Estefania Garcia, Pan Liu, Sharon E. Bone, Yinghao Wen and Yuanzhi Tang
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引用次数: 0
摘要
美国每年在燃煤过程中会产生数百万吨煤飞灰(CFA),这些煤飞灰通常被用于混凝土行业或在灰池中进行处置。煤飞灰中含有微量的有毒重金属,包括硒(Se)。由于硒的毒性取决于其种类,因此调查 CFAs 中受煤源和燃烧条件影响的硒种类有助于了解在处置或有益再利用过程中对环境和人类健康的相关影响。本研究利用同步辐射 X 射线吸收光谱(XAS)和显微 X 射线荧光光谱(μ-XRF/XAS)对一组具有代表性的 CFA 样品进行了硒的标示。含Se颗粒具有高度异质性,单个颗粒可能含有多种氧化态,包括Se(0)、Se(IV)和Se(VI)。对样品特征进行了主成分分析,包括 Al2O3、SiO2、CaO、FeO、着火损耗、平均粒度、Se 浓度和 Se 氧化态。研究发现,选择性催化还原(SCR)用于限制煤炭燃烧过程中氮氧化物(NOx)的排放,与硒氧化态降低有关,在采用 SCR 的样品中,硒(0)的含量高达 90%。除 SCR 外,氧化铁含量也可能影响硒的标示。
Systematic characterization of selenium speciation in coal fly ash†
Millions of tons of coal fly ashes (CFAs) are produced annually during coal combustion in the U.S., which are commonly beneficially used in the concrete industry or disposed of in ash ponds. CFAs contain trace amounts of a range of toxic heavy metals including selenium (Se). Because the toxicity of Se is dependent on its speciation, investigating Se speciation in CFAs as affected by coal source and combustion conditions can help understand the related environmental and human health impacts during disposal or beneficial reuse. In this study, a set of representative CFA samples were characterized for Se speciation using synchrotron X-ray absorption spectroscopy (XAS) and micro-X-ray fluorescence spectromicroscopy (μ-XRF/XAS). Se-containing particles were highly heterogeneous, and individual particles might contain multiple oxidation states including Se(0), Se(IV), and Se(VI). Principal component analysis was performed for sample characteristics including Al2O3, SiO2, CaO, FeO, loss on ignition, average particle size, Se concentration, and Se oxidation state. Selective catalytic reduction (SCR), which is used to limit nitrogen oxide (NOx) emissions during coal combustion, was found to be associated with the presence of reduced Se oxidation states, with up to 90% Se(0) observed in samples with SCR. Alongside SCR, FeO content may also influence Se speciation.
期刊介绍:
Environmental Science: Processes & Impacts publishes high quality papers in all areas of the environmental chemical sciences, including chemistry of the air, water, soil and sediment. We welcome studies on the environmental fate and effects of anthropogenic and naturally occurring contaminants, both chemical and microbiological, as well as related natural element cycling processes.