Browsing by Author "Mohammed, Jibril"

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    Preparation and surface modification of activated carbon from coconut shells for benzene and toluene adsorption from water
    (Universiti Teknologi Malaysia, 2015) Mohammed, Jibril
    The presence of volatile organic compounds (VOCs) in gaseous effluents and produced water from process industries like refineries and pharmaceuticals poses environmental challenges. In addition, waste bio-based materials cause disposal challenges, but they can be converted into value-added products like activated carbon (AC) which could serve as adsorbent for VOCs abatement. This thesis presents the preparation of ACs using potassium hydroxide and potassium acetate as activating agents under two-step activation with furnace and microwave (MW) heating, and modification with ammonia. Effects of impregnation ratio (I.R), (1-3), MW power (200-600 W) and irradiation time (I.T), (0-12 min) on the properties of AC were optimized using response surface methodology (RSM). The ACs were characterized and applied for batch and packed-column adsorption studies by varying initial VOCs concentration (50-250 mg/L), contact time, bed height (1-3 cm) and influent flow rate (3.6-9 mL/min). Isotherm and kinetics models and Matlab routine were used to validate the experimental results. MW heating was found to be faster and energy saving than the conventional heating method. Potassium acetate produced heteroporous AC with approximately 50% of both micropores and mesopores, which would suffice for a wider range of applications. Ammonia treatment improved benzene and toluene uptake by 10%. The optimum condition obtained from the RSM were MW power of 500 W, I.T of 4 min, and I.R of 1.5, which resulted in 84 and 85% removal efficiency of benzene and toluene, respectively. The range of surface area was between 478 and 1345 m2/g, which were reduced to 308 and 232 m2/g after regeneration cycles for adsorption of benzene and toluene, respectively. Scanning electron micrograph revealed good surface morphology and porosity formation; thermogravimetric analysis show the removal of moisture, cellulose, hemicellulose and lignin at temperatures between 105 - 700 oC and surface functional groups such as O-H, C=C, C-O, C-O-C and C-H were identified from the Fourier transform infrared spectroscopy. The elemental analysis of the precursor exhibited significant carbon content of 48.7%. Batch adsorption studies revealed that the adsorption capacity was highest at 250 mg/L, the maximum adsorption capacities were between 192-344 mg/g and 227-357 mg/g for benzene and toluene, respectively. Correlation of the experimental result with Langmuir, Freundlich and Temkin Isotherms revealed that the Langmuir isotherm has the best fit, while the kinetics studies revealed that the pseudo-second-order kinetic model best describes the adsorption process. In the packed-column study, the highest bed capacities of 77.30 and 69.40 mg/g were recorded for benzene and toluene, respectively at 250 mg/L which correlates with the values obtained from the Matlab simulation. Regeneration of the spent AC was carried out in MW with approximately 50% removal efficiency of benzene and toluene, and 80% yield retained after five successive regeneration cycles