Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
J Environ Manage. 2010 Nov;91(11):2322-8. doi: 10.1016/j.jenvman.2010.06.018.
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 (NaCaAsO(4).7.5H(2)O) 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.
本研究采用 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）光谱法，研究了波特兰水泥（PC）和水泥窑灰（CKD）稳定/固化（S/S）含砷土壤的机理。根据韩国标准测试（KST），采用 1 N HCl 提取法评估稳定后砷的固定程度。用 30wt%的 PC 养护 1 天，用 50wt%的 CKD 养护 7 天，改性土壤中浸出的砷浓度低于韩国对策标准（3mg/L）。PC 和 CKD 处理的浸出液的砷浓度在 pH>3 时显著降低，表明 pH 对砷的迁移性有主要影响。XRPD 结果表明，PC 和 CKD 处理的悬浮液中存在砷酸钙（Ca-As-O）和水合钠钙砷酸盐（NaCaAsO（4）·7.5H（2）O），分别是砷（III）和砷（V）固定的关键相。XANES 光谱证实，PC 和 CKD 悬浮液样品中的砷（III）和砷（V）氧化态与 XRPD 鉴定的晶体中特定形态一致。EXAFS 光谱显示在砷（III）-PC 和砷（III）-CKD 悬浮液中存在 As-Ca 键合。PC 和 CKD 固定污染土壤砷的主要机制与砷（III）或砷（V）与 Ca 的键合密切相关。
