Abstract
In this study anodic oxidation of Cr-2(SO4)(3) was carried out in an air-sparged divided parallel plate cell. Variables studied were current density, Cr-2(SO4)(3) concentration, and superficial air velocity. The rate constant of Cr-2(SO4)(3) oxidation was found to increase with increasing current density and Cr-2(SO4)(3) concentration. The effect of air sparging was found to depend on Cr-2(SO4)(3) concentrations, at high Cr-2(SO4)(3) concentration (> 0.1 M) air sparging does not affect the rate constant of the reaction denoting that the reaction is charge transfer controlled. As Cr-2(SO4)(3) concentration decreases below 0.1 M the reaction becomes under mixed diffusion and chemical control and the rate constant increases with increasing air superficial velocity, the lower Cr-2(SO4)(3) concentration the higher the contribution of diffusion to the reaction rate. The current efficiency of the process ranged from 20 to 85% depending on current density and Cr-2(SO4)(3) concentration. Electrical energy consumption which ranged from 1.8 to 14.4 kW h/kg of Cr6+ was found to increase with increasing current density and decreases with increasing Cr-2(SO4)(3) concentration. Air sparging was found to decrease electrical energy consumption in the case of dilute solutions << 0.1 M Cr-2(SO4)(3).