Title: Processing Of Rare Earth Metals: Germanium, From Coal Fly Ash: A Comprehensive Review
Authors: Kholikulov D.B., Mutalibkhonov S.S., Khudoymuratov Sh.J.
Volume: 9
Issue: 11
Pages: 73-83
Publication Date: 2025/11/28
Abstract:
- Coal fired power plants generate billions of tons of fly ash annually, containing significant concentrations of rare earth elements (REEs) and valuable trace metals, particularly germanium (Ge). Germanium, essential for semiconductor, optoelectronic, and photovoltaic applications, is typically obtained as a byproduct during zinc and coal processing, making its recovery from coal fly ash an economically and environmentally viable alternative. This review synthesizes 70 scientific publications examining extraction technologies, separation methodologies, environmental implications, and economic feasibility of germanium and other rare earth metal recovery from coal fly ash. Hydrometallurgical methods, including acid leaching, solvent extraction, ion exchange, and adsorption techniques, demonstrate germanium recovery efficiencies exceeding 90% under optimized conditions. Emerging technologies such as flash Joule heating and biosorption present promising alternatives with reduced environmental footprints. Physical preconcentration methods, including flotation and magnetic separation, enhance subsequent chemical processing efficiency. Life cycle assessment and techno-economic analyses indicate that coal ash represents a substantial untapped secondary resource, with potential to recover REE worth approximately $4.3 billion annually. Integration of multiple processing stages and technological synergies offers pathways toward sustainable, economically profitable extraction within circular economy frameworks. Future research priorities include process scalability, waste stream management, automation, and hybridization of complementary extraction technologies.