Characterization and solidification of heavy metals in sintered solid-waste ceramics made from zinc-extraction kiln...

Zinc-extraction kiln slag is a hazardous solid waste rich in heavy metals. It is a great challenge to utilize it economically and harmlessly. This study aims to convert this zinc-extraction kiln slag (proportion of 50-60%) into solid-waste ceramics, by simultaneously utilizing other solid waste, fly ash, and desulfurization gypsum. By using X-ray diffraction, leaching experiments, and SEM analysis, the paper studied the solid-waste ceramics 'ability to solidify heavy metals. Under optimal conditions, C5 (zinc-extraction kiln slag, desulfurization gypsum, and fly ash with mass percentages of 60:20:20, at a sintering temperature of 1180 °C) shows an excellent performance with 43.02 MPa bending strength and 0.74% water absorption. The solidification ratios of Cr, Mn, Ni, Cu, and Zn were all exceed 97%. The main phases in the solid-waste ceramics were diopside and hematite. Diopside can efficiently solidify Zn, Mn, and Ni, while Cr and Cu can be solidified in the minor phase of spinel. During the sintering process, the ceramics produced the liquid phase, which promoted crystallization for solid solution of heavy metals and accelerated densification by elimination of pores. The ceramic system with diopside as the main phase not only shows excellent performance but also effectively solidifies heavy metals. Therefore, it is suitable for the resource utilization of metallurgical solid wastes containing heavy metals.