Recycling of tailings from the Barruecopardo tungsten deposit for the production of glass

Abstract

Tailings from tungsten mining activities in the vicinity of Barruecopardo (Salamanca) represent high environmental pollution. In this paper we present a study of the use of these wastes as raw materials for the manufacture of glass. This procedure aims to contribute to environmental remediation of mining areas through vitrification, a process which offers an alternative for stabilization of hazardous wastes. In addition, the marketing of the obtained product would provide an additional income to the mining areas. The chemical composition of the tailings to be used as raw materials was determined by X-ray fluorescence and their mineralogy by X-ray diffraction. Wastes are of granitic composition enriched in potentially toxic elements. For this study, a representative sample of mining wastes of sandy grain size was used to make the glass. On the basis of its composition, glass was formulated by adding 29.28 mass% of CaCO3 and 14.03 mass% of Na2CO3 and a green glass was produced. Crystallisation temperatures, obtained by DTA, were 875 and 1022 °C and the melting temperature was 1175 °C. The transition temperature of glass was of 644 °C. The temperatures for the fixed viscosity points, and the working temperatures were obtained. A thermal treatment induced devitrification to produce a glass-ceramic made of nepheline and wollastonite. Leaching tests of the obtained glass confirm its capacity to retain potentially toxic elements.