首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 140 毫秒
1.
The Baiyunpu deposit lies in the southwest plunging Dachengshan anticline in central Hunan, which is a large Pb-Zn polymetallic deposit. The orebodies were surrounded by the Qiziqiao Formation limestone in the Middle Devonian, and its geological occurrence is consistent with the wall rocks. A large number of spheroidal pyrite aggregates are found unevenly distributed in the ores. The spheroidal aggregates are made up of kernels and concentric rings. The kernels are composed of approximately epigranular pyrite nanocrystals, while the rings are composed of accumulated pyrite microcrystals growing along the radial direction. The spheroidal pyrite aggregate and its outer zones can be divided into five areas(A–E). The results of electron probe micro analysis(EPMA) show that from the zone A1 to B, Co/Ni 1, the sum of Co and Ni is 0.08%–0.26%, S/Fe increases from 2.06 to 2.15. While from the zone C to E, Ni cannot be detected and S/Fe decreases from 2.22 to 2.08. Powder X-ray diffraction(XRD) analysis in the micro zone shows obvious crystalline characteristics in the aggregates. Moving from the inside outwards, the maximum diffraction peak intensity of the(111) and(220) crystal planes of pyrite increases, and the crystallinity improves. The degree of change in the(111) plane is the most prominent. Considering the theory of crystal growth along with the geologic features of the depositional environment where the spheroidal pyrite aggregates developed, we confirm that the spheroidal aggregates are the result of nano-micro crystalline gathering and growth occurring by the following sequence of processes:nano-crystalline nucleation and growth, gathering into a ball, oriented growth of microcrystals, continuous accumulation, and adjustment of grain boundaries. The formation of the spheroidal pyrite aggregates in the late Qiziqiao Formation of the Middle Devonian occurred in a neutral to weak alkaline and reductive sedimentary environment in the normal oxygen-rich shallowwater carbonate platform edge. The variations in the S/Fe ratio and crystallisation characteristics indicate that during pyrite crystal growth, the sulphur fugacity was high locally and rose constantly, the degree of supersaturation decreased locally and the growth environment was stable relatively.  相似文献   

2.
Superfine graphite powder was prepared by ball-milling exfoliated graphite containing anhydrous CuCl2 in planetary ball milling systems. Nano-scale CuCl2 graphite intercalation compounds were synthesized by heating a mixture of anhydrous CuCl2 and graphite nanosheets. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy were performed to characterize the microstructures of stage-1 nano-scale CuCl2 graphite intercalation compounds. The structure and components of the domain wall and core in the nano-scale CuCl2 graphite intercalation compounds are described. The results show that the content of CuCl2 in the mixture plays a crucial role in the size of the nano-scale CuCl2 graphite intercalation compound.  相似文献   

3.
Superfine graphite powder was prepared by bali-milling exfoliated graphite containing anhydrous CuCl_2 in planetary ball milling systems.Nano-scale CuCl_2 graphite intercalation compounds were synthesized by heating a mixture of anhydrous CuCl_2 and graphite nanosheets. Scanning electron microscopy,energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy were performed to characterize the microstructures of stage-1 nano-scale CuCl_2 graphite intercalation compounds.The structure and components of the domain wall and core in the nano-scale CuCl_2 graphite intercalation compounds are described.The results show that the content of CuCl_2 in the mixture plays a crucial role in the size of the nano-scale CuCl_2 graphite intercalation compound.  相似文献   

4.
The weathering of phosphorus-bearing mineral powder(PBMP) and calcium phosphate(CP) by Aspergillus niger was compared,and the mechanism involved was analyzed for the comprehensive utilization of PBMP.The concentration of water-soluble phosphorus(WSP),Mg2+,and Ca2+at different culture times,microstructures of particles,and mineral compositions was examined by ultraviolet-visible spectrometer(UV),atomic absorption spectrometry(AAS),scanning electron microscopy(SEM),and X-ray diffraction(XRD).Results showed that the change in the concentrations of WSP,Mg2+,and Ca2+were related to the growth of A.niger and the different mineral compositions.Compared with CP,PBMP was weathered harder by fungi.Traces of the weathered mineral were found through SEM.CP not only showed traces of erosion damage but also appeared as a rhombohedron-like substance.The XRD test indicated that the weathering minerals can form water calcium oxalate.Further analysis revealed that the mechanism of PBMP and CP weathering by A.niger was the collaborative result of mycelium biomechanical effects and the acid-soluble role of acidic metabolites.The phosphorus dissolution rate of PBMP after 20 d was 46.83%,whereas that of CP after 12 d was 91.01%.The findings of this study are significant to the effective use of waste PBMP and to the exploitation of low-grade phosphate rock resources.  相似文献   

5.
The occurrences of associated elements and their genetic factors in the No. 30 coal seam in the Zhijin Coalfield were studied using instrumental neutron activation analysis, inductively coupled plasma-atomic emission spectroscopy, and a scanning electron microscope equipped with an energy-dispersive X-ray analyzer. And, a microscope photometer system (Leitz MPV-Ⅲ) was used to observe the characteristics of coal petrology. According to the influence degree by the siliceous low-temperature hydrothermal fluids, the organic matter is divided into four types: A, B, C, and D of the hydrothermally-altered organic matter (HAOM). The study shows that the high content of Fe (2.31%) is not from pyrite, but mostly from the siliceous low-temperature hydrothermal fluids. The occurrences of the associated elements in the four organic matter types are different. The contents of Fe, Si, and Al are decreasing, but S and Cu are increasing in the order of the HAOM-A, HAOM-B, HAOM-C, and HAOM-D. The losing rate of sulfur i  相似文献   

6.
To characterize the hydrothermal processes of East Pacific rise at 9o-10oN, sulfide mineral compositions, textural, and geochemical features of chimney ores were studied using ore microscope, scanning electron microscope, X-ray diffraction analysis, and electron microprobe techniques. Results show that there are three mineral assemblages for the hydrothermal chimney ores, namely: (i) anhydrite marcasite pyrite, (ii) pyrite sphalerite chalcopyrite, and (iii) chalcopyrite bornite digenite covellite. Mineral assemblages, zonational features, and geochemical characteristics of the ore minerals indicate that ore fluid temperature changed from low to high then to low with a maximum temperature up to 400 ℃. The chimney is a typical black smoker. The initial structure of the chimney was formed by the precipitation of anhydrites, and later the sulfides began to precipitate in the inner wall.  相似文献   

7.
This paper derives the physical meanings of peak position,peak width and hight of an X-ray diffraction peak from the analyses of the Bragg‘s equation,the Scherrer‘s formula and the principle of peak intensity calculation.The geometric characteristics of an asymmetric peak are clarified by means of experimemt.The relationships between peak shape and domain size/lattice strain have been verified by geological events.Therefore thsi paper integrates the physical meanings of all 5 basic parameters for an -Xray diffraction peak.Applications of these 5 parameters are exemplified.  相似文献   

8.
A novel, cost-effective, and simple electrocatalyst based on a Pt-modified glassy carbon electrode(GCE), using cetyltrimethylammonium bromide(CTAB) as a cationic surfactant, is reported. Amphiphilic CTAB molecules were adsorbed on GCE by immersion in a CTAB solution. The positively charged hydrophilic layer, which consisted of small aggregates of average size less than 100 nm,was used for accumulation and complexation of [PtCl2. anions by immersing the electrode in Ksolution. The modified electrode was characterized using scanning electron microscopy,energy-dispersive X-ray spectroscopy, impedance spectroscopy, and electrochemical methods. The electrocatalytic activity of the Pt particles in the hydrogen evolution reaction(HER) was investigated.The results show that the CTAB surfactant enhances the electrocatalytic activity of the Pt particles in the HER in acidic solution.  相似文献   

9.
The microstructure of palygorskite from Longwang Mountain of Xuyu County, Jiangsu Province, was studied by energy dispersive X-ray analysis （EDX）, selected-area electron diffraction （SAED） and high-resolution transmission electron microscopy （HRTEM）. The average composition of the palygorskite studied is （Si7.38A10.62） （A10.96Fe^3＋ 0.62Mg2.86 0.56）Ca0.03K0.06O20（OH）2（OH2）4, which is rich in Mg. Several SAED patterns from a single crystal of palygorskite were obtained with different zone axes. The polymorphs （monoclinic and orthorhombic） are unequivocally distinguished by distant interplanar angles, even though they possess similar sets of d-values. High-resolution images of three principal zones （[010], [100] and [110]） were obtained. The lattice fringes on HRTEM images along [010] have spacings of 0.319 nm. These fringes are interpreted as periodic alterations of two tetrahedral （T） sheets and one octahedral （O） sheet （-TT-O-TT-O-）. We have directly observed trioctahedral and dioctahedral individual palygorskite particles along [100]. They are all presented as dark lines along [001], but the width of dark lines corresponding to trioctahedral crystals （0.913 nm） is twice that of the dioctahedral ones （0.456 nm）. This is because the trans.sites are occupied by cations in trioctahedral palygorskite. The width of dark lines along [110] is 1.024 nm, a bit thinner than the theoretical spacing （1.044 nm）. This is because water molecules quickly leave the structure upon the irradiation by the electron beam.  相似文献   

10.
This article presents the thermal transitions of a tobermorite-bearing sample when heated from 30°C up to 1200°C,both in vacuum and in static air,including tobermorite transforming to wollastonite,aragonite to calcite and calcite to lime.Characteristics obtained by in situ high temperature X-ray diffraction,field emission scanning electron microscopy and scanning transmission electron microscopy analyses jointly indicate that the investigated tobermorite is anomalous.The variations along the a,b,c axes and the volume changes of tobermorite with increasing temperature are described,and its thermal shrinkage coefficients therefore determined.The comparison between the refined structures at 30°C and 800°C demonstrates that the shrinkage degree (Δa/a_0) along the a axis is higher than those (Δb/b_0,Δc/c_0) along the b and c axes.The wollastonite is formed in two ways:Tobermorite converting to wollastonite and lime reacting with quartz to form wollastonite.  相似文献   

11.
In this study, the feasibility of using a low-cost adsorbent mixture composed of leonardite (L) and clinoptilolite (C) was evaluated by batch adsorption method using different parameters such as mixing ratio, contact time, pH, temperature, and adsorbent amount for the removal of Zn (II) ions from an aqueous solution. The adsorbents were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Additionally, leonardite–clinoptilolite mixture was analyzed by scanning electron microscopy coupled with energy dispersive X-ray. The Zn (II) adsorption along with an unprecedented adsorption capacity of 454.55 mg g?1 for unmodified natural sorbents was obtained by mixing leonardite and clinoptilolite (LC) without any pretreatment at a ratio of 3:1, using 0.1 g of sorbent at a pH 6, for 2 h of contact time. The experimental data showed a good fit for the Langmuir isotherm model. The thermodynamic parameters revealed that the present adsorption process was spontaneous and exothermic in nature (25–50 °C). The kinetic results of the adsorption showed that the Zn (II) adsorption onto the LC follows pseudo-second-order model. The resultant LC mixture has an excellent adsorption capacity of a Zn (II) aqueous solution, and data obtained may form the basis for utilization of LC as an unpretreated low-cost adsorbent for treatment of metalliferous industrial wastewater.  相似文献   

12.
用透射电镜、扫描电镜、热分析及矿物谱学等手段对含钙铝铁水解聚合产物(含微量硅)合成初期样品及其陈化9年后样品组成物相的形态演化进行了观察对比研究。结果表明,含钙铝铁溶液合成初期迅速形成类钙矾石双羟合结构体,其结构中部分Al3+被Fe3+取代、SO42-阴离子被Cl-离子替代,无定形的铝铁共聚物、铝硅共聚物和多种铝、铁、钙氢氧化物(氧化物)微晶竞争存在。缺氧条件下铝铁水解产物的演化由于氯、钙离子的存在而与文献的报道有所不同。陈化改变了含钙聚合铝(铁)溶液中的长程有序结构。其中的类钙矾石双羟合结构体在高Cl-、低pH环境下长期陈化过程经历了溶解-再结晶作用。大量的铁微晶相溶解形成富铝水羟合铁(ferrihydrite)胶体结构,Cl-与Ca2+以键合或共沉淀方式进入富铝水羟合铁(ferrihydrite)相。富铝水羟合铁(ferrihydrite)胶体最终的结晶相还是β-FeOOH。  相似文献   

13.
The metamict state and recrystallization of fergusonite in metamict natural samples were studied by thermal methods (TGA-DTA), X-ray powder diffraction (XRD), Raman spectroscopy (RS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and electron microprobe (EPMA). Two metamict mineral samples of fergusonite were investigated in order to identify the original premetamict crystal structure and to identify recrystallization mechanisms. The TEM data and RS provided evidence on the partial preservation of the original structure in the investigated minerals, which are X-ray amorphous. It was shown that fergusonite could recrystallize from a metamict mineral with original fergusonite structure or from metamictized pyrochlore, which was altered before or after metamictization. Two recrystallization mechanisms were recognized: (a) epitaxial growth occurring at the boundary between preserved premetamict structure fragments and completely metamictized areas, and (b) nucleation-crystal growth mechanism occurring in completely amorphous areas of the minerals, and resulting in recrystallization of the original mineral as well as in the crystallization of a new mineral with a modified chemical composition as compared to the initial matrix.  相似文献   

14.
The speciation of Mn, Fe, As, and Zn in a fast-growing (0.02mm/yr), shallow-marine, ferromanganese nodule has been examined by micro X-ray fluorescence, micro X-ray diffraction, and micro X-ray absorption spectroscopy. This nodule exhibits alternating Fe-rich and Mn-rich layers reflecting redox variations in water chemistry. Fe occurs as two-line ferrihydrite. The As is strictly associated with Fe and is mostly pentavalent, with an environment similar to that of As sorbed on or coprecipitated with synthetic ferrihydrite. The Mn is in the form of turbostratic birnessite with ∼10% trivalent manganese in the layers and probably ∼8% corner-sharing metal octahedra in the interlayers. The Zn is enriched on the rim of the nodule, associated with Mn. The Zn is completely (>90%) tetrahedrally coordinated and sorbed in the interlayers of birnessite on vacant layer Mn sites. The Zn and Mn species are similar to ones found in soils, suggesting common structural principles despite the differing formation conditions in these systems.  相似文献   

15.
The risk of Pb, Zn and Cd mobility is evaluated in soils from a depleted mine at Rubiais (Lugo, Spain). This area is under special protection because of its outstanding natural value. Soils from nine different areas were selected: at the mining zone (R1, R2, R3), at minespoils (R4, R5, R6) and soils developed on the settling pond (R7, R8, R9). A control soil (RC) was sampled outside the mine. The objectives are (i) to study the characteristics of soils with high influence on metal retention, (ii) to determine the content of Pb, Zn and Cd comparing it with the generic reference levels, and (iii) to evaluate the distribution and the interactions between the metals and the soil geochemical phases by means of sequential chemical extraction, X-ray diffraction, field emission scanning electron microscopy/energy-dispersive X-ray spectroscopy (FE-SEM/EDS) and time of flight secondary ion mass spectrometry (TOF–SIMS). The concentration of Pb, Zn and Cd ranges 850–6,761, 1,754–32,287 and 1.8–43.7 mg kg?1, respectively, and the highest proportion is in the residual fraction. The Mn oxides highly influence the retention of Cd while Pb retention is mainly influenced by Fe oxides. Zn is uniformly distributed amongst the residual fraction and the Fe and Mn oxides. TOF–SIMS and SEM/EDS techniques confirm the fractionation results, showing how Pb and Zn are as sulphide and associated with Fe and Mn oxides. Nevertheless, care should be taken since oxides and sulphides could suffer sulphide oxidation processes or alteration of the oxides causing leaching and the contamination of the protected ecosystem.  相似文献   

16.
The Barmer Basin of Rajasthan is significant for its Paleogene lignite sequences. The lignite seam occurs in Akli Formation of Barmer Basin at the depth of 06–241 m. A total of 57 lignite samples were collected from the working faces of lignite mine and were subjected to proximate analysis (moisture, ash yield, volatile matter, and fixed carbon), ultimate analysis (carbon, hydrogen, nitrogen, oxygen and sulfur), elemental analysis (Fe, Ca, Mg, Cd, Mn, K, Na, Cu, Co, Ni, Cr, Zn, and Pb) and rock-eval pyrolysis for mineral carbon (MINC). Some elements like Cu, Cd, Co, Ni, Zn, Pb, Na, and K occur in high concentration, while Mg and Ca have their concentrations lower than World Clarke average. In addition, various minerals and functional groups present in the lignite samples were analyzed through X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy. The mineral (weight and atomic) percentage has also been analyzed through scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS).  相似文献   

17.
In this study, a facile precipitation process to treat wastewater from zinc plating industry is presented. Water purification rates of Zn range between 96.40 % and 99.99 % depending on the reaction conditions. Optimal results are gained at a low pH value of 9, low temperature of 40 °C and a fast alkalization using NaOH solution containing 16 % pure NaOH. Traces of Ni, Fe, Zn, Cu and Cr present in the wastewater were almost completely removed. The precipitates were analysed by X-ray diffraction, infrared and Raman spectroscopy, electron microscopy and magnetic measurements. They consist of doped ZnO as a main phase. Although ZnO exclusively crystallizes in nanoparticle size, the morphology is directly influenced by the experimental parameters. Additionally, very small amounts of ZnCO3 and Zn(OH)2 were detected. Magnetic investigations indicate the incorporation of Ni and Fe into the ZnO lattice. The measured saturation magnetization is ~0.01 emu/g and the Curie temperature is ~75 °C.  相似文献   

18.
Dredging and disposal of sediments onto agricultural soils is a common practice in industrial and urban areas that can be hazardous to the environment when the sediments contain heavy metals. This chemical hazard can be assessed by evaluating the mobility and speciation of metals after sediment deposition. In this study, the speciation of Zn in the coarse (500 to 2000 μm) and fine (<2 μm) fractions of a contaminated sediment dredged from a ship canal in northern France and deposited on an agricultural soil was determined by physical analytical techniques on raw and chemically treated samples. Zn partitioning between coexisting mineral phases and its chemical associations were first determined by micro-particle-induced X-ray emission and micro-synchrotron-based X-ray radiation fluorescence. Zn-containing mineral species were then identified by X-ray diffraction and powder and polarized extended X-ray absorption fine structure spectroscopy (EXAFS). The number, nature, and proportion of Zn species were obtained by a coupled principal component analysis (PCA) and least squares fitting (LSF) procedure, applied herein for the first time to qualitatively (number and nature of species) and quantitatively (relative proportion of species) speciate a metal in a natural system.The coarse fraction consists of slag grains originating from nearby Zn smelters. In this fraction, Zn is primarily present as sphalerite (ZnS) and to a lesser extent as willemite (Zn2SiO4), Zn-containing ferric (oxyhydr)oxides, and zincite (ZnO). In the fine fraction, ZnS and Zn-containing Fe (oxyhydr)oxides are the major forms, and Zn-containing phyllosilicate is the minor species. Weathering of ZnS, Zn2SiO4, and ZnO under oxidizing conditions after the sediment disposal accounts for the uptake of Zn by Fe (oxyhydr)oxides and phyllosilicates. Two geochemical processes can explain the retention of Zn by secondary minerals: uptake on preexisting minerals and precipitation with dissolved Fe and Si. The second process likely occurs because dissolved Zn and Si are supersaturated with respect to Zn phyllosilicate. EXAFS spectroscopy, in combination with PCA and LSF, is shown to be a meaningful approach to quantitatively determining the speciation of trace elements in sediments and soils.  相似文献   

19.
Oxidation zones of ore deposits offer valuable insights into the long-term fate of many metals and metalloids. In this work, we have studied a paleo-acid rock drainage (ARD) system – the oxidation zone of Mississippi-valley type Zn–Pb deposits near Olkusz in southern Poland. The ARD systems exhausted their acid-generating capacity and have come almost to the conclusion of the mineral and geochemical transformations. Primary pyrite, marcasite, galena and sphalerite have been decomposed but the acidity was neutralized by the abundant carbonate host rocks. Zinc is stored in smithsonite, hemimorphite, and Zn-rich sheet aluminosilicates. Some of these minerals formed simultaneously with the oxidation zone but some precipitated in the soils in situ, thus documenting the mobility of Zn, Al, and Si in the soils. Iron oxides are represented mostly by goethite, either well-crystalline or nanocrystalline, as determined by a combination of powder X-ray diffraction, micro-X-ray diffraction, and Mössbauer spectroscopy. Iron oxides bind a substantial amount of arsenic, to a lesser extent also zinc, lead, and cadmium, as shown by electron microprobe analyses and sequential extractions. The X-ray absorption spectroscopy data of the local environment of arsenic in goethite suggest the existence of bidentate mononuclear complex, in addition to the more common bidentate binuclear complex. These results suggest that arsenic is incorporated in the crystal structure of goethite, in addition to adsorbed to the surface of the particles or occluded in the voids and pores. Zinc is bound in goethite as a mixture of tetrahedrally and octahedrally coordinated cations. This study shows that the mature system binds the metals from the primary sulfides relatively strongly. Yet, some release of the metals was observed in this study, either in the laboratory (by sequential extractions) and in nature (e.g., neoformed Zn phyllosilicates). The physical conditions in the oxidation zone and on the surface are largely similar but the metals, to a certain extent, are still mobile in the soils. We may speculate that their mobility near the surface, in the mining waste, may be enhanced by a higher water/rock ratio than in the oxidation zone. This result implies that although the studied material is relatively benign, it still has a potential to cause local environmental problems.  相似文献   

20.
The atomic scale structure and chemistry of (111) twins in MgAl2O4 spinel crystals from the Pinpyit locality near Mogok (Myanmar, formerly Burma) were analysed using complementary methods of transmission electron microscopy (TEM). To obtain a three-dimensional information on the atomic structure, the twin boundaries were investigated in crystallographic projections and Using conventional electron diffraction and high-resolution TEM (HRTEM) analysis we have shown that (111) twins in spinel can be crystallographically described by 180° rotation of the oxygen sublattice normal to the twin composition plane. This operation generates a local hcp stacking in otherwise ccp lattice and maintains a regular sequence of kagome and mixed layers. In addition to rotation, no other translations are present in (111) twins in these spinel crystals. Chemical analysis of the twin boundary was performed by energy-dispersive X-ray spectroscopy (EDS) using a variable beam diameter (VBD) technique, which is perfectly suited for analysing chemical composition of twin boundaries on a sub-nm scale. The VBD/EDS measurements indicated that (111) twin boundary in spinel is Mg-deficient. Quantitative analyses of HRTEM (phase contrast) and HAADF-STEM (Z-contrast) images of (111) twin boundary have confirmed that Mg2+ ions are replaced with Be2+ ions in boundary tetrahedral sites. The Be-rich twin boundary structure is closely related to BeAl2O4 (chrysoberyl) and BeMg3Al8O16 (taaffeite) group of intermediate polysomatic minerals. Based on these results, we conclude that the formation of (111) twins in spinel is a preparatory stage of polytype/polysome formation (taaffeite) and is a result of thermodynamically favourable formation of hcp stacking due to Be incorporation on the {111} planes of the spinel structure in the nucleation stage of crystal growth. The twin structure grows as long as the surrounding geochemical conditions allow its formation. The incorporation of Be induces a 2D-anisotropy and exaggerated growth of the crystal along the (111) twin boundary.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号