Efficient degradation of dye wastewater with a novel tribocatalytic process initiated by CQDs-Bi2MoO6 catalyst: Preparation, degradation, kinetics, DFT calculations and mechanism

Abstract

• CQDs(5 wt%)-Bi 2 MoO 6 exhibited excellent tribocatalytic performance for RhB. • h + , •O 2 − and •OH were the dominant radicals during tribocatalytic degradation. • LC-MS/MS and toxicity analysis were both performed. • Electron transition and transfer were involved in tribocatalytic mechanism. • N-deethylation and decarboxylation were degradation steps based on DFT calculations . Tribocatalysis is becoming a novel method to decompose organic pollutants. In this work, an efficient tribocatalyst CQDs-Bi 2 MoO 6 was prepared and evaluated by structural characterizations (SEM, TEM, XRD, BET, XPS, UV–vis DRS and PL) and electrical analysis (EIS, LSV, Mott-Schottky), and results displayed that the optimal dosage of CQDs was 5 wt% (namely CQDs(5 wt%)-Bi 2 MoO 6 ). Then, CQDs-Bi 2 MoO 6 tribocatalytic degradation of RhB was investigated detailedly, and results showed that almost 100% RhB was degraded within 5 h under the optimum. Intermediates were detected via LC-MS/MS and their toxicity was evaluated with T.E.S.T software. Major active free radicals were detected with ESR and scavengers’ test. Both of them proved the presence of h + , •O 2 – and •OH during tribocatalytic degradation and meanwhile the contribution order of the above-mentioned radicals was as follows: h + > •O 2 – > •OH. DFT calculations and tribocatalytic degradation kinetics were also investigated, as well. DFT calculations not only provided the orbit structure of CQDs(5 wt%)-Bi 2 MoO 6 , but also deduced the probable attack position of RhB molecule. And based on it, tribocatalytic mechanism involved in friction → electrons’ transition and transfer → forming h + , •O 2 – and •OH → decomposing RhB were proposed, providing some valuable insights for the application of tribocatalytic process to wastewater treatment.