China Nonferrous Metallurgy

The similar physicochemical properties of indium and cadmium often result in an excessively high cadmium content in crude indium produced by current smelting processes, making it difficult to meet market purity requirements. The glycerol-potassium iodide method exploits the difference in affinity between indium and impurity elements toward iodine, selectively converting cadmium into iodides, thereby enabling targeted cadmium removal. In this study, crude indium was refined using the glycerol-potassium iodide process to deeply eliminate impurities. Single-factor experiments were conducted to determine the optimal refining conditions, followed by validation tests. The main conclusions are as follows. The optimal conditions obtained are a refining temperature of 190℃, a refining time of 10 min, a liquid-to-solid ratio of 8:1, and an I₂-KI excess coefficient of 3. Under these conditions, the cadmium content in the refined indium drops to 250 ppm, the indium purity increases to 99.93%, and the direct yield reaches 98.60%. The results demonstrate that this process efficiently removes cadmium from crude indium while also synergistically eliminating impurities such as arsenic, silicon, and thallium. Consequently, indium purity is significantly enhanced without sacrificing a high direct yield. These findings provide technical support for efficient preliminary refining of crude indium.