Roadmap for recycling of germanium from various resources: reviews on recent developments and feasibility views

Germanium as a strategic metalloid is widely used in high-tech devices. The most crucial germanium resources are rare and limited to zinc minerals, i.e., especially zinc sulfides and coal-related products. Other than coals and zinc minerals, materials such as WEEEs (wastes from electrical and electronic equipment) and catalysts are considered secondary resources of germanium. Since there is no specific mineral for germanium, it should be extracted from the resources above as a by-product. Primary resources contribute to 70% of germanium production, whereas the rest is produced from recycled materials. The world refinery production of germanium enhanced by about 7% in 2020 compared to 2019. This growing demand for germanium encourages the industry to find other resources and extraction technologies. Germanium can be recovered after leaching of different resources in acidic, water, or alkaline media followed by processing using various hydro/pyrometallurgical methods. Several reviews and articles have been published to review the resources and processes for the germanium separation. However, no one did not present a final road map from feasibility views and environmental aspects. This review proposes a road map for germanium recycling based on the performance and economic availability, process efficiency, operational issues, and process feasibility.