Gold Leaching of an Auriferous Ore by Glycine Solutions and its Recovery on Activated Carbon

摘要

Cyanide utilized in the hydrometallurgical industry represents a great environmental risk due to its high toxicity, this is why an alternative method to cyanidation has been developed with the use of glycine in the recovery of gold. Glycine is a non-toxic and low-price leaching agent. In addition, gold-glycine complex can be easily adsorbed on activated carbon. In recent years, the use of organic species (e.g., amino acids as glycine) has been raised for leaching processes. Glycine-based leaching is competitive with cyanidation technique regarding costs, performance and gold recovery yields. Previous metal characterization of the ore showed that gold, silver and copper are present in concentrations of 11 g/ton, 26 g/ton and 0.05 %, respectively. Mineralogic characterization indicated that the ore is constituted by 75 % of silicates, 24 % of clays and 1 % of sulfides. Glycine-based leaching process was conducted, two times, over 96 hours, at pH 11 and hydrogen peroxide concentration of 1 %. The influence of glycine concentration (1 M, 1,5 M and 2 M) and temperature (40 °C, 50 °C and 60 °C) over gold recovery yield was studied. The increase in glycine concentration implied an increase in gold recovery yields. The temperature is also related directly to the gold recovery yield, this relationship is in agreement with predicted results of Arrhenius equation. Gold recovery yields after the leaching process were above 70 %. Finally, the gold-enriched solution followed over adsorption on activated carbon.