Efficient degradation of sulfamethoxazole by NiCoO modified expanded graphite activated peroxymonosulfate: Characterization, mechanism and degradation intermediates.

Expanded graphite (EG) immobilized nickel ferrite (NiCoO) was successfully constructed by a simple hydrothermal approach and applied for the degradation of sulfamethoxazole (SMX) in model wastewater by peroxymonosulfate (PMS) activation. The features of prepared catalysts were characterized by SEM, TEM, EDS, XRD, BET, TPD and XPS techniques. The influences of several critical parameters including the prepared NiCoO-EG dosages, PMS concentrations, temperature, initial solution pH and inorganic ions on SMX removal were studied in details. In particular, the synthesized NiCoO-EG exhibits excellent catalytic performances for SMX depredation over a wide pH range (pH 3.0-11.0). Besides, the transformation of various reactive oxygen species (SO, HO, O and O) with the change of initial pH was investigated by the electron paramagnetic resonance (EPR) and quenching tests. In addition, twelve major degradation intermediates of SMX were detected by UPLC-QTOF-MS/MS. Finally, the PMS activation mechanism in NiCoO-EG/PMS system by the synergistic coupling of EG and NiCoO were put forward. In brief, this work provided a promising and potential catalyst for PMS activation to remove SMX from wastewater.