Electrochemical Co-Degradation of Acetaminophen and Bisphenol A in Aqueous Solutions: Degradation Competition and Pathways

This study investigated the degradation competition and pathways of electrochemical co-degradation of two emerging environmental contaminants, polar acetaminophen (AP) and (moderately) non-polar bisphenol A (BPA), on a boron-doped diamond (BDD) electrode in aqueous solutions. The results showed that both compounds mainly relied on hydroxyl radicals (•OH) to trigger indirect oxidation for their electrochemical degradation, although AP also underwent direct oxidation during electrolysis. The effect of increasing current density on the increases in degradation performance was almost the same for AP and BPA. However, BPA exhibited a better performance in mono-degradation than AP, while the opposite tendency was observed for their co-degradation. Their degradation efficiencies were better in 1 M Na2SO4 solution than in a real water matrix. Both UV-vis and excitation–emission matrix (EEM) fluorescence analyses demonstrated that all the aromatic rings of AP and BPA were opened after 30 min of electrolysis at 0.5 A cm−2 in 1 M Na2SO4 solution. Regardless of the small difference in intermediate species, the pathways of electrochemical AP+BPA co-degradation were similar to those of their mono-degradation combination. A double exponential decay model is proposed to simulate the formation and degradation rate constants of benzoquinone (an intermediate).