Mathematical and Statistical Process Modeling of Hydrochloric Acid Leaching of Iron-Oxide Impurity from Inyi Kaolin: Response Surface Methodology

Abstract

The iron-oxide impurity is comparatively abundant in the low-grade kaolin from Inyi in Enugu, Nigeria. The iron-oxide impurities in kaolin make it unsuitable for industrial use. This study focused on the mathematical and statistical process modeling of iron-oxide impurity leaching from Inyi Kaolin by hydrochloric acid (HCl). Response Surface Methodology (RSM) was used to examine the combined effects of leaching temperature, solid-liquid ratio, reaction time, stirring speed, particle size, and acid concentration on the removal of iron contaminant from the local kaolin in HCl. The second-order polynomial regression equation designed with a correlation coefficient R² of 0.9959 provided the best description for the experimental data. The leaching temperature of 79.99°C, the solid-liquid ratio of 0.021, and the reaction time of the leaching temperature was 79.99°C, the solid-liquid ratio was 0.021, the reaction duration was 240 minutes, the stirring speed was 580.985 rpm, the particle size was 0.045mm, the acid concentration was 3.513mol/cm³, and the yield was at its highest point of 94.35%.