Mojtaba Esmailzadeh

Sphalerite, the primary ore for zinc production, is traditionally processed via pyrometallurgicaland hydrometallurgical methods that generate significant environmental challenges, including SO2emission and water contamination. Biocompatible alternative methods, such as solvometallurgyusing deep eutectic solvents (DESs), are being developed. In this research, direct chemical leachingof zinc sulfide concentrate (ZSC) was done in choline chloride:p-toluenesulfonic acid (Ch-PTSA)without any oxidant. The FTIR analysis indicated that the synthesis of DES has been performed, andits stability during the leaching was confirmed by minor changes in bonds. Response surfacemethodology was used to investigate effect of time, temperature, DES/ZSC, and stirring speedparameters. Analysis of variance showed that all parameters have a first-order effect and nointeraction effect on zinc leaching. Optimum conditions were determined as follows: time of 26 h,Journal Pre-proof2DES/ZSC 10, temperature of 90 °C, and stirring speed of 850 rpm. Under optimum conditions, morethan 90 % of zinc was leached directly without using any pretreatment and addition of oxidationagent, or SO2 emission. Also, ZSC characterization via FESEM-EDS before and after leaching provedalmost complete zinc extraction. Therefore, Ch-PTSA DES can be used as a suitable solvent for thedirect dissolution of zinc with a high dissolution efficiency. Molecular dynamics simulationselucidate that Zn2+ exhibits preferential, highly ordered coordination with Cl and N sites in Ch, whileinteractions with SO2, H, and OH of PTSA moieties remain comparatively weak.