COPPER LEACHING PRACTICES

This document reviews contemporary copper leaching practices with emphasis on large-scale dump and heap leaching of low-grade ores and mine wastes. It describes the evolution from incidental recovery from acid mine drainage to systematic hydrometallurgical operations producing about 300,000 tons of copper annually, mainly from in-place leaching. The paper outlines mine waste dump construction methods, including “finger” dumps and multi-lift heaps, and lists practical design guidelines to improve aeration, solution flow, and exposure of sulfide minerals. It examines dump operation characteristics such as oxygen diffusion, heat generation from sulfide oxidation, and chemical fracturing of rock. Various leach solution distribution methods—trickle systems, solution injection through drill holes, ponds, and sprays—are compared, with trickle and injection systems identified as most effective. The role of recycled acidic solutions, control of flow rates and pH, and management of iron and other dissolved salts are discussed, highlighting the importance of iron hydrolysis, precipitation, and re-acidification to maintain effective copper leaching.