Electrochemical degradation of antibiotic enoxacin using a novel PbO electrode with a graphene nanoplatelets inter-layer: Characteristics, efficiency and mechanism.

A novel PbO electrode was fabricated by adding graphene nanoplatelets (GNP) inter-layer into β-PbO active layer (called GNP-PbO) and utilized to degradation of antibiotic enoxacin (ENO). The GNP-PbO electrode had a much rougher surface than the typical PbO electrode, with smaller crystal size and lower charge-transfer resistance at the electrode/electrolyte interface. Notably, the GNP inter-layer increased the oxygen evolution potential of PbO electrode (2.05 V vs. SCE), which was very beneficial to inhibit oxygen evolution and promote ·OH production. The relatively best operating parameters for ENO removal and energy efficiency were current density of 20 mA cm, initial pH of 7, initial ENO concentration of 100 mg L and electrode distance of 4 cm. Furthermore, indirect radical oxidation was found to be the main way during electrolysis process. Based on the observed analysis of intermediate products, the main reaction pathways of ENO included hydroxylation, defluorination and piperazine ring-opening. Finally, combinating with the electro-oxidation capability, stability and safety evaluation, we can conclude that GNP-PbO is a promising anode for treatment of various organic pollutants in wastewater.