Anionic surfactant assisted interfacial polymerization enables thermally resistant nanofiltration membranes

Polymer nanofiltration membrane has been widely used in various fields. However, it generally suffers from pore expansion at high operating temperature, leading to deterioration in separation performance. It is important to develop thermally resistant membranes to meet high temperature separation requirement for energy conservation and improving economic benefit. Herein, three kinds of anionic dodecyl surfactants were used to assist the interfacial polymerization process to form polyamide layers with high crosslinking degree for high-temperature separation. Results show that the thickness of the polyamide layer increases dramatically with the addition of surfactant, and the surface wettability and surface charges change little. The appropriate addition of surfactants can increase the harmonic amide bond density of the polyamide layer. The optimal membrane exhibits excellent pore size stability as well as high-temperature separation performance with water permeance of 31.3 L m −2  h −1 bar −1 and MgSO 4 rejection of 98.0 % at 85 °C. The membrane also shows stable separation performance during cycling variations between 25 and 85 °C and a 100-h long-term operation at 85 °C. This work demonstrates a feasible and scalable method for fabricating nanofiltration membranes for high-temperature separation.