Enhancement and mechanism of electrochemical degradation of pyridine contaminated wastewater

Pyridine is an emerging contaminant in groundwater which can adversely affect human health and the electrochemical method has been a paramount method to address it. The present study investigated the degradation of pyridine with Ti/RuO2 anode and Cu-Zn cathode which were combined with a wire entanglement in an undivided catalysis cell, and the system was enhanced by an iron net. First, the enhancement of iron net on electrochemical degradation of pyridine was studied by comparing the presence and absence of iron net. Then, the influencing factors of the electro-iron system, including current density, NaCl dosage and plate distance was studied and Box-Behnken design was employed to investigate the interaction of the three parameters (current density, plate distance, and supporting electrolyte dosage) on the removal of pyridine. Moreover, the electrochemical enhanced pyridine degradation mechanism by iron net was analyzed with cyclic voltammetry (CV) analysis. The reaction pathway and intermediates of pyridine oxidation were also described. It was found that the degradation efficiency of pyridine in the electrochemical system could be increased by 11.3% by adding an iron net. Based on the response surface methodology analysis, the pyridine removal efficiency of 90.2% was achieved under the optimal conditions with a current density of 99.45 mA cm(-2), plate distance of 2.99 cm and NaCl dosage of 8.78 g L-1. The CV curve found that the electrochemical oxidation of pyridine was accomplished by indirect oxidation. Pyridine reacts with the oxide formed by Cl- to form intermediates of small organic acid, which can be further mineralized to be CO2 and H2O. Adding an iron net can reduce hydrogen by electrochemical corrosion and reduce the carbonyl group of the intermediate product to hydroxyl group, thereby promoting the degradation of pyridine. This study provides a potentially efficient method for disposing of wastewater pollution caused by pyridine.