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A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering September, 2017 / South Africa emits large amounts of carbon dioxide (CO2) due to its reliance on coal. The emission of CO2 needs to be reduced for clean sustainable energy generation. Research efforts have therefore been devoted to reducing CO2 emissions by developing cost-effective methods for capturing and storing it. Amine-based absorption using monoethanolamine solvent is the most mature technique for CO2 capture despite its huge energy consumption, corrosiveness and difficulty in solvent regeneration. However, CO2 removal by solid adsorbents is a promising alternative because it consumes less energy, and can be operated at moderate temperature and pressure. Metal organic frameworks have received attention as a CO2 adsorbent because they have large surface areas, open metal sites, high porosity and they require less energy for regeneration. This research was aimed at optimizing and scaling-up SOD-ZMOF through structural modification for enhanced CO2 adsorption by impregnating it with chitosan. Scaled-up SOD-ZMOF samples were prepared as described elsewhere and impregnated with Chitosan. Physiochemical properties obtained using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Nitrogen physisorption showed that SOD-ZMOF and SOD-ZMOF-chitosan were successfully synthesized. Qualitatively, the surface area of the SOD-ZMOF synthesized using the scaled up protocol is lower than the one prepared using the non-scaled-up protocol XRD pattern of SOD-ZMOF showed that it was crystalline and was in agreement with literature. The XRD peaks of the SOD-ZMOF decreased after chitosan impregnation showing that chitosan was impregnated on SOD-ZMOF. The FTIR spectrum of SOD-ZMOF showed functional groups present in organic linker used to synthesize SOD-ZMOF, and that of the SOD-ZMOF-chitosan revealed the same functional groups but with disappearance of carboxylic acid functional group. N2 physisorption showed a decrease in BET surface area and pore volume after chitosan impregnation on SOD-ZMOF as well. Performance evaluation of the material was carried out with a demonstration adsorption set-up using a 15%/85% CO2/N2 mixture and as a thermal gravimetric analysis (TGA) using 100% CO2. For both the packed-bed column and the TGA experiments, evaluation was conducted on SOD-ZMOF and SOD-ZMOF with chitosan for comparison. About 50 mg of the adsorbent was used at 25 oC, 1 bar and 25 ml/min for the packed-bed column. For the adsorption with the TGA, 11 mg of adsorbent was used at 25 ℃, 1 bar and 60 ml/min. SOD-ZMOF showed improved adsorption capacity after chitosan impregnation. CO2 adsorption capacity of SOD-ZMOF increased by 16% and 39% using packed-bed column and TGA, respectively, after chitosan impregnation. The increase in adsorption capacity was attributed to the impregnated chitosan that has amine groups that display a high affinity for CO2. A traditional approach was used to investigate the effect of adsorption temperature and inlet gas flowrate on the CO2 adsorption capacity of SOD-ZMOF-chitosan. This was done using both the parked bed column and the TGA. Temperature range of 25-80 ℃ and inlet gas flowrate range of 25-90 ml/min were investigated. Adsorption capacity increased with a decrease in temperature and inlet gas flowrate. For the packed-bed column, maximum of 781 mg CO2/ g adsorbent was obtained at 25℃, 1 bar, 25 ml/min and for the TGA a maximum CO2 adsorption capacity of 23 mg/ g adsorbent at 25 ℃, 1 bar, and 60 ml/min was obtained. / MT2018

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Chitin is a polysaccharide derived from the shell of crustaceans. Chitosan is a deacylated chitin derivative and ChitoRich™ is a chitosan-based formulation. Chitosan is known to inhibit dietary fat absorption. ChitoRich™ and chitosan were evaluated for their ability to control fat absorption in growing rats. Forty-eight rats (about 150 g) were fed for 4 weeks on 12 different diets containing two levels of vegetable shortening (15 and 5%) and fiber (5 and 2.5%) with cellulose, chitosan, or ChitoRich™ as the dietary fiber sources. Rats fed ChitoRich™ ate less and gained less body weight than rats fed the other fiber sources. Rats fed ChitoRich™ adapted over time; thus, the weight control effect was not significant during the third and fourth weeks. Feed efficiency of the rats fed ChitoRich™ was lower than that seen in rats fed the other fibers, indicating that calories from a higher percent of absorbed macronutrients were required to maintain their bodies. Apparent fat digest (AFD) was lower in rats fed the ChitoRich™ than in the rats fed cellulose. The reduction of AFD was not as great as that seen by other researchers, possibly due to the low solubility and high viscosity of shortening, compared to corn oil. AFD of the rats fed ChitoRich™ increased over time, suggesting an adaptation to ChitoRich&trad;. Apparent protein digestibility (APD), apparent Ca digestibility (ACaD), and weight gain per unit of protein intake were less in the rats fed ChitoRich™ than in the other fiber-fed groups. ChitoRich™-fed rats had retarded body weight gain, reduced levels of serum albumin, total liver lipids, and epididymal fat weight when compared to the other fiber groups, possibly due to the reduced caloric intake, FD, and APD. Serum cholesterol level was not affected by the fiber source. Liver iron and zinc concentrations were not different among fiber sources, indicating that chitosan and ChitoRich™ may not inhibit the absorption of trace minerals. Liver retinol concentration in the ChitoRich™-fed rats was higher than in the cellulose- or chitosan-fed groups, possibly due to the antioxidant effect of ascorbic acid. All rats were free of microscopic lesions, suggesting that chitosan and ChitoRich™ are safe sources of dietary fiber under these dietary conditions. ChitoRich™ is effective for reducing dietary fat absorption and body weight gain.

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Water polluted by metals and phosphates can be hazardous to both the environment and human health. The aim of this study was used to improve understanding of the adsorption properties of low-cost, green adsorbents for removal of pollutants from aqueous solution. Biochar was used as an adsorbent, which was produced from the gasification of pine wood waste and the fast pyrolysis of Douglas fir. Biochar is a bio-renewable product that can easily be modified, and the cost is lower compared to other adsorbents like activated carbon. The gasifier produced biochar was modified by coating the biochar surface with chitosan. Douglas fir biochar, produced by pyrolysis, was used in Mg/Al-layered double hydroxides (LDHs) and magnetization modifications. The Mg/Al-LDHs were prepared by co-precipitation using solutions of Mg and Al salts and NaOH treatment. The magnetization modification of the biochar was prepared by magnetite (Fe3O4) precipitation onto the biochar’s surface from Fe2+/Fe3+ solution upon NaOH treatment. Chapter I provides an introduction into biochar production, uses, and modification methods. Chapter II is a study of the aqueous adsorption Cu2+ and Cd2+ metals using chitosan coated and uncoated gasifier biochars. Chapter III focused on the removal of phosphate from aqueous solutions. Different ratios of Mg:Al in the LDHs were used to test the ratio’s affect on the adsorption properties of the modified adsorbents. Chapter IV describes the removal of phosphate from water using LDH modified biochars that are magnetized. This study looks at how the order in which the modifications were done influences the biochars adsorption ability. The surface chemistry and composition of each biochar in chapters II-IV were examined by SEM, SEM-EDX, TEM, PZC, XRD, elemental analysis, and surface area measurements. Each biochar’s adsorption ability was studied by pH effects, kinetics, and maximum capacity for the analyte.

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