Preparation and Characterisation of Alginate Composite Beads and Investigations into their Potential Use in Environmental Applications

The present research is concerned with the polymer sodium alginate, a naturally occurring biocompatible and biodegradable polysaccharide. The first objective was to prepare, characterise and monitor the release properties of a urease inhibitor (NBPT) from different calcium alginate hydrogel beads. Four bead types were chosen for this study, calcium alginate, charcoal-loaded and bentonite-loaded calcium alginate, and polypyrrole-coated calcium alginate beads. The surface morphology of the beads was investigated using SEM. The swelling studies on the beads showed that the polypyrrole-coated calcium alginate beads showed the lowest amount of swelling in all media tested. The stability of the NBPT as a function of pH was investigated using NMR spectroscopy, which showed that NBPT decomposes at acidic and highly basic pH values. The release of NBPT into aqueous solutions was monitored using UV/Vis spectroscopy. Release was uncontrolled if beads were agitated and was significantly slowed down when they were not agitated. The bentonite-loaded and polypyrrole-coated calcium alginate beads showed the most promising results for developing a controlled release system for NBPT. The second objective was to assess the ability of alginate beads, which contained silver(I) and silver(0), to inactivate pathogenic microorganisms in a water treatment process. The three different bead supports used were sodium alginate beads (Alg), propylene glycol alginate composite beads (PGA) and alginate beads functionalised with propyloctadecyldimethylammonium groups (TSA beads). Atomic absorption spectroscopy was used to assess the amount of silver encapsulated in the beads. Swelling studies in water indicate that the TSA beads were resistant to swelling. The beads were studied for their ability to inhibit the growth or kill one strain of fungi and five strains of bacteria. The TSA beads that contained silver(I) showed the greatest antimicrobial activity against the six micro-organisms studied, making them the most attractive polymer support, for use in materials for water disinfection