Shell-core MnO2/Carbon@Carbon nanotubes synthesized by a facile one-pot method for peroxymonosulfate oxidation of tetracycline

Abstract

• MnO 2 /C@CNT for PMS activation was fabricated via a facile one-pot method. • Increased Mn (III)/Mn (IV) and surface –OH are the basis for high catalytic activity. • SO 4 · - and · OH play dominant roles in TC degradation in the MnO 2 /C@CNT-PMS system. • The toxicity of solution finally decreased after the MnO 2 /C@CNT-PMS process. In this study, a new type of MnO 2 /carbon@carbon nanotubes (MnO 2 /C@CNT) shell-core nanohybrid for peroxymonosulfate (PMS) activation was synthesized by a one-pot method, which simultaneously achieved the synthesis of MnO 2 and assembly of components. Tetracycline (TC) degradation by MnO 2 /C@CNT-PMS was enhanced obviously, and MnO 2 /C@CNT (1.75:1)-PMS systems exhibited the best TC degradation efficiency (85.6%) at 10 min. In addition, the effects of catalyst dosage, PMS dosage, initial pH, reaction temperature, and co-existing ions on the degradation of TC were investigated. The stripping and insertion of the nanocarbon during the synthetic process were the basis for the enhancement of the Mn (III)/Mn (IV) ratio and surface –OH groups, which further accelerated electron transfer and the conversion of Mn and O species. EPR analysis along with the free-radical quenching experiments confirmed the presence of SO 4 · - and · OH during the catalytic reaction, among which SO 4 · - was the main active specie. Moreover, a comprehensive toxicity assay and prediction were performed based on bioluminescence inhibition experiments and the Ecological Structure Activity Relationships (ECOSAR) program. Finally, reasonable degradation pathways of TC were proposed based on LC-MS analysis.