Key Upgrading Technology for Flotation of Oxidized Copper Ore

The sulphidation flotation process is currently the primary method for treating oxidised copper ores and mixed copper ores, and mainly comprises direct sulphidation flotation and hydrothermal sulphidation–warm-water flotation. Compared with direct flotation, the sulphidation flotation process is widely applied and offers the following advantages: ① It is not restricted by the properties of gangue minerals and can be applied to both siliceous and calcareous-magnesian gangues; ② The main reagents—sulphidising agents and xanthates—are widely available and relatively low in cost.

The success of the sulphidation flotation process hinges on the quality of the sulphidation step, as sulphidising agents act both as effective activators for copper oxide ores and as inhibitors for sulphide copper ores or sulphidised copper oxide ores. To prevent or mitigate this effect, the dosage of sulphidising agents must be strictly controlled in production; batch dosing or other methods are frequently employed to manage their application.

a. Direct sulphidation flotation

Direct sulphidation flotation: The finely ground copper oxide ore slurry is first sulphidised using a sulphidising agent, followed by the addition of xanthate-type collectors for collection. Currently, sulphidising agents include sodium sulphide, sodium hydrosulphide, hydrogen sulphide, calcium sulphide and ammonium sulphide, among others, with sodium sulphide being the most commonly used. Collectors include ethyl xanthate, high-grade xanthate, black oil and fatty acids, though high-grade xanthate is the most commonly used.

b. Hydrothermal sulphidation flotation

Hydrothermal sulphidation flotation is, in fact, a development of the direct sulphidation flotation method. It builds upon direct flotation by intensifying the ore pre-treatment—the pre-sulphidation process—and conducting flotation in warm water. The mechanism of action involves mixing the slurry with sulphur powder; under conditions of 180°C and a pressure of 0.6–1.0 MPa, elemental sulphur undergoes a disproportionation reaction to produce S²⁻ and SO₄²⁻, causing a sulphidation reaction on the surface or within the entire particle of copper oxide to form stable, easily flotable, highly hydrophobic ‘artificial copper sulphide’. The advantages of this method include a simple process, the ability to ensure high recovery rates, and the effective mitigation of the adverse effects of fine slime on the flotation process. The disadvantages are high capital investment and high energy consumption, which limit its development and widespread adoption.