Thermally Intensified Synthesis of Polyester Membranes for Highly Selective Removal of Haloacetic Acids

Commercial polyamide nanofiltration membranes show partial success in removing toxic micropollutants such as haloacetic acids (HAAs) from drinking water. However, these tight membranes suffer from limited selectivity between mineral ions (e.g., Ca²⁺, Mg²⁺) and HAAs, causing severe scaling on the membrane surface and loss of beneficial minerals. Herein, we adopted a thermally intensified interfacial polymerization (IP) method to construct a loose and negatively charged polyester membrane. Gallic acid, rich in hydroxyl and carboxyl groups, was used as the aqueous-phase monomer to react with a preheated Isopar G solution of trimesoyl chloride (with an organic-phase temperature up to 125 °C). The elevated temperature facilitates monomer diffusion and accelerates the IP reaction by several orders of magnitude, allowing the formation of the polyester membranes within a short reaction time of merely 10 min under mild pH conditions. The optimal polyester membrane GANF-100 demonstrated >90% rejection for five regulated HAAs, outperforming commercially available polyamide membranes in terms of mineral/HAA selectivity, Ca²⁺/SO₄^2- selectivity, and antiscaling behavior. This study paves the way for the facile fabrication of polyester membranes toward the effective removal of toxic organic micropollutants.