Ettler, and 6 co-authors, reported in late 2022 that metallurgical slags enriched in Ga (144–156 mg/kg) and Ge (285–441 mg/kg) were investigated as potential sources of these technologically critical elements. Conventional mineralogical techniques (SEM/EDS, EPMA) were coupled with automated mineralogy using a Tescan Integrated Mineral Analyzer (TIMA) to quantitatively determine the partitioning of Ga and Ge in the slags.
Both elements are primarily bound in the slag glass (90.5–95.4% of Ga and 95.9–96.7% of Ge). Extraction experiments conducted in 0.5 M H2SO4, 1 M HNO3, and 1 M HCl were used to simulate the hydrometallurgical recovery in view of the potential recovery of Ga and Ge. The leaching of Ga and Ge (and other valuable metals: Zn, Pb) was investigated as a function of time (2–12 hours), temperature (25 and 70°C), and particle size (original granulated slag and ultrafine-milled slag).
Compared to other treatments, the highest Ga and Ge extractability was found in 0.5 M H2SO4. No significant effect of the particle size, temperature, and time was observed on the Ga and Ge leaching. The optimum conditions for the extraction were: sulfuric acid treatment, original granulated slag (to limit the additional cost of crushing/milling), 25°C, and at least 6 hours of extraction. Despite the high extractabilities of Ga and Ge, more tests are needed to validate the economic feasibility of their full-scale recovery, especially due to the highly fluctuating prices of these elements on the global market.
Read on: https://www.sciencedirect.com/science/article/abs/pii/S0959652622042494
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