Degradation of diclofenac by heterogeneous electro-Fenton process using magnetic single-walled carbon nanotubes as a catalyst

Abstract

Degradation of diclofenac (DCF) from aqueous solution was investigated by the heterogeneous electro-Fenton (EF) process using magnetic single-walled carbon nanotubes (MSWCNTs) as a new catalyst. The effect of parameters including initial pH, current density, initial catalyst concentration, the initial concentration of DCF and air flow rate on the efficiency of DCF removal and electrochemical production of H2O2 were studied. A removal efficiency of 97.8% for DCF and 71.12% for COD was obtained at an initial pH of 5, current density of 20 mA/cm2, MSWCNTs concentration of 80 mg/L, DCF concentration of 10 mg/L, air flow rate of 1 mL/min and reaction time of 120 min. Regarding the removal of DCF and COD, and production of H2O2, the heterogeneous EF process with MSWCNTs catalyst showed higher activity and efficiency than other electro-catalytic degradation systems. The stability tests of MSWCNTs after 5 time application confirmed its performance potential for long-term degradation of DCF in aqueous solutions. Intermediate products such as 2,3-dichlorobenzene and 2,4-dichlorophenol were identified by gas chromatography-mass spectrometry (GC–MS). Based on the identification of reactive species and the intermediate products, a possible mechanism of removal and degradation pathways for DCF was suggested.