The conversion of As vapor released from coal combustion to less hazardous solids is an important process to alleviate As pollution especially for high-As coal burning, but the roles of key ash components are still in debate. Here, we used multiple analytical methods across the micro to bulk scale and density functional theory to provide quantitative information on As speciation in fly ash and clarify the roles of ash components on As retention. Fly ash samples derived from the high-As bituminous coal-fired power plants showed a chemical composition of typical Class F fly ash. In-situ electron probe microanalysis (EPMA) was for the first time used to quantify and distinguish the inter-particle As distribution difference within coal fly ash. The spatial distribution of As was consistent with Fe, O, and sometimes with Ca. Grain-scale distribution of As in coal fly ash was quantified and As concentrations in single ash particles followed the order of Fe-oxides > aluminosilicates > unburned carbon > quartz. Sequential extraction and Wagner chemical plot of As confirmed that Fe minerals rather than Al-/Ca-bearing minerals played a vital role in capturing and oxidizing As3+ into solid phase (As5+). Magnetite content in fly ash well-correlated with the increase ratio of As before and after magnetic separation, suggesting magnetite enhanced As enrichment in fly ash. Density functional theory (DFT) indicated that the bridges O sites of octahedral structure on Fe3O4 (111) surface were likely strong active sites for As2O3 adsorption. This study highlights the importance of magnetite on As transformation during bituminous or high-rank coal combustion in power plants and has great implications for developing effective techniques for As removal.
|Journal||Journal of Hazardous Materials|
|State||Published - Aug 5 2021|
Bibliographical noteFunding Information:
This work was supported by the National Key Research and Development Project of China ( 2018YFB0605103 ), Chinese Postdoctoral Science Foundation ( 2019M662586 ), and National Natural Science Foundation of China ( 41773099 and 52006082 ). J. C. Hower thanks the ongoing support by the Commonwealth of Kentucky for research at the University of Kentucky Center for Applied Energy Research. We thank Dr. Ruoyu Sun for his suggestion on the paper.
© 2021 Elsevier B.V.
- Arsenic retention
- Capture mechanisms
- Coal-fired power plants
- Fly ashes
- Speciation determination
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal
- Health, Toxicology and Mutagenesis