Changes of dissolved organic matter fractions and formation of oxidation byproducts during electrochemical treatment of landfill leachates: Development of spectroscopic indicators for process optimization. (1st April 2023)

• Record Type: Journal Article
• Authors: Jiang, Bi-Cun; Tian, Ye-Chao; Li, Ai-Min; Han, Yu-Ze; Wu, Ze-Tao; Lu, Chang; Song, Hai-Ou; Ji, Rong; Li, Wen-Tao; Korshin, Gregory V.
• Is Part Of: Water research. Volume 232(2023)
• Publication Date: 2023-04-01
• Subjects: Electrochemical oxidation -- Size exclusion chromatography -- Boron-doped diamond -- Landfill leachate -- Humic substances -- Oxidation byproducts; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119702
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Degradation kinetics of DOM fractions were compared among EO with different anodes. The emergence of the 290 nm absorbance band was attributed to formation of chlorine. Abs420 indicated the shift of the oxidation of DOM from HA fraction to BP fraction. Abs420 indicated the shift from oxidation of DOM to formation of ClO3 − and ClO4 − . It can achieve a trade-off between DOM degradation and ClO3 − and ClO4 − formation. Abstract: Electrochemical oxidation (EO) is an attractive option for treatment of dissolved organic matter (DOM) in landfill leachate but concerns remain over the energy efficiency and formation of oxidation byproducts ClO3 − and ClO4 − . In this study, EO treatment of landfill leachates was carried out using representative active and nonactive anode materials, cell configurations and current densities. Size exclusion chromatograms coupled with 2D synchronous and asynchronous correlation analysis showed that the sensitivity of DOM fractions to EO degradation was dependent on the anode material. The nonactive boron-doped diamond (BDD) anode demonstrated the best performance for DOM oxidation. The humic acid-like fraction (HA, 2.5–20 kDa) predominated the visible absorbance of landfill leachates at λ ≥400 nm, and it generally had the highest reaction rates except the occurrence of the pH-induced denaturation and precipitation of the proteinaceous biopolymer fraction (BP, >20 kDa). During the EO treatment of landfill leachate with BDD anode, the UV absorbance spectra of landfill leachates at wavelengths <400 nm were affected by the formation of free chlorine. Instead, the decrease of Abs420 was found to be a good indicator of the shift of the oxidation from predominantly HA fraction to the proteinaceous BP fraction. The behavior of the Abs420 parameter was also indicative of the transition from the energy-efficient oxidation of DOM to the dominance of side reactions of chlorine evolution and the subsequent formation of ClO3 − and ClO4 − . These findings suggest that the EO treatment of landfill leachate can be optimized by adjusting the current density with feedback signals from the online monitoring of Abs420, to achieve a trade-off between degradation of DOM and control of ClO3 − and ClO4 − . Graphical abstract: Image, graphical abstract