Extraction of Gold from Tailings Using Ethaline Deep Eutectic Solvent.

Khuduwe, Marema Jack; Shemi, Alan; Ndlovu, Sehliselo

For over a century, cyanidation has been a highly effective method for extracting gold from gold-bearing sources. However, due to environmental, health, and safety concerns associated with this process, considerable efforts have been devoted to exploring the use of alternative, less toxic, and environmentally friendly reagents. In this study, a comparative cyanide and ethaline deep eutectic solvent (DES) leaching study of gold from the Witwatersrand gold tailings was undertaken. A Statistical Design of Experiments (DOE) was used for the screening and optimization of significant process factors to achieve optimal gold extraction. The factors investigated include the reagent concentration, leaching time, pulp density, and solution temperature. The subsequent gold recovery from leach solutions was undertaken using activated carbon (AC). Mineralogical analysis by X–ray diffraction (XRD) showed that the tailings consisted of quartz (72.13%), muscovite (7.49%), chlorite (2.65%), pyrophyllite (1.50%), clinochlore (1.30%), and other trace minerals. Mineral liberation analysis (MLA) employing the Sparse Liberation–Dual Zoom (SPL-DZ) method showed that gold was associated with iron oxides (Fe2O3, Fe3O4). Fire assay analysis (FAA) showed that the bulk tailings had a grade of 0.32 g/t Au. Ethaline was found to be the most efficient reagent, achieving up to 71.9% gold extraction, thereby exceeding the 46.9% gold extraction obtained via the cyanidation process. Moreover, gold recovery using AC from ethaline leach solution was 75%. The high gold extraction from tailings using ethaline suggests a potentially feasible alternative to the traditional cyanidation process, particularly for the processing of gold locked in iron oxide phases, offering the advantages of low toxicity, cost-effectiveness, and ease of preparation.

FIRE assay; TRACE elements; CHLORITE minerals; MINERAL analysis; FERRIC oxide

Minerals (2075-163X), 2024, Vol 14, Issue 12, p1239

2075-163X

Academic Journal

10.3390/min14121239