The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform
Zdeněk Micka - One of the best experts on this subject based on the ideXlab platform.
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study of the family of glycine Selenious Acid addition compounds crystal structure of diglycine hydrogen selenite and vibrational spectra and dsc measurement of diglycine hydrogen selenite and monoglycine Selenious Acid crystals
IEEE Journal of Solid-state Circuits, 1998Co-Authors: Ivan Němec, Ivana Cisařova, Zdeněk MickaAbstract:Abstract The X-ray structural analysis of diglycine hydrogen selenite has been carried out. The substance crystallizes in the monoclinic space group P 2 1 / c , a =12.2651(7), b =4.8079(6), c =19.9550(10) A, β =122.745(4)°, V =989.73(14) A 3 , Z =4, R =0.0338 for 1647 observed reflections. The crystal structure is formed by zwitterions of glycine (CH 2 NH + 3 COO − ), glycinium cations (CH 2 NH + 3 COOH), and hydrogen selenite anions (HSeO − 3 ) connected by an extensive system of hydrogen bonds. The FTIR and FT Raman spectra of natural and deuterated diglycine hydrogen selenite and monoglycine–Selenious Acid crystals were recorded and interpreted. The FTIR spectra were studied down to a temperature of 90 K. DSC measurements for both compounds were carried out in the temperature range 95–380 K. No phase transition was found in this temperature range by DSC and FTIR. The existence of ferroelectric properties of diglycine hydrogen selenite and monoglycine–Selenious Acid crystals can be excluded because of the centrosymmetry of their space groups.
Masahiko Chikuma - One of the best experts on this subject based on the ideXlab platform.
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isolation and characterization of thiosalicylic Acid selenotrisulfide
Fresenius Journal of Analytical Chemistry, 1994Co-Authors: Yoshihiro Saito, Masahiko Chikuma, Akimasa Iwado, Yutaka SaitoAbstract:Thiosalicylic Acid selenotrisulfide(SeT) was prepared by the reaction of thiosalicylic Acid and Selenious Acid in methanol. The precipitated SeT was partially purified by an extensive washing with methanol and pure SeT was isolated by preparative high-performance liquid chromatography (HPLC) using a reverse phase column. The HPLC method was useful both in the analysis and the isolation of SeT.
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chromatographic analysis of the reaction between thiosalicylic Acid and Selenious Acid in methanol
Journal of Chromatography A, 1993Co-Authors: Yoshihiro Saito, Masahiko ChikumaAbstract:Abstract A high-performance liquid chromatographic method using a monophenylated reversed-phase column for the determination of thiosalicylic Acid, thiosalicylic Acid disulphide and thiosalicylic Acid selenotrisulphide was developed and applied to studies of the reaction between thiosalicylic Acid and Selenious Acid in methanol. It was confirmed that the molar ratio of Selenious Acid to thiosalicylic Acid is 1:4 at the equivalence point and that equimolar amounts of thiosalicylic Acid selenotrisulphide and thiosalicylic Acid disulphide are formed in this reaction. These results are consistent with previous information on this kind of reaction in an Acidic aqueous solution.
Ivan Němec - One of the best experts on this subject based on the ideXlab platform.
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study of the family of glycine Selenious Acid addition compounds crystal structure of diglycine hydrogen selenite and vibrational spectra and dsc measurement of diglycine hydrogen selenite and monoglycine Selenious Acid crystals
IEEE Journal of Solid-state Circuits, 1998Co-Authors: Ivan Němec, Ivana Cisařova, Zdeněk MickaAbstract:Abstract The X-ray structural analysis of diglycine hydrogen selenite has been carried out. The substance crystallizes in the monoclinic space group P 2 1 / c , a =12.2651(7), b =4.8079(6), c =19.9550(10) A, β =122.745(4)°, V =989.73(14) A 3 , Z =4, R =0.0338 for 1647 observed reflections. The crystal structure is formed by zwitterions of glycine (CH 2 NH + 3 COO − ), glycinium cations (CH 2 NH + 3 COOH), and hydrogen selenite anions (HSeO − 3 ) connected by an extensive system of hydrogen bonds. The FTIR and FT Raman spectra of natural and deuterated diglycine hydrogen selenite and monoglycine–Selenious Acid crystals were recorded and interpreted. The FTIR spectra were studied down to a temperature of 90 K. DSC measurements for both compounds were carried out in the temperature range 95–380 K. No phase transition was found in this temperature range by DSC and FTIR. The existence of ferroelectric properties of diglycine hydrogen selenite and monoglycine–Selenious Acid crystals can be excluded because of the centrosymmetry of their space groups.
Vb Brudanin - One of the best experts on this subject based on the ideXlab platform.
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Development of methods for the preparation of radiopure $^{82}$Se sources for the SuperNEMO neutrinoless double-beta decay experiment
Radiochim.Acta, 2020Co-Authors: Alimardon V. Rakhimov, Ch. Bourgeois, As Barabash, A. Basharina-freshville, S. Blot, M. Bongrand, D. Breton, R. Breier, E. Birdsall, Vb BrudaninAbstract:Abstract A radiochemical method for producing 82Se sources with an ultra-low level of contamination of natural radionuclides (40K, decay products of 232Th and 238U) has been developed based on cation-exchange chromatographic purification with reverse removal of impurities. It includes chromatographic separation (purification), reduction, conditioning (which includes decantation, centrifugation, washing, grinding, and drying), and 82Se foil production. The conditioning stage, during which highly dispersed elemental selenium is obtained by the reduction of purified Selenious Acid (H2SeO3) with sulfur dioxide (SO2) represents the crucial step in the preparation of radiopure 82Se samples. The natural selenium (600 g) was first produced in this procedure in order to refine the method. The technique developed was then used to produce 2.5 kg of radiopure enriched selenium (82Se). The produced 82Se samples were wrapped in polyethylene (12 μm thick) and radionuclides present in the sample were analyzed with the BiPo-3 detector. The radiopurity of the plastic materials (chromatographic column material and polypropylene chemical vessels), which were used at all stages, was determined by instrumental neutron activation analysis. The radiopurity of the 82Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for 208Tl was 8–54 μBq/kg, and for 214Bi the detection limit of 600 μBq/kg has been reached.
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Development of methods for the preparation of radiopure 82Se sources for the SuperNEMO neutrinoless double-beta decay experiment
'Walter de Gruyter GmbH', 2019Co-Authors: Rakhimov A, Basharina-freshville A., Blot S., Bongrand M., Breton D., Breier R., Birdsall E., As Barabash, Bourgeois C, Vb BrudaninAbstract:A radiochemical method for producing 82Se sources with an ultra-low level of contamination of natural radionuclides (40K, decay products of 232Th and 238U) has been developed based on cation-exchange chromatographic purification with reverse removal of impurities. It includes chromatographic separation (purification), reduction, conditioning (which includes decantation, centrifugation, washing, grinding, and drying), and 82Se foil production. The conditioning stage, during which highly dispersed elemental selenium is obtained by the reduction of purified Selenious Acid (H2SeO3) with sulfur dioxide (SO2) represents the crucial step in the preparation of radiopure 82Se samples. The natural selenium (600 g) was first produced in this procedure in order to refine the method. The technique developed was then used to produce 2.5 kg of radiopure enriched selenium (82Se). The produced 82Se samples were wrapped in polyethylene (12 μm thick) and radionuclides present in the sample were analyzed with the BiPo-3 detector. The radiopurity of the plastic materials (chromatographic column material and polypropylene chemical vessels), which were used at all stages, was determined by instrumental neutron activation analysis. The radiopurity of the 82Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for 208Tl was 8–54 μBq/kg, and for 214Bi the detection limit of 600 μBq/kg has been reached
George P Demopoulos - One of the best experts on this subject based on the ideXlab platform.
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stannous chloride an effective reducing agent for the removal of selenium iv from Acidic solution
Journal of Chemical Technology & Biotechnology, 2012Co-Authors: Nicolas Geoffroy, George P DemopoulosAbstract:BACKGROUND: Selenium removal from aqueous solutions can be a significant industrial problem, particularly in the metallurgical industry. In order to evaluate new reducing agents for this application, the reduction of Selenious Acid (H2SeO3) species with stannous ions (Sn2+) from weakly Acidic sulfate solutions containing 300 mg L−1 of selenium at 23 °C was studied. RESULTS: At initial pH values < 1.3 and molar ratio ≥ 2, less than 0.5 µg L−1 of selenium(IV) remained in solution after reduction. The reductive precipitation reaction started as soon as the stannous ions were added to the selenium-bearing solution and was completed in less than 5 min. The reaction products, characterized using X-ray diffraction, electron microscopy, particle and surface area measurements, X-ray photoelectron spectroscopy and chemical analysis, were composed of approximately equal amounts of tin selenide and tin dioxide. In addition to tin selenide a minor amount of selenium(IV) was found to be removed via adsorption on the tin dioxide formed in situ. Tests with a complex industrial solution also resulted in full and stable selenium precipitation. CONCLUSION: Stannous ions were found to be very effective in removing Selenious ions from synthetic and industrial solutions, producing very stable precipitates. Copyright © 2012 Society of Chemical Industry
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reductive precipitation of elemental selenium from Selenious Acidic solutions using sodium dithionite
Industrial & Engineering Chemistry Research, 2009Co-Authors: Nicolas Geoffroy, George P DemopoulosAbstract:In this work, the batch-reactor reduction of Selenious Acid (H2SeO3) species with sodium dithionite (Na2S2O4) from weakly Acidic sulfate solutions containing 300 mg/L of selenium at 23 οC was studied. The results showed that, at an initial pH value of 3, <0.5 μg/L of selenium(IV) remained in solution after reduction. The reductive precipitation reaction started as soon as dithionite was added in the selenium-bearing solution and was completed within less than a minute. However, it was determined that the precipitate was not stable in the presence of the dithionite decomposition byproduct and partially redissolved after several hours. The reaction product, characterized using X-ray diffraction, scanning electron microscopy, and chemical analysis, was determined to be red amorphous selenium. The precipitate, in addition to elemental selenium, was determined to contain monoclinic sulfur that was apparently formed via a side reaction pathway involving the decomp...