An eco-friendly processing of stainless-steel slag and copper slag: Crystallization control, modification and detoxification

Abstract

Stainless-steel slag and copper slag are two kinds of bulk and unmanageable metallurgical hazardous wastes. The resource utilization and safe disposal of these slags have attracted extensive attention worldwide. Based on high temperature modification, an eco-friendly processing of stainless-steel slag and copper slag was proposed in this study to achieve control crystallization and heavy metal Cr detoxification. The effects of different mass ratios of stainless-steel slag to copper slag on the transformation of crystalline phase, the Cr enrichment and the detoxification efficiency of modified slag were investigated. The results indicated that the modified slag with the stainless-steel slag to copper slag mass ratio of 8:2 had coarse spinel grain, no obvious other crystalline phases existed, Cr could be selectively enriched to spinel phase, and the Cr enrichment degree was the highest, reaching 98.76 %. Meanwhile, the leaching concentration of Cr and other hazardous elements (Cu, Zn, Ni, Pb and As) was far lower than the leaching limit of hazardous component mass concentration for the corresponding standards, which can be further applied. Additionally, the Cr-rich spinel precipitated at high temperature will be wrapped by Fe-rich spinel generated at low temperature to form large size self-wrapped spinel, which facilitated subsequent separation and reduced the Cr^6 + dissolution risk.