上铜的主要来源。全球经济的电气化将依赖于经济上可行的从低品位黄铜矿中溶解铜,但这个过程特别缓慢。这种缓慢反应的原因已经争论了 50 多年。在这项研究中,电化学分析表明,n型黄铜矿在浸入电解液时处于积累状态,而不是通常假设的耗尽状态。浸出试验和表面分析证实在氧化浸出过程中形成了富铜表面层。此外,对铜蓝 (CuS) 进行的类似浸出试验表明,浸出动力学与黄铜矿一样慢。异地电流电压分析表明,黄铜矿表面的富铜(类铜蓝)产物层为p型半导体。因此,随着浸出的进行,黄铜矿从电阻器转变为二极管。基于这些测试,提出了黄铜矿在酸性铁介质中缓慢溶解的三种机制: 1. 黄铜矿的介电击穿电位(0.7 V vs Ag/AgCl)高于铁/亚铁氧化还原电对所能提供的(0.5 V) . 2. 化学稳定的铜蓝样表面层可防止铜进一步溶解。3. pn的快速形成浸出的黄铜矿表面上的结阻碍了电化学过程。我们假设所有这三种机制共同防止黄铜矿在环境温度下的氧化条件下完全溶解。

更新日期:2022-06-22
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