Study On The Process And Mechanism For Comprehensive Recovery Of Gold,Silver,Lead And Zinc From Pb-Ag Residue

During the traditional process of zinc hydrometallurgy, a lot of Pb-Ag residues are produced in the hot acid leaching stage. And most of the lead and silver from smelting of raw materials and a small part of the zinc metal remain in the Pb-Ag residues because of the characteristics of the hydrometallurgy process. However, the ore properties of Pb-Ag residues are so special that, at present, there is no effective method for comprehensive recovery of valuable metals from it and the residues are mainly stored up. Simple storage not only causes a waste of resources, but also leads to serious pollution in the surrounding environment resulting from heavy metals and fine particulates. Therefore, it is of important significance to comprehensively recover and utilize the valuable minerals in Pb-Ag residues. In this paper, the Pb-Ag residues produced by lead zinc smelter in the northwest of China were targeted and systematic studies had been involved to recover valuable minerals from Pb-Ag residues by hot acid leaching combined with flotation process and the optimal process parameters were obtained. Meanwhile, the characteristics of the minerals in the Pb-Ag residues, which differed from natural minerals, were analyzed by XRD, SEM, zeta potential, XPS as well as quantum chemistry. The main research results were:Mineralogy study indicated that, fine content in Pb-Ag residues was high with -53?m content accounting for 88.14% of the total. Lead, zinc and silver minerals were widely distributed in the range of -53 ?m. Zinc sulfide minerals embedded in zinc ferrite minerals in Pb-Ag residues were mostly fine particles wrapped by zinc ferrite.Using the combined hot acid leaching-flotation process, results showed that the zinc-silver concentrate was obtained with zinc grade of 22.03%, silver grade of 3286.67g/t, gold grade of 16.31g/t and zinc recovery at 59.17%, silver recovery at 85.75%, gold recovery at 90.28%. In the hot acid leaching stage, the recovery rate of zinc in the leachate was 27.46% with a weighted recovery rate at 86.63%; the lead was obtained at the grade of 45.85% and the recovery of 85.88% after a flotation-thickening-flotation The results of MLA and chemical analysis suggested that hot acid leaching stage presented both positive and negative sides on the following flotation stage.It can be verified by mineral property and quantum chemistry simulation as well as calculation that, a-ZnS and ?-ZnS possessed similar flotation characteristics. Likely, lead sulfate and anglesite had similar flotation characteristics with each other. The relationship between electronic structure and floatability of minerals provided a theoretical basis for reagent system and reaction mechanism.When the pH value was above 6, butylamine aerofloat showed collecting property on P-ZnS; at the pH value ranging from 1.8 to 2.2, Cu²⁺ cannot effectively activate ?-ZnS, but with Na₂S coexisting with Cu²⁺, ?-ZnS can be dramatically activated. Zn²⁺ and Fe³⁺ can inhibit P-ZnS with an increasing effect when the concentrations become greater. Both amyl xanthate and MTD could absorb onto the surface of lead sulfate by chemical absorption, and this absorption can be intensified by Na₂S.