Long life modified lead dioxide anode for organic wastewater treatment: electrochemical characteristics and degradation mechanism.

Recent studies have shown that the lack of ideal anodes with both good activity and stability is still one of the critical problems in electrochemical oxidation for organic wastewater treatment. The electrochemical properties, the activity and stability for anodic oxidation of various phenolic compounds, and the degradation mechanism on a novel beta-PbO2 electrode modified with fluorine resin were investigated. The anode life after modification was greatly improved to be more than 10 yr in common electrochemical current conditions. Such an anode was effective for partial degradation of phenolic compounds, but selective because reactive activities were varied with different substituents. Characterized by SEM and XRD, the crystal form of the anode was verified to be mainly beta-PbO2, and it hardly changed when used for p-nitrophenol degradation for around 320 h although there existed slow electrode corrosion. The active species generated during anodic oxidation were determined to be mainly hydroxyl radical and little ozone. The reactions between hydroxyl radical and phenolic compounds were proved to be electrophilic reactions, based on which a general electrochemical degradation mechanism for aromatic compounds was proposed. In general, such a novel anode has a good performance for organics degradation with perfect electrode life, showing potential for environmental application.