Finely tuned polyamide structure with green plasticizers to construct ultrafast water channels for effective desalination

Abstract

Highly permeable reverse osmosis (RO) membranes are desirable for alleviating the energy burden and ensuring future water sustainability. Herein, the effectiveness of green plasticizer-assisted interfacial polymerization (GPAIP) for preparing polyamide thin-film composite (TFC) RO membranes with significantly enhanced water permeability was demonstrated. The presence of green citrate plasticizers, namely tributyl citrate (TBC) or acetyl tributyl citrate (ATBC), led to the formation of new hydrogen bonds and inhibited the formation of the initial interchain amide-amide bonding, thus markedly reducing chain rigidity as demonstrated by the decreased elasticity modulus. More flexible polyamide chains resulted in the creation of more ultrafast water channels during filtration. Furthermore, TBC-modified membranes exhibited more elastic polyamide layers and higher water flux than that of ATBC-modified membranes on account of the presence of both hydrogen bond acceptors (OH) and hydrogen bond donors (C=O) in TBC molecules. Specifically, water flux of 0.6 wt% TBC-modified and 0.6 wt% ATBC-modified membranes was 83.6 L m−2 h−1 and 49.7 L m−2 h−1 respectively, more than 5 times and 3 times that of the pristine membrane. The excellent performance of TFC RO membranes fabricated via GPAIP together with the facile membrane manufacturing process offered the possibility of breaking the predicament in desalination field, which could eventually help ease the current freshwater crisis.