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

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 [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.

Size Tuning, Phase Stabilization, and Anticancer Efficacy of Amorphous Selenium Nanoparticles: Effect of Ion-Pair Interaction, −OH Functionalization, and Reuse of RTILs as Host Matrix

“…The core-level XPS spectrum shown in Figure 5b depicts a Se 3d peak with a binding energy of ∼56.3 eV, thus confirming the formation of Se NPs. 62,63 The appearance of elemental peaks (in the survey spectrum) corresponding to carbon, oxygen, and nitrogen could be attributed to the presence of RTIL molecules on the surface of NPs.…”

Speciation, Distribution, and Mobility of Hazardous Trace Elements in Coal Fly Ash: Insights from Cr, Ni, and Cu

“…Coal fly ash (CFA), a major constituent of CCR, has been the focus in recent years because of its high annual production, enrichment in HTEs, and potential for beneficial reuse. − American Society for Testing and Materials (ASTM) C 618 defines main CFA types as class F (bituminous) and class C (sub-bituminous): class F CFA is characterized by SiO 2 + Al 2 O 3 + Fe 2 O 3 ≥ 70 wt % and generally originates from the combustion of bituminous and anthracite coal; class C CFA has 50 wt % ≤ SiO 2 + Al 2 O 3 + Fe 2 O 3 < 70 wt % and a higher CaO content and generally originates from the combustion of sub-bituminous coal and lignite. Among all HTEs in CFA, much attention was traditionally paid to As and Se (e.g., refs , ) and previous findings suggested the fundamental influence of CFA chemical composition on the properties of As and Se. − For example, more As was found to occur as Ca 3 (AsO 4 ) 2 in CaO-rich class C CFA in comparison to CaO-poor class F CFA .…”

Trace Element Mass Flow Rates from U.S. Coal Fired Power Plants

“…Third, due to data limitations, our model only estimates the total amount of trace elements that partition into the gas, solid, and liquid phases and does not model trace element speciation. Speciation has significant impacts on partitioning behavior in APCDs, , as well as the efficacy of removal in wastewater treatment systems, leachability in ash ponds, distance traveled in the exhaust plume before settling to the ground, and environmental and human health damages if released into the environment. ,, Finally, our model does not account for the introduction of trace metals from chemicals used in other plant processes, such as lime used in FGD. These sources of uncertainty may contribute to poor model alignment with existing validation data available from the MATS ICR, ELG rule development process, and the Hg emissions monitoring data reported in CEMS.…”