Browsing by Author "Shina Chepkemoi"

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    Performance and Optimization Study of Shaped Aluminum Hydroxide/Hydroxyapatite Adsorbents for Removal of Fluoride from Drinking Water
    (Addis Ababa University, 2024-07) Shina Chepkemoi; Beteley Tekola
    The study aimed to investigate the efficacy of shaped Aluminium Hydroxide/Hydroxyapatite composite adsorbent in fluoride removal in continuous column experiments. Spherical and cylindrical shapes of the composite adsorbent were produced and characterized for functional groups, phase composition, and structural characteristics. The performance of breakthrough curves was examined in a continuous column adsorption experimental setup by examining the effects of changing process factors such as flow rate, bed height, initial fluoride concentration, type of binder, and pellet shape. The analysis of the breakthrough curve revealed that the cylindrical pellets outperformed the spherical pellets in terms of adsorption capacities, with 1.34 mg/g and 0.679, respectively. Additionally, the results of the bentonite-binder pellets were significantly lower than those of the corn starch binder pellets. The adsorption capacity decreased with a rise in flow rate and initial fluoride contents and increased with rise in the height of bed. Adams-Bohart Model, Thomas model, and Yoon-Nelson model were used to model the breakthrough curve of different process parameters. The R2 for the Adams-Bohart model was between 0.89-0.96 for different process conditions. The Yoon-Nelson and Thomas model yielded R2 values ranging from 0.92-0.99 for all process parameters. The bed depth service time (BDST) model was employed to illustrate the impacts of bed height on the breakthrough curve and to forecast the breakthrough and exhaustion time of the adsorbent. The reliability of the model was demonstrated by a high R 2 value of 0.987. Central Composite statistical experimental design for optimization showed a good fit to the quadratic model with R2 =0.97 and 1.41 mg/g adsorption capacity at optimum conditions of 15 ml/min flow rate, 10 cm bed height, and 5 mg/l fluoride concentration. Fluoride-saturated Al(OH)3/HAP pellets were successfully desorbed in three adsorption-desorption cycles using 10% sodium hydroxide; the desorption efficiency was 88% in the first cycle, 71% in the second, and 61% in the third.