A highly permeable loose nanofiltration membrane prepared via layer assembled in-situ mineralization

Nanofiltration membrane with high water permeability and anti-fouling nature is particularly needed to be explored in dyeing wastewater treatment. Herein, a hydrophilic calcium carbonate/polyethyleneimine-gallic acid (CaCO3/PEI-GA) loose NF membrane was prepared via a layer assembled in-situ mineralization (LAIM) strategy. This strategy endowed the membrane with the following advantages: the formation an ultrathin CaCO3/PEI-GA selective layer with a thickness of 76 nm and the highly enhanced surface hydrophilicity due to in-situ formation of CaCO3 nanoparticles. As a result, the prepared CaCO3/PEI-GA loose NF membrane showed 154% higher water flux (48.5 L/(m2 h bar) vs. 19.1 L/(m2 h bar)) compared with the control polyethyleneimine-gallic acid (PEI-GA) loose NF membrane for 100 mg/L Congo red (CR) solution, with equivalent rejection (99.6% vs. 99.7%). Moreover, this membrane also displayed outstanding anti-fouling ability, i.e. flux recovery ratio (FRR) of 94.9% for 1000 mg/L humic acid (HA) solution, and excellent performance stability in separation of dye/salt (CR/NaCl) aqueous solution for 60 h. The aforementioned advantages of the CaCO3/PEI-GA loose NF membrane indicate its promising application in dyeing wastewater treatment.