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1.
赣北石门寺钨多金属矿床是江南钨矿带上的超大型斑岩型钨矿床,具有重要的经济价值和研究意义。白云母作为常见的造岩矿物之一,能够指示岩浆和热液演化的不同阶段。从成矿的角度来看,在白钨矿成矿过程中,斜长石蚀变形成白云母和石英,提供了重要的Ca2+来源。而短波红外技术目前广泛应用于矿产勘查领域,利用白云母短波红外特征能够快速便捷地进行钨矿的勘查找矿研究。文章利用短波红外技术,对石门寺矿床中的白云母开展光谱测试,结合其岩相学特征和地球化学特征,研究了白云母对白钨矿成矿的勘查指示意义。研究结果表明：含矿岩体中的白云母多为次生白云母,Si的平均离子数为3.245,Al的平均离子数为2.52,具有富硅贫铝的特点,其Al-OH吸收位置位于2209～2216 nm;而无矿岩体中的白云母多为原生白云母,Al的平均离子数为2.85,相对含矿岩体白云母Al的平均离子数较高,Si的平均离子数相对较低为3.08,Al-OH吸收位置位于2198～2208 nm之间。n(Al)(Al离子数)与Al-OH吸收波长呈现负相关关系。研究结果证明了白云母短波红外特征对石门寺钨矿床的重要指示意义,Al-OH吸... 相似文献
2.
黏土岩型锂矿作为可利用锂资源的重要组成部分,由于其分布广、储量大而备受关注。陕西镇巴地区晚二叠世吴家坪组新发现黏土岩型锂矿(资源),Li2O最高含量可达0.39%,达到了黏土锂矿的工业指标(0.2%),具有一定的开发利用价值。为了查明陕南镇巴地区富锂黏土岩中黏土矿物种类、含量及富锂黏土岩中锂的赋存状态,本文选取陕西镇巴地区富锂黏土岩,通过偏光显微镜鉴定初步查明黏土岩的矿物组成,利用X射线衍射(XRD)、全自动综合矿物分析系统(TIMA)分析技术定量查明富锂黏土岩中黏土矿物及主要元素含量。结果表明：该黏土岩主要由高岭石、铝绿泥石、伊利石、锂绿泥石等黏土矿物以及赤铁矿组成,含少量绿泥石、金红石等矿物。TIMA分析表明样品中锂绿泥石最高含量为8.94%,对应锂含量为0.12%(Li2O含量为0.26%),略低于该样品全岩Li2O含量(0.31%)。锂绿泥石呈丝缕状,不规则粒状,嵌布于一水软铝石、伊利石、铝绿泥石之间。综合研究认为镇巴地区富锂黏土岩中锂主要赋存于锂绿泥石中,其他矿物的锂含量很低。锂绿泥石、伊利石、高岭石等层状结构... 相似文献
3.
富钴结壳是一种重要的海底矿产资源,具有独特的经济价值和科学意义,其不仅富含Mn、Co、Ni、Cu、PGE和REY等金属,而且在反演新生代以来古海洋环境记录等方面扮演着独特的角色。锰氧化物(MnO2·xH2O)和铁羟基氧化物(FeOOH)是构成富钴结壳的主要矿物,矿物颗粒十分微小(纳米级)。水羟锰矿和水钠锰矿具有层状结构且层电荷为负,通过吸附阳离子来补偿。前人通过连续浸出实验、元素相关性统计分析、吸附实验和拓展X射线吸收精细结构(EXAFS)光谱广泛研究了微量元素在矿物中的赋存状态,确定了微量元素在锰氧化物矿物中主要存在三种类型络合物:共六边(edge-sharing)、共双角(double-corner sharing)和共三角(triple-corner sharing)。综合研究表明,在最低含氧带之下铁锰氧化物(氢氧化物)从海水沉淀到周围海山坚硬基岩上形成富钴结壳的机制主要是无机胶体化学反应和矿物表面反应。最后针对已有的相关研究现状以及富钴结壳研究面临的挑战,富钴结壳的成矿物质来源及演化、微量元素富集机制、蕴含的古海洋信息等问题仍需要进一... 相似文献
4.
采空区积水在我国煤矿中广泛存在。明确在采空区封闭-半封闭环境条件下的水-岩相互作用机理,对实现煤矿区水污染减量以及地下水资源保护具有重要意义。以内蒙古某煤矿采空区积水为研究对象,设计高度还原采空区环境的箱式模拟试验,采用X射线衍射仪(XRD)和X射线荧光光谱仪(XRF)对模拟采空区填充物(煤、垮落岩体)中矿物成分及元素组成进行分析,借助离子色谱仪(IC)和电感耦合等离子体发射光谱分析仪(ICP-OES)等对水中水化学特征进行表征,探究采空区积水水质形成的水-岩相互作用机制。结果表明:水-岩相互作用主要为煤及垮落岩体中的矿物溶解-沉淀作用、阳离子交换作用、煤中黄铁矿氧化作用以及混合作用。矿物溶解作用占主导地位,采空区积水中的Na+、K+主要来源是钠长石、钾长石等硅酸盐矿物的溶解,而Ca2+和Mg2+主要来自于钙长石、方解石、绿泥石等矿物溶解;离子交换作用主要发生在采空区水-岩作用的初期(0～20 d),而后逐渐减弱;采空区底部残煤中黄铁矿氧化作用是积水SO42- 相似文献
5.
华北第三系潞王坟组膨胀岩主要造岩矿物鉴定及微观特征研究 总被引：1，自引：0，他引：1
华北上第三系泥灰岩和粘土岩都具有粘粒含量高及"半土半岩"的性质,具有遇水易崩解、膨胀的特性,呈弱~强膨胀潜势。以该区代表性膨胀岩为研究对象,通过X射线衍射实验(XRD)及电镜扫描(SEM)实验和能量光谱测试试验,分析膨胀岩土的造岩矿物的物质组成和微观结构特征。试验结果表明:泥灰岩含有非膨胀矿物方解石、石英、长石以及含有膨胀矿物蒙脱石、高岭土、伊利石等,矿物成分以方解石含量最高在38%~42%之间,其次为蒙脱石,含量在31%~35%之间。粘土岩同样含有以上矿物,但含量与泥灰岩有很大不同,粘土岩中蒙脱石含量35%~40%之间,而方解石的含量只有10%,远低于30%石英的含量。微观结构观察显示,泥灰岩中有少量方解石结晶体,局部富集半结晶的方解石,岩石中的粘土矿物呈层状局部褶曲,有溶蚀边,微细裂缝及孔洞少,而粘土岩中在电镜下未见方解石晶体,粘土矿物有大量褶曲,含大量微细裂缝及孔洞。 相似文献
6.
察哈尔右翼后旗二长花岗岩岩体位于华北板块北缘中段.岩体富SiO2、富K、富碱、低Ca和P、贫Fe和Mg,w(P2O5)与w(SiO2)呈负相关,铝指数(A/CNK)为0.96~1.15,分异指数为90.36~92.96;主要造岩矿物为条纹长石、斜长石和石英,其铁镁矿物主要为黑云母,未出现碱性铁镁矿物和富铝矿物,副矿物为锆石、磁铁矿、磷灰石、榍石和钛铁矿;可见察哈尔右翼后旗二长花岗岩属高分异钙碱性I型花岗岩类.结合较低的w(∑REE)((46.8~94.4)×10-6)、w(Th)((1.74~2.39)×10-6)、w(U)((0.27~0.39)×10-6)和微量元素判别图解,二长花岗岩岩浆源区可能为下地壳,源岩可能为岩石圈地幔.岩石轻重稀土分馏较强 ((La/Yb)N= 6.52~28.39),δEu以正异常为主(0.83~3.51),富集大离子亲石元素(LILEs,Cs、Rb、Ba和K),亏损高场强元素 (HFSEs,Nb、Ta、P和Ti).地球化学特征反映了二长花岗岩具有火山弧岩石特征,且岩体侵入新元古界埃迪卡拉系什那干群,表明岩体形成于活动大陆边缘弧环境,其侵位反映了古亚洲洋的俯冲岩浆事件. 相似文献
7.
中太平洋YJC海山富钴结壳矿物组成与元素地球化学 总被引：1，自引：0，他引：1
运用等离子光谱、等离子质谱、X射线衍射、红外光谱和场发射电镜等分析测试方法,对太平洋威克(Wake)海岭YJC海山中的富钴结壳中不同构造层的矿物组成和元素地球化学研究表明:矿石矿物是水羟锰矿和少量的钙锰矿,脉石矿物是磷灰石、石英和方解石等,微量矿物有蒙脱石、高岭石、钠沸石、斜发沸石、伊利石、水黑云母、磁铁矿和角闪石等。老结壳磷灰石的质量分数>10%,P>1%;新结壳磷灰石<10%,P<1%。老结壳相对富集Cu、Ca、P等元素,新结壳相对富集TMn、TFe、Co、Ni、Ba、Zn、Pb、Mo等元素。结壳内部纹层构造的不同位置及包体内的微区成分变化较大,TMn和TFe呈同消长关系,但TMn/TFe值相对稳定。结壳的稀土元素总量为1761.88×10-6,Ce具明显的正异常。老结壳相对富集稀土元素,新结壳略富Eu。 相似文献
8.
对西科1井生物礁碳酸盐岩样品进行了地球化学(常量组分、微量及稀土元素含量等)分析, 旨在探讨生物礁的形成演化以及所记录的环境变化信息.结果表明: 西科1井岩心在井深36 m附近存在地球化学参数的显著变化, 暗示该深度是一处重要的地层界面或环境突变界面.岩心中的常量组分可以分为3类组合: 以CaO为主, 辅以K2O的原生碳酸岩组分, 该组分对应的主要造岩矿物是方解石, 代表了未经白云岩化的生物礁原生碳酸盐沉积; 以MgO为主, 辅以Na2O和P2O5, 代表了白云岩化作用中的富集组分, 反映了相对封闭的泻湖环境; 以SiO2为主, 加以Al2O3、TiO2、Fe2O3和MnO, 代表造礁生物对这些组分的富集作用, 但不能排除火山组分少量混入的可能性.相对于全球第四纪碳酸盐岩、上陆壳及页岩的平均值, 岩心碳酸盐岩中大部分微量元素和稀土元素含量都较低.岩心中氧化还原敏感性微量元素(RSE)含量较低, 指示岛礁发育过程中大部分时期处于氧化环境条件下, 而RSE含量在岩心中的大幅波动体现出氧化/还原环境的交替变化.微量元素含量、ΣREE、ΣLREE、ΣHREE、LREE/HREE、δCe、δEu等地球化学指标在岩心中的分布与岩心样品的矿物组成无明显的相关性, 说明成岩作用和白云岩化作用并没有造成微量和稀土元素含量及特征指标的明显变化. 相似文献
9.
大别—苏鲁超高压地体中面理化含榴花岗岩的成因研究 总被引：7，自引：1，他引：6
大别—苏鲁超高压地体中的面理化花岗岩因为常含石榴石而被简称为含榴花岗岩, 其岩石类型主要为二长花岗岩、花岗岩和微斜长石花岗岩, 岩石具有花岗结构和片麻状构造.详细的野外地质研究表明, 超高压片麻岩作为超高压榴辉岩的围岩与含榴花岗岩呈渐变过渡关系, 或在含榴花岗岩中呈与面理平行的残留条带, 体现超高压片麻岩通过构造置换和部分熔融向含榴花岗岩转化.含榴花岗岩在常量元素的总体组成上, w(SiO2)为71.73%~79.15%;A/CNK为0.83~1.09, 平均0.98, 为准铝质; w(K2O+Na2O)为6.15%~9.00%, w(K2O)/w(Na2O)为0.16~1.54(绝大多数集中在0.9~1.1), 具有相对弱富钠-弱富钾特征.从标准矿物组成上看, 大别含榴花岗岩主要相当于奥长花岗岩; 山东含榴花岗岩主要相当于花岗岩; 东海含榴花岗岩主要相当于钾质花岗岩.在微量元素特征上, 含榴花岗岩的∑REE、∑LREE明显富集, δEu具有明显的负异常, 在原始地幔标准化蛛网图上, 相对亏损Nb、Ta、P、Zr、Ti等高场强元素及大离子亲石元素Sr, 富集Ba、La、Nd、Y、K等大离子亲石元素, 结合其贫w(Al)(平均11.6%)富w(Ga)(> 17×10-6)、(Fe/Mg)M(1.087~20.330)等特征, 表明其地球化学特征相当于非造山的A型花岗岩.结合前人超高压变质作用和构造演化等研究成果, 可以推断含榴花岗岩是超高压地体折返到中下地壳, 在底侵、构造体制转换等因素作用下, 由高压片麻岩的部分熔融形成的.含榴花岗岩在大别—苏鲁不同区域上的规律变化, 表明东海含榴花岗岩的出露相对于大别更低位. 相似文献
10.
山东昌乐蕴含中国最大的宝石级刚玉—蓝宝石矿床。昌乐刚玉巨晶与玄武岩界限截然,边缘圆化,沿巨晶溶蚀圆化的边缘发育富铝的尖晶石和钛磁铁矿反应环边,显示其为深源捕虏晶的岩相学特征。对刚玉等巨晶及其反应边矿物进行岩相学、电子探针和LA-ICP-MS(Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry)分析能有效揭示其成因及演化历程。昌乐刚玉2组样品(CL-1和CL-2)矿物化学和关键元素特征及Ga/Mg、Cr/Ga、Fe/Ti、Fe/Mg等关键元素比值显示为岩浆型来源,而CL-2组样品明显叠加了后期熔体交代作用的特征。反应边尖晶石具刚玉巨晶向尖晶石巨晶过渡的成分特征,关键元素特征指示两者具强烈亲缘性,尖晶石巨晶是刚玉经历复杂交代作用的产物。昌乐刚玉呈现碱性熔体中结晶的化学成分特征,极有可能源于交代富集的地幔岩低度熔融形成的富铝的碱性熔体。 相似文献
11.
Agpaitic rocks comprise most of the exposed part of the 1.16 Ga old, 8 × 17 km large and about 1700 m thick Ilímaussaq intrusion in South Greenland. Within these, more than 600 m thick sequence of sodalite-rich “naujaites” (mainly sodalite + arfvedsonite + alkali feldspar + nepheline + eudialyte + aenigmatite) are interpreted as a sodalite flotation cumulate. Sodalites show two to three different zones in cathodoluminescence (CL) and at least two zones in thin sections. The CL zones can be related to chemical differences detectable by electron microprobe, whereas relations with optical zonations are less obvious. Compositional trends in sodalite reflect trends in the evolution of volatile contents in the melt. The sodalite at Ilímaussaq is almost free of Ca and closely corresponds to the pure Na–Cl sodalite endmember with about 7 wt.% of Cl; S contents reach up to 0.9 wt.%. Cl/Br ratios range from 500 to 1700. Raman spectroscopy shows that S is present as [SO4]2− in sodalite, although sphalerite (ZnS) is a stable phase in naujaites. Peralkalinity and fO2 conditions allow S2− and [SO4]2− to be present contemporaneously.
The whole naujaite sequence is divided into two parts, an upper part with low, homogeneous S contents and Cl/Br ratios in the sodalite cores, and a lower part with strongly variable and higher S contents and with Cl/Br ratios, which are decreasing downwards. The details of the S content and the Cl/Br ratio evolution show that sodalite strongly influences the halogen contents of the melt by scavenging Cl and Br.
The naujaites were formed from a highly reduced, halogen-rich magma in equilibrium with magmatic methane at about 800 °C, which, upon ascent, cooling and fractionation, exsolved an aqueous fluid phase. Both fluids were trapped in separate inclusions indicating their immiscibility.
Micrometer-sized aegirine crystals and primary hydrocarbon-bearing inclusions are abundant in the crystal cores. The inclusions were trapped at pressures up to 4 kbar, although the emplacement pressure of the intrusion is about 1 kbar. This indicates growth of the sodalite during melt ascent and a very effective mechanism of trace element scavenging during sodalite growth. Sodalite rims are devoid of aegirine or primary hydrocarbon inclusions and probably reflect the emplacement stage. 相似文献
12.
Francesco Di Benedetto Francesco D’Acapito Gabriele Fornaciai Massimo Innocenti Giordano Montegrossi Luca A. Pardi Silvia Tesi Maurizio Romanelli 《Physics and Chemistry of Minerals》2010,37(5):283-289
An X-ray absorption spectroscopy (XAS) study of the Fe local environment in natural amethyst (a variety of α-quartz, SiO2) has been carried out. Room temperature measurements were performed at the Fe K-edge (7,112 eV), at both the X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions. Experimental results were then compared with DFT calculations. XANES experimental spectra suggest Fe to occur mainly in the trivalent state, although a fraction of Fe2+ is identified. EXAFS spectra, on the other hand, reveal an unusual short distance for the first coordination shell: = 1.78(2) Å, the coordination number being 2.7(5). These results allow to establish that Fe replaces Si in its tetrahedral site, and that numerous local distortions are occurring as a consequence of the presence of Fe3+ variably compensated by protons and/or alkaline ions, or uncompensated. The formal valence of Fe, on the basis of both experimental and DFT structural features, can be either 4+ or 3+. Taking into account the XANES evidences, we suggest that Fe mainly occurs in the trivalent state, compensated by protons, and that a minor fraction of Fe4+ is stabilised by the favourable local structural arrangement. 相似文献
13.
Polarized XANES and EXAFS spectroscopic investigation into copper(II) complexes on vermiculite 总被引：1，自引：0，他引：1
Interaction of heavy metals with clay minerals can dominate solid-solution reactions in soil, controlling the fate of the metals in the environment. In this study we used powdered and polarized extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near edge spectroscopy (XANES) to investigate Cu sorbed on Llano vermiculite and compare the results to reported Cu sorption mechanism on Wyoming (WY) smectite and reduced South African (SA) vermiculite. Analysis of the Cu K-edge spectra revealed that Cu sorbed on Llano vermiculite at high ionic strength (I) has the greatest degree of covalent bond character, followed by Cu sorbed on montmorillonite at high I, and Cu sorbed on reduced SA vermiculite at high I. Cu sorbed on clay minerals at low I has the least covalent character. EXAFS data from Cu sorbed Ca- and K-equilibrated Llano vermiculites showed the presence of a second-shell Al, Si, or Mg backscatterer at 3.02 Å. This distance is consistent with Cu sorbing via a corner-sharing monodentate or bidentate bond. Polarized XANES and EXAFS results revealed that the angle between the Cu atom and the mineral sorption sites is 68° with respect to the [001] direction. From the bond angle and the persistence of the second-shell backscatterer when the interlayer is collapsed (K-equilibration), we conclude that Cu adsorption on the Llano vermiculite is not occurring in the interlayer but rather Cu is adsorbing onto the edges of the vermiculite. Results from this research provide evidence that Cu forms inner-sphere and outer-sphere complexes on clay minerals, and does not form the vast multinuclear surface precipitates that have been observed for Co, Zn, and Ni. 相似文献
14.
In northern Saskatchewan, Canada, high-grade U ores and the resulting tailings can contain high levels of As. An environmental concern in the U mining industry is the long-term stability of As within tailings management facilities (TMFs) and its potential transfer to the surrounding groundwater. To mitigate this problem, U mill effluents are neutralized with lime to reduce the aqueous concentration of As. This results in the formation of predominantly Fe3+–As5+ secondary mineral phases, which act as solubility controls on the As in the tailings discharged to the TMF. Because the speciation of As in natural systems is critical for determining its long-term environmental fate, characterization of As-bearing mineral phases and complexes within the deposited tailings is required to evaluate its potential transformation, solubility, and long-term stability within the tailings mass. In this study, synchrotron-based bulk X-ray absorption spectroscopy (XAS) was used to study the speciation of As and Fe in mine tailings samples obtained from the Deilmann TMF at Key Lake, Saskatchewan. Comparisons of K-edge X-ray absorption spectra of tailings samples and reference compounds indicate the dominant oxidation states of As and Fe in the mine tailings samples are +5 and +3, respectively, largely reflecting their generation in a highly oxic mill process, deposition in an oxidized environment, and complexation within stable oxic phases. Linear combination fit analyses of the K-edges for the Fe X-ray absorption near edge spectra (XANES) to reference compounds suggest Fe is predominantly present as ferrihydrite with some amount of the primary minerals pyrite (8–15% in some samples) and chalcopyrite (5–15% in some samples). Extended X-ray absorption fine structure (EXAFS) analysis of As K-edge spectra indicates that As5+ (arsenate) present in tailings samples is adsorbed to the ferrihydrite though an inner-sphere bidentate linkage. 相似文献
15.
16.
Determination of Halogens (F, Cl, Br, I), Sulfur and Water in Seventeen Geological Reference Materials 总被引：5，自引：0，他引：5
Fluorine, chlorine, bromine, iodine and sulfur were determined in seventeen geological reference materials after extraction by pyrohydrolysis. Fluorine, Cl and S (as sulfate ions) were determined in the extraction solution by ion chromatography with detection limits of around 0.2 mg l−1 . Bromine and I were measured by ICP-MS with detection limits of 1 μg l−1 for Br and 0.1 μg l−1 for I. For rock samples, using normal extraction conditions (500 mg of sample and 100 ml of final solution) detection limits were 40 mg kg−1 for F and Cl, 15 mg kg−1 for S, 0.2 mg kg−1 for Br and 0.02 mg kg−1 for I. These detection limits may be improved by increasing the amount of sample and hence the concentration of the final solution. Water was also determined using an extraction technique based on H2 O degassing, reduction on zinc at 1000 °C and H2 manometry. Our results for fluorine, chlorine, sulfur and water are in good agreement with literature data. Very few reference materials have recommended values for bromine and especially for iodine. Among the analysed samples, three are new reference materials: BHVO-2, BCR-2 and AGV-2. 相似文献
17.
Uranyl and arsenate cosorption on aluminum oxide surface 总被引：1，自引：0，他引：1
In this study, we examined the effects of simultaneous adsorption of aqueous arsenate and uranyl onto aluminum oxide over a range of pH and concentration conditions. Arsenate was used as a chemical analog for phosphate, and offers advantages for characterization via X-ray absorption spectroscopy. By combining batch experiments, speciation calculations, X-ray absorption spectroscopy, and X-ray diffraction, we investigated the uptake behavior of uranyl, as well as the local and long-range structure of the final sorption products. In the presence of arsenate, uranyl sorption was greatly enhanced in the acidic pH range, and the amount of enhancement is positively correlated to the initial arsenate and uranyl concentrations. At pH 4-6, U LIII- and As K-edge EXAFS results suggest the formation of surface-sorbed uranyl and arsenate species as well as uranyl arsenate surface precipitate(s) that have a structure similar to trögerite. Uranyl polymeric species or oxyhydroxide precipitate(s) become more important with increasing pH values. Our results provide the basis for predictive models of the uptake of uranyl by aluminum oxide in the presence of arsenate and (by analogy) phosphate, which can be especially important for understanding phosphate-based uranium remediation systems. 相似文献
18.
Javiera Cervini-Silva Benjamin Gilbert Sirine Fakra Stephan Friedlich Jillian Banfield 《Geochimica et cosmochimica acta》2008,72(10):2454-2464
Highly insoluble Ce-bearing phosphate minerals form by weathering of apatite [Ca5(PO4)3.(OH,F,Cl)], and are important phosphorous repositories in soils. Although these phases can be dissolved via biologically-mediated pathways, the dissolution mechanisms are poorly understood. In this paper we report spectroscopic evidence to support coupling of redox transformations of organic carbon and cerium during the reaction of rhabdophane (CePO4·H2O) and catechol, a ubiquitous biogenic compound, at pH 5. Results show that the oxic–anoxic conditions influence the mineral dissolution behavior. Under anoxic conditions, the release of P and Ce occurs stoichiometrically. In contrast, under oxic conditions, the mineral dissolution behavior is incongruent, with dissolving Ce3+ ions oxidizing to CeO2. Reaction product analysis shows the formation of CO2, polymeric C, and oxalate and malate. The presence of more complex forms of organic carbon was also confirmed. Near edge X-ray absorption fine structure spectroscopy measurements at Ce-M4,5 and C-K absorption edges on reacted CePO4·H2O samples in the absence or presence of catechol and dissolved oxygen confirm that (1) the mineral surface converts to the oxide during this reaction, while full oxidation is limited to the near-surface region only; (2) the Ce valence remains unchanged when the reaction between CePO4·H2O and O2 but in the absence of catechol. Carbon K-edge spectra acquired from rhabdophane reacted with catechol under oxic conditions show spectral features before and after reaction that are considerably different from catechol, indicating the formation of more complex organic molecules. Decreases in intensity of characteristic catechol peaks are accompanied by the appearance of new π* resonances due to carbon in carboxyl (ca. 288.5 eV) and carbonyl (ca. 289.3 eV) groups, and the development of broad structure in the σ* region characteristic of aliphatic carbon. Evolution of the C K-edge spectra is consistent with aromatic-ring cleavage and polymerization. These results further substantiate that the presence of catechol, O2 (aq) causes both the oxidation of structural Ce3+ and the transformation of catechol to more complex organic molecules. Scanning Transmission X-Ray Microscopy measurements at the C K and Ce M4,5 edges indicate three dominant organic species, varying in complexity and association with the inorganic phase. Untransformed catechol is loosely associated with CeO2, whereas more complex organic molecules that exhibit lower aromaticity and stronger CO π* resonances of carboxyl-C and carbonyl-C groups are only found in association with the grains. These results further serve as basis to postulate that, in the presence of O2, CeO2 can mediate the oxidative polymerization of catechol to form higher molecular weight polymers. The present work provides evidence for a pathway of biologically-induced, non-enzymatic oxidation of cerium and formation of small CeO2 particles at room temperature. These findings may have implications for carbon cycling in natural and cerium-contaminated soils and aqueous environments. 相似文献
19.
石膏是矿山开采及冶炼等工业过程产生的大宗固体废弃物。工业活动产生的废液普遍有高含量的砷等有毒元素,这导致所产生的石膏也含有较高浓度的砷等有毒元素。研究砷在石膏中地球化学行为和归趋对含砷石膏的砷污染控制具有重要的理论和实际意义。然而目前对含砷石膏中不同形态的砷的定量测定和分析尚存在问题。本文在不同pH值的条件下共沉淀砷和石膏,利用电感耦合等离子体质谱(ICP-MS)、同步辐射X-射线吸收近边光谱(XANES)和电子顺磁共振(EPR)对石膏中掺杂态和表面吸附沉淀态的砷进行定量分析。ICP-MS的结果表明随着pH从2升高到12 和14,石膏中砷的含量由57×10-6 增加到 67 470×10-6和63 980×10-6。同步辐射X-射线吸收近边光谱和电子顺磁共振光谱分析表明石膏样品中主要含有五价砷。在2≤pH≤7.5时,固体样品中同步辐射吸收边后的峰形状和掺杂态砷的形状类似,而在pH≥8时,其边后峰的形状发生明显的变化;粉末电子顺磁共振(EPR)定量分析表明在2≤pH≤7.5时砷在石膏中的含量和ICP-MS的分析结果一致,而在pH≥8时其含量明显小于ICP-MS的分析结果。这些结果揭示了在2≤pH≤7.5时,砷在石膏中主要以掺杂态的形式存在,而在pH≥8时大部分砷是以吸附态或表面沉淀的形式存在。五价砷在石膏中的含量和固定机制随着pH值的变化而变化,其研究对了解尾矿中石膏对砷污染的控制作用具有重要作用。此外,研究石膏中由辐射导致的g约为2.33的[AsO3]2-自由基电子顺磁共振特征峰,有助于补充和完善石膏的电子顺磁共振特征谱在地质测年及辐射剂量学中的应用。 相似文献
20.
Glenn A. Waychunas Gordon E. Brown Jr. Michael J. Apted 《Physics and Chemistry of Minerals》1986,13(1):31-47
K-edge extended X-ray absorption fine structure (EXAFS) spectra of Fe in varying environments in a suite of well-characterized silicate and oxide minerals were collected using synchrotron radiation and analyzed using single scattering approximation theory to yield nearest neighbor Fe-O distances and coordination numbers. The partial inverse character of synthetic hercynite spinal was verified in this way. Comparison of the results from all samples with structural data from X-ray diffraction crystal structure refinements indicates that EXAFS-derived first neighbor distances are generally accurate to ±0.02 Å using only theoretically generated phase information, and may be improved over this if similar model compounds are used to determine EXAFS phase functions. Coordination numbers are accurate to ±20 percent and can be similarly improved using model compound EXAFS amplitude information. However, in particular cases the EXAFS-derived distances may be shortened, and the coordination number reduced, by the effects of static and thermal disorder or by partial overlap of the longer Fe-O first neighbor distances with second neighbor distances in the EXAFS structure function. In the former case the total information available in the EXAFS is limited by the disorder, while in the latter case more accurate results can in principle be obtained by multiple neighbor EXAFS analysis. The EXAFS and XANES spectra of Fe in Nain, Labrador osumulite and Lakeview, Oregon plagioclase are also analyzed as an example of the application of X-ray absorption spectroscopy to metal ion site occupation determination in minerals. 相似文献