Determination of Chemical Speciation of Arsenic and Selenium in High-As Coal Combustion Ash by X-ray Photoelectron Spectroscopy: Examples from a Kentucky Stoker Ash

Biao Fu; James C Hower; Shifeng Dai; Sarah M Mardon; Guijian Liu

doi:10.1021/acsomega.8b02929

Determination of Chemical Speciation of Arsenic and Selenium in High-As Coal Combustion Ash by X-ray Photoelectron Spectroscopy: Examples from a Kentucky Stoker Ash

ACS Omega. 2018 Dec 18;3(12):17637-17645. doi: 10.1021/acsomega.8b02929. eCollection 2018 Dec 31.

Authors

Biao Fu¹, James C Hower², Shifeng Dai³, Sarah M Mardon⁴, Guijian Liu¹

Affiliations

¹ CAS Key Laboratory of Crust-Mantle Materials and Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
² Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, Kentucky 40511, United States.
³ State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, China, Beijing 100083, China.
⁴ Office of Philanthropy, University of Kentucky, Lexington, Kentucky 40506, United States.

Abstract

Knowledge of the chemical speciation of arsenic and selenium in coal fly ash is essential in the evaluation of the environmental behavior of fly ash disposed in a landfill in a natural environment. In this study, a series of high-As coal fly ash from stoker boilers were collected to determine the chemical forms of arsenic and selenium. The ash surface chemical characteristics and the speciation of arsenic and selenium were characterized by X-ray photoelectron spectroscopy and X-ray-induced Auger electron spectroscopy. The results indicate that the surface enrichment ratio for selenium (63.3-309.5) is higher than that of arsenic (1.2-21.2). The Wagner chemical-state plot of arsenic indicates that As is mainly present as As(V) bonded to oxygen ligands, that is, the [AsO₄]^3- anion; Se is found predominantly as elemental Se (62.0-83.3%), followed by selenite (16.7-38%). The extreme enrichment of both arsenic and selenium arsenic is controlled by iron oxides in the coal fly ash.