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
silver occurs in occlusion in sulphides, then precious metal dissolution is
possible by first oxidizing auriferous sulfide concentrate using sodium
hypochlorite-sodium-hydroxide solution followed of pressure cyanidation of the
oxidized concentrate, for the extraction of precious metals. This process was
conducted and evaluated under cyanide and oxygen pressure. This versatile
approach offers many advantages, including low temperatures, low pressure and
less costly materials of construction than conventional pressure oxidation. In
this study, the effect of oxygen pressure, concentration of sodium
hypochlorite, temperature, and initial pH, in precious metals recovery and As
removal were evaluated using a 24 factorial design. Characterization
of the ores showed that pyrite and arsenopyrite were the main minerals present
on the concentrate. The best results for gold extraction were obtained with oxygen
pressure of 80 psi, 10% (w/w) sodium hypochlorite, temperature of 80℃, at pH=13, and
a constant stirring speed of 600 rpm. These conditions allowed an approximated
60% of gold and 90% of silver extractions in 1 hr.
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