Electrochemical enhanced oxidative decomposition of chromite ore in highly concentrated KOH solution

•An electrochemical decomposition method for chromite in KOH solution is proposed.•The extraction rate varies parabolically with alkali concentration and temperature.•The increase in slot current density and alkali-to-ore ratio favors the extraction.•The impurities, especially the aluminate, have negative effect on the extraction.•The optimal extraction process is governed by chemical reaction and inner diffusion.

A novel method which introduces an electrochemical field to enhance the oxidative decomposition of chromite in a KOH sub-molten salt medium was proposed and proven to be feasible and efficient. Under optimal reaction conditions (slot current density 750 A/m2, alkali concentration 60 wt.%, reaction temperature 150 °C, alkali-to-ore mass ratio 6:1, and particle size <200 mesh), the extraction rate of chromium reached 99%, after reacting for 480 min. In comparison with the current liquid-phase oxidation technologies, the reaction temperature in the new approach is 150–250 °C lower, and the alkali concentration of the reaction medium is lower by more than 20%, showing substantial advantages in terms of energy efficiency, equipment corrosion alleviation and prospects for industrial application. The reaction kinetics study shows that the extraction process under optimal reaction conditions is jointly governed by surface chemical reaction and solid product layer diffusion with the apparent activation energy calculated to be 17.56 kJ/mol.