Grinding-Induced Surface Renewal of Legacy Sulfide Minerals and Its Impact on Tailings Reprocessing

This study examines the impact of regrinding on the interfacial properties of sulfide minerals and the flotation performance of weathered copper–porphyry tailings. The feed material is characterized by a low copper grade (0.17%) and a high proportion of oxidized species (53.84%), which contribute to its inherent chemical stability and poor flotation kinetics. The findings indicate that regrinding serves a dual role: facilitating the liberation of mineral intergrowths and inducing mechanical surface renewal. This renewal is characterized by a significant decrease in the oxidation–reduction potential (ORP) and an intensification of the surface reactivity. Experimental results identify an optimal grinding fineness of 77%–81% passing −0.045 mm, yielding a copper recovery of 16.26% in the absence of a sulfidizing agent. The integration of sodium sulfide (400 g/t) with regrinding significantly enhances recovery to 36.37%, driven by the establishment of a reducing environment (ORP ≈ −150 mV) and the chemisorption-mediated activation of mineral surfaces. While ultrafine grinding (90%–100% passing −0.045 mm) further increases recovery to 51.47%, it is accompanied by deleterious sliming effects and a subsequent loss of process selectivity. The study confirms that mechanical surface rejuvenation and the optimization of electrochemical conditions are critical for improving the processing efficiency of anthropogenic resources, providing a theoretical framework for establishing rational beneficiation regimes.