EXTRACTION OF TELLURIUM FOR USE IN HIGH TECHNOLOGY AS A BYPRODUCT OF CURRENT MINING PROCESSES

Tellurium is classified as a (near-)critical element due to low average crustal abundance (3 μg kg^-1), extraction as a byproduct, and increasing use in high technology applications, particularly high efficiency solar panels. Currently, nearly all Te is recovered as a byproduct of Cu extraction, but, although it is not recovered, Te is also enriched in some Au/Ag ore bodies. The goals of the present study are to assess the distribution of Te between host minerals initially and throughout the extraction process and to identify points in the process when Te might be recovered.

Preliminary mass balance results indicate less than 2% of Te present in Cu ore is recovered, with particularly high losses during initial concentration of Cu ore minerals by flotation. Tellurium is principally present in the ore in tellurides (e.g., PbTe, Bi₂Te₃, and Ag-S-Se-Te phases identified using electron microprobe) with low substitution into sulfides (~10 mg kg^-1 Te in bulk pyrite and chalcopyrite). This work has also identified Te accumulation in solid-phase intermediates that could be further processed to recover Te, inducing: smelter dusts (200 mg kg^-1) and a precious metal concentrate (1300 mg kg^-1), where Te is present in both reduced and oxidized forms, as determined by X-ray absorption spectroscopy.

Tellurium is not currently recovered from any of the several high-grade Au/Ag telluride deposits in the Western US, but mines estimate capacity at tens of tons Te per year with marginal economics. This is largely due to a lack of knowledge of Te behaviour during the Au extraction process, but preliminary results indicate substantial enrichment of Te (100 mg kg^-1 relative to 6 mg kg^-1 in average ore) in several solid-phase extraction intermediates, suggesting the potential for Te recovery. These results clearly indicate that large gains in Te available to high technology industries could potentially be obtained at minimal expense from operating mines.