Enhanced photoelectrocatalytic degradation of acetaminophen using a bifacial electrode of praseodymium-polyethylene glycol-PbO2//Ti//TiO2-nanotubes

A bifacial electrode—praseodymium-polyethylene glycol-PbO2//Ti//TiO2-nanotubes—was prepared for the photoelectrocatalytic degradation of acetaminophen. The physicochemical properties of the bifacial electrode (e.g. morphology, structure, light absorption, and electrochemical behavior) were systematically characterized. The effects of solution pH, electrolyte concentration, and current density on the removal of acetaminophen were investigated. With this bifacial electrode, approximately 97% of acetaminophen and 73% of chemical oxygen demand could be removed in 180 min. Compared with photocatalysis and electrocatalysis alone, the photoelectrocatalytic process exhibited a higher average current efficiency and lower energy consumption. This improved performance was attributed to the enhancement of the generation of reactive oxygen species (e.g. HO· and H2O2). Additionally, the intermediates generated in photoelectrocatalytic processes were identified, and two possible degradation pathways were proposed (i.e. direct degradation by HO· attack and acetaminophen dimerization). The ECOSAR prediction based on the molecular structure of intermediates revealed that some products more toxic than parent compounds were formed during photoelectrocatalysis. The acute toxicity test results confirmed that the global toxicity of the treated solution increased in the first 60 min of treatment. Generally, identifying the intermediates and characterizing the evolution of toxicity is important in the acetaminophen-related wastewater treatment for minimizing the potential ecological risks of effluents.