Sustainable and efficient extracting of tin and tungsten from wolframite – scheelite mixed ore with high tin content

Abstract

The separation and extration of tin and tungsten from wolframite – scheelite mixed ore with high tin content is urgently needed given the increasingly exhaustion of the high-grade tungsten ore. However, current tungsten hydrometallurgy technologies suffer from considerably drawbacks, such as low recovery of tin, high consumption of chemicals, and large sodium salt waste water discharge. In this study, a novel reduction melting pretreatment method was used for the thorough separation of tin in the purification process and to improve the recovery of tin and tungsten. In this process, tin was first separated from tungsten and recovered in the form of SnS. Approximately 99% of tin was volatilized under the optimized conditions of the [WO3]/[CaSO4]/[C] molar ratio of 1:2:4 after blowing nitrogen at a flow rate of 3 L/min for 15 min, and the tin content in the reduction melting products was less than 0.05%. Meanwhile, wolframite was converted to scheelite and ferric calcium tungstate that then were easily digested by the mixed sulphuric-phosphoric acid solution, and the leaching ratio of tungsten reached 99%. The leaching residue of calcium sulfate was reused as the sulfurizing reagent in the reduction melting process. The efficient separation and extraction of tin and tungsten of this technology indicated its potential for industrial application.