title: Facile Modification of Reverse Osmosis Membranes by Surfactant-Assisted Acrylate Grafting for Enhanced Selectivity.
abstract: The top polyamide layer of composite reverse osmosis (RO) membranes has a fascinatingly complex structure, yet nanoscale nonuniformities inherently present in polyamide layer may reduce selectivity, e.g., for boron rejection. This study examines improving selectivity by in situ "caulking" such nonuniformities using concentration polarization-enhanced graft-polymerization with a surfactant added to the reactive solution. The surfactant appears to enhance both polarization (via monomer solubilization in surfactant micelles) and adherence of graft-polymer to the membrane surface, which facilitates grafting and reduces monomer consumption. The effect of surfactant was particularly notable for a hydrophobic monomer glycidyl methacrylate combined with a nonionic surfactant Triton X-100. With Triton added at an optimal level, close to critical micellization concentration (CMC), monomer gets solubilized and highly concentrated within micelles, which results in a significantly increased degree of grafting and uniformity of the coating compared to a procedure with no surfactant added. Notably, no improvement was obtained for an anionic surfactant SDS or the cationic surfactant DTAB, in which cases the high CMC of surfactant precludes high monomer concentration within micelles. The modification procedure was also up-scalable to membranes elements and resulted in elements with permeability comparable to commercial brackish water RO elements with superior boric acid rejection.
authors.affiliation: Technion - Israel Institute of Technology , Wolfson Department of Chemical Engineering, Technion City, 32000 Haifa, Israel.
authors.forename: Katie
authors.initials: K
authors.lastname: Baransi-Karkaby
authors.affiliation: Technion - Israel Institute of Technology , Wolfson Department of Chemical Engineering, Technion City, 32000 Haifa, Israel.
authors.forename: Maria
authors.initials: M
authors.lastname: Bass
authors.affiliation: Technion - Israel Institute of Technology , Wolfson Department of Chemical Engineering, Technion City, 32000 Haifa, Israel.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Levchenko
authors.affiliation: Technion - Israel Institute of Technology , Wolfson Department of Chemical Engineering, Technion City, 32000 Haifa, Israel.
authors.forename: Shahar
authors.initials: S
authors.lastname: Eitan
authors.affiliation: Technion - Israel Institute of Technology , Wolfson Department of Chemical Engineering, Technion City, 32000 Haifa, Israel.
authors.forename: Viatcheslav
authors.identifier: 0000-0001-8067-052X
authors.initials: V
authors.lastname: Freger
mesh_terms: D000179:Acrylates; D005374:Filtration; D008823:Micelles; D009995:Osmosis; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000179:Acrylates; D008823:Micelles; D013501:Surface-Active Agents