Hazardous elements and amorphous nanoparticles in historical estuary coal mining area

In Brazil, intense coal exploitation activities have led to environmental deterioration, including soil mortification, water contamination, loss of ecosystem, and atmospheric contamination. In addition,considerable quantities of sulfur-rich residues are left behind in the mining area; these residues pose grave environmental issues as they undergo sulfide oxidation reactions. When sulfur oxides come in contact with water, extreme acid leachate is produced with great proportions of sulfate, and hazardous elements(HEs), which are identified as coal drainage(CMD). CMD is an environmental pollution challenge, particularly in countries with historic or active coal mines. To prevent CMD formation or its migration, the source must be controlled; however, this may not be feasible at many locations. In such scenarios, the mine water should be collected, treated, and discharged. In this study, data from 2005 to2010 was gathered on the geochemistry of 11 CMD discharges from ten different mines. There are several concerns and questions on the formation of nanominerals in mine acid drainage and on their reactions and interfaces. The detailed mineralogical and geochemical data presented in this paper were derived from previous studies on the coal mine areas in Brazil. Oxyhydroxides, sulfates, and nanoparticles in these areas possibly go through structural transformations depending on their size and formation conditions. The geochemistry of Fe-precipitates(such as jarosite, goethite, and hematite) existent in the CMD-generating coal areas and those that could be considered as a potential source of hazardous elements(HEs)(e.g., Cr) were also studied because these precipitates are relatively stable in extremely low pH conditions. To simplify and improve poorly ordered iron, strontium, and aluminum phase characterization, field emission scanning electron microscopy(FE-SEM), high-resolution transmission electron microscopy(HR-TEM), micro-Raman spectroscopy, and X-ray diffraction(XRD) and sequential extraction(SE) studies were executed on a set CMD samples from the Brazilian mines. This study aimed to investigate the role of both nanomineral and amorphous phase distribution throughout the reactive coal cleaning rejects profile and HEs removal from the water mine to provide holistic insights on the ecological risks posed by HEs, nanominerals, amorphous phases, and to assess sediments in complex environments such as estuaries.     

煤中微量元素研究进展

煤炭是我国的主要能源，在煤炭开采、运输、洗选、淋溶（滤）、燃烧等其它加工利用过程中，煤中的微量元素要发生迁移、析出，并入侵到大气、水、土壤和生态环境中，最终影响人类生存和生活环境。煤中微量元素十分重要，是因为它们与环境问题、动、植物及人类健康密切相关。在研究微量元素时必须考虑微量元素的性质及毒性，它们主要依靠其含量、种类、存在形式、pH值、氧化-还原条件及其它因素。在全面综合国内外研究文献的基础上，分析了煤中微量元素的发现、分布规律、赋存状态、成因机理及微量元素的应用等方面研究的历史、现状，并对今后研究的重点内容和发展方向进行了较为详细的论述和分析，并指出在进一步深入研究煤中微量元素地球化学的基础上，加强微量元素环境学方面的研究是今后煤中微量元素环境地球化学研究的重要内容。     

Concentration and association of minor and trace elements in Mukah coal from Sarawak, Malaysia, with emphasis on the potentially hazardous trace elements

The ash yield and concentrations of twenty-four minor and trace elements, including twelve potentially hazardous trace elements were determined in Mukah coal from Sarawak, Malaysia. Comparisons made to the Clarke values show that Mukah coal is depleted in Ag, Ba, Be, Cd, Co, Mn, Ni, Se, U, and V. On the other hand, it is enriched in As, Cr, Cu, Pb, Sb, Th, and Zn. Among the trace elements studied, V and Ba are associated predominantly with the clay minerals. Manganese, Cr, Cu, Th, and Ni are mostly bound within the aluminosilicate, sulphide and/or carbonate minerals in varying proportions, though a portion of these elements are also organically bound. Arsenic, Pb and Sb are mostly organically bound, though some of these elements are also associated with the sulphide minerals. Zinc is associated with both the organic and inorganic contents of the coal. Among the potentially hazardous trace elements, Be, Cd, Co, Mn, Ni, Se, and U may be of little or no health and environmental concerns, whereas As, Cr, Pb, Sb and Th require further examination for their potential health and environmental concerns. Of particular concern are the elements As, Pb and Sb, which are mostly organically bound and hence cannot be removed by physical cleaning technologies. They escape during coal combustion, either released as vapours to the atmosphere or are adsorbed onto the fine fly ash particles.     

燃煤产物中有害元素淋滤实验的研究现状

对燃煤产物矿物学、元素地球化学以及显微岩石学特征、燃煤产物淋滤试验的研究现状进行了评述;对燃煤产物淋滤实验的类型、淋滤试验的有效性及条件选择、影响有害元素可溶性(淋滤行为)的因素进行了讨论;并给出了当前淋滤实验最为关心的元素种类。      

煤矸石中潜在有害微量元素淋溶析出研究

在煤矸石淋溶实验的基础上，研究了有害微量元素从煤矸石中淋溶析出的浓度与其在煤矸石中的含量和赋存状态的关系。结果表明，溶出浓度受淋溶时间，淋溶液温度，酸碱度的影响。淋溶液温度越高，淋溶时间越长，则有害微量元素从煤矸石中析出的浓度越高；不同的有害微量元素受淋溶液pH值大小影响程度也不相同。     

Environmental geochemistry and health of fluorine in Chinese coals

Fluorine is one of the potential hazardous trace elements in coal. Fluorine may be released into atmosphere mostly during coal combustion process. When the coal is burning indoors without any controlling methods (chimney), the fluorine will pollute the room and is absorbed by food fired (dried) over stoves. Now many people have suffered from fluorosis due to coal burning indoors in Southwest China. In this paper, the concentration, distribution, mode of occurrences and impact factors of fluorine in Chinese coals are analyzed. The environmental impacts and typical features of fluorosis are studied. It is concluded that the value of fluorine in Chinese coals ranges from 20 to 300 mg/kg, and with average value of 122 mg/kg from 5,603 coal samples. It is higher than the average value of the world coals (80 mg/kg). In provincial coalfields of the SW China, the content of F is highest and many people have been affected due to coal combustion indoors.     

煤中微量元素研究现状

煤中微量元素是世界洁净煤研究的热点；煤中微量元素的研究对于正确评价微量元素，预防煤中有毒有害元素对环境的影响，保护生态和人类生存的环境具有重要的理论指导意义和现实意义。本详细介绍了国内外煤中微量元素的研究进展，微量元素的分布规律、赋存状态及研究方法，并将其研究内容概括为基础理论研究和应用研究两个方面，详细介绍了研究方法（直接方法和间接方法），提出了今后研究的主要方向。     

Geochemistry of coals from the Elk Valley coalfield, British Columbia, Canada

The Elk Valley coalfield of British Columbia is one of the major coal producing areas in Canada. The coals are of Cretaceous and Jurassic–Cretaceous age and range in rank from high-volatile to low-volatile bituminous (%Ro_max: 0.8–1.6). Coal seams from outcrops and active mines in this coalfield were analysed for rank and maceral composition using reflected light microscopy, for geochemistry using AAS, INAA, and ICPES, and also by proximate and ultimate analyses. The Elk Valley coal seams contain low average concentrations of hazardous elements such as As, Mo, Pb, and Se. However, there are seams that contain relatively high concentrations of some of these elements, such as 8 mg/kg and 108 mg/kg of arsenic. When the geochemistry of coal seams is compared within the different parts of the coalfield, the elemental composition amongst the seams from various sections located in the central area of the coalfield is similar. Coal seams in the northern area of the coalfield have different geochemistry than coal seams in other areas of the coalfield; seams in the northern area have much higher As, Br, Cr, Cu, Fe, K, and Na content, but contain less Ca.     

面向21世纪的煤化工

煤炭是中国的主要能源和资源，但同时也是主要的污染源。从保护环境、合理利用有限的化石资源的角度和中国的具体国情考虑，应该大力开发温和化高效煤的新工艺，使煤炭资源逐步由能源型利用转化为材料型利用，近年来，我们在煤的溶剂萃取，脱硫降灰机理，煤相关模型化合物反应，煤焦油中稠环芳香族化合物的分离精制，功能性高分子单体合成及一氧化碳高效吸附剂的制备等方面做了大量的研究工作，结合这些研究工作，本文介绍了煤化工的     

纳米矿物在堆积型铝土矿床研究中的应用*

至少一维尺度上小于100ⁿm的矿物都属于纳米矿物的范畴,自然界中除了大量的人造纳米矿物之外,天然的纳米矿物分布也很广泛。随着透射电子显微镜(TEM)技术在地球科学中的应用,大量的天然纳米矿物在地壳表层和内部被发现。尤其是在矿田区域,与矿体相关的纳米矿物在各种介质中被发现,并且这些纳米矿物在矿床的研究中有着独特的作用。堆积型铝土矿床储量大,是铝土矿的重要来源。在堆积型铝土矿床中发育有大量的纳米矿物,矿石矿物也以纳米级晶体分布于矿床中,并且在纳米尺度上表现出结构和成分的变化,这些纳米矿物以及结构、成分的变化记录了铝土矿成矿过程的物理化学信息,为探究铝土矿的成因提供了独特的窗口。该综述总结了纳米矿物在研究堆积型铝土矿床中的优势,为研究堆积型铝土矿床的提供了新方法,为认识堆积型铝土矿的成因提供了新角度。     

Application of nanominerals in research on stacked bauxite deposits

Nanomineral is the mineral that is less than 100ⁿm at least one dimension. Aside from the man-made nanominerals,there is a large number of natural nanominerals. With the increasing application of transmission electron microscopy(TEM)in earth science,a large number of natural nanominerals have been discovered in the surface and interior of the Earth. Especially in ore deposit region,nanominerals related to ore bodies are found in various media,and these nanominerals play a unique role in the research of ore deposits. The stacked bauxite deposit is an important source of bauxite because of its large reserve. There are a large number of nanominerals distributed in stacked bauxite deposit,and these ore nanominerals distributed in the deposit in the form of nanocrystals. In addition,the ore minerals in stacked bauxite deposit display changes of the structure and composition in nanoscale. The nanominerals as well as the changes of structure and composition in nanoscale can record the physical and chemical information of bauxite mineralization process,providing a unique window to explore the genesis of the stacked bauxite deposit. This review summarizes the advantages of nanominerals in the research on the stacked bauxite deposit,providing a new method and a new perspective for the understanding of the genesis of bauxite deposit.     

Partitioning of elements and macerals during preparation of Antaibao coal

Analyses of the macerals, ash, sulfur and 43 major and trace elements were performed on samples of feed coal, cleaned coal, middlings and slime collected from the Antaibao coal preparation plant, China, and also on samples from coal preparation experiments. This study is focused on the partitioning of elements and macerals during coal preparation and potential environment aspects of the elements.The conclusions are as follows: (1) in comparison with the feed coal, the cleaned coal has a higher vitrinite content and relatively lower inertinite and exinite contents, whereas the middlings and slime have lower vitrinite and exinite contents, and relatively higher inertinite contents. The vitrinite contents in the size-segregated cleaned coals were observed to show a slightly increasing tendency with increasing particle size, while the inertinite contents decreased. (2) Physical coal cleaning is not only effective for removal of ash and sulfur, but also in reducing the concentration of most elements. As, Cd, Co, Cs, Hg, Fe, K, Mg, Nb and Ni are observed to show a high degree of removal, while Br, Be, Cu, U, Mn, Zn and organic sulfur are enriched in the cleaned coal and show a lower degree of removal. The large-sized cleaned coal is cleaner than the smaller sized fractions. (3) The middlings, especially the slime, are enriched in S, Hg, Cr, V, Zn, etc., so that these fractions should not be directly used as fuel. In addition, the concentration of Pb and V in the process water exceeds the limit of relevant environmental water quality standard. Consequently, it is necessary to develop new processes to remove ash, sulfur and hazardous trace elements to the maximum extent. Further studies on deep processing of the middlings and slime and cleaning of the process water should also be performed.     

铝硅酸盐纳米矿物的地质意义和资源价值再认识

本文简析了三种典型铝硅酸盐纳米矿物(埃洛石、伊毛缟石和水铝英石)的结构和性质特点;探讨了它们在其典型赋存环境中对元素迁移和富集所起的作用和机理,包括风化淋积型稀土矿床中埃洛石对稀土元素赋存所起的作用,火山灰风化壤等体系中伊毛缟石和水铝英石对重金属离子、放射性元素、阴离子和有机碳迁移所起的作用等;还浅析了这三种特殊非金属矿物的工业应用的可能性和条件。     

Geochemical study of products associated with spontaneous oxidation of coal in the Cerro Pelado Formation,Venezuela

The aim of this research work is a geochemical, mineralogical, and textural characterization of spontaneously smouldered coal-derived products in northwestern Venezuela (Cerro Pelado Formation, some 10 km from Pedregal city). Several solid samples were collected from this formation, six of unweathering coal, an other six of resulting unmelted rocks forming on a surface coal bed, and the last four of mineralizations found accumulating around gas vents. The fresh coal and the unmelted material were analysed by scanning electron microscopy, X-ray diffraction, and proximate techniques. Products such as magnetite and chabazite-K were identified in the alteration rocks. Likewise, both materials were also studied in order to determine the mobilization of 17 elements into the environment; such elements were analysed through inductively coupled plasma atomic emission spectroscopy on extracts obtained by a sequential extraction method: each sample was firstly extracted with MilliQ water and then the resultant residue was washed. This and the subsequently resulting residues are extracted according to the mentioned procedure by using, respectively, ammonium acetate, chlorhydric acid, peroxide and chlorhydric acid, nitric acid and fluorhydric acid, and nitric acid. The studied elements are classified as highly mobile (Na, Ni, ...), nearly immobile (Ti, P) and partially mobile (Mg, Fe, K, ...). In regards to mineralizations around fumaroles associated with smoldering coal seams, Fourier-transform infrared spectroscopy and X-ray diffraction analyses have revealed the presence of salammoniac, mascagnite and other solid combustion compounds formed by reaction of gas emitted from coal oxidation, in addition to previously non-reported sulfur-rich by-products associated with gas fissures, particularly ammonium thiosulfate, a phase first obtained only synthetically in the laboratory. Another objective of the research was to collect and analyse gases escaping from surficial vents. Relatively high concentrations of several aromatic compounds were detected in the gas collected at the studied coal outcrop, as well as aliphatic hydrocarbons including ethane, propane, butanes, among others. High contents of carbon monoxide, methane and carbon dioxide were also measured for gas samples.     

纳米矿物及其环境效应

纳米矿物作为连接原子/分子和块体矿物材料的桥梁,在建立矿物微观反应机制和宏观现象的研究中具有重要的意义.随着纳米地质学的迅速发展,纳米矿物在地表环境中的分布、存在形式及其反应活性引起了越来越多关注.综述了天然环境中常见的纳米矿物的成因、存在方式、特殊的尺寸效应、团聚行为、生物/非生物界面反应的分子机制,及其对地表环境和元素生物地球化学循环的影响;着重介绍了具有重要环境意义的纳米矿物与其对应的大尺寸矿物颗粒在吸附行为、溶解速率、团聚状态、催化活性、界面电子传递效率等方面的差异.对于纳米矿物与其对应的宏观矿物晶体之间差异的研究,有助于全面认识矿物对各种地质过程的作用,对于推动地球科学向更加微观和深入的方向发展具有极其重要的意义.      

Chemical and petrographical characterization of feed coal, fly ash and bottom ash from the Figueira Power Plant, Paraná, Brazil

The aim of the present study is the petrographic and chemical characterization of the coal at the Figueira Power Plant, Paraná, Brazil, prior and after the beneficiation process and the chemical characterization of fly and bottom ashes generated in the combustion process.Petrographic characterization was carried out through maceral analysis and vitrinite reflectance measurements. Chemical characterization included proximate analysis, determination of calorific value and sulphur content, ultimate analysis, X-ray diffraction, X-ray fluorescence, Inductively Coupled Plasma — Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma — Atomic Emission Spectrometry (ICP-AES) analysis, and determination of Total Organic Carbon (TOC) content.Vitrinite reflectance analyses indicate a high volatile B/C bituminous coal (0.61 to 0.73% Rrandom). Maceral analyses show predominance of the vitrinite maceral group (51.6 to 70.9 vol.%, m.m.f). Except of the Run of mine (ROM) coal sample, the average calorific value of the coals is 5205 kcal/kg and ash yields range from 21.4 to 38.1 wt.%. The mineralogical composition (X-ray diffraction) of coals includes kaolinite, quartz, plagioclase and pyrite, whereas fly and bottom ashes are composed by mullite, ettringite, quartz, magnetite, and hematite. Analyses of major elements from coal, fly and bottom ashes indicate a high SiO₂, Al₂O₃, and Fe₂O₃ content. Trace elements analysis of in-situ and ROM coals by ICP-MS and ICP-AES show highest concentration in Zn and As. Most of the toxic elements such as As, Cd, Cr, Mo, Ni, Pb, and Zn are significantly reduced by coal beneficiation. Considering the spatial distribution of trace elements in the beneficiated coal samples, which were collected over a period of three months, there appears to be little variation in Cd and Zn concentrations, whereas trace elements such as As, Mo, and Pb show a larger variation.In the fly and bottom ashes, the highest concentrations of trace elements were determined for Zn and As. When compared with trace element concentrations in the feed coal, fly ashes show a significant enrichment in most trace elements (As, B, Be, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb, Tl, and Zn), suggesting a predominantly volatile nature for these elements. In contrast, Sn is distributed evenly within the different ash types, whereas U shows depleted concentration in both bottom and fly ash samples.According to the International Classification of in-seam coals the Cambuí coals are of para/ortho bituminous rank of low grade (except for the ROM sample), and are characterized by the predominance of vitrinite macerals.     

Geochemical and mineralogical anomalies of the late Permian coal in the Zhijin coalfield of southwest China and their volcanic origin

This paper describes the influence of volcanic ash on the concentrations and occurrences of associated elements in coal in the Zhijin Coalfield in western Guizhou Province, China. Our studies reveal that the No. 9 coal seam in the Zhijin Coalfield has very high content of Fe (4.34%), Cu (369.90 μg/g), U (49.6 μg/g), Mo (63.10 μg/g), Zn (33.97 μg/g), and Zr (841.80 μg/g). The studies have also found that elements, such as Fe and Cu, do not occur as sulfides in this coal seam, in sharp contrast to many other coal seams in China. The geochemical and mineralogical anomalies of the coal seam are attributed to synsedimentary volcanic ash. In addition to normal macerals and minerals in coal, a volcanic-influenced material (VIM) derived from volcanic ash, detrital material of terrigenous origin and organic matter was identified under polarized-light reflectance microscopy and scanning electron microscopy equipped with energy-dispersive X-ray (EDX) analyzer. The volcanic-influenced material is the main carrier of the above elements in this coal. Six types of the volcanic-influenced material (VIM-1, VIM-2, VIM-3, VIM-4, VIM-5, and VIM-6) are further distinguished on the basis of their structures and compositions. To the best of our knowledge, this is the first report that presents a detailed classification of coal components with a high content of volcanic ash.     

煤中微量元素及其研究意义

煤中微量元素的研究意义重大和广泛.当前人们最为关注的是资源利用和环境污染两个方面.另外应用元素地球化学理论可以探讨成煤作用,一些微量元素可以用作煤层对比标志,微量元素对煤炭开采、加工、利用等方面都将产生影响.在我国,因煤炭的产量和消耗量巨大,研究煤中微量元素地球化学特征及其环境效应更具现实意义.     

Nanomineralogy of evaporative precipitation of efflorescent compounds from coal mine drainage

Efflorescent nanophases(NPs)are found as a transitory accumulation of potentially hazardous elements(PHEs),particularly in tropical climates.The central objective of this study was to investigate the distribution of PHEs with NPs through the evaporative formation structures(EFS)of enormously PHEs-rich coal-mine drainages(CMD).The EFS were studied in natural coal mine drainage for five months in order to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in nature.The largest coal-fired power plant in South America,located in south Brazil,is used as an example of such a problem.In this work,a novel methodology for the analysis of PHEs in CMD precipitates is proposed for this affected coal area.The analytical method,combining X-Ray Diffraction(XRD)and advanced electron microscopies,shows the importance of nanomineralogy in understanding different circumstances of coal contamination.Several ultrafine-nanoparticles(UNPs)were identified in the sampled soils and river sediments together with the PHEs.A decrease in PHEs was identified in association with UNPs.However,further investigations are required with regard to the mobility of PHEs in water,atmosphere,soils,and sediments.The EPS was thoroughly studied,acquiring suitable understanding with investigational facts for Ca and Fe-sulphates,pickeringite,and several amorphous phases.     

沁水盆地晚古生代煤中硫的地球化学特征及其对有害微量元素富集的影响

煤中硫是多种有害微量元素的重要载体。基于形态硫分析、电感耦合等离子质谱及X射线衍射等方法分析沁水盆地晚古生代煤中硫和有害微量元素的分布规律,探讨了煤中硫对有害微量元素富集的影响,运用带能谱的扫描电镜和光学显微镜划分煤中硫化物的微观赋存特征。结果表明,沁水盆地煤中硫整体上以有机硫为主,平均占全硫的78%,只有在太原组个别高硫煤中以黄铁矿硫为占优势。显微镜和扫描电镜下可识别出煤中黄铁矿的微观赋存状态包括莓球状、薄膜状、晶粒状、结核状、团窝状黄铁矿和细粒黄铁矿集合体,白铁矿的微观赋存特征包括聚片状、板状和矛头状白铁矿,部分白铁矿与黄铁矿共生。沁水盆地煤中有害微量元素含量整体较低,黄铁矿是有害微量元素As、Se和Hg的重要载体,而有机硫决定了煤中U的富集。研究认为,成煤时期海水对泥炭沼泽的影响导致太原组煤中全硫和黄铁矿硫较高,太原组煤中硫的来源具有多样性,煤中黄铁矿具有多阶段演化的特点。