In this work, oxidizing roasting was combined with leaching to separate copper, lead, and zinc from a concentrate obtained by bulk flotation of a low-grade ore sourced from the Jiama mining area of Tibet. The flotation concentrate contained 7.79% Cu, 22.00% Pb, 4.81% Zn, 8.24% S, and 12.15% CaO; copper sulfide accounted for 76.97% of the copper, lead sulfide for 25.55% of the lead, and zinc sulfide for 67.66% of the zinc. After oxidizing roasting of the flotation concentrate, the S content in the roasting slag decreased to 0.22%, indicating that most sulfide in the concentrate was transformed to oxide, which was beneficial to leaching. The calcine was subjected to sulfuric acid leaching for separation of copper, lead, and zinc; i.e., copper and zinc were leached, and lead was retained in the residue. The optimum parameters of the leaching process were: a leaching temperature of 55 °C; sulfuric acid added at 828 kg/t calcine; a liquid:solid ratio of 3:1; and a leaching time of 1.5 h. Under these conditions, the extents of leaching of copper and zinc were 87.43% and 64.38%, respectively. Copper and zinc in the leaching solution could be further separated by electrowinning. The effects of leaching parameters on the extents of leaching of copper and zinc were further revealed by X-ray diffraction and scanning electron microscopy analysis.

Titanium-bearing electric furnace slag (TEFS) was prepared from vanadium titanomagnetite and leached with sulfuric acid. The Ti leaching rate of vanadium titanomagnetite TEFS is significantly lower than that of ilmenite TEFS. The impurity content in vanadium titanomagnetite TEFS is higher than that in ilmenite TEFS. This might be one of the main factors resulting in the low leaching rate of Ti, so the leaching behaviors of various impurities under different conditions (temperature, acid/solid weight ratio, particle size, and initial sulfuric acid concentration) were investigated. The following trends were observed under different leaching conditions: The leaching rate of Fe increased rapidly and reached equilibrium quickly, that of Si increased quickly in the early stage and then decreased in the later stage, that of Ca increased initially and reached equilibrium later, and the leaching rates of Mg and Al increased gradually until the equilibrium was reached. The leaching rate of Fe was too rapid to be able to investigate its leaching kinetics, and the insoluble leached products of Si and Ca interfered with their leaching. The effects of leaching parameters on the leaching of impurities were further analyzed by X-ray diffraction (XRD) and scanning electron microscopy analysis. XRD data indicated that spinel is the major Mg- and Al-bearing mineral in TEFS. Mg and Al showed similar leaching behaviors, and their leaching conformed to a new model based on interface transfer and diffusion across the product layer, both of which affect the leaching rate.

Sulfide hemimorphite can be depressed by Fe³⁺ during flotation. In this study, the depression mechanism was studied by microflotation, inductively-coupled plasma mass spectrometry, local electrochemical impedance spectroscopy (LEIS), and X-ray photoelectron spectroscopy (XPS). Flotation test results suggested that sulfated hemimorphite can be depressed by Fe³⁺ across the entire pH range. LEIS, adsorption analysis, and XPS indicated that S species were adsorbed on hemimorphite as ZnS. The sulfide film was attenuated and no adsorbed Fe species were found after treatment with Fe³⁺. The results indicate that Fe³⁺ reacts with the ZnS film, which decreases the number S species, and this leads to hemimorphite depression.