Microwave assisted graft synthesis and characterization of low-fouling polyethersulfone-g-poly(methacrylic acid) and polyethersulfone-g-poly(maleic acid) membranes for water treatment

K. Sikhwivhilu, L. Ndlwana, R. Moutloali, J.C. Ngila
Mintek,
South Africa

Keywords: ultrafiltration membranes, methacrylic acid, maleic acid, microwave synthesis, polyethersulfone

Summary:

Conventional water treatment methods are slow, require large physical space, produce large amounts of sludg have a larger footprint, have and expensive and hence membranes have been explored provide strength, value for money and stability. Membranes however face challenges that include, among others, fouling. To counter this, hydrophilic membranes have been utilized to mitigate fouling and increase lifespan. In this work, powder composites of grafted polyethersulfone (PES) were prepared via microwave (MW) assisted synthesis. The polar and microwave active nature of methacrylic and maleic acid were exploited to graft them onto PES powder in this manner for the first time. Microwave irradiation has recently seen great interest in the preparation of nanomaterials and polymers. This is credited to the rapid nature of the MW interactions with the sample as compared to conventional heating as previously employed by other researchers. The successful grafting was determined by Fourier transform infra-red spectroscopy (FTIR) after which membranes were prepared from the powders by the phase inversion technique. Topographical analyses of the membranes and surface roughness were was also investigated by atomic force microscopy (AFM) were surface roughness increased upon grafting. Further characterization followed where the scanning electron microscopy (SEM) was used to investigate the pore structure of the membranes surface and cross-sectional morphology. Contact angle measurements showed enhanced hydrophilicity as a result of grafting. Water permeation studies were also carried out and fluxes and these parameters presented significant enhancements. The porosity of the membranes was determined by water uptake experiments which increased on grafting.