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典型高砷煤样品的连续浸取实验研究——兼论黔西南高砷煤中砷的赋存状态 总被引：7，自引：1，他引：7
根据以往研究，选取了2个砷含量差异较大的样品，利用连续浸取实验，结合仪器中子活化分析（INAA）、等离子原子吸收光谱（ICP－AES）、等离子质谱（ICP－MS）测定及X射线吸收精细结构（XAFS）分析，经低温灰化（LTA）、扫描电子显微镜（SEM－EDX）对黔西南高砷煤中砷的赋存状态进行了研究，发现50％以上的砷不能被NH4Ac、HCl、HF和HNO3等无机试剂提取出来，结合以往的研究认为砷主要以高价有机砷的形式存在。 相似文献
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利用X射线吸收精细结构分析(XAFS)和铁的穆斯堡尔谱(Mossbauer)对黔西南高砷煤中砷和铁的存在形式进行了研究.研究发现,高砷煤中的砷主要以高价砷的形式存在,也有少量以As2O3、砷黄铁矿、砷硫化物的形式存在.除1个样品中的铁全部以顺磁性针铁矿或超顺磁性的针铁矿的形式存在外,其它样品中的Fe主要是黄铁矿中的Fe,约占全铁的60%～91%;其次是黄铁钾矾中的Fe,约占全铁的9%～40%. 相似文献
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黔西南高砷煤中砷赋存状态的XAFS和铁的Moessbauer谱研究 总被引：1，自引：0，他引：1
利用X射线吸收精细结构分析(XAFS）和铁的穆斯堡尔谱(Moessbauer)对黔西南高砷煤中砷和铁的存在形式进行了研究。研究发现，高砷煤中的砷主要以高价砷的形式存在，也有少量以As2O3、砷黄铁矿、砷硫化物的形式存在。除1个样品中的铁全部以顺磁性针铁矿或超顺磁性的针铁矿的形式存在外，其它样品中的Fe主要是黄铁矿中的Fe，约占全铁的60％一91％；其次是黄铁钾矾中的Fe，约占全铁的9％一40％。 相似文献
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利用X射线吸收精细结构分析 (XAFS)和铁的穆斯堡尔谱 (M ssbauer)对黔西南高砷煤中砷和铁的存在形式进行了研究。研究发现 ,高砷煤中的砷主要以高价砷的形式存在 ,也有少量以As2 O3 、砷黄铁矿、砷硫化物的形式存在。除 1个样品中的铁全部以顺磁性针铁矿或超顺磁性的针铁矿的形式存在外 ,其它样品中的Fe主要是黄铁矿中的Fe,约占全铁的 6 0 %～ 91% ;其次是黄铁钾矾中的Fe ,约占全铁的 9%～ 4 0 %。 相似文献
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《西北地质》2020,(2)
为了研究大同煤田南部煤中伴生元素的地球化学特征,运用矿物学、煤地球化学以及岩石学等学科的理论和研究方法,利用X射线荧光光谱分析(XRF)、电感耦合等离子质谱分析(ICPMS)、X射线衍射分析(XRD)、扫描电镜+能谱分析(SEM-EDS),对五家沟矿区5号煤中伴生元素的含量及赋存特征进行研究。结果表明,五家沟5号煤中常量元素Al、Si、Ca、Fe含量较高,占到灰分总量的95%以上。Al主要以高岭石的形式存在,Si以黏土矿物和石英的形式赋存于煤中,煤中Ca的主要载体是方解石,Fe在煤中主要以黄铁矿的形式存在。煤中微量元素Li富集,Ga、Sr、Zr、Nb、Hf、Ta轻度富集。锂和镓主要赋存于高岭石中;铌和钽赋存于黏土矿物中,部分可能赋存于伊利石中;锆和铪赋存于黏土矿物中,还有部分赋存于金红石内。 相似文献
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煤中砷的赋存状态 总被引：22，自引：0，他引：22
砷是煤中常见的有害微量元素,由于其丰度较低,定量研究其赋存状态一直很困难。近年来,采用逐级化学提取实验方法对煤中不同赋存状态的砷进行了定量研究,综合分析这些研究可得出以下结论：①煤中砷的赋存状态包括硫化物态砷、有机态砷、砷酸盐态砷、硅酸盐态砷、水溶态和可交换态砷。总体上,硫化物态砷＞有机态砷＞砷酸盐态砷＞硅酸盐态砷＞水溶态和可交换态砷,但在不同的煤样品中,也表现出较大的差异性。②一般而言,煤中大部分砷存在于含砷黄铁矿中,含砷黄铁矿中的砷含量与黄铁矿的成因或类型有关。煤中的砷酸盐态砷主要与铁氧化物和氢氧化物共生;硅酸盐态砷主要进入粘土矿物晶格。③在砷含量较低的煤样品中,有机态砷含量较高,其中在褐煤和低煤级烟煤中,可提取出与腐殖酸和富里酸结合的砷。当前还难以确认有机态砷的化学结构。④贵州特高砷煤中砷的赋存状态较为复杂,在某些样品中与氧结合的有机态砷为主要的赋存状态。 相似文献
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贵州燃煤型地方性砷中毒地区煤的矿物组成 总被引：4，自引：0，他引：4
采用低温灰化（LTA）和X衍射粉晶分析（XRD）,结合带X光能谱的扫描电子显微镜（SEM—EDX）等方法研究了贵州燃煤型地方性砷中毒地区煤的矿物组成,计算了各矿物的相对含量,初步探讨了煤中主要的含砷矿物。 相似文献
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中国煤中砷的含量分布、赋存状态、富集及环境意义 总被引：14，自引：1，他引：14
砷是煤中有害微量元素之一,在煤加工利用过程中,砷会以各种形式释放出来,进入环境。本文在全面分析现有资料和文献的基础上,结合作者对中国煤中砷的研究成果,分析了中国煤中砷的含量与分布、赋存状态、富集因素以及环境意义。通过研究和分析可知,中国煤中砷的平均值约为5μg/g,但在不同地区、不同时代以及不同类型的煤中有较大的差异,除中国西南地区含量异常高外,一般含量均在10μg/g以内;煤中砷的赋存状态多种多样,主要以无机态的硫化物结合为主,并常与黄铁矿等矿物伴生,也存在有机态结合的砷;中国煤中砷的来源和富集主要是以陆源母岩、成煤植物、沉积环境和构造裂隙—热液作用等为主的多种因素综合控制的结果;在煤燃烧过程中,煤中的砷释放出来,并对长期生活在燃煤地区的环境和人体产生影响。本文还提出今后煤中砷研究的主要方向,以为煤中砷的研究提供参考资料。 相似文献
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高砷含水层沉积物矿物学特征及砷的活化 总被引：2，自引：0，他引：2
利用X射线衍射和X射线荧光分析、沉积物序列提取试验及矿物饱和度的计算,对采自江汉平原中部沙湖地区典型高砷含水层钻孔沉积物样品矿物学进行了分析,并讨论了控制含水层中砷释放和迁移的地球化学机制.对矿物在沉积物与土壤中的分布及组成的对比分析,在一定程度上指示了矿物赋存环境和/或高砷水形成的环境背景:土壤与沉积物中高岭石以低于其他3种粘土矿物的含量普遍存在,指示了含水层沉积物形成过程江汉平原存在一定的湿热古气候环境;沉积物绿泥石含量低于土壤中绿泥石,恰恰反映了土壤比沉积物略强的碱性环境;沉积物中黄铁矿的存在,显示了含水层局部的强还原性环境,指示地下水中广泛存在的Fe2+容易与二价硫发生沉淀并结合砷.砷主要以无定形铁锰氧化物结合态(平均在31％以上)形式存在,其次以碳酸盐和有机质结合态存在.无定形铁锰氧化物的还原溶解可能是控制砷迁移到地下水中主要的地球化学机制.相对高含量的绿泥石容易在含水层中发生风化,其溶解过程可以将铁释放到地下水中,从而成为影响地下水中砷活化的潜在因素. 相似文献
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《矿物学报》2013,(Z1)
Formation and dissolution of secondary arsenic minerals often play significant roles in controlling arsenic mobility in contaminated environments, especially in sulfide mines. Weathering of the orpiment and realgar-bearing tailings from the Shimen realgar deposit, the largest realgar deposit in Asia, were studied. An integrated mineralogical analysis by using X-ray powder diffraction (XRD), Raman spectrum, scanning electron microscope (SEM) and transmission electron microscope (TEM) reveals four kinds of As-bearing secondary minerals including arsenic oxides, arsenates, As-gypsum, and As-Fe minerals. The precipitation of arsenates is due to interaction of As-bearing run-off waters and the underlying carbonate rocks, or the transformation of gypsum into arsenates or As-bearing gypsum through SO42-/HAsO42- substitution. Ca-arsenates are mainly weilite and pharmacolite with Ca/As atomic ratio of 1. Scanning transmission X-ray microscope (STXM) and X-ray absorption fine structure (XAFS) reveal that the valence of arsenic is mainly +3 and +5. 相似文献
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《Applied Geochemistry》2001,16(11-12):1353-1360
Southwest Guizhou Province is one of the most important areas of disseminated, sediment-hosted-type Au deposits in China and is an important area of coal production. The chemistry of most of the coals in SW Guizhou is similar to those in other parts of China. Their As content is near the Chinese coal average, but some local, small coal mines contain high As coals. The highest As content is up to 3.5 wt.% in the coal. The use of high As coals has caused in excess of 3000 cases of As poisoning in several villages. The high As coals are in the Longtan formation, which is an alternating marine facies and terrestrial facies. The coals are distributed on both sides of faults that parallel the regional anticlinal axis. The As content of coal is higher closer to the fault plane. The As content of coal changes greatly in different coal beds and different locations of the same bed. Geological structures such as anticlines, faults and sedimentary strata control the distribution of high As coals. Small Au deposits as well as Sb, Hg, and Th mineralization, are found near the high As coals. Although some As-bearing minerals such as pyrite, arsenopyrite, realgar (?), As-bearing sulfate, As-bearing clays, and phosphate are found in the high As coals, their contents cannot account for the abundance of As in some coals. Analysis of the coal indicates that As mainly exists in the form of As5+ and As3+, perhaps, combined with organic compounds. The occurrence of such exceptionally high As contents in coal and the fact that the As is dominantly organically associated are unique observations. 相似文献
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Soils from many industrial sites in southeastern USA are contaminated with As because of the application of herbicide containing As2O3. Among those contaminated sites, two industrial sites, FW and BH, which are currently active and of most serious environmental concerns, were selected to characterize the occurrence of As in the contaminated soils and to evaluate its environmental leachability. The soils are both sandy loams with varying mineralogical and organic matter contents. Microwave-assisted acid digestion (EPA method 3051) of the contaminated soils indicated As levels of up to 325 mg/kg and 900 mg/kg (dry weight basis) for FW and BH soils, respectively. However, bulk X-ray powder diffraction (XRD) analysis failed to find any detectable As-bearing phases in either of the studied soil samples. Most of the soil As was observed by scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy (SEM/EDX), to be disseminated on the surfaces of fine-grained soil particles in close association with Al and Fe. A few As-bearing particles were detected in BH soil using electron microprobe analysis (EMPA). Synchrotron micro-XRD and X-ray absorption near-edge structure (XANES) analyses indicated that these As-rich particles were possibly phaunouxite, a mineral similar to calcium arsenate, which could have been formed by natural weathering after the application of As2O3. However, the scarcity of those particles eliminated them from playing any important role in As sequestration. 相似文献
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《International Journal of Coal Geology》2005,61(3-4):141-196
The review presented covers: (a) historical introduction; (b) some analytical comments; (c) some peculiarities of the As geochemistry in environment; (d) an estimation of coal Clarke value of As; (e) some coals enriched in As; (f) mode of As occurrence in coal; (g) factors influencing the As distribution in coal matter and coal bed; (h) genetic topics; (i) some topics related to environmental impact of As by the coal combustion.The World average As content in coals (coal Clarke of As) for the bituminous coals and lignites are, respectively, 9.0±0.8 and 7.4±1.4 ppm. On an ash basis, these contents are higher: 50±5 and 49±8 ppm, respectively. Therefore, As is a very coalphile element: it has strong affinity to coal matter — organic and (or) inorganic but obligatory authigenic. The coalphile affinity of As is like that for Ge or S.There is strong regional variability of As distribution due to geologic variability of the individual coal basins. For example, bituminous coals in Eastern Germany, Czech Republic and SE China are enriched in As, whereas the coals in South Africa or Australia are very depleted compared to coal Clarke of As. In general, some relationship exists between As content and its mode of occurrence in coals. Typically, at high As content, sulphide sites dominate (pyrite and other more rare sulphides), whereas at low As content, Asorg dominates, both being authigenic. A contribution of the terrigenic As (in silicates) is usually minor and of the biogenic Asbio (derived from coal-forming plants) is poorly known.Both organic and inorganic As can exist not only as chemically bound form but also in the sorbed (acid leacheable) arsenate form. With increasing coal rank, sorbed exchangeable arsenate content decreases, with a minimum in the coking coals (German data: the Ruhr coals).Relations of As content in coal to ash yield (or its partitioning in sink–float fractions) and to coal petrographic composition are usually complicated. In most cases, these relations are controlled by main site (form) of As — Aspyr or Asorg. If Aspyr dominates, an As accumulation in heavy fractions (or in high-ash coals) is observed, and if Asorg dominates, it is enriched in medium-density fractions (or low- and medium-ash coals). Arsenic is in part accumulated in the inertinite vs. vitrinite (Asorg ?).There are four genetic types of As accumulation on coal: two epigenetic and two syngenetic: (1) Chinese type—hydrothermal As enrichment, sometimes similar to known Carlin type of As-bearing telethermal gold deposits; (2) Dakota type—hypergene enrichment from ground waters draining As-bearing tufa host rocks; (3) Bulgarian type—As enrichment resulting from As-bearing waters entered coal-forming peat bogs from sulphide deposit aureoles; (4) Turkish type—volcanic input of As in coal-forming peat bog as exhalations, brines and volcanic ash.During coal combustion at power plants, most of the initial As in coal volatilizes into the gaseous phase. At the widely used combustion of pulverized coal, most of Asorg, Aspyr and “shielded” As-bearing micromineral phases escape into gaseous and particulate phase and only minor part of Asclay remains in bottom ash. The dominant fraction of escaping As is in fly ash. Because 97–99% of the fly ash is collected by electrostatic precipitators, the atmospheric emission of As (solid phase and gaseous) is usually assumed as rather minor (10–30% from initial As in coal). However, fly ash disposal creates some difficult environmental problems because it is potentially toxic in natural waters and soils. The As leaching rate from ash disposal is greatly controlled by the ash chemistry. In natural environment, As can be readily leached from acid (SiO2-rich) bituminous coal ashes but can be very difficult from alkali (CaO-rich) lignite ashes.If the Aspyr form dominates, conventional coal cleaning may be an efficient tool for the removing As from coal. However, organic-bound or micromineral arsenic (“shielded” grains of As-bearing sulphides) are not removed by this procedure.Some considerations show that “toxicity threshold” of As content in coal (permissible concentration for industrial utility) may be in the range 100–300 ppm As. However, for different coals (with different proportions of As-forms), and for different combustion procedures, this “threshold” varies. 相似文献
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Soil, mine tailing, and waste dump profiles above three mesothermal gold deposits in the Bohemian Massif with different anthropogenic histories have been studied. Their mineralogical, major element, and arsenic (As) contents and the contents of secondary arsenic minerals were analyzed. The As-bearing minerals were concentrated and determined using X-ray diffraction (XRD) analysis, the Debye-Scherrer powder method, scanning electron microscopy (SEM), and energy-dispersive microanalysis (EDAX). The amorphous hydrous ferric oxides (HFO), As-bearing goethite, K-Ba- or Ca-Fe- and Fe- arsenates pharmacosiderite, arseniosiderite, and scorodite, and sulfate-arsenate pitticite were determined as products of arsenopyrite or arsenian pyrite oxidation. The As behaviour in the profiles studied differs in dependence on the surface morphology, chemical and mineralogical composition of the soil, mine wastes or tailings, oxidation conditions, pH, presence of (or distance from) primary As mineralization in the bedrock, and duration of the weathering effect. Although the primary As mineralization and the bedrock chemical composition are roughly similar, there are distinct differences in the As behaviour amongst the Mokrsko, Roudný and Kaperské Hory deposits. 相似文献
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变形煤镜质组反射率演化的地化机理及其地质意义 总被引：4，自引：0，他引：4
通过X射线衍射(XRD)、电子顺磁共振(EPR)和核磁共振(NMR)等方法深入探讨了高温高压实验和构造煤样的化学结构演化特征,阐明了变形煤镜质组反射率的变化是其微观化学结构演化的外在反映。变形煤镜质组反射率的演化又受到应力和变形环境等因素的深刻影响,其真实地记录了构造变形历史中应力作用和应变环境等特征,是进行煤田构造研究的重要标志物之一 相似文献
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A. Bossy C. Grosbois S. Beauchemin A. Courtin-Nomade W. Hendershot H. Bril 《Applied Geochemistry》2010
At a watershed scale, sediments and soil weathering exerts a control on solid and dissolved transport of trace elements in surface waters and it can be considered as a source of pollution. The studied subwatershed (1.5 km2) was located on an As-geochemical anomaly. The studied soil profile showed a significant decrease of As content from 1500 mg kg−1 in the 135–165 cm deepest soil layer to 385 mg kg−1 in the upper 0–5 cm soil layer. Directly in the stream, suspended matter and the <63 μm fraction of bed sediments had As concentrations greater than 400 mg kg−1. In all these solid fractions, the main representative As-bearing phases were determined at two different observation scales: bulk analyses using X-ray absorption structure spectroscopy (XAS) and microanalyses using scanning electron microscope (SEM) and associated electron probe microanalyses (EPMA), as well as micro-Raman spectroscopy and synchrotron-based micro-scanning X-ray diffraction (μSXRD) characterization. Three main As-bearing phases were identified: (i) arsenates (mostly pharmacosiderite), the most concentrated phases As in both the coherent weathered bedrock and the 135–165 cm soil layer but not observed in the river solid fraction, (ii) Fe-oxyhydroxides with in situ As content up to 15.4 wt.% in the deepest soil layer, and (iii) aluminosilicates, the least concentrated As carriers. The mineralogical evolution of As-bearing phases in the soil profile, coupled with the decrease of bulk As content, may be related to pedogenesis processes, suggesting an evolution of arsenates into As-rich Fe-oxyhydroxides. Therefore, weathering and mineralogical evolution of these As-rich phases may release As to surface waters. 相似文献
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The mineralogical compositions of the Nos. 9 and 13 coals, which are medium-volatile bituminous coals in rank, from the Wuda Coalfield at the northwestern margin of the Ordos Basin in northern China, were investigated by optical microscopy, field emission-scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry (SEM-EDX), and X-ray powder diffraction techniques. The minerals in the Wuda coals are mainly represented by quartz, kaolinite, illite, pyrite, marcasite, apatite, dolomite, and ankerite, with trace amounts of anatase, calcite, boehmite, jarosite, gibbsite, anhydrite, and bassanite in some samples. The rod-like pyritized bacteria have been identified with SEM-EDX in Wuda coals. Moreover, the slightly reducing and alkaline environment in the original peat swamp favored bacterial action and propagation. The average concentrations of P2O5 in the Nos. 9 and 13 coals are 0.47 and 0.18 %, respectively. Phosphorus is not uniformly distributed within the Wuda coal seam. The maximum content of apatite in Wuda coals in certain horizon can reach up to 91.4 % (on an organic matter-free basis), corresponding to the fluorine and P2O5 concentrations of 2803 μg/g and 5.96 %. The high proportion of fluorine and P2O5 in the Wuda coals is mainly due to the authigenic apatite. The phosphorus in Wuda coals was probably derived mainly from phospho-proteins in the organic matter of the original peat deposits. 相似文献