Influence Of Hydration Reaction Of Mineralogical Components On AOD Slag Leaching Mechanism

AOD(Argon Oxygen Decarburization)slag,which is a by-product of the stainless steel refining process,is a recyclable slag because of its high content of calcium and silicon that is similar to cement.Chromium contained in AOD slag can be leached out under the leaching function of rainwater that threaten soil,water and human health,which limits its valorization.To explore the leaching mechanism of chromium release from AOD slag,static leaching tests,mineralogical analysis,PHREEQC simulation combined with Fact Sage have been performed.Based on the static leaching tests and mineralogical analysis,the kinetic model and the influence of mineralogical hydration reaction on Cr release from AOD slag has been explored,which provided foundation for its assessment and valorization.The static leaching tests indicated that there are two leaching stage during the whole leaching process,namely quick leaching stage and slow leaching stage.Cr leaching concentration would be enhanced with the decrease of pH and L/S and the increase of leaching temperature.The mineralogical analysis indicated that the major primary components in original AOD slag were dicalcium silicate,merwinite,periclase and pyroxene with weight content of 85.0%,7.0%,4.0% and 2.3%,respectively.C₅H₂S₂ gel and amesite would generated during acidic,neutral and alkaline leaching process.The kinetic model of Cr release from AOD slag indicated that Cr release from AOD slag was controlled by the solid product diffusion during the quick leaching stage,while by a complicated hybrid control during the slow leaching stage.PHREEQC simulation indicated that Cr release from AOD slag was controlled by the thermodynamic equilibrium of Cr(OH)₃,while super underestimated when controlled by FeCr₂O₄ and double controlled.The leaching speciations of Cr would present as trivalent chromium and difficult to transformed to hexavalent chromium in the leaching process of AOD slag.