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1.
Pan QJ Odoh SO Asaduzzaman AM Schreckenbach G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(5):1458-1466
To model the structures of dissolved uranium contaminants adsorbed on mineral surfaces and further understand their interaction with geological surfaces in nature, we have performed periodic density funtional theory (DFT) calculations on the sorption of uranyl species onto the TiO2 rutile (110) surface. Two kinds of surfaces, an ideal dry surface and a partially hydrated surface, were considered in this study. The uranyl dication was simulated as penta‐ or hexa‐coordinated in the equatorial plane. Two bonds are contributed by surface bridging oxygen atoms and the remaining equatorial coordination is satisfied by H2O, OH?, and CO32? ligands; this is known to be the most stable sorption structure. Experimental structural parameters of the surface–[UO2(H2O)3]2+ system were well reproduced by our calculations. With respect to adsorbates, [UO2(L1)x(L2)y(L3)z]n (L1=H2O, L2=OH?, L3=CO32?, x≤3, y≤3, z≤2, x+y+2z≤4), on the ideal surface, the variation of ligands from H2O to OH? and CO32? lengthens the U? Osurf and U? Ti distances. As a result, the uranyl–surface interaction decreases, as is evident from the calculated sorption energies. Our calculations support the experimental observation that the sorptive capacity of TiO2 decreases in the presence of carbonate ions. The stronger equatorial hydroxide and carbonate ligands around uranyl also result in U?O distances that are longer than those of aquouranyl species by 0.1–0.3 Å. Compared with the ideal surface, the hydrated surface introduces greater hydrogen bonding. This results in longer U?O bond lengths, shorter uranyl–surface separations in most cases, and stronger sorption interactions. 相似文献
2.
S. M. Hasany A. M. Shamsi M. A. Rauf 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(1):51-54
The sorption of hafnium on hydrous titanium oxide (TiO2·1.94 H2O) has been studied in detail. Maximum sorption of hafnium can be achieved from a pH 7 buffer solution containing boric acid and sodium hydroxide using 50 mg of the oxide after 30 minutes shaking. The value ofk
d, the rate constant of intraparticle transport for hafnium sorption, from 0.01M hydrochloric and perchloric acid and pH 7 buffer solutions has been found to be 17 mmole·g–1·min–2. The kinetics of hafnium sorption follows Lagergren equation in 0.01M HCl solution only. The values of the overall rate constantK=6.33·10–2 min–1 and of the rate constant for sorptionk
1=6.32·10–2 min–1 and desorptionk
2=2.28·10–5 min–1 have been evaluated using linear regression analysis. The value of correlation factor() is 0.9824. The influence of hafnium concentration on its sorption has been examined from 4.55·10–5 to 9.01·10–4 M from pH 7 buffer solution. The sorption data followed only the Langmuir sorption isotherm. The saturation capacity of 9.52 mmole·g–1 and of a constant related to sorption energy have been estimated to be 2917 dm3·mole–1. Among all the additional anions and cations tested only citrate ions reduce the sorption significantly. Under optimal experimental conditions selected for hafnium sorption, As(III), Sn(V), Co(II), Se(IV) and Eu(III) have shown higher sorption whereas Mn(II), Ag(I) and Sc(III) are sorbed to a lesser extent. It can be concluded that a titanium oxide bed can be used for the preconcentration and removal of hafnium and other metal ions showing higher sorption from their very dilute solutions. The oxide can also be employed for the decontamination of radioactive liquid waste and for pollution abatement studies. 相似文献
3.
S. G. Sarkar S. V. Bandekar P. M. Dhadke 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(3):803-807
Liquid-liquid extraction of Th(IV) and U(VI) has been investigated by commercial extractant PC-88A in toluene. The optimum conditions for extraction of these metals have been established by studying the various parameters like acid concentration/pH, reagent concentration, diluents and shaking time. The extraction of Th(IV) was found to be quantitative with 0.1–1.0M HNO3 acid and in the pH range 1.0–4.0 while U(VI) was completely extracted in the pH range 1.0–3.5 with 2.5·10–2M and 2.·10–2M PC-88A in toluene, respectively. The probable extracted species have been ascertained by log D-log C plot as ThR4·4HR and UO2R2·2HR, respectively. The method permits separation of Th(IV) and U(VI) from associated metals with a recovery of 99.0%. 相似文献
4.
Dong-Yong Chung Heui-Seung Seo Jae-Won Lee Han-Beom Yang Eil-Hee Lee Kwang-Wook Kim 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):123-129
A feasibility and basic study to find a possibility to develop such a process for recovering U alone from spent fuel by using
the methods of an oxidative leaching and a precipitation of U in high alkaline carbonate media was newly suggested with the
characteristics of a highly enhanced proliferation-resistance and more environmental friendliness. This study has focused
on the examination of an oxidative leaching of uranium from SIMFUEL powders contained 16 elements (U, Ce, Gd, La, Nd, Pr,
Sm, Eu, Y, Mo, Pd, Ru, Zr, Ba, Sr, and Te) using a Na2CO3 solution with hydrogen peroxide. U3O8 was dissolved more rapidly than UO2 in a carbonate solution. However, in the presence of H2O2, we can find out that the leaching rates of the reduced SIMFUEL powder are faster than the oxidized SIMFUEL powder. In carbonate
solutions with hydrogen peroxide, uranium oxides were dissolved in the form of uranyl peroxo-carbonato complexes. UO2(O2)
x
(CO3)
y
2−2x−2y
, where x/y has 1/2, 2/1. 相似文献
5.
Steven C. Smith Shane M. Peper Matthew Douglas Kate L. Ziegelgruber Erin C. Finn 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):617-621
Bench scale experiments were conducted to determine the dissolution characteristics of UO2, U3O8, and UO3 in aqueous peroxide-containing carbonate solutions. The experimental parameters investigated included carbonate countercation
(NH4
+, Na+, K+, and Rb+) and H2O2 concentration. The carbonate countercation had a dramatic influence on the dissolution behavior of UO2 in 1 M carbonate solutions containing 0.1 M H2O2, with the most rapid dissolution occurring in (NH4)2CO3 solution. The initial dissolution rate (y) of UO2 in 1 M (NH4)2CO3 increased linearly with peroxide concentration (x) ranging from 0.05 to 2 M according to: y = 2.41x + 1.14. The trend in initial dissolution rates for the three U oxides under study was UO3 ≫ U3O8 > UO2. 相似文献
6.
Robin D. Rogers Lynn K. Kurihara Matthew M. Benning 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(5):645-658
The reaction of UO2(ClO4)·nH2O with 15-crown-5 and 18-crown-6 in acetonitrile yielded the title complexes. [UO2(OH2)5] [ClO4]2·3(15-crown-5)·CH3CN crystallizes in the triclinic space groupPT with (at–150°C)a=8.288(6),b=12.874(7),c=24.678(7) Å, =82.62(4), =76.06(5), =81.06(5)°, andD
calc=1.67 g cm–3 forZ=2 formula units. Least-squares refinement using 6248 independent observed reflections [F
o5(F
o)] led toR=0.111. [UO2(OH2)5] [ClO4]2·2(18-crown-6)·2CH3CN·H2O is orthorhombicP212121 with (at–150 °C)a=12.280(2),b=17.311(7),c=22.056(3) Å,D
calc=1.68 g cm–3,Z=4, andR=0.032 (3777 observed reflections). In each complex the crown ether molecules are hydrogen bonded to the water molecules of the pentagonal bipyramidal [UO2(OH2)5]2+ ions, each crown ether having exclusive use of two hydrogen atoms from one water molecule and one hydrogen from another water molecule. In the 15-crown-5 complex the remaining hydrogen bonding interaction is between one of the water molecules and one of the perchlorate anions. The solvent molecule has a close contact between the methyl group and a perchlorate anion suggesting a weak interaction. There are a total of three U-OH...OClO3 hydrogen bonds to the two perchlorate anions in [UO2(OH2)5] [ClO4]2·(18-crown-6)·2CH3CN ·H2O. The remaining coordinated water hydrogen bond is to the uncoordinated 2H2O molecule, which in turn is hydrogen bonded to a perchlorate oxygen atom and an acetonitrile nitrogen atom. One solvent methyl group interacts with an anion, the other with one of the 18-crown-6 molecules. Unlike the 15-crown-5 structure, the hydrogen bonding in this complex results in a polymeric network with formula units joined by hydrogen bonds from one of the solvent molecules and the uncoordinated water molecule.
Supplementary data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82051 (37 pages).For Part 10, see reference [1]. 相似文献
7.
Zusammenfassung Der direkte Nachweis von H3O+-Ionen bzw. OH–-Ionen in zeolithischen Germanaten wird durch UR-spektroskopische Untersuchungen erbracht. Hydronium-Ionen liegen vor beiM(I)3HGe7O16·nH2O sowie bei Ba- und Pb-Zeolithen der FormM(II)2–x
H2x
Ge7O16·nH2O, während man in Ba- und Pb-Zeolithen der ZusammensetzungM(II)2+x
Ge7O16(OH)2x
·nH2O Hydroxyl-Ionen beobachtet.
Mit 2 Abbildungen 相似文献
By IR-spectroscopic investigations of zeolitic germanates of formulaM(I)3HGe7O16·nH2O as well as of Ba- and Pb-zeolites of formulaM(II)2–x H2x Ge7O16·nH2O the presence of H3O+-ions can be detected. On the other hand inM(II)2+x Ge7O16(OH)2x ·nH2O (M=Ba, Pb) hydroxyl ions are observed.
Mit 2 Abbildungen 相似文献
8.
O. E. Sherif Y. M. Issa M. E. M. Hassouna S. M. Abass 《Monatshefte für Chemie / Chemical Monthly》1993,124(6-7):627-635
Summary Solid complexes of 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazans were prepared and characterized by elemental analysis, IR, NMR, TGA and DTA analyses. Based on these studies, the suggested general formula for the complexes is [M(HL)
m
(OH–)
n
or (NO
3
–
or Cl–)
x
·(H2O)
y
or (C2H5OH orDMSO)
z
, where HL=formazanM=Ce3+, Th4+, and UO
2
2+
,m=1–2,n=0–3,x=0–3,y=0–4 andz=0–3. The metal ions are expected to have coordination numbers 6–8.
Strukturuntersuchungen an 3-Acetyl-1,5-diaryl- und 3-Cyan-1,5-diaryl-formazan-Chelaten mit Cer(III), Thorium(IV) und Uran(VI)
Zusammenfassung Die hergestellten Chelate wurden mittels Elementaranalyse, IR, NMR, TGA und DTA charakterisiert. Darauf basierend wird die generelle Formel [M(HL) m (OH–) n bzw. (NO 3 – oder Cl–) x ·(H2O) y oder (C2H5OH bzw.DMSO) z ] vorgeschlagen, wobei HL=Formazan,M=Ce3+, Th4+ oder UO 2 2+ ,m=1–2,n=0–3,x=0–3,y=0–4 undz=0–3. Die Metallionen haben Koordinationszahlen von 6–8.相似文献
9.
Redox potentials: E(UO
2
2+
/UO
2
+
)=60±4 mV/NHE, E(U4+/U3+)=–630±4mV/NHE measured at 25°C in acidic medium (HClO4 1M) using cyclic voltametry are in accordance with the published data. From 5°C to 55°C the variations of the potentials of these systems (measured against Ag/AgCl electrode) are linear. The entropies are then constant: [S(UO
2
2+
/UO
2
+
)–S(Ag/AgCl)]/F=0±0.3 mV/°C, [S(U4+/U3+)–S(Ag/AgCl)]/F=1.5±0.3 mV/°C. From 5°C to 55°C, in carbonate medium (Na2CO3=0.2M), the Specific Ionic Interaction Theory can model the experimental results up to I=2M (Na+, ClO
4
–
, CO
3
2–
): E(UO2(CO3)
3
4–
/UO2(CO3)
3
5–
)=–778±5 mv/NHE (I=0, T=25°C, (25°C)=(UO2(CO3)
3
4–
, Na+)–(UO2(CO3)
3
5–
, Na+)=0.92 kg/mole, S(UO2(CO3)
3
4–
/UO2(CO3)
3
5–
=–1.8±0.5 mV/°C (I=0), =(Cl–, Na+)=(1.14–0.007T) kg/mole. The U(VI/V) potential shift, between carbonate and acidic media, is used to calculate (at I=0,25°C):
相似文献
10.
Tenu R. Gentil S. Baudu S. Counioux J. J. 《Journal of Thermal Analysis and Calorimetry》1999,58(1):89-101
The binary system H2O—UO2(NO3)2 was studied by solubility measurements and constant heat flow thermal analysis. Temperature and composition of the eutectic transformation between ice and uranyl nitrate hexahydrate were accurately defined. A new hydrate with 24 molecules of water decomposes at –21°C according to the peritectoid reaction<UO2(NO3)2·24H2O> <UO2(NO3)2·6H2O> + 18<H2O>The quasi-ideal model was applied to the solid—liquid equilibria, using the following reaction hypothesis:((UO
2
2+
)) + 2((NO
3
–
))+ h((H2O)) ((UO2OH+aq)) + ((H3O+aq + 2((NO
3
–
aq))A complete calculation of the binary system was carried out with a global ionic hydration number h equal to 9 in the aqueous solutions. It allowed to the melting enthalpies of uranyl nitrate hydrates.
This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献 11.
P. C. Mandal D. K. Bardhan S. N. Bhattacharyya 《Journal of Radioanalytical and Nuclear Chemistry》1995,191(2):349-359
Reactions of carbonate radical (CO3
–), generated by photolysis or by radiolysis of a carbonate solution with nickel(II)-iminodiacetate (Ni(II)IDA) were studied at pH 10.5 and ionic strength (I)==0.2 mol·dm–3. The stable product arising from the ligand degradation in the complex is mainly glyxalic acid. Time-resolved spectroscopy and transient kinetics were studied using flash photolysis. From the kinetic data it was suggested that the carbonate radical initially reacts with Ni(III)IDA with a rate constant (2.4±0.4)·106 dm3·mol–1·s–1 to form a Ni(II)IDA species which, however, undergoes a first-order transformation (k=2.7·102·s–1) to give a radical intermediate of the type Ni(II)RNHCHCO
2
–
) which rapidly forms an adduct containing a Ni–C bond. This adduct decays very slowly to give rise to glyoxalic acid. From a consideration of equilibrium between Ni(II)IDA and Ni(III)IDA, the one electron reduction potential for the Ni(III)IDA/Ni(II)IDA couple was determined to be 1.467 V. 相似文献
12.
C. Nguyen-Trung D. A. Palmer G. M. Begun C. Peiffert R. E. Mesmer 《Journal of solution chemistry》2000,29(2):101-129
Raman spectra have been used to identify and characterize aqueous hydroxouranyl(VI) complexes from 0.0038 to 0.647M at pH from 0.24 to 14.96 adjusted witheither HCF3SO3 and/or (CH3)4NOH under ambient conditions. In acidic media(0.24 pH 5.63), the existence of four species UO2+
2,(UO2)2(OH)3+,(UO2)2(OH)2+
2, and (UO2)3(OH)+
5 was confirmed. At high uranium concentrations(U 0.1M) and in strongly acidic solutions (pH 1.94), one additional weakband was observed at 883±1 cm–1. This band was assumed torepresent thespecies UO2+
2 with a reduced hydration number.In neutral and basic solutions(5.63 pH 14.96), five complexes were postulated: (UO2)3(OH)–
7,(UO2)3(OH)2–
8,(UO2)3(OH)4–
10,(UO2)3(OH)5–
11, andUO2(OH)2–
4, based on theassigned symmetrical stretching frequencies of the UO2 group in each complex.(UO2)3(OH)–
7 is the dominant species over mostof the pH range (4.53–12.78).The stability ranges of the other trinuclear species are:(UO2)3(OH)2–
8 (10.97 pH 13.83), (UO2)3(OH)4–
10 (10.97 pH 13.85) and (UO2)3(OH)5–
11(12.53 pH 14.10), which were identified for the first time. Finally, the monomericuranate anion OU2(OH)2–
4 dominates in highly basic solution (12.48 pH 14.96). The linear correlation between the symmetrical vibrational frequency v
1of the linear O = U = O entity and the average number
of hydroxide ligandscoordinated to each uranium atom in a given species has been reaffirmed andexpanded:
The v
1 correlation was also used to predict the vibration frequencies of theundetected monomers UO2(OH)+, UO2(OH)o
2,UO2(OH)–
3 at 848±2, 826±2, and804±2 cm±1, respectively. Characteristic band areas for eachuranyl hydrolyzedspecies were determined by Raman spectra decomposition and their hydrolysisquotients log Q, were calculated. Structures of the four triuranylspecies are proposed. 相似文献
13.
Yuying Zhang Haogui Zhao Qiaohui Fan Xiaobei Zheng Ping Li Shengping Liu Wangsuo Wu 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):395-404
Sorption of U(VI) from aqueous solution to decarbonated calcareous soil (DCS) was studied under ambient conditions using batch
technique. Soil samples were characterized by XRD, FT-IR and SEM in detail and the effects of pH, solid-to-liquid ratio (m/V), temperature, contact time, fulvic acid (FA), CO2 and carbonates on U(VI) sorption to calcareous soil were also studied in detail using batch technique. The results from experimental
techniques showed that sorption of U(VI) on DCS was significantly influenced by pH values of the aqueous phase, indicating
a formation of inner-sphere complexes at solid–liquid interface, and increased with increasing temperature, suggesting the
sorption process was endothermic and spontaneous. Compared to Freundlich model, sorption of U(VI) to DCS was simulated better
with Langmuir model. The sorption equilibrium could be quickly achieved within 5 h, and sorption results fitted pseudo-second-order
model well. The presence of FA in sorption system enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH
values. In absence of FA, the sorption of U(VI) onto DCS was an irreversible process, while the presence of FA reinforced
the U(VI) desorption process reversible. The presence of CO2 decreased U(VI) sorption largely at pH >8, which might due to a weakly adsorbable formation of Ca2UO2(CO3)3 complex in aqueous phase. 相似文献
14.
Solid-solute phase equilibria in aqueous solutions,VIII: The standard gibbs energy of La2(CO3)3·8H2O
Anh Mai Nguyen Erich Königsberger Harald Marhold Heinz Gamsjäger 《Monatshefte für Chemie / Chemical Monthly》1993,124(10):1011-1018
The solubilities of lanthanum carbonate La2(CO3)3·8H2O in solutionsS
0([H+]=H mol kg–1, [Na+]=(I–H) mol kg–1, [ClO
4
–
]=I mol kg–1) at various fixed partial pressures of CO2 have been investigated at 25.0 °C. The hydrogen ion molality and the total molality of La(III) ion in equilibrium with the solid phase were determined by e.m.f. and analytical methods, respectively. The stoichiometric solubility constants
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