PHD-Department of Chemistry

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Browsing PHD-Department of Chemistry by Author "Mobegi, Erick Kiage"

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    Synthesis and Characterization of Metal Oxide Biopolymer Nanocomposite: Kinetics and Equilibrium Studies on Adsorption of Fluoride and Arsenate in Water
    (Kenyatta University, 2023-06) Mobegi, Erick Kiage
    Fluoride occurs naturally in drinking water. Fluoride levels below 1.5 ppm is beneficial to human health specifically in the strengthening of teeth and bones. However, continuous exposure to fluoride levels exceeding this limit can lead to dental and skeletal fluorosis. Arsenic is carcinogenic to human beings. Prolonged exposure to arsenic containing water with levels exceeding 10 ppb has been associated with ailments such as skin cancer. Physicochemical parameters are good indicators of water quality whose levels should not exceed the WHO limits. Methods for the reduction of fluoride and arsenic in water such as membrane technology and adsorption among others are expensive, need electrical power, and may result in secondary pollution. The goal of this study was to lower fluoride and arsenic levels while reducing certain physical and chemical parameters of drinking water quality, including pH, total dissolved solids, turbidity, electrical conductivity, alkalinity, total hardness, total suspended solids, color, and chlorides. Chitosan, titanium, iron, aluminium, and zircorium oxides were all used to generate a nano- sized granular biopolymer-mixed metal oxide nanocomposite (abbreviated as Ch- Al/FelTilZr). X-Ray Powder Diffraction, X-Ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, uigh Resolution Transmission Electron Microscopy, and Brunauer-Emmett-Teller characterization techniques were used to characteize the nanocomposite adsqrbent. The effects of adsorbent dosage, pH variation, initial concentration, co-existing ions, contact time, and equilibrium were all studied for the adsorbent using prJpared aqueous solutions in batch and continuous mode. The nanocomposite has a specific surface area of 56.4 m2g-r and is largely amorphous. The maximum adsorption capacities for fluoride was 63 mglg and that of arsenate 123 mglg. Fluoride was decreased by 90 %o and arsenate by 96 o/o, respectively. It was observed that the reduction in the nanocomposite's capacity to adsorb fluoride and arsenate was a result of the presence of some co-existing ions. Chloride ions reduced fluoride uptake from 98 %;o to 7 4 o%. Arsenate levels reduced from 99 o/o to about 7 6 %o in the presence of carbonate and bicarbonate ions. Langmuir adsorption isotherm model described the equilibrium data well for fluoride (0.99931) and arsenate (0.99518). Prototype Point-of-Use filters were fabricated using the nanocomposite and reduced 85 % of fluoride and 97 o/o of arsenate in contaminated water. Further, the filters showed over 80 %o inprovement in selected physicochemical parameters. The nanocomposite reduced fluoride and arsenate to levels within those acceptable by wHo and improved water quality parameters regarding the selected physicochemical parameters. It is thus recommended for water treatment to reduce contaminants and improve water quality.