Surfactant modified PTFE-based forward osmosis membrane with high performance and superior stability

Abstract

The absence of membranes with high stability and excellent permeation performance hinders the progress of forward osmosis (FO) technology. In this work, a high-strength polytetrafluoroethylene (PTFE) substrate was used for interfacial polymerization (IP) to fabricate FO membranes. The innovative approach enhances membrane performance by improving hydrophilicity with surfactant modification to facilitate better water transport in FO. Dodecyl trimethylammonium bromide (DTAB) was added into the aqueous phase to control the IP process, and the optimized DTAB concentration was determined to be 70 mg L⁻¹, which was labeled as PTFE-DTAB₇₀ membrane. Characterization analysis showed that DTAB stabilized carboxyl groups in the PA layer through electrostatic interactions, inhibiting amide bond hydrolysis. After immersed for 60 days under extreme pH conditions (1–13), the membrane maintained high water flux (>16 LMH) and low reverse salt flux (<0.56 g L⁻¹). Its chemical stability significantly surpassed that of commercial CTA membrane, with a 295 % increase in water flux at pH 13. When treating simulated wastewater, a 99.9 % chromium (Cr) rejection and a 96 % chemical oxygen demand (COD) rejection were obtained. The membrane showed great potential for treating high-salinity, strong acid and alkaline industrial wastewater. This study provides an innovative strategy for developing highly stable FO membranes and reveals the universal mechanism of surfactant molecular design in membrane separation.