Conversion of zinc hydrometallurgical waste to glass-ceramic materials

Abstract

The possibility of conversion of zinc waste into glass-ceramic materials had been studied. Twenty-five different glass compositions were designed. Zinc waste and other raw materials were melted at 1450°c for 1 hour. Twenty-three glasses melted homogeneously. The crystallization behavior studied by DTA showed that T[subscript g] and T[subscript c] of the twenty-five glasses were all between 550-630°C and 680-870°C, respectively. After heat-treatment at four different temperature ranges, the microstructures and properties of the glass-ceramics were examined. The results demonstrated that wollastonite-ferroan, pyroxene, anorthite quartz, and cristobalite formed either as single phase or mixed phases strongly depended on glass-compositions and heat-treatment temperature. The maximum bending strength was -119.26 MPa. The leachability characteristic of Pb in the glass-ceramics was also examined by Toxic Characteristic Leaching Procedure (TCLP). The leach out concentrations of Pb in the glass-ceramics containing pyroxene phase were all higher than the USA regulatory limit (5 ppm) whereas those of the glass-ceramics contained wollastonite-ferroan and cristobalite phases were all lower than the limit. The thermal expansion coefficients of the glass- ceramics containing pyroxene phases were the highest whereas those of the glass- ceramics containing mixed phases were mostly lower.