Acetaminophen degradation by a synergistic peracetic acid/UVC-LED/Fe(II) advanced oxidation process: Kinetic assessment, process feasibility and mechanistic considerations.

Application of peracetic acid (PAA) in Advanced Oxidation Processes (AOPs) has seen an increase in the last few years. In this study, PAA/UVC-LED/transition metal was used to degrade acetaminophen (ACT) in an aqueous solution. Amongst tested transition metals (Fe, Cu, Co, Mn, Ag), Fe(II) demonstrated the highest efficiency. The effect of pH, PAA dosage, initial concentration of ACT and Fe(II) concentration was investigated on ACT removal. More than 95% removal efficiency was obtained in 30 min employing pH = 5.0, PAA 4 mM and 0.5 mM Fe(II) (kapp = 0.0993 min-1). Scavenging experiments highlighted the contribution of oxygen-centered radicals; however, the dominant mechanism is hydroxyl radical-induced, while the superoxide radicals had a negligible role. The effect of anions in water showed that carbonate, (dihydrogen) phosphate and nitrite ions had a strong inhibitory effect, while a neutral effect was observed by sulfate, nitrate and chloride ions. Seven intermediates of ACT oxidation were determined and the ACT degradation pathway by the PAA/UVC-LED/Fe(II) is presented. The efficacy of the PAA/UVC-LED/Fe(II) process was also verified for the degradation of other contaminants of emerging concern and disinfection of fecal indicator microorganisms in real matrix (secondary WW). In conclusion, the studied PAA/UVC-LED/Fe(II) process opens a new perspective as a promising application of advanced oxidation for the degradation of organic pollutants.