Ferrous ions in enhancing chalcopyrite-molybdenite flotation separation: Insights from solution chemistry and interfacial adsorption

Molybdenum (Mo) is a rare metal in nature and primarily obtained from copper-molybdenum mines. Chalcopyrite (Ccp) has excellent floatability, which is usually necessary to add a large dosage of sodium sulfide (Na₂S) to inhibit it. The reducing properties of Na₂S make it easy to be oxidized by air, and the catalytic oxidation of sulfide surfaces will also accelerate its oxidation. Our research shows that adding ferrous (Fe²⁺) ions to the Na₂S pulp can effectively remove the dissolved oxygen (DO) in the pulp, reduce the pulp potential, and form a hydrophilic layer of the iron sulfide, hydroxyl iron, and polysulfide on the chalcopyrite surface. This not only enhances its inhibition effect but also slows down the oxidation speed of sulfur ions and effectively enhances the utilization of Na₂S. Flotation tests demonstrate that adding 3.5 kg/t ferrous sulfate synergistically reduces Na₂S dosage by 3.0 kg/t (25.0 % decrease), while concurrently upgrading the concentrate grade from 3.5 % to 4.7 %, with recovery consistently maintained at 86 %. These findings not only optimize the separation process and reduce the cost of reagents but also alleviate safety and environmental concerns. This method is simple, effective, and highly applicable, offering strong practical significance for similar types of mines.