(392o) Design of a Self-Cleaning Nanostructured Reverse Osmosis Membrane

Reverse osmosis (RO) is a pressure driven membrane technology process that finds wide applications in water treatment processes. One of the major challenges faced by this technology is the tendency of the membrane to get fouled in presence of various foulants present in wastewater. This results in significant flux decline and lower rejection values that necessitate frequent replacement of the membrane. The current project thereby aims at preparation of an anti-fouling RO membrane having better longevity without compromising it’s permeate flux and rejection properties and also without further increment in the operational cost of the process. Surface modification of commercial membranes using hydrophilic polymer brushes containing poly (ethylene glycol) (PEG) units has been implemented by several research groups. The polymer brushes can be grafted on the substrates via covalent linkages and these brushes provide resistance against fouling. Although addition of the brush layer lowers the initial flux value, the relative flux decline of the modified membrane is lesser compared to the unmodified membrane. If the underlying polyamide dense layer of commercial RO membranes be replaced by a more permeable membrane skin the overall permeability can be improved. Alternate deposition of oppositely charged polyelectrolytes to form nanostructured membrane skins has been reported as a promising technique in several papers. The layer-by-layer (LbL) technique of depositing polyelectrolytes allows control on deposition of ultrathin bilayers on a support both in terms of numbers as well as the thickness of the multilayer assembly.  Appropriate choices of the polyelectrolytes and various deposition parameters lead to improvement in permeate flux and rejection properties of the resulting membrane. The combination of these two functionalities for membrane preparation has not yet been explored yet. We propose the LbL deposition of polyelectrolyte multilayers on a porous support and attachment of polymer brush units to the topmost layer by polymer grafting techniques. The attachment of PEG-based polymer brush layer can be achieved through polymer-on-polymer stamping method wherein a thin layer of polymer can be transferred onto the multilayer surface thereby yielding a multifunctional self-cleaning RO membrane.