Fabrication of a novel composite nanofiltration membrane with excellent acid resistance and water flux via the selective bond dissociation method

The functional layer of nanofiltration (NF) membrane greatly affects its application in acid solutions, therefore the design and fabrication of functional layer have become the spot of light. A feasible method was developed to fabricate a novel functional layer of composite NF membrane with excellent acid-resistance and separation performance via the selective bond dissociation method. Briefly, dissociation bonds were formed through the interfacial polymerization of polyethyleneimine (PEI) and cyanuric chloride (CC) on the polyethersulfone substrate (PES). Glutaraldehyde (GA) was subsequently applied to cross link with unreacted amino groups of PEI. Finally, the structure of the functional layer of AGA-PEI/CC (Acid-immersed GA-PEI/CC) NF membrane was manipulated into an inhomogeneous structure by immersing the membrane prepared in the above two steps in acid solutions to remove CC molecules. The fabricated AGA-PEI/CC exhibited excellent rejection, water flux and acid-environment stability owing to the unique structure of the functional layer fabricated by selective bond dissociation method. The rejection order was Mn 2+ (97.97%) > Mg 2+ (97.48%) > Zn 2+ (95.15%) > Cu 2+ (94.45%) > Al 3+ (87.40%). The AGA-PEI/CC membrane exhibited structural stability after 2 months 0.1 mol L −1 HNO 3 solutions tests, the water flux and MgCl 2 rejection rate variation rate was −1.19% and +4.98%. We provided a potential strategy to synthesize acid-resistance NF membrane with desired separation performance by the selective bond dissociation method, and enriching the application of NF membrane in an acid environment.