Optimization Role of Potassium Carbonate in the Leaching of Guizhou’s Carlin-Type Gold Ore System with Potassium Chlorate

This study addresses the environmental pollution and safety hazards associated with the cyanide leaching process in gold mining, proposing a more environmentally friendly and cost-effective potassium chlorate leaching method. The feasibility of this method was verified through thermodynamic analysis. Building upon single-factor experiments, the study utilized a response surface methodology to investigate the effects of potassium chlorate dosage, liquid-to-solid ratio, reaction temperature, and reaction pH on leaching efficiency. Results indicate that the order of influence on leaching efficiency is KClO₃ dosage > liquid-to-solid ratio > temperature > pH, with significant interactions observed between KClO₃ dosage and temperature. Optimal process parameters were determined as follows: initial potassium chlorate dosage of 21 g, liquid-to-solid ratio of 8.2/1, reaction temperature of 34 °C, and initial reaction pH of 12, achieving a gold leaching rate of 86.37%. To further optimize leaching efficiency, potassium carbonate was introduced to maintain system pH stability, promoting the formation of soluble iron carbonate complexes to reduce the re-encapsulation of minerals by Fe(OH)₃ and prevent gold from existing as Au(OH)₃, thus hindering gold leaching. Electrochemical studies revealed that increasing the potassium carbonate dosage enhances the dissolution of the passivation film. Under conditions of a potassium carbonate dosage of 0.75 mol/L and initial pH of 12, the gold leaching rate increased to 91.69%, with the system pH maintained above 11.68. Therefore, the addition of potassium carbonate effectively reduces the re-encapsulation of gold during leaching, further improving leaching efficiency.