A New Type Of High Permeability Acid-resistant Nanofiltration (NF) Membrane For Efficient Treatment Of Acidic Wastewater

A research team led by Professor Wan Yinhua from the Institute of Process Engineering of the Chinese Academy of Sciences has developed a new type of high-permeability acid-resistant nanofiltration (NF) membrane for the efficient treatment of acidic wastewater. The research was published in the Journal of Chemical Engineering on August 14.

NF is an energy-saving and environmentally friendly industrial wastewater treatment and separation technology. However, due to the hydrolysis of amide bonds, most commercially available polyamide NF membranes exhibit low stability in strong acid solutions.

In this study, the researchers prepared an acid-resistant NF membrane with tunable separation layer characteristics based on a simple surface activation assisted, multi-step interfacial polymerization (IP) process.

In this strategy, a new low-cost aqueous monomer (3-aminobenzenesulfonamide, ABSA) is used to react with trimesoyl chloride (TMC) to prepare a poly(amide-sulfonamide) (PASA) intermediate layer, and then surface activation is performed. Finally, a defect-free PASA top layer is constructed on the middle layer.

ABSA's stable sulfonamide structure can prevent direct acid attack. Importantly, as the number of stacked PASA layers increases, the film exhibits better continuity and higher selectivity, mainly because a higher monomer content can accelerate the IP process and suppress the excess between ABSA and TMC reaction.

Interestingly, due to the hydrolysis of the newly formed PASA layer during the surface activation process, the activated PASA intermediate layer exhibits increased surface hydrophilicity, smoothness and electronegativity, which can promote subsequent IP reaction formation with higher permeability and The defect-free separation layer of salt is rejected.

Benefiting from the strong size exclusion effect, the membrane exhibits an ideal dye retention rate under acidic conditions and an acceptable decolorization efficiency of real resin eluting wastewater. In addition, it also exhibits excellent acid resistance as well as satisfactory antifouling performance and long-term stability.

This work provides a low-cost strategy for improving the permeability and antifouling ability of acid-resistant NF membranes. It is expected to be used in the treatment of acidic wastewater in the textile and food processing industries.