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Thesis (M. Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2008.

The need for clean potable water and sustainable energy are two current and pressing issues with implications affecting the global population. Renewed interests in alternative energy have prompted researchers to investigate the full capacity of biofuels. These interests have led to not only the examination of current method limitations, but also to the investigation of new conversion methods. One promising method for bioenergy production is pyrolysis of lignocellulosic feedstocks. Through pyrolysis, a single crop may produce ethanol, bio-oil, and/or gaseous energy (syngas). The remaining solid phase product is a black carbon dubbed 'biochar'. In the current study, biochar was used as a both an unamended sorbent and a precursor to form powdered activated carbons (PACs) capable of removing waterborne viruses. Biochar was activated with KOH, ZnCl2, and H3PO4 and analyzed using the Brunauer, Emmett and Teller (BET) method, a combination of Kjeldahl digest and ICP-MS, and scanning electron microscopy (SEM). Sorbents were tested in batch studies using phosphate buffered saline (PBS), surface water, and groundwater. Bacteriophages MS2 and thetaX174 served as viral surrogates. All activation treatments significantly increased surface area, up to 1495.5 m2/g (KOH-activated). While the non-activated biochar was not effective in virus removal, the KOH-activated PAC had tremendous removal in the PBS/MS2 batch (mean 98.7% removal, up to 6.2 x 109 particles/mL, as compared to the Darco S-51: 82.3%). As evidenced by this study, sorption efficiency will be governed by viral species, carbon type and concentration, and water quality. The results of this study indicate that biochar can serve as a precursor for a highly porous and effective PAC, capable of removing waterborne viruses from environmental waters.

This study combined photocatalytic technology with activated carbon adsorption to decompose gaseous pollutants. Gaseous pollutants were initially adsorbed and concentrated by activated carbon and could be further decomposed more effectively by photocatalytic technology. This study coated TiO2 on the activated carbon fiber (ACF) by a sol-gel process for conducting the adsorption and decomposition of acetone in a batch reactor. Operating parameters investigated in this study included the initial concentration of acetone (13.6 £gM and 27.2 £gM), reaction temperature (50¢J~70¢J), oxygen concentration (0.5%~20%), and water vapor (0 £gM~244.9 £gM). The incident UV light of 365 nm was irradiated by a 15-watt low-pressure mercury lamp placing above the photocatalytic batch reactor. The ACF coated with TiO2 was placed in the center of the reactor. Acetone was injected into the reactor to conduct photocatalytic tests. Reactants and products were analyzed quantitatively by a gas chromatography with electron capture detector (GC/ECD) and a flame ionization detector followed by a methaneizer (GC/FID-Methaneizer). Results from the photocatalysis tests indicated that, among the commercial TiO2 (Degussa P-25), NO3-/TiO2 and SO42-/TiO2, SO42-/TiO2 had the best photoactivity reduced acetone concentration and reaction time substantially. The end products was mainly CO2 and CO, which resulted in the mineralization ratio above 95%. Results from the operating parameter tests revealed that the increase of the initial acetone concentration enhanced the amount of acetone adsorbed on the ACF, which however did not increase the reaction rate of acetone. Although the increase of reaction temperature could reduce the amount of acetone adsorbed on the ACF, decomposition rate of acetone could be promoted, so as the yield rate and mineralization ratio of products (CO2 and CO). Increasing oxygen concentration did not influence the decomposition significantly except for oxygen concentration lower than 1%. The increase of water vapor would slightly decrease the amount of acetone adsorbed on the ACF, which did not decrease the decomposition of acetone anyway. This study revealed that the decomposition of acetone on TiO2/ACF can enhance the mass transfer of acetone substantially.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 185-202). Also available in electronic version. Access restricted to campus users.

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