Enhanced degradation of acetaminophen in wastewater by integrating ionizing irradiation with Fenton oxidation

Abstract

Acetaminophen (APAP), a widely detected pharmaceutical contaminant, which is difficult to remove by conventional biological wastewater treatment processes. In this study, the degradation of APAP by ionizing irradiation was investigated in a simulated wastewater and an actual industrial wastewater matrix, with particular emphasis on matrix effects and irradiation–Fenton enhancement. In a simulated wastewater, ionizing irradiation was efficient for APAP degradation, with removal efficiency exceeding 87% at an absorbed dose of 5 kGy. The degradation kinetics depended on the initial APAP concentration, as low-concentration systems followed pseudo first-order kinetics, whereas higher concentrations exhibited kinetic deviations caused by competition from transformation products. Although APAP can be efficiently degraded, TOC decrease was much lower, indicating incomplete mineralization. In actual wastewater, APAP degradation was strongly suppressed by background organic and inorganic constituents, as shown by the lower irradiation chemical yield. Coupling ionizing irradiation with Fenton oxidation could enhance APAP degradation, particularly at low absorbed doses, while mineralization was low due to the dissolved organic matter and intermediate products. UV–Vis, EEM fluorescence, and ion chromatography confirmed the destruction of aromatic structures and the formation of low-molecular-weight carboxylic acids. These results showed that ionizing irradiation combined with Fenton oxidation could enhance the degradation of pharmaceutical contaminants, while wastewater matrix effects critically limit the treatment efficiency.