Crystal Chemistry of Carnotite in Abandoned Mine Wastes
Crystal Chemistry of Carnotite in Abandoned Mine Wastes
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DOI：
10.3390/min10100883
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发表时间：
2020-10-01
期刊：
影响因子：
2.5
通讯作者：
Cerrato, Jose M.
中科院分区：
文献类型：
--
作者：
Avasarala, Sumant;J. Brearley, Adrian;Cerrato, Jose M.
采用光谱、电子显微镜和X射线衍射分析相结合的方法，研究了亚利桑那州东北部矿山废弃物中存在的钾铀云母（K2（UO 2）（2）（VO 4）（2）中心点3 H（2）O）的晶体化学。拉曼光谱证实，铀酰钒酸盐相存在于矿山废物是carnotite，而不是罕见的多晶型vandermeerscheite。在这些矿山废物中发生的carnotite的X-射线衍射图案与文献中报道的合成类似物一致。利用透射电子显微镜（TEM）和电子能量损失谱（EELS）分析，在该碳质岩中检测到的碳被鉴定为有机碳包裹体。在排除C并校正电子探针分析的K-漂移后，确定了钾霞石的组成为8.64%K_2O、0.26%CaO、61.43%UO_3、20.26%V_2O_5、0.38%Fe_2O_3和8.23%H_2O。实验结果表明：（K1.66Ca0.043Al（OH）（2+）（0.145）Fe（OH）（2+）（0.044））（（U-0.97）O-2）（2）（（V-1.005）O-4）（2）中心点4 H（2）O（K：U：V的原子比为1.9：2：2）与文献报道的钾钒矿（K-2（UO 2）（2）（VO 4）（2）中心点3 H（2）O）相似。使用选区电子衍射（SAED）-TEM确定的晶格间距数据表明：（1）在暴露于电子束的120 s内，钾霞石完全非晶化，和（2）文献中钾霞石的测量d-间距的良好一致性。测量值和文献d间距值之间的微小差异可能是由于天然和合成材料之间的水合程度不同。这些信息的晶体化学的矿石废物是重要的，以提高认识的发生和反应性的U，V，和其他元素在环境中。
The crystal chemistry of carnotite (prototype formula: K-2(UO2)(2)(VO4)(2)center dot 3H(2)O) occurring in mine wastes collected from Northeastern Arizona was investigated by integrating spectroscopy, electron microscopy, and x-ray diffraction analyses. Raman spectroscopy confirms that the uranyl vanadate phase present in the mine waste is carnotite, rather than the rarer polymorph vandermeerscheite. X-ray diffraction patterns of the carnotite occurring in these mine wastes are in agreement with those reported in the literature for a synthetic analog. Carbon detected in this carnotite was identified as organic carbon inclusions using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) analyses. After excluding C and correcting for K-drift from the electron microprobe analyses, the composition of the carnotite was determined as 8.64% K2O, 0.26% CaO, 61.43% UO3, 20.26% V2O5, 0.38% Fe2O3, and 8.23% H2O. The empirical formula, (K1.66Ca0.043Al(OH)(2+)(0.145) Fe(OH)(2+)(0.044))((U-0.97)O-2)(2)((V-1.005)O-4)(2)center dot 4H(2)O of the studied carnotite, with an atomic ratio 1.9:2:2 for K:U:V, is similar to the that of carnotite (K-2(UO2)(2)(VO4)(2)center dot 3H(2)O) reported in the literature. Lattice spacing data determined using selected area electron diffraction (SAED)-TEM suggests: (1) complete amorphization of the carnotite within 120 s of exposure to the electron beam and (2) good agreement of the measured d-spacings for carnotite in the literature. Small differences between the measured and literature d-spacing values are likely due to the varying degree of hydration between natural and synthetic materials. Such information about the crystal chemistry of carnotite in mine wastes is important for an improved understanding of the occurrence and reactivity of U, V, and other elements in the environment.