Unveiling the impact of monomer reactivity on the morphology and functionality of thin-film composite membranes

Abstract

This study delves into the impact of monomer selection and reaction pH on the morphology and performance of thin-film composite (TFC) membranes. The research provides an understanding of how polyamide (PA), polyester amide (PEA), and polyester (PE) membranes can be tailored for specific applications, employing piperazine (PIP) and glucose as monomers in aqueous solution alongside trimesoyl chloride (TMC) as a monomer in an organic solution. PEA-based membranes containing glucose demonstrated several notable improvements, including a reduced contact angle of 60 degrees, a smoother surface, and a more negative zeta potential. These enhancements underscore their increased hydrophilicity, decreased susceptibility to fouling, and heightened surface charge. Controlling pH during fabrication significantly changed the membrane surface charge, hydrophilicity, water flux, and rejection rate. At pH 11, the PA membrane excelled in rejection performance (99.5% Na2SO4, 32% NaCl, and 97.8% methyl orange) with a trade-off in lower water flux (56 LMH). Conversely, the PE membrane achieved the highest water flux (173 LMH) but lower rejection (58% Na2SO4, 10% NaCl, and 97% methyl orange). The PEA membrane offered notable water flux (82.5 LMH) and high rejection for methyl orange (99.3%) and Na2SO4 (99.2%). Increasing the pH reduced permeation rates but enhanced rejection, especially for NaCl. The PE and PEA membranes exhibited remarkable antifouling properties, boasting a flux recovery ratio compared to the PA membrane. This study highlights the pivotal role of monomer selection and pH control in TFC membrane performance, offering prospects for innovative design and optimization in water treatment membrane technology.