Nanofiltration membrane combining environmental-friendly polycarboxylic interlayer prepared from catechol for enhanced desalination performance

Abstract

The strategy of introducing a hydrophilic interlayer on the porous substrate has been widely applied in the modification of nanofiltration (NF) membranes. Herein, an environmentally friendly polycarboxylic interlayer is prepared from the mixture of catechol and sodium periodate (SP). Catechol is easy to oxidize to generate reactive o-quinones which undergoes phenolic polymerization to form covalent polymer with the carboxyl group, with the effect of SP initiation. Due to the introduction of carboxylic group, the interlayer is hydrophilic and can store more piperazine molecules to provide a more uniform platform for interfacial polymerization, which is conductive to form a thin and dense polyamide (PA) active layer. Compared with the traditional membrane, the modified thin film composite (TFC) membrane exhibits 1.7-fold of permeance (up to 15.4 ± 1 L·m−2·h−1 bar−1), maintaining a high rejection of Na2SO4 (98.42 ± 1.2%). Although the TFC membrane without an interlayer tends to be thick and defective in low PIP concentration, the role of the interlayer can eliminate this limitation. Besides, the modified TFC membrane possesses a high electronegativity with the fact that isoelectric point (3.29) has been lower than that of the traditional membrane, which has the potential to separate negative organic pollutants in the wastewater treatment.