Fabrication of high-performance reverse osmosis membranes via dual-layer slot coating with tailoring interfacial adhesion

Abstract

Dual-layer slot coating (DSC) is a state-of-the-art technique that can fabricate thin film composite membranes by simultaneously spreading two monomer solutions to form an unsupported ultrathin polyamide (PA) selective layer, which is subsequently adhered to a support. To demonstrate its versatility, DSC was applied to polyethylene and polysulfone supports modified with O2 plasma and/or polydopamine (PDA) coating for the fabrication of high-performance reverse osmosis (RO) membranes. PDA coating enabled the uniform and robust PA deposition by uniformly hydrophilizing supports and reinforcing PA-support interfacial adhesion through the introduction of oxygen-containing and amine groups that promote hydrogen bonding with the PA layer, thus achieving good RO performance. The O2 plasma treatment on PDA-coated supports further strengthened PA-support interfacial adhesion by increasing the number of carboxyl groups with a higher hydrogen bonding ability, hence fabricating long-term stable, high-performance RO membranes that outperform a commercial RO membrane. This superior RO performance was enabled by the extremely thin (~7 nm) and highly crosslinked PA structure as well as strong PA-support interfacial adhesion. The surface tension analysis suggested that the work of adhesion at the PA-support interface of >~110 mJ m−2 is required to achieve high membrane performance.