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Includes bibliographical references (p. 245-271).

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Carbonized organic precursors such as wood, shells and some plant seeds are very porous. They are nanostructured and tend to be hard, but have pure mechanical properties as a result of their porosities. An attempt was made to carbonize an organic precursor to produce a bulk material with much less porosity for possible use in structural applications such as reinforcement in metal and polymer matrices. A bulk nanocarbon (BNC) material was synthesized using high energy ball milling and the carbonization of corn cob. Corn cob was mechanically milled for up to 20 hours by applying high energy ball milling to produce the milled powder. The milled powder was cold-compacted and carbonized at up to 1500°C to fabricate the BNC material. The material revealed both micro and nano-porosities; the porosities decreased with carbonizing temperature and hold time. Micropores were mostly closed for samples carbonized above 1300oC, whereas they formed interconnected network at lower carbonization temperatures. BNC has a young's modulus of 120 GPa, about ten times that of extruded graphite. / Master of Science / Wood, shells, and plant seeds are examples of organic precursors. When organic precursors are carbonized, they can become very porous, nanostructured, and hard, but deliver pure mechanical properties because of their porosities. A selected organic precursor was carbonized, in an attempt, to produce a bulk material with much less porosity for possible use in structural applications such as reinforcement in metal and polymer matrices. A bulk nanocarbon (BNC) material was made using high energy ball milling and the carbonization of corn cob (the selected organic precursor). This bulk material revealed both micro and nano-porosities, and a young's modulus of 120 GPa, about ten times that of extruded graphite.

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The search for a low cost and effective technique to control and remove volatile organic chemicals (VOCs) has gathered a great attention from the adsorption process field. Advances in manufacturing technology have enabled the creation of activated carbon monoliths (ACM) as promising substitute for traditional packed beds of granular adsorbent materials. The research described in this thesis comprises an extensive experimental study of a single component adsorption process onto square and hexagonal channel Novacarb™ ACM supplied by MAST Carbon Technology Ltd. ACM characterisation methods such as nitrogen and solvent adsorption isotherms, electron microscopy, thermo-gravimetric analysis and thermal dynamic characterization have been used. High BET surface area, high total pore volume and high total solvent mass uptakes have been found. ACM were tested by obtaining column breakthrough curves mainly using dichloromethane and acetone as the adsorbates at the bench-scale. The adsorption dynamics of the ACMs studied were also compared with those of extrudates manufactured by the same process as the ACMs. The influence of humidity on the adsorption process has been studied at the bench-scale. Finally, the adsorption system was scaled-up to about 60cm length monoliths in order to study both adsorption and electrical regeneration taking advantage of the particular electrical properties held by the Novacarb™ ACM. It has been found that ACMs are able to adsorb high levels of VOCs, up to 40% by weight of DCM, good behaviour under humidity conditions and low pressure drop. In contrast, kinetics of ACMs have been found to be somewhat inferior to those of equivalent packed beds, although the ACM performance can be improved by reducing the wall thickness. Adsorption of DCM at the pilot-scale has demonstrated that the Novacarb™ ACM could easily be used in a cyclic thermal swing adsorption process with a half cycle time of less than one hour.

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.

Activated carbons used in the Platinum Group Metals extraction industry are characterised by large internal surface areas and a great affinity for platinum, palladium and ruthenium. It is therefore necessary in this study to develop a method to produce an activated carbon that is suitable and yet cost effective, for use in the extraction of PGM's. The quality of the coal-based activated carbon may not prove to be as good as activated carbon produced from other traditional sources, but the production costs involved may make South African coal a feasible alternative feedstock. The purpose of this research is to prepare activated carbon from a South African based bituminous coal by physical activation. The activated carbon produced are characterised by BET surface area, activated carbon pH and phenol adsorption studies. The results of the different characterisation methods for the prepared activated carbons are compared to the results of a commercially available activated carbon, Norit RO 0.8 (control sample). Bituminous coals from various sources including Witbank Seam 4 and New Vaal are used. The preparation method chosen is raw material activation by means of physical activation with superheated steam. The effects of process variables such as activation time (1-3 hr) and temperature (600 - 800°C) are studied in order to optimise those preparation parameters. Activated carbon surface area is characterized by means of nitrogen adsorption isotherms at 77K. BET surface area analysis showed that Witbank Seam 4 coal activated at a temperature of 800°C and activation time of 3 hours, resulted in a surface area of 340m2/g. Quality control of each sample was performed by measuring the pH of a known amount of the prepared activated carbon in distilled water over time. Results showed that the pH of some of the prepared activated carbons reached a value of 11. Phenol adsorption results for the different activated carbons prepared corresponded well to the results obtained for the Norit RO 0.8 activated carbon sample. / Thesis (M. Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2008.