Effect of Pretreatment of Sulfide Refractory Concentrate with Sodium Hypochlorite, Followed by Extraction of Gold by Pressure Cyanidation, on Gold Removal

Abstract

The majority of the refractory gold andsilver occurs in occlusion in sulphides, then precious metal dissolution ispossible by first oxidizing auriferous sulfide concentrate using sodiumhypochlorite-sodium-hydroxide solution followed of pressure cyanidation of theoxidized concentrate, for the extraction of precious metals. This process wasconducted and evaluated under cyanide and oxygen pressure. This versatileapproach offers many advantages, including low temperatures, low pressure andless costly materials of construction than conventional pressure oxidation. Inthis study, the effect of oxygen pressure, concentration of sodiumhypochlorite, temperature, and initial pH, in precious metals recovery and Asremoval were evaluated using a 24 factorial design. Characterizationof the ores showed that pyrite and arsenopyrite were the main minerals presenton the concentrate. The best results for gold extraction were obtained with oxygenpressure of 80 psi, 10% (w/w) sodium hypochlorite, temperature of 80℃, at pH = 13, anda constant stirring speed of 600 rpm. These conditions allowed an approximated60% of gold and 90% of silver extractions in 1 hr.