Dechromization Kinetics of Limonitic Laterite Ores by Alkali-Roasting Method Using Sodium Hydroxide

Abstract

A novel process was proposed for the activation pretreatment of Cr-containing limonitic laterite ores by NaOH roasting. The dechromization kinetics of the laterite ores and the effect of particle size, NaOH-ore ratio, and roasting temperature on Cr extraction were studied in detail. Experimental results indicate that decreasing the particle size and increasing the NaOH-ore ratio and roasting temperature increase the Cr extraction rate. Approximately 96% Cr in the laterite ores could be extracted under the optimal alkali-roasting conditions. The results also indicate that the Avrami model is suitable for the dechromization process and that the apparent activation energy is calculated 11.12 kJ·mol-1. The 99.5% Cr2O3 was obtained from Na2CrO4 leached in the alkali solution by liquid-phase reduction and then calcining at high temperature.