Acid-resistant polypyrrole nanofiltration membrane fabricated through interfacial oxidative polymerization medicated by bifunctional interlayer for wastewater treatment

Although nanofiltration (NF) has arisen great interest for the treatment of acid wastewater, the available materials for the fabrication of acid-resistant NF membranes remain limited. Herein, we fabricate polypyrrole (PPy) NF membrane and further explore its acid-resistant ability. Instead of traditional preparation method through in-situ polymerization reaction, the PPy membrane is fabricated through interfacial oxidative polymerization at the water-hexane interface. Moreover, the tannic acid (TA)-Fe 3+ bifunctional interlayer is employed to regulate the formation of PPy membrane. It could not only promote the uniform distribution of ammonium persulfate (APS) solution across the support surface, but also assist APS to initiate the polymerization of pyrrole due to the oxidation of Fe 3+ . Compared with traditional in-situ polymerization, this fabrication strategy effectively shortens the formation time of PPy membrane and enhances its separation performance. Furthermore, the PPy membrane features remarkable acid-resistance due to the stable C-C bond between pyrrole units, confirmed by the accelerated acid hydrolysis and long-term immersion experiments. Interestingly, the slightly deteriorated separation performance of PPy membrane after acid-treatment could be recovered by alkaline solution. This is verified to be closely to the deprotonation and counter-ion de-doping of PPy chains. In addition to the application in treating acid wastewater, the fabricated PPy membrane could also be an excellent candidate in other fields due to its reversible properties in the acid and alkaline solutions. • Polypyrrole nanofiltration membrane was fabricated by interfacial oxidative polymerization • The interlayer of tannic-Fe 3+ was employed to regulate the formation of polypyrrole layer • Polypyrrole nanofiltration membrane exhibited excellent acid-resistance