Thesis (M. Sc.)--University of Hong Kong, 2006.

No description available.

No description available.

Made available in DSpace on 2014-10-09T12:41:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:01Z (GMT). No. of bitstreams: 1 03984.pdf: 4155430 bytes, checksum: 939d4f5a69f51c8028d8c59f56de0a8e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Materials representative of those found in a Geological Disposal Facility (GDF) for the long-term storage of nuclear waste have been investigated for their ability to retard the movement of ionic species found in nuclear waste. Fe1-xO, Fe2O3, Fe3O4 (from steel corrosion) and sandstone (bedrock) used as physical barriers in the GDF have been treated using solutions of pH 7-13 which are representative of the leachate expected from concrete encapsulation of waste in contact with ground water. A mimic of portlandite cement, Ca(OH)2 was also prepared carbonate-free via a sacharate method for use in these leachate experiments. Materials have been characterised using a mixture of techniques such as Powder X-ray Diffraction (PXRD) and Infra-red Spectroscopy which focus on the bulk, short range techniques such as Extended X-ray Absorption Fine Structure (EXAFS), Scanning Electron Microscopy(SEM) and Nuclear Magnetic Resonance(NMR) and physical measurements such as diffusion experiments and fluorescence spectroscopy. Characterisation of the bulk materials before and after treatment using PXRD and SEM indicates that high purity iron oxides are affected differently by the solutions of varying pH. While not detectable by bulk techniques, SEM analysis evidence of the surface of the materials showed that Fe1-xO was deleteriously affected by solutions with pH > 7 more than the more oxidised materials. Initially needle-like crystals formed on the surface of Fe1-xO that are characteristic of goethite which at long aging times up to 168 h, showed transformation to crystal morphologies characteristic of Fe2O3. As the alkalinity increased, the transformation of Fe1-xO to Fe2O3 slowed. Dissolution of the iron surfaces in the solutions of pH 7-13 were determined by measuring the concentration of dissolved iron using ICPMS. While Fe1-xO and Fe3O4 followed first order kinetics, the dissolution kinetics for Fe2O3 appeared more complex. As the alkalinity increased, the rate constant for dissolution decreased in all cases indicating that higher pH is better for containment due to the formation of a passivated surface layer evidenced by SEM. The sorption of uranium to the iron oxide surfaces was investigated as a function of pH (7-13). In all cases, there was evidence of uranium sorption. The greatest sorption was evidenced when Ca(OH)2 was present which is most likely due to the precipitation of the known phase, calcium uranate. In the absence of calcium hydroxide, the sorption of uranium to the iron oxide surfaces decreased as the pH increased, reflecting the increase in formation of the anionic uranium species. In the presence of carbonate, the sorption of uranium onto the surfaces also decreases reflecting the formation of the soluble uranyl carbonate species. NMR spectroscopy of uranyl species in solution indicates that the chemical shift is strongly affected by pH shifting from 163 ppm to 175 ppm as the pH changes from 7 to 13 and allowing the uranium speciation to be used as a pH probe. A much -2- smaller shift in respect of temperature of less than 0.5 ppm was observed in the temperature range studied between 25 and 50°C. The quality of fluorescence spectra has been shown to be strongly affected by complexing species present in solution, the best spectra achieved with non-complexing species such as perchlorate. Migration experiments of the radionuclides uranium, thorium and technetium has been investigated by placing sandstone cores in alkaline solution and analysing both the water itself and the core to examine retention and transport. The results determined that the technetium diffused readily through the sandstone matrix. The uranium and throrium did not achieve breakthrough. This was attributed to the low solubilities and the formation of stable precipitates.

Made available in DSpace on 2014-10-09T12:38:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:47Z (GMT). No. of bitstreams: 1 05660.pdf: 7392125 bytes, checksum: eb370b9192c312fd26fdb86ad9ed35bc (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:41:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:01Z (GMT). No. of bitstreams: 1 03984.pdf: 4155430 bytes, checksum: 939d4f5a69f51c8028d8c59f56de0a8e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:38:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:47Z (GMT). No. of bitstreams: 1 05660.pdf: 7392125 bytes, checksum: eb370b9192c312fd26fdb86ad9ed35bc (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Dissertation submitted in compliance with the requirements for the Masters Degree in Technology: Biotechnology, Durban Institute of Technology, 2003. / Water is a precious and very valuable resource. Water resource shortages are problems that are plaguing the world. There is therefore a high demand for tightening water quality standards for both potable water and waters in the environment. It is becoming a necessity to treat and reuse wastewaters, especially wastewaters from industries, as these waters are of concern due to their toxic effects on the environment. In South Africa one of the industries of major concern is that of the edible oil industry and there are over a dozen ofthese industries in South Africa alone. Each of these industries utilises approximately 1.75 million m3 of water and discharges approximately 0.61 million m3 to the sewer each year. This wastewater that is being released has very high organic, inorganic and fats, oils and greases loads. Depending on the type of refinery process conducted on the crude oil, the effluent quality and quantity varies on a day to day basis. The two types of refinery procedures are the physical refining, where water is used or chemical refining where caustic soda is used. The organic load ofthe untreated effluent can range from 1 100 to 8 990 mg COD/L, the oils and greases can range from 80 to 1 360 mg/L and the pH can range from 1.8 to 10.5. / M

Saline deterioration in the South African public water system has been documented and disposal of brine wastes has been identified as part of the problem. The broad aim of this research programme was to undertake an initial technical study to evaluate the feasibility of integrating algal biotechnology into a disposal function for these wastes. A demonstration of utility in the form of products and waste treatment could produce a beneficiation of saline effluents and provide incentives necessary to deal with the disposal issue. The study attempted to demonstrate a synthesis between the two main thrusts in algal biotechnology that have produced large-scale practical applications - stable, predictable algal production in saline media and the cost effective High Rate Oxidation Ponding (HROP) process for incorporating algal production into a waste treatment function. Tannery organic saline effluents and the biotechnology of Dunaliella salina culture producing β- carotene were chosen as paradigms for the study. 1. The alga was shown to grow in certain tannery effluents producing enhanced biomass yields compared to defined inorganic medium cultivation. The potential for amino acid or protein supplementation of defmed culture media was noted. 2. A reduction in organic load simultaneous with the growth of D.salina was recorded in laboratory-scale simulations of the HROP process. Rates similar to the fresh water HROP equivalent were demonstrated. 3. These results suggested the uptake and storage of organic nitrogen by D.salina. The consequent inhibition of β-carotene accumulation by the organism presented a potentially insurmountable obstacle to the feasibility of β-carotene production in this medium. Uptake and release of organic compounds, previously demonstrated in phytoplankton and other micro-algae, was confirmed in this study for D.salina. The evidence acquired indicated the internalization of both glycine and bovine serum albumin. An ultrastructural study demonstrated mechanisms by which this process might occur. 4. The release of substantial quantities of glycerol was shown. A mechanism whereby D. salina may use this to regulate ammonia availability via control of its associated bacterial population was observed. Glycerol release was identified as presenting an application in treating refractory organic wastes, such as secondary sewage sludges, by elevating C:N ratios. This could demonstrate a significant utility for brine waste impoundments. 5. A multistage production process was proposed to deal with the problem of β-carotene inhibition by separation of the growth and metabolite accumulation functions into separate unit operations. It was shown in this study that the stress of nitrogen deficiency combined with high salinity provides for effectiveβ-carotene accumulation under the conditions of low illumination that pertain in dense cultures. Subjected to these conditions effluent-grown cells show delayed but unimpaired {j-carotene accumulation. 6. A role for the plant hormone abscisic acid in mediating the stress response was demonstrated in D.salina. Fluorescence induction studies suggested the presence of a signalling process forming part of a sensitivity control mechanism. Stress induction of β-carotene accumulation could occur through four clearly defined stages. Potential was identified for using this response as a physiological probe for monitoring and regulating the stress induction process. 7. The multistage processing concept requires effective algal cell separation technology. The use of cross-flow ultrafiltration and diafiltration with a polyethersulfone tubular membrane system was demonstrated as an effective process for the recovery and washing of D. salina. Cell concentrates were produced in a viable form. 8. Process designs incorporating the findings of the research programme are presented demonstrating how effluent and organic waste treatment functions may be combined with the production of D.salina and its products. Application of the multi-stage processing concept to β-carotene production in a defined medium process was identified as offering a potential four-fold yield enhancement. This could have a significant impact on a high cost, marginal algal biotechnology process. Aspects of novelty have been claimed in provisional patents applications. A provisional demonstration of the feasibility of D.salina production in tannery effluent indicates that algal biotechnology may provide a utility for, and hence the beneficiation of saline effluent wastes.