Chromium containing slags from stainless steelmaking may be leached by acidic environments, therefore they should be treated before being stockpiled or land filled. In this work, synthetic slags were prepared and the effect of CaO/SiO2, Cr2O3, MgO and Al2O3 contents on the stability of the mineralogical species formed was analysed. The morphology and composition of the slags were determined by XRD and SEM‐EDS, whilst their chemical stability was evaluated by leaching with an aqueous acetic acid solution. It was found that CaCr2O4 and CaCrO4 are present in slags prepared with neither MgO nor Al2O3. The Al2O3‐based slags mainly produced Ca2Al2SiO7 and the Cr(VI)‐containing oxide complex Ca4Al6CrO16, whilst MgO‐based slags produced Mg Cr2O4 as main mineralogical species. Additionally, Eh‐pH diagrams for the Ca‐Cr‐H2O and Mg‐Cr‐H2O systems at 25°C were constructed. The results showed that the lowest chromium concentration levels in the leaching liquors corresponded to MgO‐based slags owing to the stable binding of chromium in spinel with MgO. It was also observed in the Al2O3‐based slags that when increasing the slag basicity from 1 to 2, the leachability of the slags was notably increased.

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The evaluation of the thermodynamic properties as well as the phase diagrams for the binary Na 2 O-SiO 2 , K 2 O-SiO 2 , and Li 2 O-SiO 2 systems are carried out with a structural model for silicate melts and glasses. This thermodynamic model is based on the assumption that each metallic oxide produces the depolymerization reaction of silica network with a characteristic free-energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analyzed and represented with a small number of parameters. The resulting equations represent the thermodynamic and phase diagram data for these alkali metal oxide-silica systems within experimental error limits. In particular, the measured limiting liquidus slope at X SiO2 ¼ 1 is well reproduced.

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