Abstract
With a telluride-type gold ore flotation concentrate as the research object, the Na2S + NaOH collaborative leaching process was applied to selectively separate tellurium before the cyanide leaching of gold and silver. The effects of process parameters including the type of leaching agent, the amount of leaching agent, liquid-solid ratio, leaching temperature, and leaching time on the leaching rate of tellurium were investigated. The results showed that the tellurium leaching rate could reach 78.14% under the optimum conditions of −0.038 mm (95%) grinding fineness, 80 g/L Na2S concentration, 30 g/L NaOH concentration, 4:1 liquid-solid ratio, 80°C leaching temperature and 3 h′s leaching time. The kinetic analysis showed that the leaching process of tellurium from telluride-type gold concentrate was a mixed type of chemical reaction control and diffusion control. The grain parameter in the leaching process was 0.26263 and the apparent activation energy E = 17.12 kJ/mol. Tellurium could be pre-leached from the telluride-type gold flotation concentrate through the Na2S + NaOH alkaline leaching process to achieve the effective separation of tellurium from noble metals, which, when eliminating the adverse effects of telluride on the leaching of gold and silver, provides new ideas for the extraction of rare element tellurium.
Highlights
Tellurium, a rare element, is widely used in metallurgy, chemical industry, electronics, aerospace, medical and other fields (Wang, 2011)
When HCl was used as the leaching agent, the leaching was the worst, with a leaching rate of 53.68%, while HCl converted the silver to insoluble silver chloride, which made it difficult for tellurium to be subsequently separated from the precious metal, and hexavalent tellurium could oxidize HCl and produce chlorine gas which can dissolve gold (Chen and Li, 2008)
The Na2S + NaOH cooperative leaching process is adopted in the pretreatment of telluride-type gold concentrate
Summary
A rare element, is widely used in metallurgy, chemical industry, electronics, aerospace, medical and other fields (Wang, 2011). As an additive in metallurgy, tellurium can improve the cutting properties of steel and copper, and enhance the hardness and wear resistance of "baffle alloys" (Wang, 2011); CdTe thin-film solar cells are a kind of solar cells with low price and their highest photoelectric conversion efficiency could reach 21%, holding the greatest promise for the future of thin film (Lee and Ebong, 2017; Geisthardt et al, 2015); Tellurium compounds such as ammonium trichloro(dioxo ethylene-O, O′)tellurate (AS101) have attracted much attention in cancer treatment (Sredni, 2012); besides, tellurium and its compounds have gradually become research hotspots in thermoelectric conversion, biology, and electronics (Lin et al, 2016; Ba et al, 2010; Chivers and Laitinen, 2015).
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