Enhanced acid leaching behavior of curing silver concentrate by oxygen pressure

In view of the high recovery value of flotation silver concentrate and the shortcomings of existing treatment technology, the technological route of sulfuric acid curing oxygen pressure acid leaching was put forward. Firstly, the flotation silver concentrate produced in zinc hydrometallurgy process was taken as the research object, and the strong oxidation of concentrated sulfuric acid was used to destroy the flotation residual organic reagent mineral inclusions. Secondly, the unique technical advantages of pressurized hydrometallurgy was used to oxidize and dissolve low-priced metal sulfides. Finally, the principle of technological process, the leaching behavior of Zn, Cu and In in the process of aging silver concentrate and oxygen pressure acid leaching, and the phase evolution law in leaching residue were emphatically studied. The results show that the P—O and —OH polar groups of residual flotation reagents on the surface of silver concentrate particles are destroyed by concentrated sulfuric acid oxidation, which avoids the formation of hydration film and mineral inclusions and promotes the efficient leaching of valuable elements. Under the condition of high-temperature oxidation and assisted by Fe3+/Fe2+ valence-changing ions, the mineral phase composition of silver concentrate is mainly composed of sphalerite(ZnS), zinc-iron spinel(ZnFe2O4), orpiment(FeS) and cuprous chloride(CuCl), and has evolved into elemental sulfur(S8) and ferric alum(MeFe3(SO4)2(OH)6, Me: 1/2Pb、 Na、 K). Appropriately increasing reaction temperature and initial mass concentration can promote the leaching of Zn, Cu and In, but too high temperature will aggravate the coprecipitation of indium and iron, and reduce the leaching rate of zinc and indium. Too high acidity will reduce the oxidation ability of oxygen to ZnS and Fe2+ and inhibit the dissolution of silver concentrate. Prolonging the reaction time and increasing the liquid-solid ratio are beneficial to the dissociation and leaching of silver concentrate. Increasing the oxygen partial pressure can enhance the oxidation ability of Fe3+, promote the oxidation of ZnS and ZnxFe(1−x)S, and facilitate the dissolution of silver concentrate. Under the conditions of reaction temperature of 155 ℃, initial mass concentration of 160 g/L, reaction time of 180 min, oxygen partial pressure of 0.8 MPa and liquid-solid ratio of 7 mL/g, the leaching rates of Zn, Cu and In in silver concentrate are 94.84%, 98.36% and 91.13%, respectively, and the enrichment rates of lead and silver in leaching residue are 2.88% and 7 754 g/t, respectively. © 2024 Central South University of Technology. All rights reserved.