A Mineral Composition–Based Conceptual Approach for Predicting Sphalerite Depression in Flotation — Linking Mineral Composition to Depressant Dosage Selection through Copper Activation of ZnS

To meet the growing demand for copper (Cu), the higher impurity levels commonly associated with secondary raw materials have increased the demand for cleaner copper concentrates derived from primary ores in Cu production. Under such conditions, effective separation of Cu from impurities, including zinc (Zn), in mineral processing—particularly flotation—has become increasingly important and is expected to be even more critical in the future to ensure stable downstream metallurgical processing. Selective flotation of Cu sulfides, including chalcopyrite (CuFeS2), from Cu sulfide ores is often hindered by unwanted activation of sphalerite (ZnS). Pyrite (FeS2) enhances the release of Cu ions via the galvanic dissolution of CuFeS2, thereby promoting Cu activation of ZnS. Although zinc sulfate (ZnSO4) is commonly used to depress ZnS, extensive flotation testing is still required in practice to determine the appropriate ZnSO4 dosage for ores varying mineral compositions. To address this issue, the present study proposes a mineral composition–based conceptual approach for predicting ZnS depression in flotation. First, the degree of Cu activation of ZnS at pH 9 was evaluated by quantifying the amount of Zn released from ZnS after conditioning with different mineral compositions, represented by the CuFeS2/ZnS and FeS2/CuFeS2 ratios. Second, an empirical model was established to estimate the degree of Cu activation of ZnS based on these mineral composition parameters. Finally, by combining the empirical model with flotation results, a concept was proposed to predict the appropriate ZnSO4 dosage as a guideline for ZnS depression. The proposed approach can provide a systematic basis for reducing trial-and-error flotation testing and may support more robust Cu/Zn separation across Cu sulfide flotation systems with variable mineral compositions.