Mechanism of dry detoxification of chromium slag by carbon monoxide

Dry detoxification is a major technology used at the industrial scale for remediation of chromium slag. However, the mechanism of this reaction is poorly known, in particular the kinetics and the role of minerals. Here, we studied elemental and mineralogical compositions during chromium slag detoxification by carbon monoxide, using data from X-ray powder diffraction, electron backscattered diffraction, energy-dispersive spectrometry and chemical analysis. The detoxification kinetics were studied by thermal analysis techniques using thermogravimetric and differential thermogravimetric analysis. Results show that the decomposition of Cr(VI)-containing minerals is responsible for the reduction process. The apparent activation energy is 41.36 kJ mol−1, from a calculation using the Flynn–Wall–Ozawa iso-conversional method.