A Bio-Inspired Surface Modification to Increase Membrane Biofouling Resistance

Abstract

Membrane processes have gained significant traction over competing technologies in many real-life water purification applications. However, fouling is still a major obstacle facing wide-spread implementation of membrane systems. Surface modifications of common membranes have been effective at remediating fouling of a number of common contaminants, including emulsified oils, proteins, and biofoulants. Nevertheless, many problems arise with most surface modifications. For example, harsh treatments and chemicals may damage a membrane and most modifications are membrane-specific. Here we report an effective membrane modification that can be universally applied to all membranes. Polydopamine was recently found to non-selectively deposit from solution on virtually every surface with which it came into contact. Seven membranes with various properties were modified using polydopamine and showed reduced fouling while filtering a synthetic oil-water emulsion. Because polydopamine forms a non-selective coating on any surface so far tested, its deposition provides a route to universal membrane modification, eliminating the need to choose appropriate, membrane-specific chemistries for further surface modification. Poly(ethylene glycol) ad-layer formation on the polydopamine surface further improved membrane performance. Membranes modified with polydopamine and with an additional poly(ethylene glycol) ad-layer were also tested for protein and bacterial adhesion. Protein and bacteria adhesion, a precursor to biofilm formation and membrane biofouling, universally occurs in water treatment facilities and in membrane bioreactors. All seven polydopamine-modified membranes showed reduced adhesion of both bovine serum albumin and lysozyme relative to unmodified membranes. Futher reduction in adhesion of both proteins was observed for membranes with an additional poly(ethylene glycol) ad-layer. Adhesion of Pseudomonas aeruginosa, a bacterium commonly found in freshwater drinking reserves and notorious cause of robust biofilm growth in water purification operations, was also explored and will be presented. The simplicity and versatility of polydopamine deposition on membranes gave it distinct advantages over other common modification. Due to the adaptable nature of the polydopamine modification, we anticipate that this technology will be a building block upon which other, more sophisticated anti-fouling surfaces can be based.