Highly efficient MnO2-modified antifouling loose nanofiltration membrane for dye/salt separation

Loose nanofiltration (NF) membranes are promising in textile wastewater treatment due to their selective separation capabilities for dyes and salts. However, their widespread applications are hindered by complex manufacturing processes and membrane fouling. This work focuses on fabricating antifouling loose NF membranes using a facile method. Thereinto, amine-functionalized loose NF matrixes were first prepared using polyelectrolyte-complex induced phase inversion, where polyethyleneimine (PEI) in a coagulation bath as an inducer triggered an instantaneous phase inversion via electrostatic interactions with sulfonated polysulfone (SPSF) in dope solution. The acquired NF matrix has a dense skin layer with a mean pore size of 0.72 nm, endowing it with excellent dye retention. Consequently, the Fenton catalyst, MnO 2 , was in situ grown on the membrane via the interaction between amine and Mn 2+ followed by a one-step mineralization reaction. The MnO 2 -loaded loose NF membrane could achieve 99.7 % CR rejection while allowing only 1.67 % rejection of Na 2 SO 4 in a mixed solution of 60 mg/L Congo Red (CR) and 20 g/L Na 2 SO 4 at the permeability of 51.6 L m −2  h −1 ·bar −1 . After cleaning with H 2 O 2 , the flux recovery rate of the membrane remains above 97 %, attributed to the catalytic effect of MnO 2 on the membrane surface. Additionally, the membrane displayed similar performance in dealing with real wastewater, underscoring its potential for practical applications in textile wastewater treatment.