Conditions for mutual conversion of Cr(Ⅲ) and Cr(Ⅵ) in aluminum chromium slag

The conditions for the mutual conversion of Cr(III) and Cr(VI) are investigated to realize safe application of aluminum chromium slag. Aluminum chromium slag is sintered with conventional refractory oxides in different atmospheres and at different temperatures to examine the phase of the sample and...
Ausführliche Beschreibung

The conditions for the mutual conversion of Cr(III) and Cr(VI) are investigated to realize safe application of aluminum chromium slag. Aluminum chromium slag is sintered with conventional refractory oxides in different atmospheres and at different temperatures to examine the phase of the sample and its Cr(Ⅵ) content in an aqueous solution. The results show that the slag system contains CaO and MgO that facilitate Cr(Ⅵ) formation, Al2O3 that inhibits Cr(Ⅵ) formation, TiO2, Fe2O3, and SiO2 that reduce Cr(Ⅵ) to Cr(III). In a reducing atmosphere, even if the alkaline environment condition is satisfied, Cr(Ⅵ) in the aluminum chromium slag is reduced to Cr(Ⅲ), thus detoxifying the slag. In addition, under alkaline environment and oxidizing atmosphere conditions, the slag temperature corresponding to the transition of Cr(Ⅵ) to Cr(III) is between 900 °C and 1000 °C. Thus, the transition of Cr(III) to Cr(VI) in aluminum chromium slag requires three conditions, alkaline environment, oxidizing atmosphere, and high temperature, and all the three conditions are indispensable. Consequently, the safe application of aluminum chromium slag can be realized by controlling the conditions for the mutual conversion of Cr (III) and Cr (VI). Ausführliche Beschreibung