This study investigated the migration law of ion release and adsorption in the flotation pulp of oxide zinc ore, and found that numerous different ions existed in the pulp. The total concentrations and major sources of various ions (Pb²⁺, Zn²⁺, Fe³⁺, Ca²⁺, Mg²⁺, SO₄^2-, etc.), released from the minerals after grinding, were determined. The zeta potential tests indicated that a mixed-ion solution strongly influences the surface charge of the minerals. The flotation tests show that the migration law of ions is detrimental to the separation and concentration of minerals.

In this study, FeSO₄·7H₂O was used as an auxiliary depressant to improve the selective depression effect on fluorite. Microflotation tests using oleic acid as the collector showed that the pre-addition of FeSO₄·7H₂O and subsequent addition of sodium silicate (SS) resulted in a stronger selective depression effect on fluorite compared with SS alone. Addition of FeSO₄·7H₂O reduced the required dosage of SS and had little negative effects on scheelite recovery. The selective depression mechanism of FeSO₄·7H₂O was investigated in detail. X-ray photoelectron spectroscopy indicated that the difference in the number of surface active sites was the mechanism for improved differential flotation of scheelite from fluorite. The improved depression of fluorite was attributed to both ferrous and sulphate ions. The pre-adsorption of ferrous species increased the number of active sites, enhancing the adsorption of silicate species on the fluorite surface. Simultaneously, sulfate ions were selectively adsorbed on the fluorite surface to form hydrophilic calcium sulfate, reducing the floatability of fluorite.

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.