Low-temperature Oxygen-plasma Ashing Research Articles

Optimization of Operating Parameters for Coal Low-Temperature Ashing: A Suitable and Efficient Treatment Method for Mineral Analysis in Coal

Low-temperature oxygen-plasma ashing plus X-ray diffraction analysis is one of the effective techniques to identify minerals in coal. However, previous publications have not provided any details of the exact low-temperature degrees and corresponding working conditions of ashers, and this could lead to two adverse effects without proper operating guidance: (1) a relatively high temperature (e.g., >150 °C) may cause alteration of minerals (particularly clay minerals), and (2) a relatively low temperature (e.g., <80 °C) may cause a long ashing time and incomplete ashing of organic matter. In this study, the authors introduced the most frequently used low-temperature plasma ashers (PVA TePla IoN 40 made in America and Quorum K1050X made in Britain) to reveal optional operating parameters for low-temperature ashing. The ashing effects were analyzed from the aspects of ash mass, X-ray diffraction patterns, and the qualitative and quantitative analysis of minerals. Considering all the factors above, it is concluded that the ashing is the best when the running power is 200 W for the IoN 40, at which the diffraction peaks of chlorite d(004) and kaolinite d(002) can be clearly distinguished by LTAs-XRD analysis. In addition, different low temperatures have certain influence on the crystal structure of minerals. When the power rises to above 300 W (about 150 °C), the crystal structure of minerals undergoes changes. The symmetry and integrity of the mineral peaks became worse, and destructive interference occurred between the spacing of reflection planes, resulting in significant decrease in diffraction peak intensity; thus, some trace minerals were unable to be identified. The study on the working parameters of the instrument would be helpful to ash coals more effectively and make qualitative and quantitative analysis of minerals more accurate.

Effects of oxygen plasma ashing treatment on carbonate clumped isotopes.

For clumped isotope analysis (Δ47 ), hydrocarbon and organic molecules present an important contaminant that cannot always be removed by CO2 purification through a Porapak-Q trap. Low-temperature oxygen plasma ashing (OPA) is a quick and easy approach for treatment; however, the impact of this treatment on the original carbonate clumped isotope values has never been fully studied. We tested the isotopic impact of OPA using three natural samples with a large range of initial Δ47 values. Crushed and sieved (125 μm mesh) samples were placed into a Henniker Plasma HPT-100 plasma system and treated at a flow rate of 46 mL/min and a power of 100 W at a vacuum of 0.2 mbar for 10, 20, 30 and 60 min before clumped isotope analysis using two MAT 253 isotope ratio mass spectrometers modified to measure masses 44-49. OPA treatment for 30 min or more on calcite powder samples has the potential to alter the clumped isotopic composition of the samples beyond analytical error. A systematic positive offset is observed in all samples. The magnitude of this alteration translates to a temperature offset from known values ranging from 4°C to 13°C. We postulate that the observed positive offset in Δ47 occurs because the bonds within lighter isotopologues are preferentially broken by plasma treatment, leading to an artificial increase in the 'clumping' value of the sample. We recommend that any laboratory performing OPA treatments should reduce the runs to 10-20 min or carry out successive runs of 10 min followed by sample stirring, as this procedure showed no alteration in the initial Δ47 values. Our results validate the use of OPA for clumped isotope applications and will allow future research to use clumped isotopes for challenging samples such as oil-stained carbonates, bituminous shales or host rocks with very high organic carbon content.

Migration and transformation of sodium during staged coal combustion of Zhundong coal and influence of carbon coating

Staged coal combustion is a promising solution to the alkali-induced slagging issue. It innovatively separates coal pyrolysis and char combustion into different reactors. This study investigated migration and transformation of sodium during staged coal combustion of two Zhundong coals in a fixed-bed apparatus. Behavior of sodium during coal pyrolysis and char combustion are integrated. Carbon coating on sodium species was experimentally confirmed for the first time by low-temperature oxygen-plasma ashing and ultrafine grinding. Up to 62 wt% of initial water-soluble Na in ZJ coal and 51 wt% in WCW coal were coated with the carbon matrix during coal pyrolysis. Coated water-soluble Na appeared from 500 °C and its amount reached a peak value at around 700 °C, followed by decrease over 700–1000 °C. Thermoplastic behavior of coal during pyrolysis is expected to play an important role in the formation of coating which hinders pretreatment of sodium. During char combustion, all coated water-soluble sodium species were exposed and participated in the subsequent release. Part of them can also react with minerals to generate insoluble and HCl-soluble sodium species. Char combustion is the main period of the sodium release while coal pyrolysis is the principal period of the generation of HCl-soluble Na.

Evaluation of a sample preparation procedure for total-reflection X-ray fluorescence analysis of directly collected airborne particulate matter samples

This paper investigates in detail a sample preparation procedure for the total-reflection X-ray fluorescence (TXRF) analysis of airborne particles using a three-stage Dekati™ PM10 cascade impactor. The impactor was modified in such a way, that 30 mm diameter quartz reflectors suitable for TXRF spectrometers can be inserted as collection plates below the impactor's nozzle arrays with cut-off diameters of 10, 2.5 and 1 μm. Smaller particles are collected in a backup filter, which can be analyzed using classical energy-dispersive XRF. As an internal standard 5 ng Y were pipetted centrally onto each reflector after collection. The reflector surface has to be coated in order to reduce particle bounce-off. Two surface coatings, silicone oil and petroleum jelly (“Vaseline”), were compared in this study. Before TXRF analysis this coating layer was removed by low-temperature oxygen plasma ashing. A new approach was introduced, which involves masking of the quartz reflectors in order to remove the outer ring of the spot pattern, which consists of two concentric circles, and to produce a sample, which lies entirely inside the detectable area. Results of this approach were compared to those obtained from unmasked samples and discussed in detail. Angle scans show residue-like behavior of the samples in each stage. Samples were taken on the roof of the Atominstitut building in January 2017 on 10 days during working hours.

Effect of ash preparation method on the sintering characteristics of ashes from combustion of coal and biomass blends

Sintering behaviour of ashes from combustion of coal and biomass blends was experimentally investigated with a focus on the effect of ash preparation method. Blends of a Chinese anthracite, Jincheng coal, and two biomass materials, a wheat straw and a pine sawdust, respectively, were subjected to three different ash preparation procedures, namely, a low temperature oxygen plasma ashing device operating at ca 150°C, combustion in a Muffle furnace at 815°C and in a drop tube furnace at 1500°C. The resulting ash samples were then subjected to the sintering temperature measurement using a pressure-drop sintering device, morphological and mineralogical characterisation using scanning electron microscope (SEM) fitted with X-ray energy dispersive spectroscopy (EDS) and X-ray diffractometry analyser (XRD), respectively. For the same coal and biomass blends but different ash preparation methods, the sintering temperatures were always the lowest for the ash samples from the plasma ashing device and the highest from drop tube furnace. SEM imaging showed that the texture of ash samples from the plasma ashing device was irregular, loose and more fibrous, indicating little interactions among the different mineral and inorganic constituents in the individual fuels. The muffle furnace and drop tube furnace ashes were denser and more uniform in shape as the mineral matter and inorganics became fused together. In addition, the drop tube furnace ashes were mostly in spherical-shape, indicating ash melting had occurred during combustion. The XRD analysis revealed that different minerals were present in the ash samples due to different ash preparation temperatures, with high temperature minerals present in the drop tube furnace ash. Biomass addition in the blends lowered the sintering temperature of corresponding ash; the higher the proportion of biomass in the blend, the lower the ash sintering temperature regardless the ashing method. At the same biomass addition ratio, the ash sintering temperature of the blend with the wheat straw addition was lower than that with the pine sawdust addition, because the wheat straw had a higher K and Cl content but lower Ca than the pine sawdust. The EDS and XRD analyses confirmed that the ashes of coal/wheat straw blends contained more K-bearing minerals, while the ashes of the coal/pine sawdust contained more Ca and K-bearing minerals. Both Ca and K-bearing minerals reacted with other minerals in the ash to form low temperature eutectics, leading to the reduction of sintering temperatures of the coal and biomass blends. However, the melting points of the K-containing minerals are higher than the Ca-containing minerals, therefore, the sintering temperatures of ash with the wheat straw addition were lower than those with the pine sawdust addition.

Inorganic matter in Victorian brown coals

A common method to quantify the mineral matter in coals is to remove the carbonaceous matter by low-temperature oxygen plasma ashing (LTA) followed by X-Ray Diffraction (XRD) analysis. However, some low-rank coals, such as Victorian brown coals (lignites), have low levels of mineral matter and contain significant amounts of non-mineral inorganics (organically associated elements and salts dissolved in the coal pore's water), which form artifact phases during low-temperature ashing. The presence of these phases also lowers the concentration of the low abundant mineral species in the ash below the detection limit of the XRD. Some of the non-mineral-matter components can be removed by leaching of the coal prior to ashing, but the leaching conditions have to be chosen so that the mineral matter is not removed. In this study, sequential leaching was performed on three Victorian brown coals (Hazelwood, Yallourn and Loy Yang) in order to increase the concentration of the mineral species in the low-temperature ashes by removing the non-mineral inorganics. We introduced diammonium ethylenediaminetetraacetate (NH4-EDTA) solution into the leaching process, because of its potential to extract ion-exchangeable cations without dissolving acid-sensitive mineral matter or contaminating the extract solution with introduced metal cations. The leaching protocol was stepwise extraction by water, ammonium acetate, NH4-EDTA, hydrochloric acid and nitric acid. Sequential leaching enabled quantification of the minerals that occur in very small amounts in the coals. K-feldspar, pyrite, augite and kaolinite were the additional minerals quantified in the leached coals beside quartz, plagioclase (calcian albite), marcasite and calcite, which were found in the original coals. Most non-mineral inorganics, which produce large amounts of artifact phases in the low-temperature ashes, were removed by water, ammonium acetate and NH4-EDTA. NH4-EDTA effectively removed significant amounts of inorganic elements, which most likely occur in coordination complexes and would be extracted in conventional leaching studies only by strong acids. This procedure makes it possible to discriminate between inorganic elements that occur organically associated and mineral matter that is dissolved by strong acids.

Mineralogy of Furnace Deposits Produced by South African Coals during Pulverized-Fuel Combustion Tests

Pilot-scale combustion tests were carried out on coals with low (13.5%) and high (39.6%) ash percentages from the Highveld Coalfield of South Africa, using the ALS-ACIRL 100–200 kW Combustion Test Facility. The mineral matter in the feed coals and also the chemistry and mineralogy of the ash deposits from different parts of the test furnace were analyzed using quantitative X-ray diffraction and X-ray fluorescence techniques, and the results were used to develop an understanding of the mineralogical processes taking place in the different parts of the pulverized-fuel combustion system. Low-temperature oxygen-plasma ashing and quantitative X-ray diffractometry showed that the mineral matter of both coals contained abundant kaolinite, lesser but still very significant proportions of quartz and carbonates (ankerite and calcite), and minor proportions of pyrite and other minerals. A small but significant proportion of nonmineral Ca also occurs in the organic matter, especially of the low-ash coal. The chemical composition of the combustion products taken from the different sampling points in the test facility (slagging panels, furnace ash, and fouling probes, etc.) was overall very similar for each coal sample. However, the percentages of the different crystalline minerals in the combustion products showed a wide range of variation at the different sampling points. Anorthite, derived from interaction between Ca and the aluminosilicate components, was formed from both coals at temperatures above 1300 °C, mostly as part of sintered aggregates that built up and became detached from the slagging panel in the highest temperature part of the combustion system. Anhydrite was formed by interaction of Ca with SO2; lime and periclase were also formed from the low-ash coal, where insufficient sulfur was available for complete sulfate development.

Understanding of mineralogy and residence of trace elements in coals via a novel method combining low temperature ashing and float-sink technique

For understanding the mineralogical characteristic and trace element affinities to specific minerals in coals, a combined method has been adopted and evaluated, which is low temperature oxygen-plasma ashing followed by float-sink density separation in bromoform. Mineral matter would be isolated from coals, and light (<2.89g/cm3) and heavy (>2.89g/cm3) mineral fractions would be separated from coal low temperature ash residues. Coals collected from three coalfields in China, namely Xiaolongtan (XLT), Huolinhe (HLH) and Yangquan (YQ), have been studied. Mineralogical characteristic of coals was characterized by X-ray diffraction and a field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. The distributions of trace elements in coals, low temperature ashes, and light and heavy mineral fractions were determined by inductively coupled-plasma mass spectrometry.The results show that minerals of different densities in coal can be successfully isolated and separated into two mineral fractions with the help of the combined method. Phase-mineral compositions in light mineral fraction of each coal are very similar to those in the respective low temperature ashes as a whole. Phases identified in the heavy mineral fraction are completely different from those in the low temperature ash and the light mineral fraction of each coal. Pyrite dominates in the heavy mineral fractions from the three coals, which constitutes up 48.7wt.%, 82.9wt.%, and 100wt.% in the heavy mineral fraction of YQ, XLT, and HLH coals, respectively. Pyrite particles mostly occur as euhedral crystals, which display well-defined shapes, such as pentagonal dodecahedra, tetrakaidecahedra, cubes, decahedra, and regular octahedra. Framboid and massive pyrite are also clearly observed. Trace elements Pb, Cd, Mo, Cu, Tl, Sn, Sb, and Zn have a strong affinity to pyrite; elements Ni and Co are likely to occur in pyrite or ankerite; elements Sr, Hf, Li, V, Ga, Rb, Ba, Nb, Cs, U, Th, and Zr are associated with clay minerals and quartz; rare earth elements are clearly associated with clay minerals.

Organic matter removal for the analysis of carbon and oxygen isotope compositions of siderite

The measurement of stable carbon (C) and oxygen (O) isotope compositions in siderite from sediments and soils can be useful to constrain carbonate genesis processes and/or to reconstruct paleoclimates. In order to evaluate our ability to determine C and O isotope compositions of siderite in modern sediments and soils containing immature organic matter, we prepared and analyzed synthetic samples made of variable proportions of pure siderite and yeast (selected for representing an immature organic matter because of its potential high reactivity to H3PO4 digestion). Replicate analyses of CO2 produced by phosphoric acid (H3PO4) digestion of our pure siderite standard at 130°C provided δ13Csid and δ18Osid values of −12.3±0.1‰ and −16.2±0.3‰ (2σ) relative to PDB. Analysis of the synthetic sample mixtures shows δ13C and δ18O values undistinguishable from those of pure siderite within uncertainties, for proportion of yeast in the mixture equal to or lower than 10wt.% (corresponding to ~5wt.% of total organic carbon). In contrast, samples with proportions of yeast higher than 10wt.% were progressively shifted to more negative values (down to −21.8‰ for C and −19.6‰ for O) with increasing proportion of yeast, as a result of an increasing contribution of CO2 produced by the reaction of yeast with H3PO4 at 130°C. Although in the case of natural samples this organic matter CO2 contribution probably strongly depends on both organic matter source organisms and diagenetic history, our data indicate that the removal of organic matter prior to siderite analysis may be often required. We thus tested three different methods for organic matter removal on our synthetic samples, using either oxidation in solution with NaOCl or H2O2, or oxidation in low-temperature oxygen-plasma ashing system. For both methods based on oxidation in aqueous solution, we show that the determination of δ13C and δ18O is improved for concentration of yeast lower than 75wt.% in the “siderite–yeast” mixture but is still shifted to lower values by 4.1 and 0.7‰ for C and O respectively, for a yeast proportion higher than 75wt.%. Moreover, these two methods induce partial siderite dissolution, preventing determination of siderite content in the samples. The best method of yeast removal for coupled C and O isotopes analysis is the oxidation by low-temperature oxygen-plasma ashing, which strongly improves the accuracy of the δ13C and δ18O measurements and perfectly preserves siderite. In conclusion, any study of siderite isotope composition in organic-rich samples should include an evaluation of the need for organic matter removal using low-temperature oxygen-plasma ashing, the only method shown here to be efficient while preserving the siderite.

Geochemistry and nano-mineralogy of two medium-sulfur northeast Indian coals

The petrology, mineralogy, and inorganic geochemistry of two contrasting high-sulfur, vitrinite-rich subbituminous to bituminous coals from the North Eastern Region (NER) of India have been studied using a combination of optical microscopy, quantitative X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM/SAED), and chemical analysis techniques. The study reveals that the Fe nano-particles are present in Indian high-sulfur Tertiary coals including nano-pyrite, Fe-oxyhydroxides and a small amount of sphalerite. The pyrite is present as framboids and unsymmetrical cubic crystals (rhombohedral). They contain potentially hazardous elements viz. As, Pb, and Se measured by EDS techniques. Mineral-matter residues isolated from the coals by low-temperature oxygen-plasma ashing are dominated by carbonate minerals (calcite, dolomite, ankerite), pyrite and pyrite oxidation products (jarosite and coquimbite), kaolinite, illite, and quartz. Sulfate-bearing phases such as tschermigite, bassanite and gypsum are also present, probably as artifacts of the plasma-ashing process.

Partitioning of mineralogical and inorganic geochemical components of coals from Santa Catarina, Brazil, by industrial beneficiation processes

Comparative studies of the mineral matter and trace elements in 12 pairs of run-of-mine (ROM) and clean-coal products from beneficiation plants in Santa Catarina, southern Brazil, have been carried out using low-temperature oxygen-plasma ashing, X-ray diffraction and chemical analysis techniques with the aim of evaluating the effect of coal preparation on the mineralogy and chemical composition of the final coal products. The results show that substantial reductions in mineral matter and ash percentages are associated with beneficiation of coals mined from the different deposits. These reductions are accompanied by changes in the percentages of Fe2O3 in the respective coal ashes, due to the reduction in the proportion of pyrite in the mineral matter, and also by a reduction in the percentage of Na2O, possibly due to ion exchange within the clay minerals. The relative proportions of quartz, clay minerals, and minor phases such as calcite and feldspar (mainly albite) within the mineral matter are not, however, significantly changed by the beneficiation processes.The concentrations of most trace elements in the beneficiation products are similar to the respective concentrations in the relevant ROM materials, or are reduced to an extent similar to that of the total mineral matter percentage for the respective coal samples. This suggests an association mainly with the clay-rich mineral matter. The concentrations of As and Pb, however, are reduced to a greater extent for most samples by the beneficiation processes, consistent with a pyrite association. Concentrations of Ge, U and Zr are higher in many of the clean coals than in the respective run-of-mine materials, suggesting the possibility of preferential association, at least for some deposits, with the organic-rich fractions of the coals concerned.

Mineralogy of lignites and associated strata in the Mavropigi field of the Ptolemais Basin, northern Greece

The mineralogy of five lignite layers and the associated roof, floor and intercalating strata has been analysed using low-temperature oxygen-plasma ashing and quantitative X-ray diffraction techniques. The lignite contains quartz, kaolinite, illite and smectite, and in some cases small proportions of feldspar, thought to represent mainly detrital minerals in the original peat deposits. One sample also contains crystalline calcium oxalates, with weddellite present in the raw lignite and whewellite in the low-temperature ash (LTA) of the same lignite sample. Minor proportions of gypsum are present in some of the raw lignite samples, possibly in part derived from precipitation of dissolved Ca and SO 4 in the pore waters on drying. All the LTAs, however, contain much higher proportions of bassanite and/or gypsum compared to the other minerals present, consistent with production of calcium sulphate artefacts from interaction of abundant organically-associated Ca and S in the lignite during the plasma-ashing procedure. The inorganic strata are mainly carbonate rocks, consisting almost entirely of calcite with minor aragonite, small proportions of illite, traces of pyrite and in some cases siderite. Some non-carbonate rocks are also associated with the lignite seams; these are dominated by plagioclase feldspar and mica, along with illite, kaolinite and a relatively minor proportion of quartz. The mineral assemblages can be related to the palaeoenvironmental conditions under which the various sediments (including lignite) were deposited. Comparison of the mineral abundances in the samples to the chemical composition of the materials shows that the quantitative XRD technique provides results consistent with ash analysis data. Although abundant in the associated rocks, calcite does not occur in the lignite samples. While part of the relatively abundant Ca in the lignite occurs as either gypsum or weddellite, most of it appears to be organically-bound. Mine products that incorporate calcareous rocks of the type associated with the lignite may, however, contain separate calcite phases and display high carbonate CO 2 contents.

Assessment of oxygen plasma ashing as a pre-treatment for radiocarbon dating

This study investigates the potential of low-temperature oxygen plasma ashing as a technique for decontaminating charcoal and wood samples prior to radiocarbon dating. Plasma ashing is demonstrated to be rapid, controllable and surface-specific. Different organic materials clearly ash at different rates, however, the ability of plasma ashing to selectively ash different organic components is limited in heterogeneous sample matrices. This is because oxidation is confined to the immediate sample surface. Comparison of radiocarbon dates obtained from identical aliquots of contaminated ancient charcoal pre-treated by acid–base–acid (ABA), acid–base-oxidation-stepped combustion (ABOx-SC) and plasma ashing suggests that the technique performs as well as the ABA pre-treatment but does not remove as much contamination as the ABOx-SC technique. Plasma ashing may be particularly useful in cases where sample size is limiting.

Quantitative evaluation of minerals in coal deposits in the Witbank and Highveld Coalfields, and the potential impact on acid mine drainage

This study has investigated the quantitative distribution of minerals in coals and other lithological units in the coal-bearing successions of the Witbank and Highveld Coalfields in the Mpumalanga Province of South Africa, using low-temperature oxygen-plasma ashing (LTA), high temperature ashing, X-ray diffraction, and X-ray fluorescence spectrometry techniques. Mineral matter makes up approximately 8 to 35 wt.% of the coal samples. SiO 2 concentrations in the coal vary between 0.0 and 35.0 wt.%, Al 2 O 3 between 0.5 and 16.0 wt.%, Fe 2 O 3 between 0.03 and 10.0 wt.%, and S between 0.15 and 8.0 wt.%. Minor concentrations of CaO (0.0 to 8.0 wt.%) and MgO (0.0 to 1.0 wt.%) are also present. P 2 O 5 occurs in concentrations of 0.0 to 3.5 wt.% and K 2 O is in the order of 0.0 to 1.3 wt.%. Na 2 O varies between 0.0 and 0.45 wt.%, with the Highveld coals showing an enrichment in Na 2 O (0.0 to 0.51 wt.%) in comparison with the Witbank coals. The minerals in the coals are dominated by quartz and kaolinite, with varying proportions of calcite, dolomite and pyrite, as well as accessory phosphate phases. Higher (normalised) K 2 O and Na 2 O concentrations are present in the sandstones than in the associated siltstones and carbonaceous shales, partly reflecting the presence of feldspars and clay minerals such as illite. Acid–base accounting was used to investigate the potential of the coal and coal-bearing units to produce acid mine drainage conditions. According to the screening criteria, all the coal and coal-bearing units, except the unit between the No. 1 and No. 2 coal seams, are potentially acid generating. The average Net Neutralising Potential (NNP) values suggest that the No. 5 coal seam, the No. 4 Upper coal seam, and the unit between the No. 4 and No. 2 coal seams are potentially acid generating. With such techniques it is possible to predict the types of situations that might arise concerning groundwater quality, and implement proper prevention or remediation programs.

04/01822 Method and equipment for production of activated carbon: Kashiwagi, Y. Jpn. Kokai Tokkyo Koho JP 2003 226,551 (Cl. C01B3/08), 12 Aug 2003, Appl. 2002/30,463. (In Japanese)

The petrology, mineralogy, and inorganic geochemistry of two contrasting high-sulfur, vitrinite-rich subbituminous to bituminous coals from the North Eastern Region (NER) of India have been studied using a combination of optical microscopy, quantitative X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM/SAED), and chemical analysis techniques. The study reveals that the Fe nano-particles are present in Indian high-sulfur Tertiary coals including nano-pyrite, Fe-oxyhydroxides and a small amount of sphalerite. The pyrite is present as framboids and unsymmetrical cubic crystals (rhombohedral). They contain potentially hazardous elements viz. As, Pb, and Se measured by EDS techniques. Mineral-matter residues isolated from the coals by low-temperature oxygen-plasma ashing are dominated by carbonate minerals (calcite, dolomite, ankerite), pyrite and pyrite oxidation products (jarosite and coquimbite), kaolinite, illite, and quartz. Sulfate-bearing phases such as tschermigite, bassanite and gypsum are also present, probably as artifacts of the plasma-ashing process.

Analysis and significance of mineral matter in coal seams

The material described as “mineral matter” in coal encompasses dissolved salts in the pore water and inorganic elements associated with the organic compounds, as well as discrete crystalline and non-crystalline mineral particles. A range of technologies, including but not restricted to low-temperature oxygen-plasma ashing, may be used to evaluate the total proportions of minerals and other inorganic constituents in a coal sample. The relative proportions of the individual minerals in the coal may be further determined by several different techniques, including Rietveld-based X-ray powder diffractometry, computer-controlled scanning electron microscopy (CCSEM), and normative interpretation of chemical analysis data. The mode of occurrence of particular minerals may be evaluated by optical or electron microscopy techniques. The minerals in coal may represent transformed accumulations of biogenic constituents such as phytoliths and skeletal fragments, or they may be of detrital origin, introduced as epiclastic or pyroclastic particles into the peat bed. Other minerals are produced by authigenic precipitation, either syngenetically with peat accumulation or at a later stage in cleats and other pore spaces by epigenetic processes. They may represent solution and reprecipitation products of biogenic and detrital material, or they may be derived from solutions or decaying organic matter within the peat bed. Non-mineral inorganics may be derived from a range of subsurface waters, and possibly redistributed within low-rank seams by post-depositional ion migration effects. They may also be expelled in different ways from the organic matter with rank advance. Quantitative analysis of minerals and other inorganics contributes significantly to defining coal quality. It may also be useful as an aid to stratigraphic correlation, either between seams in a coal-bearing sequence or between sub-sections within an individual coal bed. Mineralogical analysis may help in identifying the mode of occurrence and mobility of particular trace elements, including potentially toxic components such as arsenic and mercury. Knowledge of the mineral matter can also be used to evaluate the behaviour of particular coals in different utilization processes, including the processes that control the characteristics of fly ashes, slags and other combustion by-products.

Clays and other minerals in coal seams of the Moura-Baralaba area, Bowen Basin, Australia

The clays and other minerals in a succession of Late Permian coals of high-volatile bituminous to semi-anthracite rank have been identified, using low-temperature oxygen plasma ashing and X-ray diffraction, and evaluated to identify the relative roles in mineral matter formation of detrital input, early diagenesis in the peat swamp and late diagenesis associated with rank advance. Although well-ordered kaolinite of probable early diagenetic origin is abundant throughout the succession, the uppermost and lowermost seams of the sequence, regardless of rank, contain relatively abundant illite and/or interstratified illite/smectite, along with a small but significant proportion of chlorite. These clays are thought to be essentially of detrital origin, washed or blown into the peat deposit in relative abundance during the establishment and subsequent overwhelming of an extensive and long-lived swampy environment. Quartz is also abundant in the lower seams of the sequence, especially close to the regional sediment source area. Illite is unusually abundant in the topmost seam in both high- and low-rank parts of the succession, and thus appears to represent detrital input from a particular source material. Although significant changes are reported in the clays of the associated strata due to rank advance, the principal effect of rank advance on the minerals in the coal itself appears to be the development of an ammonium illite, and possibly some additional fine-grained chlorite, in the semi-anthracite material. Isolation within the organic matter of the coal is thought to have inhibited access for ions such as K +, which might otherwise have become involved in metamorphic reactions and given rise to mineralogical changes commonly found in non-coal sedimentary successions.

Distribution and forms of fluorine in whole blood of human male

Distribution and absolute concentration of three kinds of fluoride/fluorine, i.e., free ionic, ionizable, and organic fluorine, in human whole blood and serum were determined. The method is based on low temperature oxygen plasma ashing, acid hydrolysis, gas chromatography using chlorotrimethylsilane, and fluoride ionspecific electrode. A large part (40%) of the total F is distributed in clot of the whole blood and 74% of the total F is in the form of organic fluorine.

Geochemical and mineralogical changes in a coal seam due to contact metamorphism, Sydney Basin, New South Wales, Australia

The mineralogical changes in a bituminous coal seam, thermally altered by a small basaltic intrusion, have been investigated using electronic low-temperature (oxygen plasma) ashing, X-ray diffraction and other laboratory techniques. An assemblage dominated by montmorillonite and well-crystallized kaolinite, in the area away from the intrusion, passes laterally to one dominated by illite and poorly crystallized kaolinite, along with abundant dolomite and calcite, at the actual contact point. Geochemical considerations of both the mineral matter and the igneous rock suggest that the changes in the clay fraction were produced by heating to temperatures of between 400 and 650°C for a relatively short period, coupled with migration of potassium from the intrusive body into the coal seam. Heating at lower temperatures, although causing an increase in vitrinite reflectance, does not appear to have had a particularly significant effect at all on the clay minerals in the coal seam.

Analysis of environmental samples by spark source mass spectrometry—I. Trace elements in water

Spark source mass spectrometry is ideally suited to the determination of trace elements in natural waters. In the work described, almost all of the elements present in lake or river waters at concentrations of one part in 1011 parts of water and higher were routinely determined. In the particular waters investigated 30 or more elements were found in each sample.The main features of the procedure were freeze-drying for sample preconcentration, low temperature oxygen plasma ashing to eliminate organic ion interferences, sample presentation to the mass spectrometer in counter-electrodes tipped with a homogeneous conducting ashcarbon mixture, and newly-perfected electrical detection and measurement of the mass-resolved ion beams.Precisions achieved for individual elements in a rapid 10 min electromagnetic scan from mass number 238 down to mass number 7 averaged ± 30 per cent. Using the electrostatic peak switching mode and the expenditure of considerably more time, precisions of better than 5% were possible. Accuracy is dependent upon the availability of suitable calibration standards and upon the concentration range of the particular elements determined.