| 1. |
- Datta, Shuvo Jit, et al.
(författare)
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Removal of Sr-90 from highly Na+-rich liquid nuclear waste with a layered vanadosilicate
- 2019
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 12:6, s. 1857-1865
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Tidskriftsartikel (refereegranskat)abstract
- Capture of trace amounts (parts per trillion or ppt level) of Sr-90 from highly Na+-rich (5 M or 115 000 parts per million) liquid wastes produced from reprocessing of spent nuclear fuel rods is crucial for continuous operation of nuclear power plants. However, no sorbents have shown such abilities. We now report that a novel layered vanadosilicate, SGU-7, with the unit cell parameters of a = 23.58 A, b = 30.04 A, c = 12.31 A, b = 100.28, and space group of P12(1)/a1, can effectively capture Sr-90 from a 5 M Na+ solution containing 6.2 ppt of Sr-90. It also effectively captures 1-ppb level Ra-226 from 2 M NaCl solution, and Cs+ and Sr2+ from groundwater, demonstrating that it can be immediately used to remedy groundwater and soil contaminated with Ra-226, Sr-90, and Cs-137.
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| 2. |
- Datta, Shuvo Jit, et al.
(författare)
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CO2 capture from humid flue gases and humid atmosphere using a microporous coppersilicate
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 350:6258, s. 302-
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Tidskriftsartikel (refereegranskat)abstract
- Capturing CO2 from humid flue gases and atmosphere with porous materials remains costly because prior dehydration of the gases is required. A large number of microporous materials with physical adsorption capacity have been developed as CO2-capturing materials. However, most of them suffer from CO2 sorption capacity reduction or structure decomposition that is caused by co-adsorbed H2O when exposed to humid flue gases and atmosphere. We report a highly stable microporous coppersilicate. It has H2O-specific and CO2-specific adsorption sites but does not have H2O/CO2-sharing sites. Therefore, it readily adsorbs both H2O and CO2 from the humid flue gases and atmosphere, but the adsorbing H2O does not interfere with the adsorption of CO2. It is also highly stable after adsorption of H2O and CO2 because it was synthesized hydrothermally.
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| 3. |
- Tung, Cao, et al.
(författare)
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Capture of iodine and organic iodides using silica zeolites and the semiconductor behaviour of iodine in a silica zeolite
- 2016
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 9:3, s. 1050-1062
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Tidskriftsartikel (refereegranskat)abstract
- During the reprocessing of spent nuclear fuel rods, a highly moist off-gas mixture containing various volatile radioactive species, such as iodine (I-2), organic iodides and nitric acid, is produced. Efforts have been made to devise materials, which can effectively capture radioactive iodine (I-2) and organic iodides from the off-gas mixture without being damaged by moisture, nitric acid, and I-2. In the investigation described herein, we observed that all-silica zeolites, such as silicalite-1 and Si-BEA, are stable in 5 M nitric acid and adsorb I-2, CH3I, and CH3CH2I from highly acidic off-gas mixture to much greater extents than activated carbon does. In particular, the hydrophobicity-intensified silicalite-1 performs best. We further found that I-2 forms a unique semiconducting three-dimensional supramolecular network within the silicalite-1 channels. The conductivity of the fully I-2 loaded silicalite-1 is observed to be ca. 10(4) S m(-1), which is ca. 10(8)-fold higher than that of solid I-2.
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| 4. |
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| 5. |
- Han, Lu, et al.
(författare)
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Silica-Based Nanoporous Materials
- 2014
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Ingår i: Zeitschrift für Anorganische und Allgemeines Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 640:3-4, s. 521-536
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Forskningsöversikt (refereegranskat)abstract
- Ordered nanoporous structures are among the most fascinating and industrially important materials currently in use. The archetypal zeolite material has now been joined by an eclectic array of new structures that exhibit porosity over a wide range of length scales and with order/disorder expressed in a multitude of ways. This raises the bar in terms of characterization and extends a real challenge to the scientific community to fully understand the properties and potential future applications of such materials. In this review we discuss the importance of modern microscopy tools combined with diffraction in this endeavour and show how the details of even the most complex quasi-crystalline nanoporous architectures can be elucidated. We show by using the appropriate spherical aberration (C-s) corrections in scanning transmission electron microscopy it is possible to decipher all the individual silicon and aluminum atoms in a zeolite structure. Automated routines for using large electron diffraction datasets for crystal structure determination of nanocrystals is described making the need for large single crystal synthesis less-and-less important. The power of complementary combinations of surface tools such as atomic force microscopy and high-resolution scanning electron microscopy is discussed to elucidate crystal growth mechanisms. For mesoporous materials synthesized from self-organized organic mesophases electron microscopy reveals the details of the complex hierarchy of porosity so crucial for the functional performance of the structure.
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| 6. |
- Sun, Qiming, et al.
(författare)
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High performance nanosheet-like silicoaluminophosphate molecular sieves : synthesis, 3D EDT structural analysis and MTO catalytic studies
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488. ; 2:42, s. 17828-17839
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Tidskriftsartikel (refereegranskat)abstract
- Nanosheet-like silicoaluminophosphate (SAPO) molecular sieves SAPO-34 (CHA-type) and SAPO-18 (AEI-type) with different silicon contents were synthesized under hydrothermal conditions by using tetraethylammonium hydroxide as the template. Three-dimensional electron diffraction tomography (3D EDT) technique was applied for ab initio structure solutions. Electron microscopy observations confirmed the existence of defects, i.e., intergrowth of CHA- and AEI-type frameworks caused by the different stacking manners of double 6-ring layers, but the layers were highly coherent along c direction. Compositions, acidities, chemical environments, and texture properties of all the samples were characterized by ICP, EDS, NH3-TPD, MAS NMR, and N-2 adsorption-desorption measurements. The catalytic performances of methanol-to-olefin (MTO) reactions over nano SAPO catalysts with different silicon contents were systematically studied. All of these catalysts showed excellent catalytic activity, among which SAPO-34 showed superior catalytic performance compared to SAPO-18. DFT calculations were utilized to study the different catalytic performance of CHA and AEI. Significantly to date, SAPO-34 with the lowest silicon content exhibited the longest catalyst lifetime and the lowest coking rate in the MTO reaction than any of the reported catalysts, tested under similar conditions. The straight 8-ring pore channel along the c direction provided the optimum diffusion pathway as well as the shortest diffusion length for reactant and generated olefins, thus significantly reduced the coking rate. This work demonstrates that a 3D EDT approach combined with TEM and EDS analysis from a single nanocrystal can provide a clear crystal structure, crystal orientation and compositional information of nanocrystals, which are useful for the better understanding of the catalytic performance of nanosized crystalline catalysts.
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