Green Hydrometallurgical Extraction of Gold from Low-Grade Sulfidic Ore Using a Choline Chloride-Urea Deep Eutectic Solvent and Iodine

Gold leaching from low-grade sulfide ores using environmentally benign alternatives to cyanide has attracted increasing attention in hydrometallurgy. In this study, a low-grade sulfide gold ore assaying ۰.۶ g/t Au and dominated by pyrite with quartz as the main gangue mineral was leached using a choline chloride-urea (۱:۲) deep eutectic solvent (DES) in the presence of iodine. The effects of temperature, particle size, iodine concentration, and pulp density on gold recovery were systematically investigated. Gold recovery increased with both temperature and time, reaching ۹۶.۲% at ۸۰ _x۰۰۱۷_۶C, while finer particles improved extraction efficiency, with the highest recovery of ۹۴.۸% obtained for the -۵۳ _x۰۰۰۳_bc m fraction. Increasing iodine concentration strongly enhanced gold dissolution up to a practical plateau, and ۱۰ g/L I۲ was identified as the most efficient reagent level, yielding ۹۳.۵% recovery. In contrast, increasing pulp density adversely affected leaching performance, with recovery decreasing from ۹۵.۱% at ۵۰ g/L to ۶۸.۷% at ۳۰۰ g/L, indicating stronger mass transfer limitations at higher solid loadings. Kinetic analysis showed that the leaching process was best described by the Ginstling-Brounshtein diffusion-controlled model, with rate constants increasing from ۰.۰۰۱۲ min at ۴۰ _x۰۰۱۷_۶C to ۰.۰۰۵۱ min at ۸۰ _x۰۰۱۷_۶C and excellent model fits (R۲ = ۰.۹۸۴-۰.۹۹۳). Arrhenius analysis gave an activation energy of ۳۲.۵ kJ/mol and supported a diffusion-controlled mechanism. Overall, the choline chloride-urea-iodine system demonstrated strong potential as a green and technically feasible alternative for gold recovery from low-grade sulfide ores under relatively mild operating conditions.

کلیدواژه ها:

Gold leaching ، Deep eutectic solvent ، Choline chloride-urea ، Iodine ، Sulfide ore ، Diffusion-controlled kinetics ، Ginstling-Brounshtein model