Surface hydrophilic modification of RO membranes by plasma polymerization for low organic fouling

Abstract

Trimethylene glycol dimethyl ether (triglyme), a Polyethylene glycol (PEG)-like hydrophilic polymer, was deposited by plasma polymerization to reduce RO membrane’s organic fouling tendency. This method has the great advantage of achieving modification in one single step. A series of plasma deposition experiments were undertaken. The successful coating of the polymer was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Water contact angle measurements and permeation experiments using a protein solution were conducted to evaluate the change of hydrophilicity and anti-fouling properties. Salt rejection tests were performed to evaluate membrane performance. A reduction in contact angles from 32 o to 7 o was achieved for the treated membranes, indicating enhanced hydrophilicity. The permeation experiments revealed that the modified membranes achieved an excellent maintenance of flux compared to the untreated membranes. Specifically, after 210 minutes of filtration, no flux decline was found for the modified membranes, while a 27% reduction of the initial flux was observed for the untreated membrane. Flux recovery after cleaning by water only was up to 99.5% for the modified membranes, while for the untreated it was only 91.0%. The surface hydrophilic modification of RO membranes by plasma polymerization has shown a clear improvement in membrane anti-fouling performance.