Surface Sulfur Conversion of Chalcopyrite for Efficient Kerosene Desorption and Cu–Mo Flotation Separation

Porphyry copper–molybdenum deposits are major sources of both metals, yet efficient separation of chalcopyrite and molybdenite remains challenging, especially in the presence of pre-adsorbed collectors. This study demonstrates a surface sulfur conversion strategy using sodium metabisulfite (SMBS) to remove pre-adsorbed kerosene and restore selective depression of chalcopyrite. Micro-flotation tests show that pre-adsorbed kerosene severely impairs the depressive effect of sodium thioglycolate (STG) on chalcopyrite, resulting in poor separation performance. SMBS treatment, in combination with STG, achieves a Cu–Mo recovery differential exceeding 90 percentage points, while molybdenite floatability remains virtually unaffected. Mechanistic investigations via contact angle measurements, FT-IR, zeta potential analysis, XPS, and electrochemical characterization reveal that SMBS treatment results in a decrease in hydrophobic disulfide species and an increase in hydrophilic sulfate species on the chalcopyrite surface. This surface transformation disrupts the pre-adsorbed kerosene film, enhances chalcopyrite hydrophilicity, and facilitates subsequent STG adsorption for sustained depression. These findings establish surface sulfur conversion as a mechanistic platform for non-polar collector desorption and offer a chemically driven, environmentally sustainable approach to selective Cu–Mo flotation separation.