Degradation of chloramphenicol by pulsed discharge plasma with heterogeneous Fenton process using Fe3O4 nanocomposites

Abstract

Pulsed discharge plasma (PDP) was coupled with Fe3O4 nanocomposites for promoting degradation of chloramphenicol (CAP) based on Fenton reaction. The prepared Fe3O4 nanocomposites were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and vibrating sample magnetometer. The results showed that Fe3O4 could be successfully prepared by hydrothermal method with reasonable composition. The magnetic intensity reached 71.99 emu/g, which could be easily separated from the solution when an external magnet was applied. Compared to PDP alone, the removal efficiency, kinetic constant and energy efficiency enhanced when Fe3O4 was added. Synergetic effect was achieved between PDP and Fe3O4. The optimal catalytic performance was obtained when the dosage was 0.26 g/L. CAP was beneficial to decomposition with higher peak voltage, lower initial solution concentration and lower initial pH value. With increasing air flow rate, the removal efficiency enhanced firstly and then declined. Although four times use, Fe3O4 still maintained a higher stability. The concentration of H2O2 and O3 generated by PDP were all declined when Fe3O4 was added. With the treatment time prolonged, the pH value declined but conductivity improved. The conjugate heterocyclic structures were destroyed during CAP degradation. The degradation pathway mainly related to the cleavage of phenyl-nitryl, COH, CCl and CN bonds, resulting in the formation of intermediates containing benzene ring. The benzene ring of intermediates were underwent rupture and transformed to small organic acids and inorganic acids, which were mineralized into Cl−, NO3−, CO2 and H2O finally. The toxicity of CAP was alleviated after plasma-catalytic treatment. The overall findings provided a new insight into wastewater treatment by PDP with heterogeneous Fenton catalyst.