Three dimensional electro-Fenton oxidation of diclofenac and naproxen with magnetic bentonite as a novel particle electrode

Abstract

ABSTRACT Magnetic bentonite (MBt) and Ti/TiO2 nanotube/PbO2, for the first time, were investigated as particle electrodes and anode of three dimensional electro-Fenton process (3DEF) for the degradation of diclofenac (DCF) and naproxen (NPX). The characteristics of the electrodes were determined by X-ray diffraction(XRD), scanning electron microscope(SEM) and energydispersive X-ray spectroscopy(EDS) analyses and the effects of operating parameters on degradation were studied. The results showed that adsorption and electrochemical processes have lower removal efficiency than the 3DEF process at neutral pH. This efficiency was due to the greater production of hydroxyl radical (•OH) through the anode and MBt surface. The results of the scavenging experiments confirmed an increase in the amount of production of •OH. The maximum removal efficiency of DCF and NPX was obtained at pH of 6, MBt dosage of 500 mg/L, current density of 25 mA/cm2and electrolysis time of 120 min. The electrodes reusability was confirmed by consecutive reaction cycle and the Fourier-transform infrared spectroscopy (FTIR) and SEM-mapping analysis explained their stability. The results of continuous electro-oxidation reactor showed proper removal of the chemical oxygen demand(COD) from real wastewater. The degradation by-products were identified by gas chromatography mass-spectrometry (GC-MS) analysis coupled with dispersive liquid–liquid microextraction (DLLME). Based on comparative tests and products identification, the possible mechanism and pathway of drugs degradation were suggested.