Effects of dry and wet grinding on Chalcopyrite surface reactivity, liberation, and flotation performance

Grinding environment strongly influences chalcopyrite surface reactivity and flotation, but direct dry-wet comparisons are often confounded by size and liberation effects. This study presents a mechanistically controlled comparison of dry and wet grinding effects on chalcopyrite by achieving closely matched particle size distributions and comparable liberation for both a model mineral and a low-grade copper ore. Under these controlled conditions, pronounced differences in surface chemistry and electrochemical reactivity were observed. Dry-ground particles exhibited higher oxygen demand, indicating highly reactive, minimally passivated surfaces, whereas wet-ground particles showed greater surface oxidation, which intensified with increasing temperature due to galvanic interactions and oxyhydroxide formation. These surface modifications directly translated into flotation behaviour: dry grinding consistently yielded higher copper recoveries and grades, while wet grinding particularly at elevated temperatures led to reduced collector adsorption and flotation performance. Grinding additives had negligible effects on the model mineral and only modestly improved recovery in the real ore, without altering dominant oxidation trends. Overall, the results demonstrate that, under equivalent liberation conditions, chalcopyrite flotation performance is governed primarily by grinding-induced surface chemistry rather than bulk mineral exposure.