Fabrication of a multi-layer CNT-PbO2 anode for the degradation of isoniazid: Kinetics and mechanism

Abstract

In this study, the CNTs were successfully compounded in PbO2 electrode through composite electrodeposition technology to obtain multi-layer CNT-PbO2 electrode. Scanning electron microscope, X-ray diffraction and X-ray Photoelectron Spectroscopy were comprehensively used to characterize the lead dioxide electrode and the electrochemical performance were also tested by cyclic voltammetry, and electrochemical impedance spectroscopy. Results showed that CNT-PbO2 significantly improved the electrochemical performance, which was attributed to that the compound of CNTs in PbO2 improved the active sites on the surface, with higher oxidation peaks, smaller particle size, larger specific surface area, and lower charge transfer resistance. In the degradation experiment, the chemical oxygen demand removal efficiency of isoniazid by CNT-PbO2 electrode were 1.37 times of that by pure PbO2 electrode. The main influence factors on the degradation of ISN, such as initial ISN concentration, Na2SO4 concentration, current density and initial pH value was analyzed in detail. Considered comprehensively the effects of ISN removal efficiency, COD and average current efficiency, the degradation of ISN and COD reached 99.4% and 86.8%, respectively, after the electrode was degraded by electrochemical oxidation for 120 min under the best conditions. In addition, the degradation mechanism of ISN in electrochemical oxidation was studied. According to the intermediate products detected by GC-MS, the possible degradation pathway of ISN in electrochemical oxidation system were proposed.