Fouling Resistant Nanofiltration Membranes From Self-Assembled Quaternary Ammonium Monomers

Nanofiltration membranes with uniform and tunable pore sizes are highly sought after for wastewater treatment. Macromolecular organics and oily species are prevalent in wastewater streams and are challenging drivers of fouling that lead to decreased membrane performance. Efforts to reduce fouling therefore remain of interest in the development of new nanofiltration membranes. We report that nanostructured thin film composite membranes fabricated from a self-assembled mesophase of a polymerizable surfactant [2-(acryloyloxy)ethyl]dimethyl tetradecyl ammonium bromide (AETDAB) demonstrate excellent fouling resistance to protein solutions and oil-in-water emulsions. AETDAB lyotropic mesophases were cast atop a support membrane and crosslinked, forming hexagonally packed polymer cylinders arrayed in the plane of the membrane. The evenly spaced cylinders create channels with diameters of ~1 nm that represent the transport limiting dimension for the system. The composite membranes showed outstanding antifouling characteristics, retaining ~95% of permeance over a 72-hour period while completely rejecting a model organic foulant, bovine serum albumin (BSA). The membrane also demonstrated similarly strong fouling resistance during the filtration of oil-in-water emulsions, retaining ~95% of its permeance. The fouling resistance highlight the membrane’s potential to be used for challenging nanofiltration applications, while retaining its performance over long periods of time.