Incomplete transformations of Pb to pyromorphite by phosphate-induced immobilization investigated by X-ray absorption fine structure (XAFS) spectroscopy
Incomplete transformations of Pb to pyromorphite by phosphate-induced immobilization investigated by X-ray absorption fine structure (XAFS) spectroscopy
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DOI：
10.1016/j.chemosphere.2009.04.049
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发表时间：
2009-07-01
期刊：
影响因子：
8.8
通讯作者：
Tanida, Hajime
中科院分区：
文献类型：
--
作者：
Hashimoto, Yohey;Takaoka, Masaki;Tanida, Hajime
为了准确评估固定化技术，有必要说明目标金属物质向最终产品的转化。本研究采用扩展 X 射线吸收精细结构 (EXAFS) 光谱与线性组合拟合 (LCF) 相结合来确定经过磷酸盐改良剂处理的污染土壤中的铅形态及其比例。从射击场收集的铅污染土壤分别用磷酸钙（CP）、陶瓷废料合成的羟基磷灰石（CHA）和焚烧的家禽垃圾（PW）进行处理。土壤在含水量32%的条件下培养7天和380天。 EXAFS-LCF 分析表明对照土壤中的 Ph 形态包括有机复合相 (Pb-org, 32%)、PbO (22%)、PbCO3 (28%) 和 Pb-3(CO3)(2)(OH)(2) (8%)。随着培养时间的延长，CHA中氯磷氯铅矿[Pb-5(PO4)(3)Cl]的比例从20%增加到27%，CP土壤中从19%增加到31%。 Pb-org、PbO 和氯磷氯铅矿的组合（比例分别约为 20%、45% 和 23%）可以充分再现 PW 改良土壤的光谱。孵育 380 d 后，以氯磷氯铅矿比例表示的修饰对 Pb 固定的有效性顺序为 CP (31%) > CHA (27%) > PW (23%)。我们的研究表明，约 70% 的 Pb 形态并未以氯磷氯铅矿的形式固定，并且额外供应磷酸盐改良剂几乎不会促进氯磷氯铅矿的形成。 EXAFS-LCF 方法表明，有机复合 Pb 在所有改良土壤中均持续存在，这表明丰富的土壤有机碳可能是磷氯铅矿转化的抑制因素。 (C) 2009 Elsevier Ltd. 保留所有权利。
For an accurate assessment of immobilization technologies, it is necessary to illustrate the transformation of target metal species into their final products. The present study employed extended X-ray absorption fine structure (EXAFS) spectroscopy combined with linear combination fitting (LCF) to determine Pb species and their proportions in contaminated soils treated with phosphate amendments. Lead contaminated soils collected from a shooting range were separately treated with calcium phosphate (CP), hydroxyapatite synthesized from ceramic waste (CHA), and incinerated poultry litter (PW). Soils were incubated at 32% water content for 7 and 380 d. The EXAFS-LCF analysis illustrated that Ph speciation in the control soil included organically-complexed phases (Pb-org, 32%), PbO (22%), PbCO3 (28%), and Pb-3(CO3)(2)(OH)(2) (8%). As the incubation period increased, the proportion of chloropyromorphite [Pb-5(PO4)(3)Cl] increased from 20% to 27% in CHA and from 19% to 31% in CP soils. The spectra of PW-amended soils were reproduced adequately with a combination of Pb-org, PbO, and chloropyromorphite in the proportion of about 20%, 45%, and 23%, respectively. The effectiveness of amendments on Pb immobilization as indicated by the chloropyromorphite proportion was in the order of CP (31%) > CHA (27%) > PW (23%) after 380 d of incubation. Our study indicates that about 70% of Pb species was not immobilized as a form of chloropyromorphite, and the additional supply of phosphate amendment scarcely promoted chloropyromorphite formation. The EXAFS-LCF approach illustrated that organically-complexed Pb was persistent in all amended soils, suggesting that an enriched soil organic carbon may be an inhibitory factor for pyromorphite transformations. (C) 2009 Elsevier Ltd. All rights reserved.