Temat: scheelite - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Effective flotation separation of scheelite and calcite by applying methylene phosphonic acid sodium as a novel and green depressant
Autorzy:: Zhou, Hepeng
Wu, Handan
Guo, Jiangfeng
Tang, Xuekun
Huang, Wen
Luo, Xianping
Tematy:: scheelite
calcite
inhibition mechanism
flotation separation; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/24086193.pdf Link otwiera się w nowym oknie
Opis:: It is known that the flotation separation of scheelite and calcite is quite difficult due to their similar surface properites. To slove the problem, ethylenediaminetetra (methylene phosphonic acid) sodium (EDTMPS), an environmentally friendly reagent, was employed as an efficient depressant for flotation separation of calcite for the first time. In flotation experiments, it demonstrates that EDTMPS could strongly inhibit the flotation of calcite but barely affect the flotaiton behavior of scheelite, showing excellent dpress ability and selectivity. Based on a series of measurements including contact angle analysis, zeta potential, and XPS analysis, it was found that large amout of EDTMPS could be absorbed on the surface of calcite through strong chemical chelation reaction and thus inhibiting the further adsorption of NaOL. On the contrary, little EDTMPS was absorbed on that of scheelite owing to the negatively charged tungstate ions on the surface in relative terms. All in all, these results exhibit EDTMPS has excellent selective inhibition ability on calcite, which can be potentially applied in actual scheelite and calcite flotation separation process.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Flotation separation of scheelite from calcite using sodium polyacrylate as depressant
Autorzy:: Zhang, Y.
Chen, R.
Li, Y.
Wang, Y.
Luo, X.
Tematy:: scheelite
calcite
flotation
sodium polyacrylate
selective depression; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/110896.pdf Link otwiera się w nowym oknie
Opis:: The depressing properties of sodium polyacrylate (PA-Na) for calcite from scheelite were studied by microflotation experiments, zeta potentials, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation. Flotation results revealed that the selective depression effect of PA-Na was better than that of sodium silicate (Na2SiO3), and PA-Na can depress calcite more effectively than scheelite. The flotation recovery of scheelite and calcite kept at about 75% and 15% respectively at the pulp pH 9.3~9.6 and PA-Na concentration from 37.5 mg/dm3 to 50 mg/dm3. The zeta potentials of the minerals were significantly altered and the zeta potential of calcite became more negative than scheelite. XPS analysis deduced the occurrence of chemisorption between PA-Na and mineral surfaces, and the chemisorption of PA-Na on calcite was stronger than on scheelite. The results from DFT calculation demonstrated that the absolute value of the adsorption energy in the presence of PA-Na on the surface of calcite {104} was larger than on the surface of scheelite {111}. With the combination of the analysis, it could be concluded that calcite was more easily depressed than scheelite, and this finding remarkably matched with the microflotation experimental results. Furthermore, by using PA-Na as depressant, the flotation separation of scheelite from calcite can be achieved by controlling the flotation pH and PA-Na dosage.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Quinic acid as a novel depressant for efficient flotation separation of scheelite from calcite
Autorzy:: Huang, Zheyu
Kuang, Jingzhong
Yu, Mingming
Ding, Dan
Tematy:: quinic acid
scheelite
calcite
depression
selective adsorption; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/24085979.pdf Link otwiera się w nowym oknie
Opis:: There are difficulties to the conventional depressant for achieving separation of scheelite from calcite for the sake of their similar surface properties. The paper reported that a new depressant quinic acid (QA) was used for separating scheelite from calcite. The adsorption experiments, zeta potential experiment, contact angle, FTIR, XPS analysis and crystal chemistry analysis were utilized to known the depression mechanism of selectivity. The results showed that the recovery of calcite decreased drastically after QA added, whereas hardly influenced on scheelite. The tungsten concentrate could reach 66.24% WO3 grade and 89.46% recovery with 1.5×10-4 mol•L-1 QA at pH=9. The surface adsorption quantity of the QA on calcite was much greater than scheelite, which enhanced significantly the hydrophilicity of calcite surface. Due to its negative charge, QA could be adsorbed on the surface of calcite which had positive charge instead of that of scheelite with negative charge. Subsequently, free carboxyl groups of QA could chelated with Ca2+ species on the calcite surface to form stable chemical adsorption in order to prevent the Pb-BHA to form further adsorption on that, so there was no increase significantly on hydrophobicity. However, QA was obviously weak for adsorbing while Pb-BHA which could still be chemically adsorbed on scheelite surface of pre-treated with QA.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Placer scheelite and gold from alluvial sediments as indicators of the primary mineralization – examples from SW Poland
Autorzy:: Mikulski, S.Z.
Wierchowiec, J.
Tematy:: gold
scheelite
placer
prospecting
Lower Silesia
Sudetes; Pokaż więcej
Wydawca:: Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/2060602.pdf Link otwiera się w nowym oknie
Opis:: Detailed morphologic studies of detrital scheelite and gold grains from clastic Cenozoic sediments (alluvial and eluvial-colluvial) in two selected areas of the Lower Silesia region allowed to describe their specific features (size, roundness, lustre, and lack or remnants of primary intergrowths with other minerals). It allows estimating length of hydrodynamic transport and distance from the source area. Such features are also an important tool in determining the source of ore mineralization and to establish the parent area for detrital accumulations. Moreover, electron microprobe (EMPA) investigation of detrital gold allowed to recognized internal structure and chemical composition of placer gold grains. The grains commonly revealed zonal structures due to chemical supergene gold mobility recognized nearly in all studied pan-concentrate samples.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Effect of manganese ions addition orders on the flotation behavior of scheelite
Autorzy:: Lu, Kuanwei
Chen, Rong
Zhang, Ying
Luo, Hongying
Yang, Hu
Cai, Jiaozhong
Tematy:: manganese ion
addition order
scheelite
sodium silicate
flotation; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/1845215.pdf Link otwiera się w nowym oknie
Opis:: In this study, the effect of MnCl2 on scheelite flotation with sodium oleate (NaOL) as a collector and sodium silicate as a depressant was assessed by a combination of flotation experiments, Fouriertransform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and solution chemistry. The flotation experiments confirmed that the addition of MnCl2 before sodium silicate showed an adverse effect on flotation and the recovery of scheelite gradually decreased as the amount of MnCl2 was increased. When MnCl2 was added afte r sodium silicate, the recovery of scheelite gradually increased with an increase in the amount of MnCl2. The results of FTIR, XPS, and solution chemistry indicated that MnCl2 acted on the surface of scheelite in the form of manganese ions. When MnCl2 was added before sodium silicate, manganese ions adsorbed on the surface of scheelite reacted with sodium silicate to form a hydrophilic silicate, which covers the surface of scheelite and blocks the adsorption of NaOL. However, when MnCl2 was added after sodium silicate, manganese ions are continued to be adsorbed on the surface of scheelite, which increases the cations on the surface of scheelite, and hence the condition becomes conducive for the interaction between scheelite and NaOL.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Application of diethylenetriaminepenta pentasodium salt as an eco-friendly depressant to effectively improve the flotation separation of scheelite and calcite
Autorzy:: Zhou, Hepeng
Wu, Handan
Guo, Jiangfeng
Tang, Xuekun
Huang, Wen
Luo, Xianping
Tematy:: flotation
scheelite
calcite
diethylenetriaminepenta pentasodium salt
depressant
adsorption; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/27323649.pdf Link otwiera się w nowym oknie
Opis:: Diethylenetriaminepenta (methylene-phosphonic acid) pentasodium salt (DTPMPA), an eco-friendly reagent, was tried for the first time as a depressant for flotation separation of scheelite from calcite. Micro-flotation tests show that DTPMPA can selectively depress the floatability of calcite. In contrast, DTPMPA barely affects the flotation behavior of scheelite. Based on the selective depress effect, floatation separation of scheelite and calcite can be effectively achieved by using DTPMPA as depressant in artificially mixed minerals flotation tests. Based on a series of measurements, it found the surface of calcite was positively charged due to the existence of Ca ion site, which can be chelated with –PO3H- functional group on the surface of DTPMPA. In the flotation process, DTPMPA can be chemically absorbed on the surface of calcite to inhibit further collector adsorption. On contrast, little DTPMPA was adsorbed on the surface of scheelite due to the spatial site resistance and electrostatic repulsion induced by surface WO42+. All in all, these results exhibit DTPMPA has excellent selective depression ability on calcite, which can be potentially applied in the actual scheelite flotation process.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Acidified water glass in the selective flotation of scheelite from calcite, Part I: performance and impact of the acid type
Autorzy:: Kupka, Nathalie
Möckel, Robert
Rudolph, Martin
Tematy:: acidified water glass
scheelite calcite separation
froth flotation; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/109345.pdf Link otwiera się w nowym oknie
Opis:: To improve the performance of sodium silicate in scheelite flotation and allow the selective separation of scheelite from other semi-soluble salt-type minerals such as calcite, three acids, sulfuric, oxalic and for the first time hydrochloric are used to acidify sodium silicate (also called water glass). A literature review of previous usage of acidified water glass shows that no comparison between acids was made before, that comparisons with alkaline water glass were limited and that the idea that acidified water glass is more efficient at lower dosages has not been proven in scheelite flotation. As a consequence, the impact of the acid type, the ratio between acid and sodium silicate and acid dosage is tested in single mineral flotation and batch flotation experiments. All three acids allow a higher performance of acidified water glass compared to alkaline water glass at lower dosages and with little addition of acid: the tungsten recovery and grade are improved while silicates and to a lesser extent calcium-bearing minerals float less. The dosage of acid is less determining than the mass ratio of the acid to sodium silicate, except in the case of hydrochloric acid. Overall, the acid type does not matter as all three acids perform well in flotation, whereby oxalic and hydrochloric acid are better.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant
Autorzy:: Kupka, Nathalie
Kaden, Peter
Jantschke, Anne
Schach, Edgar
Rudolph, Martin
Tematy:: acidified water glass
scheelite calcite separation
froth flotation
mechanism; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/1845224.pdf Link otwiera się w nowym oknie
Opis:: Sodium silicate is one of the main depressants against calcite and fluorite in the scheelite flotation industry. In the first part of this article, the authors acidified sodium silicate (AWG) with three acids (sulfuric, oxalic and hydrochloric) to improve its performance. Results showed that acidified water glass outperforms alkaline water glass in terms of selectivity: it increases mainly the grade by further depressing silicates and calcium-bearing minerals. In most cases, AWG requires lower dosages to do so. The effect of acidified water glass is evaluated through Mineral Liberation Analysis (MLA), froth analysis, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy in order to hypothesize its mechanism. MLA shows that AWG affects silicates and sulfides more intensely than semi-soluble salttype minerals. Froth observations indicate other species in solution associated to the acid having an impact on the flotation results. Raman spectroscopy and NMR measurements indicate that the solution undergoes deep depolymerization when water glass is acidified. Lower molecular weight silica species, specifically Si-O monomers such as SiO(OH)3- will be responsible for the depression of the gangue minerals and are the drivers of the selectivity of AWG, more than orthosilicic acid. Depolymerization is more or less effective depending on the mass ratio of the acid to water glass and depending on the acid.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Studies of temperature and fabrication methods influence on structure and microstructure of BiNbO4 microwave electroceramics
Badania wpływu temperatury i procesu wytwarzania na strukturę oraz mikrostrukturę mikrofalowej ceramiki BiNbO4
Autorzy:: Płońska, M.
Czekaj, D.
Tematy:: niobian bizmutu
struktura szelito-podobna
ceramika
bismuth niobate
scheelite-like structure
microwave ceramics; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/352991.pdf Link otwiera się w nowym oknie
Opis:: The bismuth-based ceramics are well known as potential materials for microwave or microelectronics applications. One of them is a bismuth niobate (BiNbO4), which belongs to the family of the scheelite-like stibiotantalite structure A3+B5+O4. This low temperature co-fired dielectric ceramics is also reported as a good microwave dielectric material, using i.e. in multilayer microwaves systems. In the present studies depends of fabrication methods and temperature conditions on basic properties of bulk BiNbO4 are reported. Technological process included two stages. First, the ceramic powder was obtained from the high purity oxides (99.99%), by MOM method. The second stage involved consolidation of such prepared powders by free sintering and the hot uniaxial pressing methods. Goal of this study was to investigate how the fabrication processes i.e. temperature and sintering conditions influence on prepared powders and samples of bismuth niobate, like its structure and microstructure.
Ceramika na bazie bizmutu znana jest jako potencjalny materiał do zastosowan w technice mikrofalowej oraz mikroelektronice. Jednym z jej przedstawicieli jest niobian bizmutu (BiNbO4), który należy do rodziny związków o strukturze szelito podobnej, tantalanu antymonu A3+B5+O4. Ceramika dielektryczna tego typu, wypalana niskotemperaturowo, przedstawiana jest również jako materiał o dobrych właściwościach mikrofalowych, wykorzystywany np.: w wielowarstwowych układach mikrofalowych. W przedstawionej pracy omówiono wpływ stosowanych metod wytwarzania oraz ich warunków temperaturowych, na podstawowe właściwości ceramiki BiNbO4. Proces technologiczny składał sie z dwóch etapów. W pierwszym z nich, technika MOM otrzymano proszki ceramiczne z wysokiej czystości tlenków (99.99%). Drugi etap obejmował zagęszczanie przygotowanych proszków za pomocą metod spiekania swobodnego i jednoosiowego prasowania na gorąco. Celem pracy było zbadanie wpływu procesu wytwarzania, tzn. temperatury i metod spiekania na otrzymane proszki oraz próbki ceramiczne BiNbO4, na ich strukturę oraz mikrostrukturę.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The temperature - and stress fields of valves of IC engine
Autorzy:: Jaskólski, J.
Krzyżak, R.
Tematy:: intake valve
output valve
YSZ
ferberite
scheelite
silicides
pyroxene
composite
joining of materials
thermal conductivity
radiative transfer
thermal expansion; Pokaż więcej
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Powiązania:: https://bibliotekanauki.pl/articles/243403.pdf Link otwiera się w nowym oknie
Opis:: The paper concerns building up one exhaust valve of composite-steel and two intake ceramics-steel valves of a hypothetical adiabatic engine. The input temperatures were computed using three diverse FORTRAN95 programs, solving a shortened optical integral equation with radiative transfer, transient differential equation while starting and switching off the engine and a rod like diff. Equation with 'progonka' (Thomas) solution. The ANSYS11 programme was fed up with the output of the programs. It turns out that, generally, a mineralogical, crystal-chemical approach to the joining of materials results in stresses known from the common metal engines. Such problems as CTE enhancing (partly hypothetical) by means of doping the anionic compounds by cationic ones, swelling of structures, compressibility versus coefficient of thermal expansion (CTE) , compatibility of crystal motifs while joining, thermal shock resistance, switching the bonds, mechanical longevity, radiation protection etc were addressed. It turns out that true nature of the temperature and stress field, especially of the exhaust valve is closer to the FORTRAN temperature computation than, e.g. From the heat film coefficients (ANSYS11).
Dostawca treści:: Biblioteka Nauki

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