Nanoconfined Cobalt Ferrite Composite Carbon Nanotube Membrane Oxidation-Filtration System for Water Decontamination

Constructing a membrane-confined peroxymonosulfate (PMS) activation system has emerged as a promising strategy for efficient water decontamination. Herein, a novel cobalt ferrite (CoFe2O4)-filled open-end carbon nanotube (OCNT) membrane filtration system was proposed, aiming to integrate dual metal centers and nanoconfinement for enhancing PMS activation (MFPA) toward water decontamination. The optimal CoFe2O4@OCNT MFPA process displayed 100% phenol removal within a residence time of 5.7 s, whose k (1.17 s–1) was 3.0, 5.6, and 3.9 times higher than that of CoO@OCNT, FeO@OCNT, and CoFe2O4/CCNT (surface-loaded closed end cap CNT), respectively. Experimental results and theoretical calculations jointly unravel the nonradical-dominated (1O2 and electron transfer) oxidation mechanism, leading to the wide-pH adaptation and superior stability in the complex water matrix. Mechanism analysis showed that fast cycling of Co2+/Co3+ was achieved via synergistic promotion between dual metal centers and the nanoconfinement effect, which coboosted the PMS consumption as well as reactive oxygen species generation (especially 1O2). Compared with the single metal center, the dual metal centers of internal CoFe2O4 exhibited coenhanced electron cloud density (amount of charge transfer) and adsorption energy for PMS, resulting in O–O cleavage and elongated O–H. Meanwhile, the oxygen vacancy defect (Odef) on CoFe2O4 also contributed to the nonradical process, which not only served as the precursor of 1O2 generation but also acted as a transfer station for electrons.