Assessing the role of CNTs in H2O2/Fe(III) Fenton-like process: Mechanism, DFT calculations and ecotoxicity evaluation

Abstract

In recent years, multi-walled carbon nanotubes (CNTs), which are emerging nanocatalysts, have received much attention in advanced oxidation processes. CNTs were introduced into H2O2/Fe(III) Fenton-like process to enhance the degradation of bisphenol A (BPA) in this study. The results of the study suggests that CNTs could effectively promote electron transfer from H2O2 to Fe(III) and directly reduce Fe(III) to Fe(II) to accelerate Fe(III)/Fe(II) cycles, in which carbonyl groups and structural defects of CNTs were identified as the major active sites via SEM, Raman, XRD, FTIR and XPS analyses. It was revealed that hydroxyl radical (·OH) majorly contributed to the degradation of BPA, and the generation efficiency of ·OH was significantly increased by 3.2 times with the addition of CNTs. Also, nine intermediate products were identified, and the possible degradation pathways of BPA were proposed through the density functional theory (DFT) calculations and HPLC-MS/MS analysis. The ecotoxicity evaluation of BPA demonstrates that the oxidative degradation of BPA in CNTs/H2O2/Fe(III) system could effectively reduce its environmental risk. The critical experimental parameters including the dosage of Fe(III), H2O2, CNTs, initial pH and various anions (Cl−, HCO3–, SO42−) were investigated, and the reusability experiments indicate that CNTs maintained high stability and reusability during the reaction.