Confining peroxymonosulfate activation in carbon nanotube intercalated nitrogen doped reduced graphene oxide membrane for enhanced water treatment: The role of nanoconfinement effect.

Coupling membrane filtration with peroxymonosulfate (PMS) activation is promising to overcome the selectivity-permeability trade-off in membrane-based water treatment. However, the PMS catalytic efficiency of membrane still needs improvement to offset the insufficient reaction time during filtration process. Herein, an oxidized carbon nanotube intercalated nitrogen doped reduced graphene oxide (NRGO-OCNT) membrane with PMS activation function was firstly designed and prepared, which confined PMS activation in membrane interlayer for enhanced water treatment. The influence of confinement scale on membrane performance was studied through changing the OCNT intercalation ratio. Under the optimal confinement condition, the NRGO-OCNT membrane filtration integrated with PMS activation (MFPA) could realize 100% 4-chlorophenol removal at a high permeate flux of 290.2 L m-2 h-1 bar-1 (retention time of only 0.36 s), whose performance was 2.8, 1.7 and 5.0 times higher than that of filtration alone, NRGO MFPA (excessive confinement) and NRGO-OCNT powder-based batch reaction (no confinement), respectively. Moreover, NRGO-OCNT MFPA preferentially removed smaller-sized organics which easily entered and diffused in confined interlayer. The outstanding performance of NRGO-OCNT MFPA was owing to the nanoconfinement effect in appropriate confined interspacing, where the mass transfer rate of reactants was greatly boosted for enhanced generation of SO4- and OH towards pollutant.