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.