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

Abstract

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 (O_def) 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.