Coating zwitterionic amino acid l-DOPA to increase fouling resistance of forward osmosis membrane

In this study, the HTI Forward Osmosis (FO) membrane surfaces were modified by the deposition of poly amino acid 3-(3,4-Dihydroxyphenyl)-l-alanine (l-DOPA), a zwitterionic polymer on the membrane surface in order to enhance the fouling resistance of the FO membranes. The modification took place on the porous layer/side of the membranes. The modified membrane surfaces became more hydrophilic with a reduced initial water contact angle. Accelerated fouling experiments were conducted in pressure retarded osmosis (PRO) mode, in which the porous layer of membrane faced the feed solution. The feed solution comprised alginic acid sodium salt (AAS) and calcium ions (CaCl₂). The filtration results proved an effective improvement of fouling resistance of the l-DOPA coated membranes. The membrane samples with a 12-hour coating achieved 30% less fouling compared to the uncoated sample. The l-DOPA coating method is simple and direct; it has the potential for scaled up industrial applications.