7558-02-3Relevant articles and documents
Enhanced liquid phase catalytic hydrogenation reduction of bromate over Pd-on-Au bimetallic catalysts
Zhou, Juan,Zhou, Xin,Li, Liyuan,Chen, Quanyuan
, p. 142 - 149 (2018)
Pd-Au/TiO2 bimetallic catalysts with varied Au contents were prepared by the sequential photocatalytic deposition method and the liquid phase catalytic hydrogenation reduction of bromate over these catalysts was investigated. The catalysts were characterized using X-ray diffraction, transmission electron microscope, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, H2 chemisorption and energy dispersive spectroscopy. Characterization results showed that Pd atoms were site-deposited on the surface of varied size Au cores and formed Pd-on-Au core-shell like bimetallic nanoparticles on TiO2. The bimetallic catalysts showed higher Pd dispersions and more exposed active sites than that of Pd/TiO2, and the amount of exposed active sites first increased then decreased with Au content. For a similar Pd loading, the bimetallic catalyst exhibited volcano-shape activity as a function of Au loading and the highest activity was identified on Pd-Au(1.0)/TiO2 with Au core size around 8.4 nm. In addition, the catalytic reduction of bromate could be well-fitted by the Langmuir-Hinshelwood model, reflecting an adsorption controlled mechanism.
Measurement of local reactivity at liquid/solid, liquid/liquid, and liquid/gas interfaces with the scanning electrochemical microscope: Principles, theory, and applications of the double potential step chronoamperometric mode
Slevin,Macpherson,Unwin
, p. 10851 - 10859 (1997)
A numerical model for scanning electrochemical microscopy (SECM) double potential step chronoamperometry (DPSC) has been developed and examined experimentally. The concept of this new mode of SECM is to generate a reactant in an initial potential step at a tip ultramicroelectrode (UME) positioned close to a target interface. The electrogenerated species diffuses from the tip to the interface, where it may be involved in a chemical process. The reactant is subsequently collected by electrolysis in a second potential step, and the form of the corresponding current-time curve provides information on the nature of the interaction between the initial tip-generated species and the interface. If the species is consumed in an irreversible interfacial process, the current flow during the second potential step is less than when the interface is inert with respect to the species of interest. The theoretical predictions are first examined with DPSC studies on the electrogeneration and collection of ferricyanide ions from aqueous ferrocyanide solutions, at a tip positioned close to aqueous/glass, aqueous/1,2-dichloroethane (DCE), and aqueous/air interfaces, as model examples of inert liquid/solid, liquid/liquid, and liquid/gas interfaces. The case of an active interfacial process is illustrated through studies of the electrogeneration and collection of Br2, from aqueous sulfuric acid solutions of potassium bromide, at a tip positioned close to aqueous/DCE and aqueous/air interfaces. The transfer of Br2 across these interfaces is found to be irreversible and effectively diffusion-controlled on the SECM time scale, putting a lower limit on the interfacial transfer rate constant of 0.5 cm s-1. The experiments carried out at aqueous/air interfaces represent the firs demonstration that SECM can be used to probe liquid/gas interfaces, thereby further diversifying the range of novel environments that can be studied with this instrument.
Synthesis and characterization of K8-x(H2) ySi46
Neiner, Doinita,Okamoto, Norihiko L.,Yu, Ping,Leonard, Sharon,Condron, Cathie L.,Toney, Michael F.,Ramasse, Quentin M.,Browning, Nigel D.,Kauzlarich, Susan M.
, p. 815 - 822 (2010)
A hydrogen-containing inorganic clathrate with the nominal composition, K7(H2)3Si46, has been prepared in 98% yield by the reaction of K4Si4 with NH4Br. Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. Elemental analysis and 1H MAS NMR confirmed the presence of hydrogen in this material. Type I clathrate structure is built up from a Si framework with two types of cages where the guest species, in this case K and H2, can reside: a large cage composed of 24 Si, in which the guest resides in the-6d position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position (cubic space group Pm3 n). Potassium occupancy was examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The highangle annular dark-field (HAADF) STEM experimental and simulated images indicated that the K is deficient in both the 2a and the 6dsites. 1H and 29Si MAS NMR are consistent with the presence of H2 in a restricted environment and the clathrate I structure, respectively. FTIR and 29Si{1H} CP MAS NMR results show no evidence for a Si-H bond, suggesting that hydrogen is present as H2 in interstitial sites. Thermal gravimetry (TG) mass spectrometry (MS) provide additional confirmation of H2 with hydrogen loss at ～400 °C.
CERTAIN ASPECTS OF HETEROPHASE ION EXCHANGE
Esikova, I. A.,Danilova, O. I.,Yufit, S. S.
, p. 1569 - 1572 (1991)
Ion exchange between an aqueous solution of KCl and a solution of tetraoctylammonium bromide in toluene has been studied at 20-70 deg C.Equilibrium exchange constants were measured.The free energy of the ion exchange is determined to a large extent by Coulombic interaction, which increases with decrease in the radius of the ion.The strength of the Q+X- bond is weakened on passing from the normal onium salt to the hydrate and the rate of ion exchange increases.The position of equilibrium during approach to it from different sides may be affected by different formation processes of complexes with low activity in respect to exchange.
Complex antimony(III) oxohalides: Synthesis and physicochemical properties
Panasenko,Zemnukhova,Kavun,Merkulov
, p. 163 - 168 (2012)
Complexes of the formula MSb2BrF4O (M = K, Rb, and NH4) were obtained from aqueous solutions of SbF3 and MBr and examined by chemical analysis, X-ray diffraction, thermal analysis, and IR, Raman, and 19F NMR spectroscopy. It was found that the red reflectance is 74-97% and the UV reflectance is 7-15%. The highest averaged reflectance (93%) was observed for KSb2BrF4O. The decomposition temperatures of MSb2BrF4O (M = K, Rb, and NH4) are 230, 197, and 223°C, respectively. Pleiades Publishing, Ltd., 2012.
Effect of anion doping on the thermal decomposition of potassium bromate
Das,Patnaik
, p. 879 - 883 (2000)
Structural defects were introduced into the potassium bromate (PB) lattice in the form of SO42 and Cl- ions in the process of crystal growth. It was assumed that these doped crystals PB(Cl-) and PB(SO42-) are composed of a two phase system, one being the perfect PB lattice and the other distorted regions due to induced defects. Isothermal decomposition of doped and normal PB samples was carried out gasometrically between the temperature range 653-663 K. The α-t plots reveal that the process occurs though initial gas evolution, acceleratory and decay stages. It also confirmed that doping enhances the rate of the reaction, the effect being more pronounced in the case of PB(SO42). The data are found to be well fitted to the Prout-Tompkins and Avrami-Erofe'ev mechanisms.
Synthesis and thermolysis of tris(triethoxysiloxy)aluminum and its complexes with potassium and sodium triethoxysilanolates
Shcherbakov,Basova,Khorshev,Malysheva,Domrachev
, p. 394 - 397 (2002)
Reaction of potassium (or sodium) triethoxysilanolate with AlBr 3 in benzene in a 3:1 or 4:1 ratio yields, respectively, tris(triethoxysiloxy)aluminum Al[OSi(OEt)3]3 or potassium (or sodium) tetrakis(triethoxysiloxy)alumin
A novel zero valent metal bismuth for bromate removal: Direct and ultraviolet enhanced reduction
Huang, Hong,Liu, Guoshuai,Wang, Xiuheng
, p. 4148 - 4155 (2020/02/04)
Bromate (BrO3-) is a carcinogenic and genotoxic by-product of the ozone disinfection process. In this study, a new zero-valent metal, bismuth, was used to reduce bromate. Bismuth samples were prepared by a solvothermal method and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The morphology of the bismuth powder was microspheres assembled with dense nanosheets. The kinetics of the direct bromate reduction by bismuth accorded with the pseudo-first-order kinetics model. The rate coefficients of the initial bromate concentration of 1.00 mg L-1, 2.50 mg L-1, 5.00 mg L-1 were identically close to 0.08 min-1. For 0.20 mg L-1, a reaction rate coefficient near 0.10 min-1 was obtained. The reducing products of bromate included bromide ions (Br-) and bismuth oxybromides. The bromate removal efficiency was enhanced remarkably in the presence of ultraviolet (UV) light, and the corresponding kinetic coefficient was 4 times higher than that of direct reduction. The mechanism of ultraviolet enhancement was analyzed by diffuse reflectance spectroscopy (DRS), the density functional theory (DFT) calculation, open circuit potential (OCP) analysis, photocurrent measurement and linear sweep voltammetry (LSV). Besides, the influence of dissolved oxygen (DO) on bromate reduction efficiency and the sustainability of the as-prepared sample were investigated. DO inhibited the reduction rate obviously, but showed a slight effect on the formation of bromide ions. In the long-term periodic experiments, the kinetic coefficient decay occurred in both direct (without UV irradiation) and ultraviolet assisted bromate reduction. However, the kinetic coefficient of UV-assisted reduction (0.115 min-1) was about 2 times higher than that of the direct reduction in the last cycle of periodic experiments. In conclusion, the novel bromate reduction strategy based on the zero-valent bismuth metal material has been proved efficient and sustainable, which contributes to the development of drinking water treatment technologies.
Eu(O2C-C≡C-CO2): An EuII Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion
Gramm, Verena K.,Smets, Daniel,Grzesiak, Ireneus,Block, Theresa,P?ttgen, Rainer,Suta, Markus,Wickleder, Claudia,Lorenz, Thomas,Ruschewitz, Uwe
, p. 2726 - 2734 (2020/02/20)
Anhydrous EuII–acetylenedicarboxylate (EuADC; ADC2? = ?O2C-C≡C-CO2 ?) was synthesized by reaction of EuBr2 with K2ADC or H2ADC in degassed water under oxygen-free conditions. EuADC crystallizes in the SrADC type structure (I41/amd, Z=4) forming a 3D coordination polymer with a diamond-like arrangement of Eu2+ nodes (msw topology including the connecting ADC2? linkers). Deep orange coloured EuADC is stable in air and starts decomposing upon heating in an argon atmosphere only at 440 °C. Measurements of the magnetic susceptibilities (μeff=7.76 μB) and 151Eu M?ssbauer spectra (δ=?13.25 mm s?1 at 78 K) confirm the existence of Eu2+ cations. Diffuse reflectance spectra indicate a direct optical band gap of Eg=2.64 eV (470 nm), which is in accordance with the orange colour of the material. Surprisingly, EuADC does not show any photoluminescence under irradiation with UV light of different wavelengths. Similar to SrADC, EuADC exhibits a negative thermal volume expansion below room temperature with a volume expansion coefficient αV=?9.4(12)×10?6 K?1.
Ion Exchange of Layered Alkali Titanates (Na2Ti3O7, K2Ti4O9, and Cs2Ti5O11) with Alkali Halides by the Solid-State Reactions at Room Temperature
Ogawa, Makoto,Saothayanun, Taya Ko,Sirinakorn, Thipwipa Tip
, p. 4024 - 4029 (2020/04/08)
Ion exchange of layered alkali titanates (Na2Ti3O7, K2Ti4O9, and Cs2Ti5O11) with several alkali metal halides surprisingly proceeded in the solid-state at room temperature. The reaction was governed by thermodynamic parameters and was completed within a shorter time when the titanates with a smaller particle size were employed. On the other hand, the required time for the ion exchange was shorter in the cases of Cs2Ti5O11 than those of K2Ti4O9 irrespective of the particle size of the titanates, suggesting faster diffusion of the interlayer cation in the titanate with lower layer charge density.
