Sphalerite passivation during the leaching sodium nitrate and sulphuric acid solution

Abstract

Zinc is extracted from sphalerite and complex concentrates by pyrometallurgical or hydrometallurgical processes, whereby the hydrometallurgical processes have received considerable attention in recent years. Thair application provide better metal recoveries and reduced emission of gaseous and toxic agenses in the environment. This paper studies the leaching process of the sphalerite with sodium nitrate in sulphuric acid solution. Chemical reactions of leaching and their thermodynamic probabilities are predicted based on the calculated Gibbs energies and analysis of E-pH diagrams. Thermodynamic analysis, experimental data, chemical, XRD, TG/DTA, and SEM/EDX analyses for the phases present in both the complex concentrate and leach residue were performed to determine the leaching process. Elemental sulphur is the main solid product of reaction, and a minor amount of sulphide sulphur is oxidized to sulphate during the leaching. It also indicates that the sulphur precipitated at the particle surfaces, and slowed down the rate of the leaching process.