Polyamide Nanofiltration Membranes with Exceptional Thermal Stability Enabled by Dodecyl Phosphate Regulation

Traditional thin-film composite (TFC) polymer membranes suffer performance deterioration in high-temperature liquid separation due to insufficient thermal stability. Herein, a facile and effective strategy was proposed to fabricate TFC nanofiltration membranes with enhanced thermal stability by using mono- n -dodecyl phosphate (MDP) as an oil-soluble surfactant to regulate the interfacial polymerization. MDP molecules markedly reduce the water/hexane interfacial tension and act as transport carriers to promote the diffusion of amine monomers, as validated by density functional theory (DFT) calculations. By adjusting the concentration of MDP in the organic phase, the polyamide thickness and compactness, surface properties, and the separation performance of the TFC membranes at high temperature can be effectively modulated. The optimal TFC membrane exhibits exceptional thermal stability, maintaining rejection to MgSO 4 > 98.5% and water permeance >35 L m −2 h −1 bar −1 during a continuous operation at 85 °C for 100 h. Temperature-dependent pore size analysis further confirms the enhanced structural integrity of the MDP-regulated TFC membranes under high temperature. This research establishes a novel paradigm for developing nanofiltration membranes with high thermal stability.