Chloride–hypochlorite leaching and hydrochloric acid washing in multi-stages for extraction of gold from a refractory concentrate

• Chloride–hypochlorite leaching of gold from a pyritic concentrate was investigated.
• Formation of iron hydroxide layer on the pyrite particles decreased the gold recovery.
• Removing the layer by HCl and further leaching increased the gold recovery.

In this research, chloride–hypochlorite leaching of gold from a highly refractory pyritic concentrate was conducted and effects of stirring speed, temperature and particle size on the leaching rate were investigated. Results showed that the particle size had a significant positive effect on the gold recovery. In this system, iron hydroxide layer formed on the pyrite particles, decreasing the gold recovery. Removing this layer by hydrochloric acid and further leaching by chloride–hypochlorite increased the gold recovery. About 96% of gold was extracted from the concentrate after three stages of chloride–hypochlorite leaching/hydrochloric acid washing.