Synergistic effect of ferrous ion and copper oxide on the oxidative degradation of aqueous acetaminophen at acid conditions: A mechanism investigation

A synergistic effect of Fe(II) and copper oxide (CuO) was observed on the degradation of acetaminophen (ACT) in the presence of O 2 . The results showed that 89% of ACT (50   mg/L) was degraded within 6   h by 10   mM Fe 2+ with 5   g/L CuO powder at pH 3.0, among which about 30% of ACT was mineralized. The sorbed Fe(II) on the CuO surface which is more reactive than the dissolved Fe(II) was capable of reducing both Cu(II) and O 2 . The resulting Cu(I) significantly accelerated the destruction of ACT by serving as an electron-mediator between the sorbed Fe(II) and O 2 . In addition, the hydrogen peroxide (H 2 O 2 ), hydroxyl radical ( OH) and superoxide anion radical ( O 2 − ) were identified as the main reactive oxygen species (ROSs) generated in Fe(II)/CuO suspension by Electron paramagnetic resonance (EPR) technique and quenching studies; however, only OH was found to have caused the decomposition and mineralization of ACT. First O 2 − was generated by reduction of O 2 through a one-electron transfer pathway. Then the generated O 2 − mediated the production of H 2 O 2 , which further decomposed into OH by Cu(I)- and Fe(II)-catalyzed Fenton reactions. The effects of Fe(II) concentration, CuO dose, solution pH and the degradation pathway were investigated, respectively.