Effects on Copper Leaching Rate in High-arsenic Copper Smelting Ash by Roasting and Its Thermodynamics

The insoluble smelting ash with 22% arsenic content,which was obtained from copper pyrometallurgy,was treated by oxidizing roasting followed by copper leaching process with dilute acid.The effects of roasting time and temperature on the copper leaching rate were investigated and its thermodynamics was then analyzed.The results showed that copper leaching rate reached 45% by directly leaching with 2 mol/L H2SO4 at a liquid-to-solid ratio of 4∶1.After roasted at a temperature of above 500 ℃ for 1 h,the copper leaching rate can be up to 98% at the same conditions.Meanwhile,more than 95% arsenic trioxide in the ash can be recovered.Thermodynamic analysis and calculations showed that the copper compound was changed to CuSO4 and CuO liable to be leached,resulting in leaching rate increased.