Hydroxyl multi-walled carbon nanotube-modified nanocrystalline PbO₂ anode for removal of pyridine from wastewater

We prepared a hydroxyl multi-wall carbon nanotube-modified nanocrystalline PbO₂ anode (MWCNTs-OH-PbO₂) featuring high oxygen evolution potential, large effective area, and excellent electrocatalytic performance. The oxygen evolution potential and effective area of the MWCNTs-OH-PbO₂ electrode were 1.5 and 3.7-fold higher than the traditional PbO₂ electrode. Electrochemical degradation of pyridine in aqueous solution was investigated by using the MWCNTs-OH-PbO₂ anode. Based on pyridine decay rate (93.8%), total organic carbon reduction (84.6%), and energy consumption (78.8WhL^-1order^-1) under the optimal conditions, the MWCNTs-OH-PbO₂ electrode modified with MWCNTs-OH concentration of 1.0gL^-1 exhibited higher electrochemical oxidation ability than the traditional PbO₂ electrode. The intermediate, hydroxypyridine, was found at the first stage of electrolysis. The primary mineralization product, NO₃^-, was detected in aqueous solution after electrolysis. A possible electrochemical mineralization mechanism including two potential routes, i.e., via formation of small organic molecules by ring cleavage reaction and direct mineralization to CO₂ and NO₃^-, was proposed. The results demonstrated that the MWCNTs-OH-PbO₂ electrode exhibited high efficiency for pyridine mineralization in aqueous solution under mild conditions.