Rapid construction of cyclodextrin polyester layer on polyamide for preparing highly permeable reverse osmosis membrane

Abstract

Hydrophilic modification of reverse osmosis (RO) membrane is a common method to enhance membrane permeance. However, it is usually hard to improve the membrane permeance obviously by introducing hydrophilic substances onto membrane surface as a result of the formation of a new mass transfer resistance layer. Besides, most hydrophilic modification methods are time-consuming, which is not conducive to industrial application. In this work, hydrophilic hydroxyl-rich macrocycles (cyclodextrin, CD) with a hydrophobic lumen and large intrinsic cavity were introduced on polyamide (PA) layer by second interfacial polymerization (IP) between acyl chloride and hydroxyl in only 5 s with the assistance of 4-dimethylaminopyridine (DMAP), forming a highly hydrophilic and loose polyester layer on the top of PA, which is beneficial to water adsorption and transport. The permeances of CD-modified RO membranes are nearly three times as large as the unmodified membrane while maintaining the high rejection (RNaCl = 98.75–98.88%). This work provides a straightforward, industry-friendly, effective, and rapid strategy for preparing highly water permeable RO membranes.