Conductive Membranes for Fouling Mitigation and Permeate Flux Control
Membrane filtration is an important purification and separation technique for drinking water generation, sterilization and beverage production. However, the performance of membrane filtration slowly degrades with continuous fouling on the membrane surface in the course of filtration progress. This thesis explores fouling mitigation and permeate flux control through conductive modification of the microfiltration membrane, namely coating a layer of conducting polymer on the membrane surface, to improve the function and, subsequently, cost-effectiveness of filtration systems. In this work, a microfiltration membrane was first fabricated by electrospinning of an elastomeric polymer sulfonated polystyrene-block-poly(ethylene-ran-butylene)-blockpolystyrene (sSEBS), followed by the coating of poly(3,4-ethylenedioxythiophene) (PEDOT) on the fibres’ surface. The conductive filtration membrane sSEBS/PEDOT showed an electrical resistance response towards the fouling from a model wine solution with a much higher sensitivity comparing to the permeate flux measurements. Hydrophilic modification was then carried out on the electrospun fibre mat coated with PEDOT copolymer embedded with atom transfer radical polymerisation (ATRP) initiator. A uniform, antifouling brush was successfully grafted on the conductive fibre surface by filtering the polymerisation solution through the conductive membrane to complete the surface-initiated ATRP. The grafted conductive fibre mat showed a reduced non-specific adsorption from the protein, providing a proof-of-concept for this innovative polymerization methodology. The conductive modification was then carried out on a commercially available microfiltration membrane. A layer of PEDOT was coated on an as-received microfiltration membrane through vapour-phase polymerisation. This conductive modification addresses the trade-off between filtration performance and electrical conductivity. The redox reactivity of the PEDOT coating led the ingress/egress of dopant ions to provide a swelling/de-swelling action. Such morphological changes provided a reversible permeate flux control on the conductive membrane via the electric input. The conductive modifications of microfiltration membranes in this thesis provide an insight into improving the function and cost-effectiveness of a filtration system through an electrical input/output of the conducting polymer coating on the membrane for fouling mitigation and permeate flux control, which could be valuable for the filtration industry.
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