Fabrication and characterisation of poly (ethylene-co-vinyl alcohol) nanofibers with biocidal additive for water filtration

Motsi, Margaret (2018-03)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Water is an undeniable right for all humans and their wellbeing is dependent upon equitable access to a safe, adequate and affordable water supply. The world is facing formidable challenges in meeting rising demands of clean water as the available supplies of fresh- water are decreasing due to (i) extended droughts, (ii) population growth, (iii) more stringent health- based regulations, and (iv) competing demands from a variety of users. The aim of this study is to prepare and compare three types of poly (ethylene-co-vinyl alcohol) (EVOH) nanofibers and determine which type of fibre will be most suitable for the application in water sanitation. Testing of antimicrobial activity of the AquaQure containing EVOH nanofibers, as well as leaching out of metal ions which could imply toxicity and reusability of the EVOH nanofibers modified with the AquaQure biocide will be investigated. As an effort to do away with the conventional methods of water purification that involve the use of chemicals which introduce harmful substances to the environment, fabrication and characterization of anti-microbial polymer nanofibers with a nanobiocide will be done in this study. Secondly, the problem of biofouling on filtration membranes will be addressed by fabricating and testing polymer nanofibers with different degrees of hydrolysis. To address water sanitation, three types of EVOH nanofibers, (i) 27 mol. % (ii) 32 mol. % and (iii) 44 mol. % ethylene content are to be prepared using single needle electrospinning. AquaQure an aqueous antimicrobial agent containing mainly Cu2+ and Zn2+ ions will be used as an additive to the polymer solutions. The nanofibrous mats, neat EVOH and modified EVOH/AquaQure were successfully fabricated using the conventional single needle electrospinning. The incorporation of the biocide was confirmed by EDX, ATR-FTIR, TGA, DSC and SEM techniques were used to do chemical and thermal analysis of the nanofibers in comparison with neat EVOH nanofibers. The hydrophobicity of nanofibrous mats was measured using static contact angle measurements. The testing of antimicrobial activity of the AquaQure containing EVOH nanofibers against the gram positive and gram negative bioluminescent strains of Staphylococcus aureus Xen-36 and Escherichia coli Xen-14 respectively. The antimicrobial tests were confirmed with non-culture-based techniques namely bioluminescent imaging and LIVE/DEAD Baclight to determine the antimicrobial efficiency against viable but non-culturable (VNBC) cells. This was done to quantify the cells that enter a dormant state during contact with the antimicrobial fibres and to eliminate the chances of overestimating the antimicrobial efficiency of the nanofibers.

AFRIKAANSE OPSOMMING: Water is 'n onmiskenbare regte vir alle mense en hul welstand is afhanklik van gelyke toegang tot 'n veilige, geskikte en bekostigbare watervoorsiening. Die wêreld in die gesig staar formidabele uitdagings in die vergadering stygende eise van skoon water as die beskikbare voorraad van vars- water verminder weens (i) langdurige droogtes, (ii) bevolkingsgroei, (iii) strenger gesondheidsverwante gebaseer regulasies, en (iv) mededingende eise van 'n verskeidenheid van gebruikers. Die doel van hierdie studie is om voor te berei en te vergelyk drie tipes van poli (etileen mede -vinyl alkohol) (EVOH) nanovesels en bepaal watter tipe vesel meeste geskik is vir die toepassing in water sanitasie sal wees. Toetsing van antimikrobiese aktiwiteit van die AquaQure bevat EVOH nanovesels, sowel as loging uit metaalione wat toksisiteit en herbruikbaarheid van die EVOH nanovesels verander word met die AquaQure biologiese middels kon impliseer sal ondersoek word. As 'n poging om weg te doen met die konvensionele metodes van watersuiwering dat die gebruik van chemikalieë wat skadelike stowwe bekend stel aan die omgewing, vervaardiging en karakterisering van anti- mikrobiese polimeer nanovesels met 'n nanobiocide sal gedoen word in hierdie studie betrek. Tweedens sal die probleem van bio op filtrasie membrane aangespreek word deur die vervaardiging en toets polimeer nanovesels met verskillende grade van hidrolise. Om water sanitasie, drie tipes EVOH nanovesels, spreek (i) 27mol% (ii) 32mol% en (iii) 44mol% etileen inhoud om voorbereid te wees met behulp van enkele naald elektrospin. AquaQure 'n waterige antimikrobiese agent wat hoofsaaklik Cu2+ en Zn2+ -ione sal gebruik word as 'n toevoeging tot die polimeer oplossings. Die nanofibrous matte, netjiese EVOH en verander EVOH / AquaQure is suksesvol vervaardig met behulp van die konvensionele enkele naald elektrospin. Die inlywing van die biologiese middels is bevestig deur EDX. ATR-FTIR, TGA, is DSC en SEM tegnieke wat gebruik word om chemiese en termiese analise van die nanovesels doen in vergelyking met netjiese EVOH nanovesels. Die hydrophobicity van nanofibrous matte is gemeet deur statiese kontak hoek metings. Die toets van antimikrobiese aktiwiteit van die AquaQure bevat EVOH nanovesels teen die gram positiewe en Gram negatiewe Bioluminescent stamme van Staphylococcus aureus Xen- 36 en Escherichia coli Xen-14 onderskeidelik. Die antimikrobiese toetse bevestig met nie-kultuur gebaseer tegnieke naamlik Bioluminescent beelding en leef / dooie Baclight om die antimikrobiese doeltreffendheid teen lewensvatbare maar nie-culturable (VNBC) selle te bepaal. Dit is gedoen om die selle wat 'n dormante staat voer tydens kontak met die antimikrobiese vesels kwantifiseer en om die kanse van die oorskatting antimikrobiese doeltreffendheid van die nanovesels te skakel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103701
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