Nanofiltration membranes containing CHA zeolite with pompom-like morphology

Abstract

Thin-film composite (TFC) nanofiltration membranes are widely used for water treatment due to their energy efficiency and high salt rejection, however they are highly susceptible to biological fouling. CHA zeolite with pompom-like morphology was prepared from an organic structure-directing template-free synthesis gel in the presence of sodium and cesium. The zeolite was added to the polyamide (PA) layer of TFC membranes prepared via interfacial polymerization. M-0.01 and M-0.05 TFC membranes prepared with addition of 0.01 wt% and 0.05 wt% CHA zeolite to the aqueous piperazine monomer solution, displayed a thinner PA layer and higher permeability compared to zeolite-free M-0 membranes. The rejection of 2000 ppm Na₂SO₄ and MgSO₄ solutions of the M-0.05 membrane was slightly reduced compared to M-0 and M-0.01 but nevertheless remained higher than 90%. Ag-CHA zeolite suspensions showed antibacterial activity against Escherichia coli, whereas CHA zeolite was inactive. Following bacterial exposure, M-0 control membranes exhibited bacterial growth after 24 h compared to the 0 h count, which was not observed for M-0.05 membranes, where there was no significant difference in the count between 0 h and 24 h. As a bacterial population reduction was not observed in either case, these materials are considered not to be antimicrobial. No bacteria survived on the surface of Ag-treated M-0 and M-0.05 membranes, demonstrating antimicrobial activity. The methodology described in this work could be used to increase the resistance of TFC membranes to biological fouling and increase their operational lifetime.