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

The majority of the refractory gold and\nsilver occurs in occlusion in sulphides, then precious metal dissolution is\npossible by first oxidizing auriferous sulfide concentrate using sodium\nhypochlorite-sodium-hydroxide solution followed of pressure cyanidation of the\noxidized concentrate, for the extraction of precious metals. This process was\nconducted and evaluated under cyanide and oxygen pressure. This versatile\napproach offers many advantages, including low temperatures, low pressure and\nless costly materials of construction than conventional pressure oxidation. In\nthis study, the effect of oxygen pressure, concentration of sodium\nhypochlorite, temperature, and initial pH, in precious metals recovery and As\nremoval were evaluated using a 24 factorial design. Characterization\nof the ores showed that pyrite and arsenopyrite were the main minerals present\non the concentrate. The best results for gold extraction were obtained with oxygen\npressure of 80 psi, 10% (w/w) sodium hypochlorite, temperature of 80℃, at pH = 13, and\na constant stirring speed of 600 rpm. These conditions allowed an approximated\n60% of gold and 90% of silver extractions in 1 hr.