Browsing by Author "Ouma, Linda"

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    Optimization studies of BTX removal by magnetite coated oleic acid obtained from microwave‑assisted synthesis using response surface methodology
    (Scientific Reports, 2022-12-13) Masuku, Makhosazana; Ouma, Linda; Sanni, Saheed; Pholosi, Agnes
    Benzene, toluene and xylene (BTX) are volatile organic compounds released into the environment, that require urgent removal to avoid adverse health effects. In this work, the modelling and optimization of the preparation factors for magnetite coated oleic acid (MNP-OA) composite from microwave synthesis using response surface methodology were conducted to maximize BTX removal, and iron content. The influence of five crucial preparation variables: the Fe3+/Fe2+ solution volumes, microwave power, volume of ammonia water (VAW), reaction time and volume of oleic acid (VOA) on the iron content (% Fe), and BTX adsorption capacity were investigated. The analysis of variance results revealed that VOA and VAW were the most influential factors for high % Fe content, and improved BTX removal. The % Fe, and BTX adsorption capacity for MNP-OA composite at optimized experimental conditions were estimated to be 85.57%, 90.02 mg/g (benzene), 90.07 mg/g (toluene), and 96.31 mg/g (xylene).
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    Probing the interaction effects of metal ions in MnxFe(3 x)O4 on arsenite oxidation and adsorption
    (Royal Society of Chemistry, 2019-12-27) Ouma, Linda; Ofomaja, Augustine
    Wastewater treatment is still a global concern and materials capable of pollutant sequestration continue to be improved in a bid to ensure water reusability and curb water shortages. Some of the most promising materials so far are nanosized materials because of their unique properties and the ease of manipulation to improve their properties. In this work we investigated the effects of varying Fe3+ : Fe2+ ratios in magnetite nanoparticles and the influence of manganese doping. Diffraction measurements indicated that the manganese introduced into the magnetite matrix displaced some Fe atoms resulting in the formation of a uniform phase matching the card data for magnetite with no additional manganese phases being formed. XPS confirmed the presence of manganese on the surface of the doped nanomaterials and that both As(III) and As(V) were bound on the adsorbent surface. The central composite design (CCD) of response surface methodology (RSM) was used to determine the effects the nanoparticle compositions had on As(III) adsorption and oxidation. A quadratic equation was used to model the experimental data with a correlation coefficient close to unity indicating that the model was a good fit for the data. The interaction between Fe3+ and Mn had a positive influence in the reduction of As(III) in solution while Fe3+/Fe2+ interactions had antagonistic effects and the Fe2+/Mn interactions were found to be insignificant. Increasing the amounts of Fe3+ and manganese therefore resulted in the highest reduction in As(III) concentration.