Kinetic model of chromium release from argon oxygen decarburisation (AOD) slag in a neutral leachate

Valorisation of argon oxygen decarburisation (AOD) slag, a suitable recycling resource, is limited by the release of a notable amount of heavy metals, such as chromium. The mineralogical component of AOD slag was characterised by X-ray diffraction and scanning electron microscopy-energy-dispersive X-ray spectrometry. To explore the release kinetics of chromium from AOD slag, neutral leaching tests were performed at various temperatures. The results indicated the existence of two leaching stages: quick and slow leaching stages. In 2 h, the chromium release fraction increased sharply as the leaching time increased. As the leaching time increased, the chromium release rate gradually decreased. Based on the shrinking core model, chromium release kinetic models for the quick and slow leaching stages from the AOD slag were independently determined. The chromium release was controlled by solid product diffusion during the quick leaching stage and a complicated process in the slow leaching stage. The activation energy of chromium leaching was calculated based on the Arrhenius equation. Solid product diffusion was the velocity-determining step during the 2 h leaching process. In the slow leaching stage, chromium release was controlled by complicated hybrid control dominated by solid product diffusion.