Nano-filtration performance and temperature dependency of thin film composite polyamide membranes embedded with thermal responsive zwitterionic nanocapsules

Incorporation of thermal responsive nanofillers is a promising strategy to induce thermal responsiveness in thin film nanocomposite (TFN) polyamide NF membranes. In this work, thermal responsive zwitterionic nanocapsules (ZNCs) were embedded in the polyamide (PA) active layers to form thermal responsive water transporting channels for thermal responsive nanofiltration performance. The impact from loading level, diameter, cross-linker ratio, and core/shell ratio of ZNCs on the structure, nanofiltration (NF) performance, and thermal responsive sensitivity of TFN membranes were systematically investigated. It was found that ZNCs with the diameter of 100–110 nm, cross-linker ratio of 50 wt% and core/shell ratio of 3:1, and loading level of 0.01% w/v in aqueous phase had induced the highest permeance change slope of 1.04 L m−2 h−1·bar−1 °C−1 (LMHBC) and flux change slope of 6.24 L m−2·h−1·°C −1(LMHC) for ZNCs-TFN membrane, which was 8.7 times higher than that of the pristine TFC-PA NF membranes. The water flux of such ZNCs-TFN membrane increased from 57 L m−2 h−1 (LMH) to 88 LMH at 0.6 MPa from 25 °C to 30 °C without losing its salt rejection rates.