Effect of hydrogen peroxide and lead(II) nitrate on gold cyanide leaching of Malaysian mesothermal deposit gold ore

The gold extraction from Malaysian mesothermal lode gold ore through the cyanidation method was performed. The effect of hydrogen peroxide (H2O2) and lead nitrate Pb(NO3)2 were investigated on the percentage of gold recovery. The statistical analysis method using a response surface design-central composite design was applied to find the optimum condition for gold extraction. The studied parameters were NaCN concentration (300-500 ppm), H2O2 concentration (205-410 ppm), and Pb(NO3)2 concentration (50-150 ppm). It was found that increasing the amount of NaCN and H2O2 as well as decreasing the amount of Pb(NO3)2 in the studied range, increased the gold recovery. The analysis of variance suggested the linear model for the gold extraction with the optimum condition at 467.3 ppm NaCN, 94.96 ppm Pb(NO3)2, and 340 ppm H2O2. The gold extracted from the ore at the optimum condition was 88.97% as compared to 62.02% from conventional cyanidation. The characterization study of the gold ore indicated that the finely gold particles interlocked in the aluminosilicate phase (grain size of ~10.0 μm). The Van’t Hoff differential method justified that the cyanidation was of second order with a specific reaction rate of 0.0501/hour.