China Nonferrous Metallurgy

There are valuable elements such as gold, silver, lead, bismuth, arsenic, selenium and tellurium in Venturi sludge. When it is returned to Kaldor furnace for smelting, tellurium forms compounds with gold and silver in Venturi sludge, and enter smelting slag, resulting in loss. If tellurium is removed before Venturi sludge returning to Kaldo furnace, not only the tellurium resource is recycled, but also the gold and silver recovery rate is increased. In this paper, by using the inhibition of lead leaching by sodium sulfide, the experiment of NaOH-Na2S leaching Venturi sludge and preparation of tellurium dioxide and crude selenium was carried out. The following conclusions are obtained. The leaching rate of tellurium and selenium can reach 90.06% and 30.58% respectively under the optimum conditions of sodium hydroxide concentration of 100g/L, sodium sulfide addition of 4%, reaction temperature of 80℃ and alkali leaching for 2h. Compared with the process without sodium sulfide, the quality of crude tellurium dioxide can be increased from 80% to more than 90%. The results of kinetic analysis show that the leaching of tellurium in the sulfide alkali leaching stage of Venturi sludge is controlled by the diffusion model. This process can not only improve the recovery rate of gold and silver, recover tellurium resources, but also improve the production efficiency. The purity of tellurium dioxide produced is more than 99%, and the purity of crude selenium by-product is more than 90%. The economic benefit is remarkable.