M.Sc. / Water that is free from toxic organic pollutants is essential to human health and the environment at large. Organic contaminants may affect the endocrine system of animals and humans, even when present in very low concentrations (i.e. levels ppb). Current technologies fail to remove these organic compounds efficiently from water at ppb levels. So, the development of new technologies that are capable of removing and degrading organic pollutants from water is crucial. Hence, recently in our laboratories cyclodextrin (CD) polymers have demonstrated that they are capable of removing organic pollutants from water at ppb levels. The research has also demonstrated that both functionalized and unfunctionalized CD polymers can remove organic species to as low as parts per billion (ppb) from water. In this project, Si and Ti based compounds which have been reported to degrade organic compounds through photocatalysis in an aqueous media were incorporated. Firstly, attempts were made to attach the silicon (Si) and titanium (Ti) pendent chains onto the CD moiety to form silicon-based cyclodextrin (Si-CD) and titanium based cyclodextrin (Ti-CD) precursors. The Si-CD precursor was synthesized by attaching the 3-(triethoxysilyl)propyl isocyanate onto the native b-CD moiety. The synthesis of the Si-CD precursor was successful and high yields (80%) of the product were obtained. A hydrolysis of this Si-CD precursor in an inert atmosphere led to the formation of silanol. This was followed by curing the silanol in air, after adding TiO2 nanoparticles, and the Ti-CD precursor was formed. The polymerization of Si-CD with suitable bifunctional linkers was a success and water-insoluble polymers were produced. An attempt to polymerize the Ti-CD precursor failed, because the precursor was decomposed. The Si-CD polymers were tested for their capabilities to encapsulate and destroy organic pollutants from water. 1H NMR, FT-IR and EDX spectroscopic techniques were used to prove the formation of the Si-CD and Ti-CD precursors and their corresponding polymers. The Si-CD polymers showed capabilities of being able to remove organic pollutants (33-55%) from water. Unfortunately, the removal is slightly less efficient than the corresponding native CD polymers. However, their efficiency in removing organic pollutants improved when exposed to light. Moreover, the polymers formed display good thermal stabilities, since they decompose at about 300- 400°C. This is observed from the thermograms obtain ed from DSC and TGA. Their morphological studies showed that most of the Si-CD polymers formed were crystalline. This was observed from the SEM images obtained. Based on the information provided by the FT-IR spectroscopy, the synthesis of the Ti-CD precursor was success. However, the challenge was the fact that it decomposed after a while. Hence, it was difficult polymerize it into a water insoluble polymer. The explanation of this phenomenon is not yet established.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:6749 |
| Date | 08 April 2010 |
| Creators | Mbuli, Bhekani Sydney |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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