A human being weighting 70 kg needs to drink 2.1 litres of water per day to sustain life. Yet 1% of the water available on earth is drinkable. This means that one of the major challenges of the 21^st century will be to overcame the severe problem of guaranteeing the safe drinking water for rapidly increasing world population.

Our research is focused on development of novel water prefiltration media functionalised towards antimicrobial and biocidal properties. As a final goal, commercial polypropylene (PP) candle filters will be modified using silver (Ag) or zinc oxide (ZnO) nanoparticles or composite materials of such nanoparticles deposited on multiwall carbon nanotubes (MWCNTs). Our current research achievements include successful functionalization of non-woven polypropylene (NWPP) fabrics by mentioned above nanomaterials. Preliminary tests of antimicrobial and biocidal properties of synthesized materials show promising results, especially in the case of Ag or Ag/MWCNTs modified fabrics.

Scope of research

Commercially available MWCNTs were subjected to thorough cleaning and hydrophilization using strong acidic/oxidising solution treatment. Such prepared MWCNTs were dispersed in isopropyl alcohol under ultrasonication and/or by high pressure stream (Microfluidics).

Commercial PP fabrics made via MeltBlown technique with average fibre diameter of few micrometers were chosen as a base filtrate material. Surface of the fibres were directly modified by in situ formation of ZnO or Ag nanoparticles using sol-gel or reduction method, respectively.

MWCNTs deposition on PP fibres were realized by flushing of the fabrics with low concentration nanotubes suspensions in isopropyl alcohol. Such MWCNTs decorated fabrics were further subjected to nanoparticles formation process.

Due to the poor coverage ratio especially in the case of ZnO and Ag nanoparticles preliminary PP fibre surface activation process via oxygen plasma treatment was developed.

Antimicrobial and biocidal properties of modified fabrics were tested against Escherchia coli, Pseudomonas fluorescens, Staphylococcus aureus, Salmonella typhimurium and Enterococcus faecalis.

Results

1. Plasma pretreated and Ag/MWCNTs modified PP fabrics showed the best biocidal properties. Biocidal activity of this material was observed against all types of bacteria. The strongest effect was observed for Gram-positive E. coli and S. typhimurium (living cell reduction by factor of 10⁶ and 10⁵ respectively).
2. Plasma pretreated and Ag modified material was found to be less effective (reduction factor 10⁶ and 10⁴). This material was inactive against P. fluorescens.
3. Materials modified without plasma pretreatment were found to be much less effective.

Research has been funded by NCRD within the MNT-ERA.NET programe no. ERA-NET/MNT/NFSM/1/2011.

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