Browsing by Author "Ocident Bongomin"

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    Characterization and treatment effects on Mutaka kaolin for additive in coatings: Mineral composition, thermal and structural modifications
    (Heliyon, 2024-01-15) Andrew Kasumba Buyondo; Hillary Kasedde; John Baptist Kirabira; Ocident Bongomin
    Previous studies in Uganda have primarily explored kaolin’s applications in composites, pottery, bricks, and insulation, neglecting its potential for coatings and paints, which is crucial for industrialization and saving foreign exchange. This study investigates the transformation of kaolin through various treatments and analyzes their impacts on its physical and chemical properties for potential use in coating applications. Thermal analysis, X-ray Fluorescence Spectroscopy (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEMEDS), and transmission electron microscopy (TEM) techniques were employed to assess these alterations. The results show that thermal treatment of kaolin at 45.9 ◦C had minimal impact on mass loss, while the crystallinity of kaolinite was found to be lost around 600 ◦C, resulting in structural changes. XRF result demonstrates variations in SiO2 and Al2O3 composition, with low TiO2 content desirable for paint and coating applications. XRD results showed well-defined diffractions associated with kaolinite in all treated and untreated kaolin samples. The presence of K-feldspar and quartz are also identified. However, the thermal treatment at 800 ◦C transforms kaolinite into metakaolin, essential for enhancing coating properties. SEM-EDS results indicate increased porosity and reduced impurities in the thermal-treated sample, which might enhance the whiteness and suitability of pigment and binder dispersion in coatings. TEM images confirmed the hexagonal nature of kaolinite platelets and demonstrated the amorphous nature of kaolin nanoparticles with ammonium molybdate treatment, which led to the delamination and exfoliation of kaolinite layers, improving dispersibility. Kaolin thermally treated exhibited good crystallinity, solid growth, cubic morphology, and uniform size distribution. These findings suggest that tailored treatments can optimize kaolin’s properties, making it a promising additive for high-performance coatings.
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    Effects of thermal and chemical modification on the physical properties of Ugandan Mutaka Kaolin
    (2023-08-12) Andrew Kasumba Buyondo; Hillary Kasedde; John Baptist Kirabira; Ocident Bongomin
    This study investigates the impact of thermal treatment at temperatures ranging from 600 ​°C to 1050 ​°C and chemical treatment using (COOH)2·2H2O and Al2(MoO4)3 ​at concentrations of 0.01 ​M, 0.05 ​M, and 0.1 ​M. The modified kaolin samples’ pH, oil adsorption capacity, refractive index, specific gravity, and viscosity were examined. Comprehensive analyses were performed to characterize the modified kaolin samples. The spectrum results revealed dealumination, with a corresponding increase in silicon content due to chemical treatment, while the aluminum content decreased compared to thermal treatment results. As observed with the calcined kaolin sample, a significant portion of the OH stretch groups vanished with disappearance stretches along the bands at 1229.6 and 1009.2 ​cm−1, corresponding to Si–O stretching vibrations. The specific gravity of calcined kaolin was observed to be relatively lower than TiO2. Furthermore, the obtained pH of 4.0 or lower, or a pH of 9.0 or higher, is classified as corrosive. The ideal temperature range for achieving optimal oil absorption lies within the 800 ​°C–900 ​°C range, where metakaolin properties favor effective oil uptake. The chemical concentration had a notable impact on the dispersion of kaolin powders, in contrast to calcined kaolin. At 800 ​°C, calcined kaolin attained an almost ideal refractive index for water-based paints, closely aligning with the refractive index of water.