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Characterization of Lead Uptake by Nano-Sized Hydroxyapatite: A Molecular Scale Perspective
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2018-04-13 00:00:00 , DOI: 10.1021/acsearthspacechem.8b00020
Dong-Xing Guan 1 , Chao Ren 1 , Jingzhao Wang 1 , Yinian Zhu 2 , Zongqiang Zhu 2 , Wei Li 1, 3
Affiliation  

Sequestration of toxic metals (e.g., Pb) by hydroxyapatite (HAP) has attracted wide attention in soil remediation. In this study, a comprehensive investigation on Pb uptake by HAP was conducted using combined batch method, X-ray diffraction (XRD), Fourier-transform infrared, and high-resolution transmission electron microscopy (HRTEM). Results revealed that the Pb uptake mechanism involves not only surface adsorption and precipitation but also incorporation depending on the initial Pb concentration. At low Pb concentrations (e.g., 0.1 mM), surface adsorption may contribute considerably to the total Pb uptake as no changes were observed in the XRD analysis. At medium concentrations of 0.5–5.7 mM, formation of lead phosphate precipitates was evidenced by XRD analysis with new peaks at 2θ of ∼30.3° and can be indexed to crystalline hydroxypyromorphite (HPY). This was also consistent with the ratios (0.9–1.0) of Pbsorbed/Cadissolved at Pb level of 2.5–5.7 mM. At higher Pb concentrations (≥6.6 mM), larger ratios (1.2–1.9) of Pbsorbed/Cadissolved were observed, and surprisingly, the XRD signal denoting HPY was weakened. This may imply that Pb has incorporated through substituting the Ca sites into the HAP crystal lattice different from the dissolution–precipitation process occurring at the medium Pb concentration range. Direct observation of PbxCa5–x(PO4)3OH solid solutions with high Ca content from HRTEM further supported this argument. Overall, the molecular level understanding of the fundamental geochemistry for Pb interaction with HAP provided by this research could improve the efficiency of the application of HAP material for environmental remediation.

中文翻译:

纳米羟基磷灰石对铅的吸收特性:分子尺度的角度。

羟基磷灰石(HAP)隔离有毒金属(例如,Pb)在土壤修复中引起了广泛关注。在这项研究中,使用混合间歇法,X射线衍射(XRD),傅里叶变换红外和高分辨率透射电子显微镜(HRTEM)对HAP吸收Pb进行了全面研究。结果表明,铅的吸收机理不仅涉及表面吸附和沉淀,而且还取决于初始的铅浓度。在低Pb浓度(例如0.1 mM)下,由于XRD分析中未观察到变化,表面吸附可能对总Pb吸收有很大贡献。在0.5–5.7 mM的中等浓度下,X射线衍射分析证实了磷酸铅沉淀的形成,并在2θ〜30处出现了新的峰。角度为3°,并且可以索引为结晶羟基焦晶石(HPY)。这也与铅的比率(0.9-1.0)一致吸附的/ Ca以2.5–5.7 mM的Pb浓度溶解。在较高的Pb浓度(≥6.6 mM)下,观察到较大的Pb吸附/ Ca溶解比(1.2–1.9),并且令人惊讶的是,表示HPY的XRD信号减弱了。这可能意味着Pb通过将Ca位置取代到HAP晶格中而掺入,这与在中等Pb浓度范围内发生的溶解-沉淀过程不同。直接观察到Pb x Ca 5– x(PO 43HRTEM中高Ca含量的OH固溶体进一步支持了这一论点。总体而言,这项研究提供的有关Pb与HAP相互作用的基本地球化学的分子水平理解可以提高HAP材料在环境修复中的应用效率。
更新日期:2018-04-13
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