Degradation of mefenamic acid using magnetic multi-walled carbon nanotube as a novel particle electrode in a three-dimensional electro-Fenton process

Abstract

Electrocatalytic degradation of mefenamic acid (MFA) by magnetic multi-walled carbon nanotubes (MMWCNTs), as a novel particle electrode, was studied in a three-dimensional electro-Fenton (3DEF) reactor. The physicochemical properties of MMWCNTs were determined by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction (XRD) techniques. The effect of variables and their interaction during the oxidative degradation of MFA was evaluated using response surface methodology (RSM) based on 5 levels of 5 factorials central composite design (CCD). The RSM results showed a suitable quadratic polynomial model for explaining the relationship between electrocatalytic activity and operational parameters (R-2 = 99.6). The optimization results indicated that maximum MFA degradation efficiency (98.36) could be obtained at pH of 6.2, MFA concentration of 6.19 mg/L, the current density of 19.94 mA/cm(2), MMWCNTs dosage of 69.13 mg/L, and reaction time of 82.95 min. Comparative experiments showed further production of hydroxyl radical (*OH) and higher electrocatalytic activity of the 3DEF system. The MMWCNTs particle electrode showed excellent stability and reusability for MFA oxidation. 3,4-dimethyl benzaldehyde and 3-methylbut-2-enoic acid were identified as MFA degradation intermediates using dispersive liquid-liquid microextraction combined with gas chromatography-mass spectrometry (GC-MS).