Degradation of salicylhydroxamic acid in mineral beneficiation wastewater by dielectric barrier discharge and La-Fe3O4-doped activated carbon: Parametric optimization, kinetics, activation process, and transformation pathway

Abstract

In this study, the degradation of salicylhydroxamic acid (SHA) in industrial beneficiation wastewater was investigated using dielectric barrier discharge (DBD) and La-Fe3O4-doped activated carbon (La-Fe3O4/AC). The physical and chemical properties of La-Fe3O4/AC were studied using several characterization techniques including scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The response surface methodology was used to optimize three critical experimental parameters of the catalyst: its dosage and the mass ratios of La and Fe3O4. These parameters contributed to the SHA degradation in the following decreasing order: mass ratio of La > catalyst dosage > mass ratio of Fe3O4. The SHA degradation efficiency reached 98.6%, and the synergistic factor was 2.83 at a peak-to-peak discharge voltage of 23 kV. The results showed that the DBD-La-Fe3O4/AC system improved the SHA degradation efficiency and exhibited a significant synergistic effect. Pb2+ and Cu2+ slightly increased the SHA degradation efficiency. Quenching experiments on activated substances confirmed that •OH and O2– were crucial to the degradation of SHA. The O3 and H2O2 generated by the DBD-catalyst system were absorbed by the La-Fe3O4/AC catalyst to produce more •OH. Ten main intermediates were detected in the degradation process of the DBD-catalyst system using HPLC-MS, and three degradation procedures were proposed.