ABSTRACT

Due to the scarcity of water in many parts of the world, wastewater generated by hydrometallurgical processes has been recognized as a valuable resource for recovery or reuse. A method for reusing hydrometallurgical raffinate in the leaching of low-grade oxide copper ore in a counter-current leaching process was evaluated. In the first stage of the investigation, the influential factors on copper leaching, such as the amount of acid consumed (200–400 g/kg of ore), the initial iron concentration of the raffinate (5–25 g/L), the liquid-to-solid ratio (2–10 mL/g), and the duration of the leaching process (15–75 min), were examined using response surface methodology coupled with central composite design. Two responses, copper recovery and final copper concentration, were selected to determine the optimal conditions for the leaching process. Based on the statistical model, it was found that using 325 g/kg of ore of consumed acid, an initial iron concentration of 10 g/L, a liquid-to-solid ratio of 4 mL/g, and a leaching time of 60 min would result in higher values for both responses. Confirmation runs were conducted to validate the selected conditions and the suitability of the statistical model. Additionally, compositional and morphological characterization of samples before and after the leaching process was conducted using field diffusion scanning electron microscopy and X-ray diffraction analysis, which showed the dissolution of compounds such as tenorite and cuprite. In the second stage, a two-unit counter-current leaching system was adopted, as hydrometallurgical processes are usually carried out in multiple stages on an industrial scale. This leaching system was designed to maximize copper dissolution by considering the information obtained from the response surface methodology. The use of this leaching system increased the overall leaching efficiency by up to 80%. By characterizing the solid samples, it was found that the copper extraction percentage in a counter-current leaching system could be increased by simultaneously precipitating iron-bearing compounds.

摘要

由于世界许多地区缺水，湿法冶金工艺产生的废水已被认为是可回收或再利用的宝贵资源。评价了逆流浸出低品位氧化铜矿浸出湿法冶金残液的回用方法。第一阶段考察了铜浸出的影响因素，如酸消耗量（200~400 g/kg矿石）、萃余液初始铁浓度（5~25 g/L）、使用响应面方法结合中心复合设计检查液固比（2-10 mL/g）和浸出过程的持续时间（15-75 分钟）。选择铜回收率和最终铜浓度这两个响应来确定浸出过程的最佳条件。根据统计模型发现，废酸矿石用量为325 g/kg，初始铁浓度为10 g/L，液固比为4 mL/g，浸出时间为60 min 会导致两个响应的值更高。进行确认运行以验证所选条件和统计模型的适用性。此外，利用场扩散扫描电子显微镜和 X 射线衍射分析对浸出过程前后样品的成分和形态进行了表征，结果显示了镁钠长石和赤铜矿等化合物的溶解。第二阶段采用双单元逆流浸出系统，因为湿法冶金工艺通常在工业规模上分多阶段进行。该浸出系统旨在通过考虑从响应面方法获得的信息来最大化铜的溶解。该浸出系统的使用使整体浸出效率提高了80%。通过表征固体样品，发现逆流浸出系统中的铜提取率可以通过同时沉淀含铁化合物来提高。