Molecular insight into DOM fate using EEM-PARAFAC and FT-ICR MS and concomitant heavy metal behaviors in biologically treated landfill leachate during coagulation: Al speciation dependence

Libing Liu; Lei Du; Sen Lu; Bo Yang; Xu Zhao; Deli Wu; Xunchang Fei; Hongping He; Dongsheng Wang

doi:10.1016/j.jhazmat.2023.132374

Molecular insight into DOM fate using EEM-PARAFAC and FT-ICR MS and concomitant heavy metal behaviors in biologically treated landfill leachate during coagulation: Al speciation dependence

J Hazard Mater. 2023 Oct 15:460:132374. doi: 10.1016/j.jhazmat.2023.132374. Epub 2023 Aug 27.

Authors

Libing Liu¹, Lei Du¹, Sen Lu², Bo Yang¹, Xu Zhao³, Deli Wu⁴, Xunchang Fei⁵, Hongping He⁶, Dongsheng Wang⁷

Affiliations

¹ College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China.
² State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Shenzhen, Guangdong 518055, China.
³ State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
⁴ State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, China.
⁵ School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore.
⁶ College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China. Electronic address: hehp@szu.edu.cn.
⁷ College of Environmental and Resource Science, Zhejiang University, Hangzhou, Zhejiang 310058, China.

PMID: 37683350
DOI: 10.1016/j.jhazmat.2023.132374

Abstract

Various combined processes with pre-coagulation have been developed for biologically treated landfill leachate, but the microscopic-level processes occurring during coagulation remain largely unknown. Herein, dissolved organic matter (DOM) fate using fluorescence excitation emission matrix spectroscopy combined with parallel factor analysis and electrospray ionization coupled Fourier transform-ion cyclotron resonance mass spectrometry and concomitant heavy metal (HM) behaviors were explored at the molecular level. In addition, AlCl₃ and two polyaluminum chloride (PACl) species (dominated by [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ and [(AlO₄)₂Al₂₈(OH)₅₆(H₂O)₂₆]¹⁸⁺, respectively) were used. The results show that all coagulants are efficient at removing DOM. PACl was found to be advantageous over AlCl₃ in overcoming pH fluctuation, which is ascribed to the different dominant mechanisms, namely, entrapment and sweep flocculation for AlCl₃ and charge neutralization for PACl. Consequently, PACl was more effective at removing humic substances, usually high-molecular-weight, oxygen-rich and unsaturated, than protein substances. For HM removal, PACl was likewise better and more stable, where As, Cu, Ni, Co and Hg were removed predominantly via adsorption, and Cr, Zn, Pb, Cd and Mn were removed via coprecipitation. Correlation analysis showed that humic substances tended to complex with HMs and be removed synergistically due to the ubiquitous occurrences of aromatic structures and oxygen-containing functional groups.

Keywords: Biologically treated landfill leachate; Coagulation; Dissolved organic matter fate; FT-ICR MS; Heavy metal behavior.