The excellent properties and solidifying effect of Cr providing by micro-crystal grain in slag glass-ceramics

Using stainless steel slag (SSS) and coal fly ash as raw materials to prepare glass-ceramics with excellent properties, the toxic and unstable Cr (VI) in the SSS was non-toxic converted into Cr (III). By Differential scanning calorimetry (DSC), X-ray diffraction (XRD), Scanning electron microscope (SEM) and performance testing methods, the relationship among phase composition, microstructure and properties of the CaO–MgO–Al2O3–SiO2 (CMAS) system slag glass-ceramics prepared at Tg = 750 °C and Tc = 950 °C was studied (Tg, glass transition temperature; Tc, crystalline temperature). The heavy metal Cr was solidification in the slag glass-ceramics by the toxicity characteristic leaching procedure (TCLP), which was satisfied the limitation of standard "DZ/T 0279.2-2016" of China and the solidifying effect of glass-ceramics was more obvious than that of glasses. The detoxification effect was verified through X-ray photoelectron spectroscopy (XPS). The experimental results showed that the physical performance of glass-ceramics increased with the increase of the content of SSS. As for the products from the mixed sources, the best product properties of G42 (1.05 wt % Cr2O3) glass-ceramics (bending strength, 230.58 ± 13.21 MPa; hardness, 878.30 ± 18 N/cm2) was the SSS content of 21 %. Moreover, the generation of spinel phase was the key crystal phase for solidifying heavy metal Cr. With the increase of the SSS, the spinel phase increased. In contrast, G42 was the most superior product performances of solidified Cr. In addition, it can be found that the unstable ratio (UR) of G42 is the smallest (UR = 0.01544) for heavy metal Cr in the leaching solution. It was further confirmed that the heavy metal Cr is effectively solidified in the glass-ceramics.