Effect of Al2O3 modification on enrichment and stabilization of chromium in stainless steel slag

Spinel phase is considered to be the optimal phase for stabilization of chromium in stainless steel slag. In order to restrain chromium leaching from slag for the effective environmental protection, Al2O3 was utilized for the modification treatment, and the effects on the enrichment and stabilization of chromium were investigated. The mineral phases and the existence state of chromium in slag with various Al2O3 contents at different basicities (wCaO/wSiO2) were analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The results showed that chromium mainly existed in the glass and spinel phases at basicity of 1.0 and 1.5. As the slag basicity increased to 2.0, chromium was also found in periclase phase. Al2O3 in the stainless steel slag reacted with MgO and Cr2O3, which could generate the Al-rich Mg(Crx Al1-x)2O4 solid solution. Moreover, the addition of Al2O3 was favorable to reduce the solubility of chromium oxide in liquid phase and suppress the precipitation of periclase phase. The experimental results demonstrated that Al2O3 modification has a positive influence on the enrichment and the stabilization of chromium in the stainless steel slag.