A “sandwich layer” of N-doped carbon nanotubes coated on the surface of oxidized iron-foam is used to drive peroxymonosulfate activation

Abstract

In this work, a new “sandwich layer” N-doped carbon nanotube (CNTs-N)coated on the surface of oxidized foam iron composite (denoted as F-F@FeO@CNTs-N). The simultaneous in-situ formation of two active components, FeO and CNT-N, activated peroxymonosulfate (PMS) to generate free and non-free radicals, resulting in 93.7 % tetracycline (TC) degradation within 15 min. The results of experiments and density functional theory (DFT) calculations show that the unique CNTs-N can be used as the active site of TC enrichment, and the enriched TC can react in situ on the surface of F-F@FeO@CNTs-N. Importantly, coating the surface of CNTs-N successfully prevented the dissolution of iron ions during the catalytic process. The degradation mechanism and pathway of TC by F-F@FeO@CNTs-N/PMS were proposed. It is worth noting that the filtration-degradation system based on F-F@FeO@CNTs-N still achieved a TC removal rate of 84.9 % after 15 consecutive cycles in the self-circulation mode.