scholarly journals Composition and probable ore igneous rocks source of columbite from alluvial deposits of Mayoko district (Republic of the Congo)

2020 ◽  
Vol 242 ◽  
pp. 139
Author(s):  
Idylle Plachini LOUFOUANDI MATONDO ◽  
Mikhail IVANOV
Keyword(s):  
Fine Fraction ◽  
Rare Metal ◽  
Coarse Fraction ◽  
Electron Microscopic ◽  
Rare Element ◽  
Alluvial Deposits ◽  
Loose Deposits ◽  
Optical Electron ◽  
Size Groups ◽  
Republic Of The Congo

The article presents the results of optical, electron microscopic and electron microprobe studies of columbite group minerals, collected during heavy mineral concentrate sampling of alluvial deposits in the Mayoko region (Republic of the Congo). The aim of the study is revealing tantalum niobates ore body in this region. We found that these minerals in loose deposits are represented by two grain-size groups: less than 1.6 mm (fine fraction) and 1.6-15 mm (coarse fraction). The grains of both fractions belong mainly to columbite-(Fe), less often to columbite-(Mn), tantalite-(Mn) and tantalite-(Fe), contain impurities of Sc, Ti, and W. The crystals have micro-scaled zoning (zones varies slightly in the Ta/Nb ratio values) and contains a lot of mineral inclusions and veins represented by zircon, pyrochlore supergroup minerals and others. Columbite-(Fe) and columbite-(Mn) are characterized by an increased content of Ta2O5 up to the transition to tantalite-(Fe) and tantalite-(Mn). This allows us to exclude the formation of subalkaline rare-metal granites, their metasomatites (albitites and greisenes) and carbonatites, from the list of possible columbite ore rocks source in the Mayoko district. Thus, beryl type and complex spodumene subtype rare-element pegmatites of the mixed petrogenetic family LCT-NYF (according to P.Černý) should be considered as a probable root source. The results of the research should be taken into account when developing the methodology for prospecting in this area.

scholarly journals Modification of the phase composition of low-grade gibbsite-kaolinite bauxites

2021 ◽  
Vol 317 (2) ◽  
pp. 94-102
Author(s):  
R.A. Abdulvaliyev ◽  
◽  
S.B. Dyussenova ◽  
A.I. Manapova ◽  
A. Akcil ◽  
...  
Keyword(s):  
Phase Composition ◽  
Chemical Activation ◽  
Fine Fraction ◽  
Sodium Bicarbonate Solution ◽  
Microscopic Analysis ◽  
Coarse Fraction ◽  
Low Grade ◽  
Optimal Regime ◽  
Electron Microscopic ◽  
Activation Temperature

The known methods of processing low-quality bauxite have a number of disadvantages that make it difficult or impossible to use them in the conditions of production of JSC "Aluminum of Kazakhstan", therefore, it is necessary to effectively develop a technology for preliminary enrichment. Enrichment of low-quality bauxites is possible by separating the clayey - high-siliceous and coarse-crystalline fractions. Electron-microscopic analysis of the original bauxite showed that the coarse-crystalline fraction is tightly pressed by the fine one. The total silicon modulus of the sample is 2.49. The silicon modulus of the fine fraction is 2.19, and that of the coarse fraction is 3.89. When enriching bauxite, as a result of the separation of fines, it is possible to increase the silicon modulus. After the chemical activation of bauxite in a sodium bicarbonate solution, the finely dispersed fraction is effectively separated from the coarse one and the phase composition changes - the calcium silicate phase disappears and the calcite phase is formed. With an increase in the activation temperature, the content of kaolinite and siderite decreases, and the content of quartz and hematite increases. Studies have shown that at temperatures of chemical activation of 120 ° C, duration of more than 120 minutes and 200 ° C, duration of more than 40 minutes, a dawsonite phase is formed in bauxite, which densifies the mineral structure. When determining the optimal regime for carrying out chemical activation, it is necessary to take into account the negative possibility of dawsonite formation.

Long-term variations in individual particle types in the aerosol of Phoenix, Arizona, as determined using automated electron microprobe analysis and multivariate statistical techniques

1993 ◽  
Vol 51 ◽  
pp. 742-743
Author(s):  
Karen A. Katrinak ◽  
James R. Anderson ◽  
Peter R. Buseck
Keyword(s):  
Electron Microprobe ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Motor Vehicles ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
X Ray ◽  
Mineral Particles ◽  
Anthropogenic Air Pollutants

Aerosol samples were collected in Phoenix, Arizona on eleven dates between July 1989 and April 1990. Elemental compositions were determined for approximately 1000 particles per sample using an electron microprobe with an energy-dispersive x-ray spectrometer. Fine-fraction samples (particle cut size of 1 to 2 μm) were analyzed for each date; coarse-fraction samples were also analyzed for four of the dates.The data were reduced using multivariate statistical methods. Cluster analysis was first used to define 35 particle types. 81% of all fine-fraction particles and 84% of the coarse-fraction particles were assigned to these types, which include mineral, metal-rich, sulfur-rich, and salt categories. "Zero-count" particles, consisting entirely of elements lighter than Na, constitute an additional category and dominate the fine fraction, reflecting the importance of anthropogenic air pollutants such as those emitted by motor vehicles. Si- and Ca-rich mineral particles dominate the coarse fraction and are also numerous in the fine fraction.

scholarly journals Aerosol characterisation including oxidative potential as a proxy of health impact

2019 ◽  
Vol 29 (2) ◽  
Author(s):  
Miroslav Josipovic ◽  
Catherine Leal-Liousse ◽  
Belinda Crobeddu ◽  
Armelle Baeza-Squiban ◽  
C. Keitumetse Segakweng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Fine Fraction ◽  
Health Impact ◽  
Coarse Fraction ◽  
Dry Season ◽  
Wet Season ◽  
Oxidative Potential ◽  
Ionic Content ◽  
Vaal Triangle

This study aimed to characterise aerosols sampled in the vicinity of a major industrialised area, i.e. the Vaal Triangle. It included thedetermination of oxidative potential as a predictive indicator of particle toxicity. Aerosol samples were collated through the cascadefiltering during an eight-month period (12 h over three days in one week). Three size fractions were analysed for organic carbon(OC), black carbon (BC) and oxidative potential (OP), while ionic content was presented as monthly and seasonal concentrations. Thecontinuous measurement of black carbon by an optical attenuation instrument was collated concurrently with cascade filtering. Thecarbonaceous content was low compared to the ionic one. Within the carbonaceous concentrations, the organic carbon was higherthan concentrations of black carbon in both seasons in the ultra-fine fraction; the opposite was the case for the fine fraction, whilethe coarse fraction concentrations of organic carbon in the dry season had higher concentrations than black carbon in the wet seasonand organic carbon in the wet season. The OP tended to increase as the size was decreasing for wet season aerosols, whereas, forthe dry season, the highest OP was exerted by the fine fraction. The ultrafine fraction was the one showing the most contrasting OPbetween the two seasons. Continuous monitoring indicated that the higher BC concentrations were recorded in the dry/winter partof the year, with the daily pattern of concentrations being typically bimodal, having both the morning and evening peaks in bothseasons. Within the ionic content, the dominance of sulphate, nitrate and ammonium was evident. Multiple linear correlations wereperformed between all determined compounds. Strong correlations of carboxylic acids with other organic compounds were revealed.These acids point to emissions of VOC, both anthropogenic and biogenic. Since they were equally present in both seasons, a mixtureof sources was responsible, both present in the wider area and throughout the year.

scholarly journals ESTABLISHING THE ROTATION SPEED VARIATION RANGE LIMITS FOR AUTO-EXCITATION OF SELF-OSCILLATING GRINDING IN A TUMBLING MILL

2020 ◽  
Vol 4 ◽  
pp. 32-35
Author(s):  
Kateryna Deineka ◽  
Yurii Naumenko
Keyword(s):  
Visual Analysis ◽  
Rotation Speed ◽  
Relative Size ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
The Self ◽  
Cement Clinker ◽  
Crushed Material ◽  
Degree Of Filling ◽  
Tumbling Mill

The influence of the structure of a two-fraction polygranular feed of the chamber on the value of the drum rotation speed at auto-excitation of self-excited oscillations with a maximum swing is considered. Such a pulsating mode of movement of the charge is used in the self-oscillating process of grinding in a tumbling mill. The coarse fraction simulated the grinding bodies was steel bullets with a relative size ψdb=0.026. The fine fraction, simulated the particles of the crushed material, was a cement clinker with a relative particle size ψdm=0.00013. Variable factors of experimental studies were: the degree of filling the chamber in the state of rest κbr=0.25; 0.29; 0.33 and the degree of filling the gaps between the particles of the coarse fraction with particles of the fine fraction κmbgr=0.0625; 0.375; 0.6875; 1. The method of visual analysis of transient processes of self-oscillating modes of feed behavior in the cross section of the rotating drum chamber is applied. Measurements of the speed limits of the drum rotation were carried out with auto-excitation of self-oscillations of the filling. The magnitude of the self-oscillation swing was estimated by the increase in the difference between the maximum and minimum values of the filling dilatancy for one period of pulsations. An increase in the upper limit of the speed range ψω2 with a decrease in κbr and κmbgr was established. The growth rate of ψω2 increases at low values of κbr and κmbgr. Some increase in the lower limit of the ψω1 range with a decrease in κbr and κmbgr was revealed. An increase in the range of speeds of rotation was recorded at the maximum range of self-oscillations ψω1–ψω2 with a decrease in the connected interaction of the intra-mill filling. This coherent interaction is due to an increase in κbr and κmbgr. The value of the ψω1–ψω2 range varies from 1.01–1.03 at κbr=0.33 and κmbg=1 to 1.22–1.66 at κbr=0.25 and κmbgr=0.0625. The range gets its maximum value with fine and superfine grinding

scholarly journals Investigating Subantarctic 14C Ages of Different Peat Components: Site and Sample Selection for Developing Robust Age Models in Dynamic Landscapes

Radiocarbon ◽  
2019 ◽  
Vol 61 (4) ◽  
pp. 1009-1027 ◽  
Author(s):  
Zoë A Thomas ◽  
Chris S M Turney ◽  
Alan Hogg ◽  
Alan N Williams ◽  
Chris J Fogwill
Keyword(s):  
Bulk Material ◽  
Sample Selection ◽  
Fine Fraction ◽  
Systematic Difference ◽  
Coarse Fraction ◽  
Sedimentary Sequences ◽  
Subantarctic Islands ◽  
Dynamic Landscapes ◽  
Age Model ◽  
Selection For

ABSTRACTPrecise radiocarbon (14C) dating of sedimentary sequences is important for developing robust chronologies of environmental change, but sampling of suitable components can be challenging in highly dynamic landscapes. Here we investigate radiocarbon determinations of different peat size fractions from six peat sites, representing a range of geomorphological contexts on the South Atlantic subantarctic islands of the Falklands and South Georgia. To investigate the most suitable fraction for dating, 112 measurements were obtained from three components within selected horizons: a fine fraction <0.2 mm, a coarse fraction >0.2 mm, and bulk material. We find site selection is critical, with locations surrounded by high-ground and/or relatively slowly accumulating sites more susceptible to the translocation of older carbon. Importantly, in locations with reduced potential for redeposition of material, our results show that there is no significant or systematic difference between ages derived from bulk material, fine or coarse (plant macrofossil) material, providing confidence in the resulting age model. Crucially, in areas comprising complex terrain with extreme relief, we recommend dating macrofossils or bulk carbon rather than a fine fraction, or employing comprehensive dating of multiple sedimentary fractions to determine the most reliable fraction(s) for developing a robust chronological framework.

Clinoptilolite from zeolitized tuffs of Azerbaidzhan

1976 ◽  
Vol 40 (313) ◽  
pp. 501-511 ◽  
Author(s):  
M.-A. Kashkai ◽  
I. A. Babaev
Keyword(s):  
Previous Literature ◽  
Electron Microscopic ◽  
X Ray ◽  
Geological Conditions ◽  
Infra Red ◽  
Optical Electron ◽  
Lesser Caucasus

SummaryA study has been made of a large clinoptilolite deposit in the Lesser Caucasus (Azerbaidzhan SSR). The geological conditions have been examined and a number of samples investigated by optical, electron-microscopic, chemical, X-ray, thermal, and infra-red methods. Based on these investigations and on comparison with previous literature, mineralogical, chemical, and geochemical conclusions are drawn and conditions for clinoptilolite genesis are considered.

scholarly journals In situ physical and chemical characterisation of the Eyjafjallajökull aerosol plume in the free troposphere over Italy

2014 ◽  
Vol 14 (2) ◽  
pp. 1075-1092 ◽  
Author(s):  
S. Sandrini ◽  
L. Giulianelli ◽  
S. Decesari ◽  
S. Fuzzi ◽  
P. Cristofanelli ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Gamma Ray ◽  
Fine Fraction ◽  
Chemical Properties ◽  
Analytical Techniques ◽  
Ground Level ◽  
Coarse Fraction ◽  
Volcanic Plume ◽  
Physical And Chemical ◽  
Aerosol Plume

Abstract. Continuous measurements of physical and chemical properties at the Mt. Cimone (Italy) GAW-WMO (Global Atmosphere Watch, World Meteorological Organization) Global Station (2165 m a.s.l.) have allowed the detection of the volcanic aerosol plume resulting from the Eyjafjallajökull (Iceland) eruption of spring 2010. The event affected the Mt. Cimone site after a transport over a distance of more than 3000 km. Two main transport episodes were detected during the eruption period, showing a volcanic fingerprint discernible against the free tropospheric background conditions typical of the site, the first from April 19 to 21 and the second from 18 to 20 May 2010. This paper reports the modification of aerosol characteristics observed during the two episodes, both characterised by an abrupt increase in fine and, especially, coarse mode particle number. Analysis of major, minor and trace elements by different analytical techniques (ionic chromatography, particle induced X-ray emission–particle induced gamma-ray emission (PIXE–PIGE) and inductively coupled plasma mass spectrometry (ICP-MS)) were performed on aerosols collected by ground-level discrete sampling. The resulting database allows the characterisation of aerosol chemical composition during the volcanic plume transport and in background conditions. During the passage of the volcanic plume, the fine fraction was dominated by sulphates, denoting the secondary origin of this mode, mainly resulting from in-plume oxidation of volcanic SO2. By contrast, the coarse fraction was characterised by increased concentration of numerous elements of crustal origin, such as Fe, Ti, Mn, Ca, Na, and Mg, which enter the composition of silicate minerals. Data analysis of selected elements (Ti, Al, Fe, Mn) allowed the estimation of the volcanic plume's contribution to total PM10, resulting in a local enhancement of up to 9.5 μg m−3, i.e. 40% of total PM10 on 18 May, which was the most intense of the two episodes. These results appear significant, especially in light of the huge distance of Mt. Cimone from the source, confirming the widespread diffusion of the Eyjafjallajökull ashes over Europe.

scholarly journals Geochemical perspectives from a new aerosol chemical mass closure

2007 ◽  
Vol 7 (6) ◽  
pp. 1657-1670 ◽  
Author(s):  
B. Guinot ◽  
H. Cachier ◽  
K. Oikonomou
Keyword(s):  
Urban Areas ◽  
Conversion Factor ◽  
Major Ions ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Urban Environments ◽  
Data Set ◽  
K Value ◽  
Mass Closure ◽  
Chemical Mass Closure

Abstract. The aerosol chemical mass closure is revisited and a simple and inexpensive methodology is proposed. This methodology relies on data obtained for aerosol mass, and concentration of the major ions and the two main carbon components, the organic carbon (OC) and the black carbon (BC). Atmospheric particles are separated into coarse (AD>2 μm) and fine (AD<2 μm) fractions and are treated separately. For the coarse fraction the carbonaceous component is minor and assumption is made for the conversion factor k of OC-to-POM (Particulate Organic Matter) which is fixed to the value of 1.8 accounting for secondary species. The coarse soluble calcium is shown to display a correlation (regression coefficient f, y axis intercept b) with the missing mass. Conversely, the fine fraction is dominated by organic species and assumption is made for dust which is assumed to have the same f factor as the coarse mode dust. The fine mode mass obtained from chemical analyses is then adjusted to the actual weighed mass by tuning the k conversion factor. The k coefficient is kept different in the two modes due to the expected different origins of the organic particles. Using the f and k coefficient obtained from the data set, the mass closure is reached for each individual sample with an undetermined fraction less than 10%. The procedure has been applied to different urban and peri-urban environments in Europe and in Beijing and its efficiency and uncertainties on f and k values are discussed. The f and k coefficients are shown to offer consistent geochemical indications on aerosol origin and transformations. f allows to retrieve dust mass and its value accounting for Ca abundance in dust at the site of investigation may serve as an indicator of dust origin and aerosol interactions with anthropogenic acids. f values were found to vary in the 0.08–0.12 range in European urban areas, and a broader range in Beijing (0.01–0.16). As expected, k appears to be a relevant proxy for particle origin and ageing and varies in the 1.4–1.8 range. For Beijing, k exhibits high values of about 1.7 in winter and summer. Winter values suggest that fresh coal aerosol might be responsible for such a high k value, which was not taken into account in previous works.

scholarly journals Anthropogenic and natural constituents in particulate matter in the Netherlands

2010 ◽  
Vol 10 (11) ◽  
pp. 26513-26549 ◽  
Author(s):  
E. P. Weijers ◽  
M. Schaap ◽  
L. Nguyen ◽  
J. Matthijsen ◽  
H. A. C. Denier van der Gon ◽  
...  
Keyword(s):  
Particulate Matter ◽  
The Netherlands ◽  
Mineral Dust ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Sea Salt ◽  
Mitigation Strategies ◽  
Balanced Distribution ◽  
Chemical Distribution ◽  
Pm2.5 And Pm10

Abstract. To develop mitigation strategies for reducing concentrations of both PM2.5 (and PM10), the origin of particulate matter (PM) needs to be established. An intensive, one-year measurement campaign from August 2007 to August 2008 was carried out to determine the composition of PM10 and PM2.5 at five locations in the Netherlands, aiming at reducing the uncertainties on the origin of PM. Generally, a considerable conformity in the chemical composition of PM2.5 (and PM10) was observed. From all the constituents present in PM2.5, the secondary inorganic aerosol is the most dominant (42–48%), followed by total carbonaceous matter (22–37%). Contributions due to sea salt (maximum 8%), mineral dust and metals (maximum 5%) are relatively low. For the first time, a detailed overview can be presented of the composition of the coarse fraction. Compared to the fine fraction, contributions of the sea salt, mineral dust and metals are now larger resulting in a more balanced distribution between the various constituents. Through mass closure a considerable part of the PM mass could be defined (PM2.5: 80–94%). The chemical distribution on days with high PM levels showed a distinct increase of nitrate as well as in the mass not accounted for. Contributions of the remaining constituents remained equal of were lower (sea salt) when expressed in percentages. A correspondence between nitrate and the unknown mass was observed hinting at the presence of water on the filters. The contribution from natural sources in the Netherlands was estimated to be about 25% for PM10 and 20% for PM2.5.

scholarly journals PRODUCTION OF POPPED SORGHUM WITH USING MICROWAVE TREATMENT

2018 ◽  
Vol 18 (2) ◽  
Author(s):  
D. O. TYMCHAK ◽  
Y. Y. KUIANOV
Keyword(s):  
Microwave Radiation ◽  
Fine Fraction ◽  
Morphological Structure ◽  
Microwave Treatment ◽  
Coarse Fraction ◽  
Climatic Conditions ◽  
Technological Scheme ◽  
Human Organism ◽  
Sorghum Grains ◽  
High Yields

This article describes main methods of using the method of microwave treatment in food industry and in grain processing in particular. Main principles of this technology as well as using this technological approach for popping grain have been considered. Scientific works aimed at researching possibility of using microwave radiation for preparation of popped grains have been reviewed. Factors influencing the process of preparing popped grain have been considered; these factors include morphological structure and chemical composition of grains. Sorghum is one of the main food crops in the world agriculture (especially in such countries as India, PRC, Ethiopia, Morocco, Sudan) taking agriculture areas of about 50 million hectares. Popularity of growing sorghum in Ukraine can be explained in particular through its ability to produce high yields in warm and dry climatic conditions. Human organism does not performabsorption of nutrients from sorghum in full amount due to the fact that there are kafirins in endosperm of sorghum and these substances agglutinate starch granules. That is why a peculiar attention in this article has been paid to influence of microwave treatment on digestibility of sorghum starch and proteins. The goal of carrying out scientific researches consisted in defining parameters of microwave radiation influence on the process of popping sorghum grains depending on grain particle size (fractional composition) as well as in developing a technological scheme of popping sorghum.The process of microwave treatment of sorghum grains has been researched. Microwave processing of grains was performed in microwave oven with working frequency of 2,450 MHz and the following levels of power were applied: 450, 600, 700 W with exposure time 120–150 s. Grain sorghum “Fulgus” was used for carrying out the research. Effect of microwave radiation on the start of the popping process and on yield of popped sorghum previously divided into two fractions has been determined. In addition to this influence of microwave treatment on increasing the volume of coarse fraction and fine fraction sorghum grains has been determined. A technological scheme of producing popped sorghum with using microwave treatment has been developed. Thistechnological scheme includes the following operations: cleaning grains from various contaminations, calibration, conditioning, microwave treatment, cooling, optical sorting, packing. The technological process within the developed technological scheme has been described and a clear sequence of operations for preparation of popped sorghum has been provided. The proposedtechnological scheme has two variants of execution. The first variant consists in using air-sieve separators and concentrators or combined machines for cleaning and calibration of sorghum grains. The second variant consists in combining procedures of cleaning and calibration into a single stage with a help of up-to-date technological equipment.

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