Nitrogen-doped carbon nanotube modified ultrafiltration membrane activating peroxymonosulfate for catalytic transformation of phosphonate and mitigation of membrane fouling

Abstract

The nitrogen-doping carbon nanotube modified polyethersulfone membrane (NCNT@PES) was prepared by vacuum-assisted filtration. The catalytic activity and anti-fouling capacity of NCNT@PES/peroxymonosulfate (PMS) system were both systematically investigated. Selecting ethylenediamine tetra(methylene phosphonic acid) (EDTMP) as a target phosphonate, the NCNT@PES/PMS system degraded almost 100% of EDTMP, and about 60% of the total phosphorus (TP) in EDTMP could be transformed into orthophosphate (PO43−) within 1 min. Scavenger experiments and electron paramagnetic resonance (EPR) technique verified that the surface-bound radicals were mainly contributed the degradation and transformation of EDTMP in the NCNT@PES/PMS system. The presence of HCO3−, SO42− and NOM weakened the catalytic reactions, nevertheless, the NCNT@PES/PMS system still showed considerable effectiveness on the transformation of EDTMP in real sewage effluent. Moreover, the anti-fouling experiment proved that NCNT@PES/PMS system were superior on the removal of fluorescent components in the real sewage effluent, and their removal rates for the dissolved organic matter (DOC) and UV absorbance at 254 nm (UV254) were also improved. During the filtration cycles, the NCNT@PES/PMS system mitigated the membrane fouling significantly, which had been verified by the slower decline of normalized flux, less ultrapure water flux loss rates and higher ultrapure water flux recovery rates. This study provided a novel but simple way for effective EDTMP decontamination, at the same time, confirmed the potential of NCNT@PES membrane coupled with PMS activation on anti-fouling and water purification ability.