Tellurium in gold processing

Dr. Laurence G. Dyer

Tellurium demand has risen significantly (and is projected to continue as such) as cadmium telluride materials are a vital component in photovoltaic cell technology. Currently the majority of supply is produced via conventional processing of copper anode slimes, however the scope for expansion of these activities is limited and actually expected to decline with decreasing global copper ore quality. Thus exploiting alternate sources of the metal is of great importance.

Several gold deposits worldwide contain significant proportions of refractory telluride minerals. Two regions (Kankberg, Sweden and Dashuigou and Majiagou, China) reportedly produce tellurium as a byproduct of their gold operations, but there is limited information regarding their process. The Emperor process in Fiji produced tellurium between 1975 and 1986, first oxidising the tellurium with calcium hypochlorite to release the gold, then a reducing leach (Na2S) to solubilise the tellurium and finally precipitation with Na2SO3 to recover it from solution. While this section of the plant was abandoned when the Te price dropped, it displays a viable pathway for production from gold ore.

As the pretreatment options for refractory gold processing vary significantly in their impact on the concentrate, the pathway and potential for tellurium recovery will also differ. For example Kalgoorlie consolidated gold mines (KCGM), Western Australia historically operated an oxidative roast prior to cyanidation, but recently switched to ultra-fine grinding. This alters tellurium speciation and leach chemistry. Where the bulk of previous work on the topic focussed on gold extraction, this paper uses behaviour of tellurium in simulated systems to describe the likely behaviour of tellurium under different pretreatment regimes and the potential impact on its recovery.