Leaching Behavior of Oxidized Copper Ore from Almalyk Mine Heap Site

Abstract

Hydrometallurgical methods including heap leaching are widely used to extract copper from secondary minerals by using sulfuric acid, H2SO4 as a commonly lixiviant. However, previous studies have failed to reflect the industrial level ore leaching processes, since they were focused on short-term leaching of powdery ore particles. Here, laboratory scale leaching experiments were conducted at varied sulfuric acid concentrations on oxidized copper ore of not only fine particle size but also relatively coarse particle size, which is applied in actual heap leaching. The semi-long-term leaching behavior of oxidized copper ore was examined. The source minerals of copper and other gangue minerals were identified through physicochemical and mineralogical analysis of the field ore. The economic feasibility of the leaching conditions was also discussed by assessing the acid consumption compared to the copper recovery.

The copper-bearing mineral in the ore was identified as malachite, Cu2(OH)2CO3. Leaching experiments (for 7 days) results revealed that smaller the ore particle size and higher the H2SO4 concentration, greater was the copper recovery. The leaching rate of copper was faster when the ore particle size was smaller. Significant amount of iron, aluminum, and magnesium were also leached out due to the dissolution of silicate gangue minerals. Calcium was also released due to the dissolution of carbonate gangue minerals. Additional short-term leaching experiment determined that the leaching kinetics of the ore followed the diffusion control model through product ash layer, regardless of particle size. The acid consumption increased rapidly with increasing dissolution of gangue minerals in the late period of the leaching, which resulted in the economic losses.