Pseudo first order kinetics and proposed transformation products pathway for the degradation of diclofenac using graphite-PVC composite as anode.

Abstract

The electrochemical degradation kinetics of diclofenac (DCF) using graphite–PVC composite as anode was assessed in pure water and effluent wastewater. Effects of initial concentration of diclofenac, chloride ion (Cl−) loading, type of sample and applied voltage were determined to test and validate a kinetic model for the oxidation of diclofenac by the electrochemical oxidation process. The results revealed that the electrochemical oxidation rates of diclofenac followed pseudo first-order kinetics. The rate constant values ranged from 0.018 to 0.173 /min, depending on the operating parameters. However, 6 V and 4 g/L NaCl were selected for further experiments (96.9% removal of diclofenac and 0.0078 kWh/g diclofenac consumption energy) after 30 min and at 20 mg/L of diclofenac. High consumption energy (0.0303 kWh/g diclofenac) was accompanied with high applied voltage of 10 V so it was not considered in this study. Liquid chromatography time-of-flight mass spectrometry (LC–ToF/MS) was used for the elucidation of the main transformation products (TPs) which are resulted from the degradation of diclofenac (DCF) during the application of graphite–PVC composite as anode in aqueous matrices. The toxicity of DCF and its TPs was assessed against E. coli bacteria at different incubation time.