The Preparation Of High Purity Indium

With the development of high technology, the application of high purity metals is more and more wide. High-purity indium as a very important industry material is used widely in some fields such as electronic components, ITO thin-film, semiconductorand metallorganic compound etc.. It is important to research its production technology in order to improve economical profit in indium industry and promote the development in related industry.The status of the study about indium, properties, applications and production of indium and the recent development on preparation of indium at home and abroad were reviewed in this dissertation. The new technology, preparing 5N indium by vacuum distillation-electrorefining from rich indium(99.995%), was brought forward.Based on theoretical analysis new technology of preparing 5N indium is obtained through experiments.The theories of vacuum distillation and the electrochemical refining were analyzed. Regarding the unique advantage of vacuum distillation, we adopt the vacuum distillation instead of the traditional way using reagent to remove cadmium and thallium from the rich indium. Then the electrochemical refining process was used to remove elements that have different electric potential with indium. And the craft conditions were researched and the optimum technology paramenters as follows:(1)According to the theoritical analysis of vacuum distillation, experiments were carried out in an inner-heated vacuum furnance. The influences, of the distillation time and the distillation temperature on the diversification of the evaporation rate, and the removal behaviors of impurity elements were discussed. The best experimental result has been reached. The optimum technology paramenters to remove cadmium and thallium from the rich indium are distillation time 120min, distillation temperature 950℃and vacuum degree 10～20 Pa. On the above condition, the content of impurity Cd,Tl can less than thelevel of "5N" high purity and the recovery ratio of indium can attain 97.72%.(2) The influences of some technological parameters such as the pH of electrolyte, concentration of In³⁺ and bath voltage on the purity of indium were discussed. The optimum technology parameters are electrolyte temperature 25℃, In³⁺100 g/L, pH 2.5～3, bath voltage 0.3V, chlorinated soda 80g/L, gelatin 0.5g/L, current density 60～80A/m².(3) The purity of the sample was examinationed by Glow Discharge Optical Emission Spectrometer, and the result indicates that the 5N high-purity indium in GB8003-87 was obtained by the vacuum distillation and electrorefining process. And the contents of impurity elements reaches the level of the 6N high purity indium.