FeOx/MnOy modified oxidized carbon nanotubes as peroxymonosulfate activator for organic pollutants degradation

In this work, the FeOx/MnOy decorated oxidized carbon nanotubes (CNTs-Fe-Mn) composites were synthesized and used as catalysts to activate peroxymonosulfate (PMS) for organic pollutants degradation. The catalytic ability of the CNTs-Fe-Mn catalyst was strongly correlated with the oxidation of CNTs and the molar ratio of Fe/Mn. When the CNTs was oxidized by 30 wt% HNO3 and the modified molar ratio of Fe/Mn was 0.5, the 30%-CNTs-Fe-Mn-0.5 showed highest efficiency for rhodamine B (RhB) degradation via activating PMS, and the removal rate of 95% was achieved in 60 min at room temperature in 15 mg L-1 RhB solution with catalyst dosage of 0.1 g L-1. Fe and Mn multivalent oxide species coexisted were randomly distributed on the outer surface and encapsulated into the channels of oxidized CNTs in the 30%-CNTs-Fe-Mn-0.5 catalyst. The XPS results of catalysts before and after reaction proved that the redox cycles between the multivalent states of Fe and Mn ensured the superior catalytic activity of the 30%CNTs-Fe-Mn-0.5 for PMS activation. The radical quenching tests and D 2 0 experiments confirmed that SO4 center dot, HO center dot and O-2 center dot radicals were the main reactive oxidized species for the oxidation of pollutants in the 30%-CNTs-Fe-Mn-0.5/PMS system. In addition, the influences of operation parameters including initial pH, pollutant concentration, catalyst dosage, and PMS dosage on catalytic degradation were investigated. (C) 2020 Elsevier Inc. All rights reserved.