Nano-confined catalysis with Co nanoparticles-encapsulated carbon nanotubes for enhanced peroxymonosulfate oxidation in secondary effluent treatment: Water quality improvement and membrane fouling alleviation

•Co nanoparticles were encapsulated in the internal cavities of carbon nanotubes.•Co@CNT/PMS-UF integrated system was proposed for secondary effluent treatment.•Nano-confined effect from tube-encapsulated structure boosted pollutant degradation.•Membrane fouling induced by effluent organic matter was effectively alleviated.•Confinement-based oxidative pretreatment improved the purification efficiency of UF. Despite widespread deployment and investigation of ultrafiltration (UF) for secondary effluent purification, the challenge of membrane fouling due to effluent organic matter (EfOM) remains formidable. This study introduced a novel pretreatment method utilizing Co nanoparticles-encapsulated carbon nanotubes activated peroxymonosulfate (Co@CNT/PMS) to degrade EfOM and mitigate membrane fouling. Characterization of Co@CNT revealed the efficient encapsulation of Co nanoparticles within nanotubes, which notably enhanced the catalytic degradation of bisphenol A and typical organics. The tube-encapsulated structure increased the concentration of reactive species within the confined nanoscopic space, thereby improving the probability of collisions with pollutants and promoting their degradation. The Co@CNT/PMS pretreatment led to substantial reductions in aromatic compounds, fluorescent components, and both high and middle molecular weight substances. These changes proved crucial in diminishing the fouling potential in subsequent UF processes, where reversible and irreversible fouling resistances decreased by 97.1 % and 72.8 %, respectively. The transition volume from pore blocking to cake filtration markedly increased, prolonging the formation of a dense fouling layer. Surface properties analysis indicated a significant reduction of pollutants on membrane surfaces after the Co@CNT/PMS pretreatment. This study underscored the efficacy of confinement-based advanced oxidization pretreatment in enhancing UF performance, presenting a viable resolution to membrane fouling. [Display omitted]