Integrated Development and Pilot-Scale Validation of a Flotation Process for Reprocessing Historical Copper Tailings

Historical copper tailings represent a potentially valuable secondary source of copper; however, their reprocessing is commonly constrained by complex mineral associations, insufficient liberation of copper-bearing minerals, and secondary alteration of mineral surfaces. This study develops and experimentally validates an integrated approach to the flotation reprocessing of historical copper tailings, combining chemical, mineralogical, phase, and particle-size characterization with optimization of grinding and reagent conditions, closed-circuit flotation tests, mathematical modeling, and pilot-scale validation. The investigated tailings contained approximately 0.2% Cu, with copper occurring predominantly as chalcopyrite together with secondary copper sulfides closely associated with pyrite, magnetite, and gangue minerals. Laboratory experiments established suitable grinding and flotation conditions and demonstrated the effectiveness of Na2S for sulfidization of altered copper minerals and a combined potassium butyl xanthate–AERO 9863 collector system. Closed-circuit tests showed that preliminary classification of the feed combined with regrinding of the rougher concentrate prior to cleaning provided the best separation performance among the investigated flowsheet configurations, producing a combined concentrate containing 6.74% Cu at a copper recovery of 46.09%. A statistically significant quadratic regression model (R2 = 0.9494) was developed to quantify the effects of the main flotation variables and identify a favorable reagent operating region. Pilot-scale testing of 5.15 t of historical tailings confirmed the technological applicability of the proposed flowsheet, producing a combined copper product containing 8.08% Cu at 55.38% recovery while reducing the Cu content of the final tailings to 0.1%. The results demonstrate the technological feasibility of recovering residual copper from the investigated historical tailings and highlight the value of integrating mineralogical characterization, process optimization, mathematical modeling, and pilot-scale validation for the development of tailings reprocessing flowsheets.