KINETICS AND MECHANISMS OF ORIEMBA-AKPUGO CLAY DISSOLUTION IN HYDROGEN PEROXIDE SOLUTION FOR POTENTIAL ALUMINIUM RECOVERY
Abstract
ABSTRACT
This research explored the potential of clay sourced locally as a raw material for aluminium production. The clay sample, collected from Oriemba-Akpugo in Nkanu West L.G.A., Enugu State, Nigeria, was processed and analyzed to determine its chemical and mineralogical properties. X-ray fluorescence (XRF) analysis revealed an alumina (Al₂O₃) content of about 26.17 wt%, indicating its suitability as a possible aluminium source. X-ray diffraction (XRD) identified the mineral phases present in the clay as Quartz (SiO₂), Orthoclase (Al₂O₃·K₂O·6SiO₂), Albite (NaAlSi₃O₈), Goethite (Fe₂O₃·H₂O), and Muscovite (H₂KAl₃(SiO₄)₃), with Orthoclase being the principal aluminium-bearing mineral. Further morphological characterization using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) supported the XRF and XRD findings. Leaching experiments were carried out in hydrogen peroxide solutions of different concentrations, while the influence of stirring speed, temperature, solid-to-liquid ratio, and particle size was also investigated. Results showed that aluminium recovery increased with hydrogen peroxide concentration up to 2 M, beyond which dissolution decreased. Higher stirring speeds and elevated temperatures enhanced leaching efficiency, whereas larger particle sizes and higher solid-to-liquid ratios reduced it. Kinetic modelling, performed using the least-squares method, indicated that the mixed kinetic model provided the best fit to the data, with diffusion through the product layer being the rate-controlling step. The activation energy was determined to be 0.831 kJ/mol, and the frequency factor was estimated at 0.0056 s⁻¹, further confirming product layer diffusion control. Overall, about 86.7% of the aluminium was successfully leached into solution. These results demonstrate that Oriemba-Akpugo clay is a promising alumina source with significant potential for use in aluminium production industries.
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