Recovery of Gold from Transition Gold Ores via Response Surface Methodology—Process Variables Optimisation

The depletion of free-milling and oxide gold ores has necessitated the beneficiation of gold from complex transition gold ores which contain pyrite and carbonaceous matter (CM) that poses numerous recovery challenges. This study offers a comprehensive optimisation of cyanidation parameters by Response Surface Methodology (RSM) to enhance gold recovery from these ore types. Eight critical factors (dissolved oxygen (6-30 ppm), pyrite content (0-1%), CM content (0-2.5%), cyanide concentration (250-750 ppm), lead nitrate dosage (0-200 g/t), activated carbon concentration (0-20 g/L), particle size (75-106 µm), and gravity pre-concentration (Yes/No)) were systematically assessed using the Central Composite Design (CCD). With 94 design experimental runs undertaken in the laboratory, a statistically significant reduced cubic model (F-value = 14.14, p < 0.0001) was developed which was able to explain 83% of recovery variability (R<sup>2</sup> = 0.831). The most significant parameters were the concentration of activated carbon (p < 0.0001) and the content of CM (p < 0.0001). Per the interactions, significant improvement in gold recovery was observed when activated carbon contents were increased. Validation experiments recorded experimental recoveries of (89-95%) which strongly aligned with the predicted recoveries. This projected the robustness of the model to accurately predict. Consequently, this framework can serve as a basis for process and reagent optimisation for mining companies treating complex transition gold ores.