High Flux and Thermal-Responsive Nano-Filtration Membranes from Structurally Controlled Zwitterionic Nanocapsules

Abstract

Incorporation of nano fillers into membrane materials is a promising method to improve the performance of thin film nanocomposite (TFN) membranes, especially in breaking the trade-off between permeability and rejection of TFN membranes. Embedding structurally controllable zwitterionic nanocapsules (ZN_Cs) in the polyamide (PA) active layers could provide ultrafast water transporting channels to improve water permeability without sacrificing salt rejections. Unprecedentedly high thermal- responsiveness of the TFN membranes was also observed due to the thermal sensitivity of the included ZN_Cs. The loading level, diameter, crosslinker ratio, and core/shell ratio of ZN_Cs affected not only the structure and nano-filtration (NF) performance, but also the thermal responsive sensitivity of TFN membranes. ZN_Cs -TFN membrane made of ZN_Cs with the diameter of 100-110 nm, crosslinker ratio of 50 wt% and core/shell ratio of 3:1, at the loading level of 0.01% w/v in aqueous phase, could increase its water flux from 50 L·m^-2·h^-1 (LMH) to 88 LMH from 20 °C to 30 °C without losing salt rejection rates, possessing unprecedentedly high flux change slope of 3.84 L·m^-2·h^-1 /°C (LMHC) for NF membranes, 5.5 times higher than that of control thin film composite (TFC) NF 2 membranes.

Keywords: Zwitterionic, Nanocapsules, Nanofiltration, Thermal-responsive