2026 Zhou Oxygen enriched leaching of copper sulfide concentrate

The accumulation of low-grade, refractory copper sulfide concentrates from secondary resources, such as smelting slag-flotation products, represents a growing challenge in the copper industry. This study develops and validates an atmospheric oxygen-enriched leaching process that requires neither grinding nor high pressure, targeting a typical slag-flotation copper sulfide concentrate. Systematic mineralogical analysis shows that copper is 95% in secondary sulfides, with quartz, chlorite, and muscovite as major gangue. Batch leaching optimization identifies the following conditions: H2SO4 250 g/L, temperature 90 °C, leaching time 8–12 h, pulp density 30–33% solids, and oxygen-enriched air (80–90% O2) at a flow rate ensuring sufficient oxygen mass transfer. Under these conditions, copper extraction reaches 97–99% without grinding. Continuous pilot-scale trials (over 500 kg dry feed) compare a five-stage mechanically agitated tank train and a four-stage tower reactor. The tank train achieves a stable copper extraction of 97.1% with a residue grade of 0.53% Cu at 8 h residence time and acid consumption of 857 kg/t concentrate, significantly outperforming the tower reactor. Reducing oxygen purity from 100% to 90% has no measurable effect on extraction, while 80% O2 gives only a 2% loss. The process eliminates grinding, operates at ambient pressure, and uses widely available reactor technology, offering a potentially low-capital and technically robust solution for recovering copper from such refractory secondary sulfide concentrates.