Purification principles and methodologies to produce high-purity tellurium

This review paper reconstructs the current development of tellurium purification technologies with their setups to obtain high-purity tellurium. Since the uptrend of the solar industry in the early 2000s, the demand for tellurium, especially high-purity quality, has increased sharply to enable the production of e.g. solar modules, solar panels and semiconductor. This paper focuses on both primary as well as secondary routes of purification. Especially the recycling aspects can contribute to a close-to-zero-waste process and circular economy horizons. For this purpose, a general introduction on tellurium sources and global primary production along with price trends were provided to show the path up to high purity grades. Recovery processes through secondary sources such as CdTe and Bi2Te3 were introduced, followed subsequently by a thorough review on two refining methods for tellurium. Vacuum distillation and zone refining processes were discussed in terms of their effectiveness in purifying tellurium as well as their challenges by reviewing relevant research. Through this review, several knowledge gaps can be identified to motivate further development of refining processes.