Engineering TA-APTES coatings for the preparation of thermally stable nanofiltration membranes

Thermally stable thin-film composite (TFC) nanofiltration (NF) membranes are essential for high-temperature separation in various industrial applications. Herein, we present a rapid and scalable surface modification of polyvinylidene fluoride (PVDF) ultrafiltration membrane using tannic acid (TA) and 2-aminopropyltriethoxysilane (APTES), which can be used as the substrate membrane for the preparation of thermally stable NF membranes. The modified PVDF substrate shows enhanced mechanical strength and thermal stability, with tensile strength rising from 1.5 to 4.7 MPa, decomposition temperature increasing from 459 to 482 °C, and a coefficient of thermal expansion (CTE) reduced by 36.4%. These improvements ensure the structural integrity and strong adhesion between the substrate and polyamide layers, thereby further improving the reliability of the TFC NF membrane during long-term operation under high-pressure and high-temperature conditions. Consequently, the PVDF-based TFC NF membranes sustain >97.5% MgSO 4 rejection and remarkable water permeance (42.1 LMH/bar) during 100-h operation at 70 °C. This rapid and scalable modification method provides a practical route toward the fabrication of robust PVDF-based TFC NF membranes for high-temperature separation.