Experimental Study of Pretreatment of a Refractory Gold Mineral for the Recovery of Gold in the Goldmins SRL Mining Company

Abstract

A significant sample of “refractory tails” product of a gravimetric concentration of primary ore, provided by Empresa Minera Goldmins SRL, with an approximate gold content of 31 g/t, was treated experimentally at the laboratory level. It was subjected to a mineralogical characterization by Fluorescence and X-Ray Diffraction, reporting a sulfur (S) content of 15%, iron (Fe) 23%, silica (SiO₂) 7%, and arsenic (As) 3% as the main cyanicide. Based on the result of the characterization, two important stages were developed for the recovery of gold from these tailings: pretreatment and conventional cyanidation. The pretreatment involved grinding to two particle sizes (75 and 105 µm) followed by oxidation using hydrogen peroxide (H₂O₂). Subsequently, stirred tank cyanidation was carried out. It was possible to develop nine experimental tests considering constant the parameters of the percentage of solids, temperature, speed of agitation, and pH. Including a leaching without oxidation, whose recovery was less than 10% for 24 h. The remaining eight tests, oxidized and cyanide, reported recoveries above 59% for the same time. The best recovery, 84% for 24 h, was under the following conditions: grinding at −75 μm, oxidation with H₂O₂ at 25 g/L, and leaching at a NaCN concentration of 3.77 g/L.