Abstract
Stainless steel slag has been applied to other silicate materials due to its CaO-SiO2-based system. This is done to improve the utilization rate of stainless steel slag and apply it more safely. This paper investigated the occurrence of chromium in synthetic stainless steel slag containing FetO and its leaching behavior. The phase composition of the equilibrium reaction was calculated by FactSage 7.3 Equlib module. XRD, SEM-EDS and IPP 6.0 were used to investigate the phase compositions, microstructure and count the size of spinel crystals. The results indicate that the increase of Fe2O3 content can promote the precipitation of spinel phases and effectively inhibit the formation and precipitation of α-C2S in a CaO-SiO2-MgO-Cr2O3-Al2O3-FeO system. Fe2O3 contents increased from 2 wt% to 12 wt%, and the crystal size increased from 4.01 μm to 6.06 μm, with a growing rate of 51.12%. The results of SEM line scanning show the Cr-rich center and Fe-rich edge structure of the spinel phase. Comparing the TRGS 613 standard with the HJ/T 299-2007 standard, the leaching of Cr6+ in the FetO samples is far lower than the standards’ limit, and the minimum concentration is 0.00791 mg/L in 12 wt% Fe2O3 samples.
Highlights
Stainless steel slag is a CaO-SiO2 -based slag system, containing parts of MgO, Al2 O3, Cr2 O3, FeO, Fe2 O3 and other components, and is suitable to be applied to other silicate materials, such as cement, ceramics, glass and refractories [1,2,3,4,5]
Yang et al [11] prepared a glass ceramics with the addition of stainless steel slag into a kind of pre-melted slag, and the results revealed that the Fe2 O3 content ranges from 5.4 to 5.6 wt%, and the Cr2 O3 contents were 0 wt%, 0.2 wt%, 0.5 wt%, 0.7 wt% and 0.9 wt%, respectively
The results indicated that spinel crystal (Mg, Fe) (Al, Fe, Cr)2 O4 formed an Fe-rich shell structure
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. For a high temperature remelting process, it is necessary to consider the influence of products basicity, compositions and subsequent cooling regimes on the phase compositions of the system in order to reduce the leaching toxicity of the products [13]. The temperature and atmosphere under processing conditions of the products should be considered during the service period [14] in order to improve the utilization rate of stainless steel slag and explore the stabilization method. The effect of FeO on spinel crystallization and chromium stability in CaO-SiO2 -MgOAl2 O3 -Cr2 O3 was studied in the previous work [21]. Mou et al [22] studied the effects of Fe2 O3 on the CaO-SiO2 -MgO-Al2 O3 -Cr2 O3 system and found that the addition of Fe2 O3 raised the content of the liquid phase. Fe2 O3 is added as extra content in the CaO-SiO2 -MgO-Al2 O3 -Cr2 O3 -8 wt% FeO system
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