Synthesis of intermediate-valence tungsten oxides via carbon reduction and their dissolution behavior in hydrogen peroxide

Abstract

In this research, an ammonia-free recycling method for tungsten scraps is proposed, involving the preliminary oxidation of waste tungsten carbide, reduction to intermediate-valence tungsten oxides, and subsequent dissolution in hydrogen peroxide to produce peroxotungstic acid (PTA), a valuable precursor for tungsten products. The study emphasizes stabilizing intermediate-valence tungsten oxides during carbon reduction to achieve higher dissolution efficiency in hydrogen peroxide. Experimental results demonstrate that controlling the roasting conditions effectively regulates the degree of oxidation, while optimization of carbon reduction parameters ensures stable formation of intermediate-valence tungsten oxides. Dissolution experiments further confirm that tungsten dioxide (WO₂) serves as an optimal precursor due to its high solubility and relatively low hydrogen peroxide consumption. Under optimized carbon reduction conditions (1000 °C, WO₃:C molar ratio of 1:2), process enhancements enabled a dissolution rate exceeding 97 %, ensuring efficient tungsten recovery while reducing hydrogen peroxide consumption.