Enhanced Hydrometallurgical Recovery of Copper from Balkhash Copper Concentrate Through High-Energy Milling

This study investigated the influence of high-energy milling and leaching conditions on copper extraction from an industrial copper concentrate obtained from the Balkhash copper smelter. The concentrate was subjected to high-energy milling in a planetary ball mill for 15, 30, 45, and 60 min, followed by leaching in ammonium hydroxide and citric acid solutions. The structural, morphological, and physical changes induced by milling were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), particle-size distribution (PSD), and Brunauer–Emmett–Teller (BET) specific surface area analysis. XRD analysis showed that the principal mineral phases, including chalcopyrite, quartz, copper sulfides, magnetite, and lead sulfate, remained detectable after milling, whereas changes in diffraction peak shape and relative intensity indicated modification of the structural state of the concentrate. SEM observations demonstrated progressive disruption and fragmentation of the initial coarse particles. Quantitative particle-size analysis confirmed substantial particle refinement, with the D50 and D90 values decreasing from 5.030 and 57.365 μm for the untreated concentrate to 1.193 and 5.101 μm, respectively, after 30 min of milling. The BET specific surface area increased from 0.5086 m2/g for the untreated concentrate to a maximum of 1.7801 m2/g after 30 min, followed by a non-monotonic variation at longer milling times. Under the selected leaching conditions, copper extraction from the untreated concentrate reached 67% in ammonium hydroxide solution and 77% in citric acid solution. High-energy milling further increased copper extraction to 81% after 45 min in ammonium hydroxide and to 86% after 60 min in citric acid. The combined XRD, SEM, PSD, and BET results demonstrate that high-energy milling substantially modified the structural, morphological, particle-size, and accessible surface characteristics of the concentrate. However, the different milling durations corresponding to the maximum BET surface area and maximum copper extraction indicate that enhanced leaching performance cannot be attributed to surface-area enlargement alone and is associated with the combined effects of particle fragmentation, accessible surface-area changes, and milling-induced structural modification.