Tungsten extraction from scheelite hydrochloric acid decomposition residue by hydrogen peroxide

Abstract

Listen

Translate article

• W was leached from crude tungstic acid or residue by an efficient and clean method. • H 2 O 2 dissolved W from crude tungstic acid or residue selectively. • The W leaching ratio exceeded 96% for crude tungstic acid and 99% for the residue. • Pure tungstic acid was obtained from peroxotungstic acid solution. • More than 99.6% of W was precipitated from peroxotungstic acid solution. To reduce the amount of ammonia wastewater produced during traditional tungsten metallurgy, a novel method has been developed. Hydrogen peroxide was first used to selectively dissolve tungsten from crude tungstic acid and scheelite hydrochloric acid decomposition residue. Then, the peroxotungstic acid solution obtained was heated to prepare pure tungstic acid through thermal decomposition . The results showed that when the temperature was 40–45 °C, the molar ratio of hydrogen peroxide to tungstic acid was 2:1, and the reaction time was 60 min, more than 96 % of the crude tungstic acid was dissolved. Tungsten was easily leached from the hydrochloric acid decomposition residue under the conditions of a hydrogen peroxide concentration of 1.95 mol/L, 60 min, and 30 °C. The tungsten leaching ratio was 99.4 %. Using a decomposition temperature higher than 95 °C, seed addition amount more than 2.5 g/L, an acid concentration of 1 mol/L, and a reaction time of 120 min, the final W concentration in the mother liquor was 0.5 g/L and the decomposition ratio of peroxotungstic acid was more than 99.6 % with the product being WO 3 ·H 2 O. This research showed that hydrogen peroxide could dissolve tungstic acid and scheelite hydrochloric acid decomposition residue, and that the peroxotungstic acid obtained was readily decomposed into tungstic acid, which made it possible to leach scheelite cleanly and efficiently.