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 degrees 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.