Oxidative Dissolution of Tungsten Metal in Na₂CO₃ under Ar–O₂–CO₂ Atmosphere

Abstract

A novel process for the recycling of tungsten from hard tool scraps using carbonate molten salts is proposed. As a fundamental study, the oxidative dissolution of tungsten metal into molten Na2CO3 under Ar-O2 and Ar-O2-CO2 atmospheres was investigated at 1173 K. The results of the oxidative dissolution experiments and the detection of CO gas evolution by infrared spectroscopy revealed the existence of multiple oxidation mechanisms by peroxide/superoxide ions and carbonate ions. The feasibility of each oxidant was discussed by calculating potential-CO 2 diagrams in molten Na2CO3 at 1173 K. The relationship between the potential and the reaction was investigated using cyclic voltammetry and potential-CO 2 diagrams.

Redox properties of the carbonate molten salt Li2CO3Na2CO3-K2CO3

“…stable in the carbonate salt. It is oxidised to Na2WO4 with formation of C. Yasuda et al thermodynamic calculations in Na2CO3 molten salt at 1173 K led to the same result[9].…”

“…Carbonate molten salts can also be used for metals recycling. Yasuda et al used sodium carbonate to dissolve and to recycle tungsten and tungsten carbide [9]. Thermodynamic, chemical and electrochemical properties of alkali carbonate molten salts have already been presented [10]- [13].…”