Production of silver-loaded zeolites and investigation of their antimicrobial activity
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Williams, Craig D.
Kenward, M. A.
Kibble, Kevin A.
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AbstractThe production of silver-loaded zeolites either by ion exchange method or by isomorphous substitution of silver ions into zeolites frameworks and their antimicrobial activity is presented. Silver-loaded zeolites produced by ion-exchange in this work include silver-exchanged zeolite X, silver-exchanged zeolite A and silver-exchanged high-alumina Phillipsite. Silver-doped Analcime was produced by isomorphous substitution of silver ions into the Analcime framework. The silver-loaded zeolites were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, particle size analysis and Fourier transformed infrared (FTIR) spectroscopy. Studies showed that the amount of silver ions loaded into the zeolites frameworks differed for each zeolite. XRD analysis showed little or no changes in the phase purity of all zeolites before and after ion exchange or before and after substitution of silver ions. SEM analysis and particle size analysis showed that the morphology of each zeolite particles was closely related before and after ion exchanged or before and after substitution of silver ions. The antimicrobial activity of these silver-loaded zeolites was investigated by exposing Escherichia coli K12W-T, Staphylococcus aureus NCIMB6571 and Pseudomonas aeruginosa NCIMB8295 suspended in tryptone soya broth (TSB) to the silver-loaded zeolites. The first stage of the investigation involved the exposure of the strains to silver-loaded zeolites in TSB for a duration of 24 hours at different concentration of silver-loaded zeolites. The second stage involved the exposure of the strains to silver-loaded zeolites in TSB over a period of two hours. The persistency of antimicrobial activity of silver-loaded zeolites was investigated by retrieving each silver-loaded zeolite from the first exposure cultures, washed copiously with de-ionised water and adding to fresh bacterial suspensions. To understand the mode of antimicrobial activity of the silver-loaded zeolites, the uptake of silver ions by the strains, composition of fatty acid, as well as the DNA content of Escherichia coli K12W-T was studied. The results obtained showed silver ions appeared to elute from the zeolites frameworks into the TSB in anomalous trend. All three microorganisms were completely inhibited within one hour with the silver-loaded zeolites retaining their antimicrobial activity. The release of silver ions from the zeolites frameworks followed first-order kinetics with varying rate constants and half-lives. The fatty acid composition of all strains as well as the DNA content of Escherichia coli K12W-T were affected by the action of silver ions.
PublisherUniversity of Wolverhampton
TypeThesis or dissertation
DescriptionA thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy