Evolution of sulfur species on malachite surfaces in the presence of calcium and magnesium ions and implications for xanthate flotation

The depletion of mining resources has led to a sharp increase in gangue minerals. The use of flotation technology with seawater, which is rich in Ca²⁺ and Mg²⁺, has gradually increased. However, these ions may affect the flotation process. Herein, we study the effects of the addition of Ca²⁺ and Mg²⁺ on the process and products of malachite sulfidization. Analysis of the S layer on the mineral surface indicates that the quantities of S components generated on the malachite surface decrease in the presence of Ca²⁺ and Mg²⁺. Additionally, Ca²⁺ and Mg²⁺ induce the excessive generation of oxidized S species (SO_n²⁻) during sulfidization, which inhibits the formation of Cu₂S. Furthermore, both the solubility of malachite and the consumption of collector ions in the solution increase in the presence of Ca²⁺ and Mg²⁺. Microflotation experiments confirm that Ca²⁺ and Mg²⁺ result in insufficient sulfidization properties on the malachite surface and reductions in the activity of the sulfidization products, leading to a decrease in sample floatability.