Assessment of Owhe kaolinite as potential aluminium source in hydrochloric acid and hydrogen peroxide solutions: Kinetics modeling and optimization

Abstract

In this study, the effectiveness of hydrochloric acid and hydrogen peroxide binary solution as lixiviant for alumina recovery from Owhe kaolinite is investigated by kinetic and optimization studies. The experimental results fitted into the Dickinson and Heal modified diffusion control model while the rate determining step was established as diffusion through the product layer. The activation energy was established as 53.92 kJ/mol while Arrhenius constant was estimated as 2.19×106 s−1. The result revealed that about 88.9% alumina was recovered from the kinetic study, while the overall rate constant was estimated to be 3988.73 s−1. Optimization studies carried out by response surface methodology (RSM) revealed that about 87.75% alumina recovery was recorded at a reaction temperature of 78.16 °C, acid concentration of 5.67 M, stirring rate of 422.28 rpm, reaction time of 104.39 min, and hydrogen peroxide concentration of 5.14 M. Particle swarm optimization (PSO), however, predicted about 84.99% alumina recovery. Post-leaching analysis by energy dispersive spectrometry (EDS) revealed the presence of silicon, aluminum and titanium as major elements in the residue while mineralogical analysis of the residue by XRD indicated that quartz, sanidine, kaolinite, illite and davyne were contained in the residue. Hence, the kinetic models used were sufficient to analyze the experimental data while RSM and PSO proved to be viable tools for optimization.

Keywords

• Kaolinite
• HCl
• Kinetics
• Hydrogen peroxide
• Alumina
• Optimization