Facile hydrophilization of polyethylene substrate by in situ polymerization of m-phenylenediamine for preparing high-performance polyamide reverse osmosis membrane

Abstract

Polyethylene (PE) microporous membrane-supported thin-film composite (TFC) polyamide membranes have received growing attention owing to their low cost, superior separation performance, and excellent chemical robustness. Developing facile and cost-effective methods to hydrophilize PE membranes is essential for the scale-up of PE-supported TFC membranes. Here, a facile approach of in situ polymerization of m-phenylenediamine (MPD) was employed to hydrophilize the PE membranes for the first time. Characterizations showed that both the outer surface and the interior of the PE membrane were homogeneously coated with poly(m-phenylenediamine) (PMPD). The hydrophilicity of the modified PE membrane was dramatically enhanced with the water contact angle decreasing from ∼120° to ∼72° and water flux at 2 bar increasing from 0 to ∼640 L m−2 h−1. The high surface porosity and appropriate surface hydrophilicity of the MPD-modified PE membrane together with the excellent coating uniformity favor the formation of a highly permselective polyamide active layer. The outstanding coating stability was demonstrated through different tests. The cost of the MPD-modified PE membrane is estimated to be less than 1% of that of the conventional substrates. Furthermore, high-performance and low-cost reverse osmosis (RO) membranes were prepared via interfacial polymerization on the MPD-modified PE substrates. The PE-supported RO membrane exhibited an excellent separation performance with NaCl rejection of 99.3%, pure water permeance of 1.3 L m−2 h−1 bar−1, and long-term operating stability. The proposed hydrophilization strategy of PE membrane is facile, low-cost, environmentally friendly, and reliable, and thus has a brilliant prospect for industrialization.