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 [AsO
4
]
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.
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