[期刊论文][Full-length article]

出版年：2022

Cl₂^•− can be the dominant radical species when high salinity wastewater is treated by advanced oxidation processes (AOPs). In this study, the steady-state concentrations of HO^•, Cl^• and Cl₂^•− were determined during the Fenton treatment of two landfill leachate concentrates with significantly different Cl⁻ concentrations (XPNF: 1406 mg/L; SNNF: 8036 mg/L). Based on the steady-state concentrations of the radical species and measured second-order rate constants with dissolved organic matters (DOM), HO^• accounted for 76.2% of DOM transformation in XPNF, while Cl₂^•− accounted for 96.5% in SNNF. The DOM transformation dominated by HO^• or Cl₂^•− was then thoroughly compared to investigate the reactivities of HO^• and Cl₂^•− with DOM at molecular level using high-resolution mass spectrometry. The results showed that formulas with low oxidation degree (O/C < 0.5) were preferentially removed by HO^• and HO^• was more reactive towards compounds with high saturation degree (H/C > 1.5) compared with Cl₂^•−. In contrast, Cl₂^•− was more reactive to the compounds with lower saturation level (H/C < 1.5) and the reaction of Cl₂^•− with DOM was less dependent on DOM oxidation degree. In addition, HO^• preferentially reacted with the CHON compounds with low N content, while Cl₂^•− was more reactive to CHON compounds with higher N content compared with HO^•. To our knowledge, this is the first study to distinguish the difference in the reactivity of HO^• and Cl₂^•− towards DOM at molecular level.

Landfill leachates ; Dissolved organic matters ; Advanced oxidation processes ; Reactive oxygen/chlorine species ; High resolution mass spectroscopy