Fabrication of amino-alcohol based polyesteramide thin film composite membranes for nanofiltration

Although polyesteramide (PEA) nanofiltration membranes exhibit multi-functionalities such as superior antifouling property and chlorine resistance, their low water permeability poses a major impediment for water treatment. In this study, new PEA-based thin film composite (TFC) membranes were constructed by utilizing the amino-alcohol monomers [tris(hydroxymethyl)aminomethane: THAM, and 2-amino-2-methyl-1,3-propanediol: AMPD)] via interfacial polymerization (IP) with trimesoyl chloride (TMC). The THAM monomers with one more hydroxyl group endow the synthesized TFC membranes with higher hydrophilicity and more negative charges contrasted to AMPD-TFC membranes. Interestingly, the AMPD containing non-polar methyl groups were found to attain more compact TFC membranes with a MWCO of 579 Da. This is because more rapid diffusion of AMPD toward the organic phase promotes a more adequate IP reaction, leading to high-crosslinked membranes with smaller pore sizes. The resulting THAM-TFC membrane with a larger pore size exhibit a high water permeability (17.7 LMH bar−1), and superior salt rejection (Na2SO4: 98.0 %), outperforming the reported polyester NF membranes. Due to the inactive chlorination reaction site of the polyester group, the PEA membranes exhibited stable separation performance after immersion in a harsh chlorine environment up to 96 h. This study comprehensively compared the effects of two structural-similar monomers on membrane structures and performance, providing a guidance of using suitable monomers to fabricate the high-flux NF membranes.