Mechanism for the stabilization/solidification of arsenic-contaminated soils with Portland cement and cement kiln dust.
Mechanism for the stabilization/solidification of arsenic-contaminated soils with Portland cement and cement kiln dust.
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DOI：
10.1016/j.jenvman.2010.06.018
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发表时间：
2010-11
影响因子：
8.7
通讯作者：
I. Yoon;D. Moon;Kyoung-Woong Kim;Keunyoung Lee;Ji‐Hoon Lee;Min Gyu Kim
中科院分区：
文献类型：
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作者：
I. Yoon;D. Moon;Kyoung-Woong Kim;Keunyoung Lee;Ji‐Hoon Lee;Min Gyu Kim
利用1 N HCl提取液、X射线粉末衍射（XRPD）、X射线吸收近边结构（XANES）和扩展X射线吸收精细结构（EXAFS）光谱研究了波特兰水泥（PC）和水泥窑灰（CKD）对砷（As）污染土壤的稳定/固化（S/S）机理。稳定后的固定化程度进行了评估，使用1 N盐酸提取的基础上，韩国标准试验（KST）。在用30wt%PC固化1天和用50wt%CKD固化7天后，从改良土壤中浸出的As浓度低于韩国对策标准（3 mg L-1）。当pH > 3时，PC和CKD处理后的渗滤液中As浓度显著降低，表明pH对As的迁移性有显著影响。XRPD结果表明，在PC和CKD处理的泥浆中，亚砷酸钙（Ca-As-O）和水合砷酸钙钠（NaCaAsO 4·7. 5 H2O）分别是固定As（III）和As（V）的关键相。XANES光谱证实PC和CKD浆料样品的As（III）和As（V）氧化态与通过XRPD鉴定的晶体中的物种形成形式一致。EXAFS光谱显示As（III）-PC和As（III）-CKD浆料中的As-Ca键合。PC和CKD固定As污染土壤的主要机制与As（III）或As（V）与Ca之间的结合密切相关。
In this study, the mechanism for the stabilization/solidification (S/S) of arsenic (As)-contaminated soils with Portland cement (PC), and cement kiln dust (CKD) using 1 N HCl extraction fluid, X-ray powder diffraction (XRPD), X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) spectroscopy was investigated. The degree of As immobilization after stabilization was assessed using a 1 N HCl extraction on the basis of the Korean Standard Test (KST). After 1 day of curing with 30 wt% PC and 7 days of curing with 50 wt% CKD, the concentration of As leached from the amended soils was less than the Korean countermeasure standard (3 mg L−1). The As concentrations in the leachate treated with PC and CKD were significantly decreased at pH > 3, indicating that pH had a prevailing influence on As mobility. XRPD results indicated that calcium arsenite (Ca–As–O) and sodium calcium arsenate hydrate (NaCaAsO4·7.5H2O) were present in the PC- and CKD-treated slurries as the key phases responsible for As(III) and As(V) immobilization, respectively. The XANES spectroscopy confirmed that the As(III) and As(V) oxidation states of the PC and CKD slurry samples were consistent with the speciated forms in the crystals identified by XRPD. EXAFS spectroscopy showed As–Ca bonding in the As(III)-PC and As(III)-CKD slurries. The main mechanism for the immobilization of As-contaminated soils with PC and CKD was strongly associated with the bonding between As(III) or As(V) and Ca.