Recovery of tellurium from high tellurium-bearing materials by alkaline sulfide leaching followed by sodium sulfite precipitation

A novel process of tellurium recovering from high tellurium-bearing materials by alkaline sulfide leaching followed sodium sulfite precipitation is developed. The influences of Na2S concentration, leaching temperature, liquid to solid ratio and leaching time were studied during the leaching process while the effects of Na2SO3 excess coefficient, reduction temperature and reduction time on tellurium precipitation from alkaline sulfide solutions were investigated. It was found that 91.24% of Te and 92.51% of Sb were extracted into leaching solution under the optimum conditions: Na2S concentration 100 g/L, 80 °C of leaching temperature, 10:1 mL/g of liquid to solid ratio and 60 min of leaching time. 98.85% of Te was precipitated selectively at 30 °C for 15 min with addition of 1.5-fold excess of Na2SO3 while the antimony precipitation was closed to zero. XRD pattern and chemical analysis indicated that the precipitate was elemental tellurium with a purity of 99.11%. SEM image showed that the shapes of elemental tellurium were spindle with an average particle size of 1-2 μm. Antimony in Te-free solution was recovered as NaSb(OH)6 by hydrogen peroxide oxidation.