- Solvent-free ageing reactions of rare earth element oxides: From geomimetic synthesis of new metal-organic materials towards a simple, environmentally friendly separation of scandium
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The development of cleaner methodologies for the separation and processing of rare earth elements, including scandium and yttrium, is of high importance to materials science and industry. Here, we explore the use of simple, solvent-free and low-energy accelerated ageing reactions, inspired by geochemical processes of mineral weathering and neogenesis, to convert eight rare earth (RE) element oxides, specifically Sc, Y, La, Yb, Eu, Gd, Lu and Nd, into metal-organic oxalate derivatives. The reactions can readily be directed towards the formation of topologically distinct framework structures by introduction of additional oxalate ions in the form of simple alkaline metal or ammonium salts, providing not only simple, solvent-free access to novel metal-organic RE element architectures from readily accessible precursors, but also enabling a proof-of-principle of a simple route to separate scandium from at least seven other rare earth elements in a mixture of metal oxides. Specifically, the metal-organic structures obtained by ageing a mixture of scandium and other RE element oxides in presence of ammonium or sodium oxalates exhibit significant differences in aqueous solubility at boiling point of water, providing high scandium separation factors ranging from approximately 102-103, without requiring elaborate complexation reagents, toxic extractants, acidic media, or solvents other than water. This journal is
- Arhangelskis, Mihails,Fri??i?, Tomislav,Huski?, Igor
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supporting information
p. 4364 - 4375
(2020/07/14)
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- Unexpected Dimeric Spiro-Borate Complexes from Lewis-Acid Induced Transformation of Oxalatoborates
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Oxalatoborates were transformed into dimeric spiro-borate complexes by abstraction of oxalate ligands by Lewis acidic lanthanide trichlorides. Oxalatoborates with different anions and cations were investigated containing either bis-oxalatoborate or catecholato-oxalatoborate anions and lithium as well as EMIM (1-ethyl-3-methyl-imidazolium) and BMIM cations (1-n-butyl-3-methyl-imidazolium) from the respective ionic liquids (ILs). Depending on the amount of oxalate groups and the different cations, the oxalate groups are partly or fully abstracted and transferred to the lanthanides. The reaction of anhydrous PrCl3with Li[B(C6H4O2)(C2O4)] (lithium catecholato-oxalatoborate = Li[Catbox]) in pyridine (py) led to a conversion of the borate anion to the complex [B2O(C6H4O2)(py)4][PrCl5(py)] (1). The use of the ILs [EMIM][Catbox] and [BMIM][Catbox] indicates complete transfer of the oxalate groups to the lanthanide ions in reactions with lanthanide chlorides and nitrates yielding the well-known lanthanide oxalates Ln2(C2O4)3·10H2O (Ln = La, Eu). In contrast, the reaction of anhydrous YCl3with Li[B(C2O4)2] (lithium bis-oxalatoborate = Li[BOB]) in N,N-dimethylformamide (dmf) results in the formation of [B2O(C2O4)2(dmf)2] (2). Transfer of one oxalate group per boron onto the yttrium ion is revealed by the formation of the one-dimensional coordination polymer∞1[LiYCl2(C2O4)(dmf)3] (3) as additional product. The products were characterized by single-crystal X-ray diffraction as well as powder X-ray diffraction, IR spectroscopy and elemental analysis.
- Zottnick, Sven H.,Sorg, Jens R.,Sprenger, Jan A. P.,Finze, Maik,Müller-Buschbaum, Klaus
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supporting information
p. 53 - 59
(2017/02/05)
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- Proton conduction: Via lattice water molecules in oxalato-bridged lanthanide porous coordination polymers
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The proton conducting properties of two different structural types of porous coordination polymers [La2(ox)3(H2O)6]·4H2O (1) and [Er2(ox)3(H2O)6]·12H2O (2), where ox2- = oxalate, were investigated. 1 has a two-dimensional layered structure, whereas 2 has a three-dimensional structure. Both 1 and 2 have hydrophilic one-dimensional channels filled by lattice water molecules with hydrogen-bonding networks. The coordinated H2O molecules are Lewis acidic due to the lanthanoid ions donating protons to lattice-filling H2O molecules, thereby forming efficient proton conduction pathways. Alternating-current impedance analyses of 1 and 2 indicated significant proton conduction (σ = 3.35 × 10-7 S cm-1 at 368 K for 1, 1.79 × 10-6 S cm-1 at 363 K for 2 under RH = 100%, with Ea = 0.35 eV for 1 and 0.47 eV for 2), which was attributed to the Grotthuss mechanism via the lattice H2O molecules.
- Ishikawa, Ryuta,Ueno, Shunya,Yagishita, Sadahiro,Kumagai, Hitoshi,Breedlove, Brian K.,Kawata, Satoshi
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p. 15399 - 15405
(2016/10/13)
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- Proton Conduction Study on Water Confined in Channel or Layer Networks of LaIIIMIII(ox)3·10H2O (M = Cr, Co, Ru, La)
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(Chemical Equation Presented). Proton conduction of the LaIIIMIII compounds, LaM(ox)3·10H2O (abbreviated to LaM; M = Cr, Co, Ru, La; ox2- = oxalate) is studied in view of their networks. LaCr and LaCo have a ladder structure, and the ladders are woven to form a channel network. LaRu and LaLa have a honeycomb sheet structure, and the sheets are combined to form a layer network. The occurrence of these structures is explained by the rigidness versus flexibility of [M(ox)3]3- in the framework with large LaIII. The channel networks of LaCr and LaCo show a remarkably high proton conductivity, in the range from 1 × 10-6 to 1 × 10-5 S cm-1 over 40-95% relative humidity (RH) at 298 K, whereas the layer networks of LaCr and LaCo show a lower proton conductivity, ~3 × 10-8 S cm-1 (40-95% RH, 298 K). Activation energy measurements demonstrate that the channels filled with water molecules serve as efficient pathways for proton transport. LaCo was gradually converted to LaIIICoII(ox)2.5·4H2O, which had no channel structure and exhibited a low proton conductivity of less than 1 × 10-10 S cm-1. The conduction-network correlation of LaCo(ox)2.5·4H2O is reported.
- Okawa, Hisashi,Sadakiyo, Masaaki,Otsubo, Kazuya,Yoneda, Ko,Yamada, Teppei,Ohba, Masaaki,Kitagawa, Hiroshi
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p. 8529 - 8535
(2015/09/21)
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- Non-isothermal studies of the decomposition course of lanthanum oxalate decahydrate
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The thermal decomposition of lanthanum oxalate hydrate La2 (C2O4)3·10H2O till 900°C, in air, is investigated by non-isothermal gravimetry and differential thermal analyses. Intermediates and final solid products were characterized by X-ray diffraction (XRD) and IR-spectroscopy, the results show that La2(C2O4) 3·10H2O dehydrates in stepwise at 86-360°C and decomposes to La2O3 at 710°C through different intermediates, La2(C2O4)3, La2O(CO3)2 and La2O2CO3, that form at 400, 425 and 470°C, respectively. The final product La2O3 obtained at 800 °C has a surface area of 13.4 m2/g. The activation energy, ΔE of the observed thermal processes is obtained by the non-isothermal method.
- Balboul, Basma A.A.,El-Roudi,Samir, Ebthal,Othman
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p. 109 - 114
(2008/10/08)
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- Thermal analysis of La-Ba oxalate and role of γ-irradiation there on
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Lanthanum-barium oxalate was prepared and characterised by chemical and thermal analysis, X-ray diffraction and plasma emission spectroscopy. X-ray analysis showed the presence of a uniphase system. The kinetics of decomposition of oxalates of La and Ba as well as coprecipitated La-Ba oxalate have been investigated in air using dynamic thermogravimetry. The decomposition of mixed oxalate occurred with two over-lapping exotherms, corresponding to the decomposition of lanthanum oxalate followed by that of barium. The kinetics of decomposition of the irradiated salt was studied over the same temperature range as that of the unirradiated one in air and activation energies obtained from the slopes of Coat-Redfern's plot. Kinetic analyses following various theoretical models of solid state reactions showed that the best fit was obtained for a third order reaction and geometrical models. It was evident that though there was increase in the activation energy as well as frequency factor with increasing radiation dose, reverse phenomenon takes place in the case of reaction rate. The effect of γ-irradiation on the process and the mechanism involved therein has been discussed.
- Nayak,Bhatta
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- The use of Hi-Res TGA, TG-FTIR, HT-DRIFT and HT-XRD in the study of the decomposition of La2(C2O4)3·10H2O
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Using a combination of various techniques, more intermediate products could be detected during the thermal decomposition of La2(C2O4)3·10H2O than from conventional TGA measurements. In this way a more complete and detailed decomposition mechanism is proposed. Direct identification of the intermediate phases with HT-DRIFT revealed the presence of another oxycarbonate La2O(CO3)2, while with Hi-Res TGA a thermally unstable intermediate La2(CO3)3 was detected. All this information is consistent with the data obtained from TG-FTIR spectroscopic measurements. (C) 2000 Elsevier Science B.V.
- Vanhoyland,Nouwen,Van Bael,Yperman,Mullens,Van Poucke
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p. 145 - 151
(2008/10/08)
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- Thermal decomposition of rare-earth-doped calcium oxalate. Part 1. Doping with lanthanum, samarium and gadolinium
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The thermal decomposition of calcium oxalate doped with lanthanum, samarium or gadolinium has been investigated using thermogravimetry (TG) and differential thermal analysis (DTA). The kinetics of the decomposition steps have been studied by the non-isothermal TG technique. The doped oxalates decompose in a similar way to pure CaOx. After dehydration, decomposition of doped oxalates proceeds in two overlapping exothermic stages, i.e. decomposition of lanthanide oxalates followed by that of calcium oxalate. Samples heated up to 1000°C reveal the existence of CaO and Ln2O3 in separate phases.
- Patnaik, Usharani,Muralidhar
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p. 261 - 272
(2008/10/09)
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- Crystal structure of lanthanum(III) oxalate decahydrate
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La2(C2O4)3*10H2O crystallizes in space group P21/c (No. 14) with a = 11.382(6), b = 9.624(5), c = 10.502(8) Angstroem, β = 114.52(4) deg, and Z = 2.The structure (R = 0.029 for 3190 Mo Kα data) is composed of two-dimensional networks of edge-sharing 1:5:3 coordination polyhedra matching the (020) set of planes, each La(III) atom being surrounded by three η4 chelating oxalate groups and three aqua ligands with La-O distances in the range 2.518(4)-2.622(4) Angstroem.The remaining water molecules are disordered over seven principal sites in the intervening space.
- Huang, Sheng-Hua,Zhou, Gong-Du,Mak, Thomas C. W.
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p. 127 - 131
(2007/10/02)
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- Preparation of LaNiO3 powder from coprecipitated lanthanum-nickel oxalates
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Coprecipitation of lanthanum and nickel oxalates in a water-alcohol mixed solution of an oxalic acid resulted in a simultaneous and homogeneous deposition of the respective oxalate particles with a desired cation ratio. The coprecipitated oxalate could be readily converted to a fine powder (5 to 6 m2 g-1) of LaNiO3 by heating at 800 to 850° C. Examination of precipitation conditions established an optimum procedure for the powder synthesis of LaNiO3. Thermal analysis showed that La2NiO4 (high temperature form) is transiently produced prior to the formation of LaNiO3. Mixed valency of the nickel ion was quantitatively determined by means of the oxidation-reduction titration, suggesting that the chemical formula of the powders might be LaNiO2.85 to 2.90.
- Takahashi,Toyoda,Ito,Takatsu
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p. 1557 - 1562
(2008/10/08)
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- THERMAL ANALYSIS OF THE OXALATE HEXAHYDRATES AND DECAHYDRATES OF YTTRIUM AND THE LANTHANIDE ELEMENTS.
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Simultaneous thermogravimetry and differential thermal analysis data are presented for yttrium and the tervalent lathanide oxalate decahydrates (Y, La - Er excluding Pm) and hexahydrates (Y, Er - Lu). The dehydration and the oxalate and intermediate dioxy
- Fuller,Pinkstone
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p. 127 - 142
(2008/10/08)
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