Retarding fouling evolution in ultrafiltration via single-atom-catalyst-functionalized nanochannels: An in-depth exploration of foulant migration pathways

Membrane fouling hinders the further expansion of ultrafiltration technology in water purification, necessitating persistent exploration and development of effective fouling control strategies. Herein, we engineered a high-performance separation-catalysis membrane reactor (SCMR) by functionalizing pore channels with cobalt single-atom catalysts. This hierarchical nanoarchitecture, once integrated with peroxymonosulfate (PMS), simultaneously intercepted large foulant flocs and degraded of foulant molecules migrating into pores, greatly enhancing decontamination performance (95.2% humic acid removal) and reducing the irreversible membrane resistance ratio to 18.2%. The entire migration pathway of foulants was divided into three stages from membrane-front, onto membrane surface and into the intra-pore channels. Specifically, foulant floc aggregation driven by PMS addition was observed at the membrane-front. While this facilitated foulant removal, it may induce more severe irreversible fouling. Fouling model calculation and tracer tests confirmed the contribution of the functionalized nanochannels within the SCMR on retarding foulant accumulation on the membrane. Fourier transform-ion cyclotron resonance-mass spectrometry, integrated with quenching experiments, further validated the structural transformation of aromatic moieties to oxidized products through high-valent cobalt-oxo species, which enabled regulation of foulant migration pathways via the attenuation of hydrophobic adhesion. Our work demonstrated an efficient strategy for foulant removal and membrane fouling control via nanochannel functionalization.