Abstract
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.