Strong metal-support interaction between carbon nanotubes and Mn-Fe spinel oxide in boosting peroxymonosulfate activation: Underneath mechanisms and application

This study has revealed how the strong metal-support interaction (SMSI) between carbon nanotubes (CNTs) and Mn0.65Fe2.35O4 (MnFeO) in boosting peroxymonosulfate (PMS) activation for rapid sulfamethoxazole (SMX) degradation. As synergized by CNTs, the PMS-activation efficiency of MnFeO could be enhanced by>24 times, but with the similar PMS-activation mechanism. It was explored that the SMSI-induced abundant surface hydroxyl groups, in cooperation with the highly hydrophobic CNTs, favored the rapid in situ interfacial degradation of SMX. This feature also endowed the MnFeO-CNTs catalyst resistance to high salinity waters containing inorganic anions (e.g., Cl- and NO3–) of weak complexing abilities. Moreover, the SMSI allowed the greatly accelerated redox cycle rate of Mn species by electron-rich CNTs, resulting in efficient PMS activation. Furthermore, the application feasibility of the MnFeO-CNTs/PMS system was demonstrated for a SMX-spiked real reverse osmosis (RO) concentrate. It was found that higher concentration of PMS could realize the complete removal of SMX, despite the existence of electron-rich tyrosine-like substances would compete with the SMX degradation in the MnFeO-CNTs/PMS system. This study demonstrated that the SMSI could boost the PMS activation, and could serve as an effective material strategy for in situ interfacial organics degradation in the high salinity wastewater.