Fouling of polyelectrolyte multilayer based nanofiltration membranes during produced water treatment: The role of surfactant size and chemistry

Large volumes of water become contaminated with hydrocarbons, surfactants, salts and other chemical agents during Oil & Gas exploration activities, resulting in a complex wastewater stream known as produced (PW). Nanofiltration (NF) membranes are promising alternative for the treatment PW to facilitate its re-use. Unfortunately, membrane fouling still represents major obstacle. In present work, we investigate effect surface chemistry on NF based polyelectrolyte multilayers (PEM), artificial water. To this end, oil-in-water (O/W) emulsions stabilized four different surfactants (anionic, cationic, zwitterionic non-ionic) were treated PEM-based having same multilayer, but top layer polymer chemistry: crosslinked poly(allylamine hydrochloride) (PAH, nearly uncharged), poly(sodium 4-styrene sulfonate) (PSS, strongly negative), poly(sulfobetaine methacrylate-co-acrylic acid) (PSBMA-co-AA, zwitterionic) Nafion (negative hydrophobic). First, study adsorption surfaces model interfaces. Second, by hollow fiber characterized multilayer our surfaces. Third, solution without oil. Very high oil retention (>99%) was observed when filtering all O/W emulsions, while physicochemical interactions between determined extent well surfactant retention. Unexpectedly, results show that membranes, treatment, is mainly due active caused uptake inside PEM coating, rather than cake formation. Indeed, it not determines fouling, interaction bulk PEM. A denser would stop these molecules, benefit decreasing issues, use slightly more bulky cannot penetrate