In-situ surface modification of a reverse osmosis membrane with acrylic polymers: Transport and retention of a small neutral organic micropollutant

Abstract

Highly selective in-situ surface grafting approaches were designed to improve the rejection of 1H-benzotriazole (BTA) by a reverse osmosis (RO) membrane. A commercial FT30 membrane was grafted in-situ for the first time with 2-(diethylamino)ethyl methacrylate (DEAEMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), respectively, and compared with the state-of-the-art polydopamine (PDA) modification method. The TMSPMA grafting enhanced the BTA rejection from 88.4% to 98.4%, with a minor drop in water permeability (0.3%) compared to the pristine membrane. The FT30-TMSPMA membrane performed considerably better than the FT30-DEAEMA and FT30-PDA membranes. The improved rejection after TMSPMA modification can be ascribed to enhanced steric exclusion and hydrophobic interactions. The boosted hydrophobicity of the FT30-TMSPMA membranes is the result of the hydrophobic nature of the propyl/methyl groups present in TMSPMA, resulting in an 11.3% and 8.8% higher selectivity of BTA compared to the pristine FT30 and FT30-PDA membrane, respectively. The A/B ratio (which indicates the membrane selectivity to water against the solute) of the FT30-TMSPMA membrane increased by 714%, which is the highest enhancement compared to other modified materials reported in the literature until now. This new modification approach is thus highly promising for membrane functionalization to improve the rejection of small neutral organic micropollutants.