Synergistic effect of ferrous ion-activated hydrogen peroxide and persulfate on the degradation of phthalates in aquatic environments by non-target analysis

Oxidative degradation of most recalcitrant organics in the wastewater by exciting the oxidative potential and high efficacy of economic and environmental compatible oxidants is currently an extensively studied field of research. In this study, an efficient phthalate esters (PAEs) degradation method utilizing dual oxidants persulfate (PS) and hydrogen peroxide in the presence of ferrous ions was developed with high removal efficiency, small oxidant dosage and wide pH range. Compared with the degradation efficiency of single systems including Fe2+/ H2O2 (40 %), PS (24 %) and Fe2+/PS (49 %) for dimethyl phthalate (DMP) degradation, the combining PS and H2O2 activated by Fe2+ is more effective, with the removal efficiency of 95 %. The synergistic effect of PS and H2O2 in the Fe2+-containing system on PAEs degradation was reflected by the degradation products determined by non-target analysis of various oxidation processes. The results showed that the degradation of DMP in two single oxidant systems was dominated by aromatic compounds via dealkylation, hydroxyl addition and decarboxylation, while DMP in the PS/H2O2/FeSO4 system was mainly deeply oxidized to aliphatic molecules through further dearomatization, which was vulnerable for the mineralization of DMP to CO2 and H2O. In addition, the EPR technique combined with DMPO captured SO4•− and •OH signals in the presence of the same Fe2+ and oxidant dosage, revealing that a higher intensity of ·OH and SO4•− generated in the combined oxidative process resulted in a high removal of DMP. This work lays the groundwork for recalcitrant organics removal to apply synergistic activation mode in the AOPs system.