An environmental-friendly process for efficient recovery of Cr and harmless utilization of stainless steel slag via supergravity

Stainless steel slag is classified as a hazardous waste owing to the presence of soluble poisonous Cr(VI), which is harmful to the surrounding environment and human health. In this study, an environmental-friendly process was proposed for efficient recovery of Cr resources and harmless utilization of stainless steel slag. Cr element was selectively enriched from molten slag into the Cr-spinel crystal with the decrease of temperature and efficiently immobilized into the Cr-spinel with a stable valence state of Cr(III) at the temperature of 1573 K in molten stainless steel slag. In addition, almost all Cr-spinel crystals were fully recovered from the molten slag under the supergravity field, where the recovery rate of Cr was up to 95.24 % and the mass fraction of Cr2O3 in Cr-spinel phase reached 19.96 wt%. Moreover, the total leaching amount of Cr in both Cr-spinel and residue phases is as low as 0.67 mg/L and 0.13 mg/L and both products were further recycled, which indicated that Cr elements were completely immobilized in both green and environmental-friendly products.