Investigation of Antibacterial and Fouling Resistance of Silver and Multi-Walled Carbon Nanotubes Doped Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composite Membrane.

Lutendo Macevele,Kgabo Moganedi,Takalani Magadzu

doi:10.3390/membranes7030035

Abstract

Composite membranes were successfully prepared using a phase-inversion method. The X-ray powder diffraction (XRD) and energy dispersive X-ray (EDX) profiles has confirmed formation of 4.8 wt % Ag/poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), 3 wt % Ag-MWCNTs/PVDF-HFP (EDX surface composition of Ag nanoparticles) and 1.5 wt % MWCNTs/PVDF-HFP composite membranes. The MWCNTs crystallites are mainly encapsulated by a layer of PVDF-HFP, as evidenced by disappearance of graphitic peak. The scanning electron microscopy (SEM) images have depicted the formation of microporous structure, with few MWCNTs on the surface and strongly interacting with PVDF-HFP as demonstrated by thermogravimetric analysis (TGA), XRD and Fourier transform infrared (FTIR) data. The data indicated an increase in porosity, swellability and water content of the PVDF-HFP membrane with the addition of MWCNTs and/or Ag nanoparticles, showing an improved hydrophilicity. The 1.5 wt % MWCNTs/PVDF-HFP composite membrane showed good desalination and fouling resistance rates, which correlates with a low water contact angle. The combined effects of Ag nanoparticles and MWCNTs do not promote fouling resistance of PVDF-HFP membranes, as shown during NaCl microfiltration (this is linked with high water contact angle as compared to that of MWCNTs/PVDF-HFP composite). Both 1.5 wt % MWCNTs/PVDF-HFP and 3 wt % Ag-MWCNTs/PVDF-HFP composite membranes prevented the bacteria passing through the membrane (100% bacterial load reduction). The surface of 3 wt % Ag-MWCNTs/PVDF-HFP showed good bactericidal and non-leaching properties of the dopant materials (MWCNTs and Ag), as evidenced by bacterial growth on the edges of the membranes.

Highlights

Clean drinking water availability is a major problem for developing countries [1]
This broad peak disappears upon addition of 1.5 wt % MWCNTs onto the structure of poly(vinylidene fluoride) (PVDF)-HFP
The two sharp peaks seen in the X-ray powder diffraction (XRD) profiles of Ag/PVDF-HFP and Ag-MWCNTs/PVDF-HFP membranes are indexed to (111) and (200) planes, confirming the presence of Ag nanoparticles

Summary

Introduction

Clean drinking water availability is a major problem for developing countries [1]. Scarcity of safe drinking water remains a global problem and is expected to rise with increasing population growth and environmental changes [2]. Drinking polluted or contaminated water can cause serious health problems; for example, cholera and diarrheal diseases cause many deaths of children in developing countries [3,4]. The World Health Organization (WHO) recommended that any water intended for drinking should contain fecal and total coliform counts of 0.00 in any 100 mL sample [5]. When bacteria are encountered in water samples, immediate investigative action should be taken [5].

Methods

Results

Conclusion