Photothermally enhanced permeability and peroxydisulfate activation on carbon nanotube intercalated reduced graphene oxide membrane for ultrafast organic pollutant removal and fouling inhibition

Catalytic membrane based water treatment process always suffers from the contradiction between permeability and catalytic performance. Herein, an oxidized carbon nanotube intercalated reduced graphene oxide (RGO-OCNT) membrane with unique photothermal conversion ability (61.8 °C at 1.4 kW m-2) and peroxydisulfate (PDS) activation function was constructed, which realized simultaneously improved permeability and PDS activation under photothermal assistance for high-efficiency water treatment. Under light irradiation, the permeability of RGO-OCNT membrane was 5.9 times higher than that of membrane alone. The RGO-OCNT membrane under PDS activation and light irradiation (PDCM) exhibited ∼100% removal and ultrahigh degradation rate (0.072 ms-1) towards PE within ultrashort retention time (0.07 s), whose performance was 3.6 or 5.3 times higher than that of filtration under PDS activation alone (DCM) or filtration alone. Meanwhile, the RGO-OCNT PDCM also displayed effective fouling mitigation on both membrane surface and pores, whose flux loss during humic acid treatment was 2.1 or 3.6 times lower than that of DCM or filtration alone. Furthermore, the RGO-OCNT catalytic membrane still maintained high performance under natural sunlight irradiation and real water matrix. The photothermal effect played dual role in enhancing membrane performance: For one thing, it improved membrane hydrophilicity and water diffusion for facilitating water permeation; for another, it accelerated reactants mass transfer, promoted electron transfer from catalytic layer to PDS and reduced reaction enthalpy change for favorable PDS activation into radicals (mainly SO4•−) for pollutants removal.