XANES/EXAFS and quantum chemical study of the speciation of arsenic in the condensate formed in landfill gas processing: Evidence of the dominance of As-S species

Po-An Chen; H Paul Wang; Andrey M Kuznetsov; Alexei N Masliy; Siqi Liu; Chao-Lung Chiang; Gregory V Korshin

doi:10.1016/j.jhazmat.2022.130522

XANES/EXAFS and quantum chemical study of the speciation of arsenic in the condensate formed in landfill gas processing: Evidence of the dominance of As-S species

J Hazard Mater. 2023 Mar 5:445:130522. doi: 10.1016/j.jhazmat.2022.130522. Epub 2022 Nov 30.

Authors

Po-An Chen¹, H Paul Wang², Andrey M Kuznetsov³, Alexei N Masliy³, Siqi Liu⁴, Chao-Lung Chiang⁵, Gregory V Korshin⁴

Affiliations

¹ Department of Environmental Engineering, National Cheng Kung University, Tainan, Taiwan; Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195-2700, USA.
² Department of Environmental Engineering, National Cheng Kung University, Tainan, Taiwan.
³ Department of Inorganic Chemistry, Kazan National Research Technological University, K. Marx Street 68, 420015, Russian Federation.
⁴ Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195-2700, USA.
⁵ National Synchrotron Radiation Research Center, Hsinchu, Taiwan.

PMID: 37055954
DOI: 10.1016/j.jhazmat.2022.130522

Abstract

The XANES/EXAFS data and quantum chemical simulations presented in this study demonstrate several features of the chemistry of arsenic compounds found in the condensates and solids generated in landfill gas (LFG) processing carried out for renewable natural gas (RNG) production. The XANES data show the decrease in the position of the absorption edge of As atoms, similar to that characteristic for sulfur-containing As solutes and solids. The EXAFS data show that the As-O and As-S distances in these matrixes are similar to those in thioarsenates. Quantum-chemical calculations demonstrated the close agreement between the experimental and modeled As-S and As-O distances determined for a range of methylated and thiolated arsenic solutes. These calculations also showed that the increase of the number of the As-S bonds in the coordination shell of arsenic is accompanied by a consistent decrease of the charges of As atoms. This decrease is correlated with the number of the As-S bonds, in agreement with the trend observed in the XANES data. These results provide insight into the intrinsic chemistry and reactivity of As species present in LFG matrixes; they may be helpful for the development of treatment methods to control arsenic in these systems.

Keywords: Arsenic; EXAFS; Landfill gas condensate; Quantum chemical modeling; Speciation.