Cd和Al共混对针铁矿结构和性能的影响,ACS Earth and Space Chemistry

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Cd和Al共混对针铁矿结构和性能的影响
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2018-11-05 00:00:00 , DOI: 10.1021/acsearthspacechem.8b00159
Hui Yin ₁ , Qian Wang ₁ , Zhaohui Li ₂ , Wei Li ₁ , Lu Liu ₁ , Chuanqin Huang ₁ , Guohong Qiu ₁ , Xionghan Feng ₁ , Wenfeng Tan ₁ , Huifang Xu ₃ , Fan Liu ₁

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针铁矿是土壤中最常见和最活跃的羟基氧化铁矿物质之一。尽管已广泛研究了针铁矿中Fe的单金属替代，但很少有人同时引入Al和Cd进行研究，这在某些金属污染的生态系统中更为常见。在这项研究中，在室温下合成了一系列Al和Cd共取代的针铁矿晶体，并通过粉末X射线衍射，Rietveld结构细化，湿化学分析，透射电子显微镜和红外光谱进行了表征。Al和Cd对Fe的最高取代水平分别为〜7.8和〜9.9mol％。针铁矿中Cd浓度的增加伴随着晶体尺寸和结晶度的降低。Cd在针铁矿结构中的掺入几乎不受Al的影响，但是Cd大大抑制了Al的掺入。Rietveld结构细化分析显示晶胞尺寸，晶体密度和Cd浓度之间存在显着正相关。沿Me-Me（Me = Fe，Al和Cd）的边缘共享距离c轴，随着Al浓度的增加，拐角共享的Me–Me减小，而随着Cd浓度的增加，拐角共享的Me–Me增大，而沿b的边缘共享的Me–Me距离之间存在正相关轴和镉浓度。随着Al和Cd的总浓度增加，红外活性基团γOH的波数向更高的波数移动，而δOH的位置与δOH和γOH的分离与Al浓度之间观察到显着的正相关，并且观察到显着的负相关。在τO和Cd浓度之间。讨论了在实验条件下，镉在针铁矿中普遍掺入铝的基本机理。结果将帮助我们更好地了解共存阳离子对针铁矿晶体的微观结构和理化性质的协同或拮抗作用。

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Effect of Cd and Al Coincorporation on the Structures and Properties of Goethite

Goethite is one of the most common and active Fe oxyhydroxide minerals in soils. Although single metal substitution for Fe in goethite is extensively studied, investigation is rare on simultaneous incorporation by Al and Cd, which is more common in some metal-polluted ecosystems. In this study, a series of Al and Cd cosubstituted goethite crystals were synthesized at room temperature and characterized by powder X-ray diffraction, Rietveld structure refinement, wet chemical analysis, transmission electron microscopy, and infrared spectroscopy. The highest substitution levels of Al and Cd for Fe are ∼7.8 and ∼9.9 mol %, respectively. Increasing Cd concentration in goethite is accompanied by decreasing crystal size and crystallinity. Incorporation of Cd into the goethite structure is hardly affected by Al, but the incorporation of Al is greatly inhibited by Cd. Rietveld structure refinement analysis shows a significantly positive relationship among unit-cell dimensions, crystal density, and Cd concentration. Distances of edge-sharing Me–Me (Me = Fe, Al, and Cd) along the c axis, and the corner-sharing Me–Me are decreased with increasing Al concentration and increased with the increment of Cd concentration, while a positive relationship is observed between edge-sharing Me–Me distances along the b axis and Cd concentration. The wavenumber of infrared active group γOH shifts to higher wavenumbers as the total concentration of Al and Cd increases, while remarkable positive relationships are observed between the positions of δOH and the separation of δOH and γOH with Al concentration, and a significant negative correlation is observed between τO and Cd concentration. Underlying mechanisms of the prevailing incorporation of Cd over Al in goethite at the experimental conditions are discussed. The results will help us better understand the synergetic or antagonistic effects of coexisting cations on the microstructure and physicochemical properties of goethite crystals.

更新日期：2018-11-05

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