The conventional sulfidation-xanthate flotation process that consists of sulfidization with sodium sulfide, activation by heavy-metal ions, and collection with xanthate is not sufficiently efficient for treating hemimorphite, and the dosages of the sulfurizing reagent and metal ions are large. In this study, the sulfidation flotation (Pb²⁺ + Na₂S + Pb²⁺ + xanthate) of hemimorphite was strengthened by pretreating with Pb²⁺ before sulfidation. Microflotation test results indicated that the recovery of hemimorphite increased by 5–10% after pretreatment with Pb²⁺. The comprehensive results of adsorption experiments, scanning electron microscopy–energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy indicated that a large amount of Pb²⁺ was adsorbed on the hemimorphite surface and entered the lattice, forming Zn_(4−x)Pb_xSi₂O₇(OH)₂·H₂O. The newly formed component had an increased amount of surface sulfidation active sites and had the effect of induced crystallization, making the surface more effective for sulfidation. After the Pb²⁺ was added to the pulp, a large number of uniform and dense PbS species were formed on the hemimorphite surface, increasing the number of adsorption sites for xanthate and reducing the competitive adsorption of residual S²⁻ on the xanthate.

Surface roughness is a crucial factor that affects the flotation performance of minerals. In this study, the effect of sulfuric acid corrosion on the surface roughness of calcite flotation was investigated through microflotation tests, scanning electron microscopy (SEM–EDS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and contact angle analysis. Microflotation test results show that sulfuric acid treatment has a serious negative effect on the floatability of calcite. When the sulfuric acid dosage was 4 mL (3 mol/L), the flotation recovery of calcite was reduced to less than 19%. SEM–EDS and AFM results verified that the sulfuric acid treatment significantly changed the surface morphology of calcite, reduced the average surface roughness and surface area, and reduced the amount of active Ca²⁺ sites on the calcite surface. As characterized by FT-IR and contact angle analyses, the sulfuric acid treatment enhanced the hydrophilicity of the calcite surface and reduced the amount of sodium oleate adsorbed on the calcite surface. Consequently, sulfuric acid corrosion can reduce the average surface roughness of calcite and have a serious negative effect on the flotation performance of calcite.