Search Results
Abstract
The extraction of Co2+ from a 0.1M ionic strength acetate buffer by acetylacetone, and a mixture of acetylacetone and pyridine or triethylamine was investigated at various temperatures. The enthalpy and entropy change data for the synergistic extraction support a model in which the Co2+ ion in the acetylacetonate complex expands its coordination number from four to six in order to accomodate the two N-base molecules. The steric hindrance caused by triethylamine is also reflected in the thermodynamic data.
Abstract
Field observations suggest that plutonium and americium in the environment are present in very different chemical forms in the interstitial waters of an intertidal sediment. Themodynamic modelling using the PHREEQE code predicts that plutonium is present entirely in oxidation state (V) as the PuO2CO 3 – ion, whereas americium is present entirely in oxidation state (III), largely as the uncharged Am(OH)CO3 species, but with significant concentrations of the Am3+ and the AmSO 4 + ions. There are, however, differences between these predictions and others published for a very similar system which apparently arise from uncertainties in the thermodynamic data. Field data cannot resolve these differences unambiguously.
Abstract
The extraction of Co2+ by mixtures of acetylacetone (acac) and either pyridine (Py), benzylamine (ba), triethylamine (tea) or tripyridylamine (tpa) bases in xylene solvent was investigated from an aqueous phase containing salts of LiCl, NaCl, KCl, RbCl and CsCl in concentrations varying up to 3M. The different hydration properties of the alkali metal cations is show to affect very slightly the synergistic solvent extraction of Co2+. This result, together with previously obtained thermodynamic data indicating the nonexistence of water molecules in the extracted synergistic species, may explain the fact that these salts have no effect on the extraction of Co(acac)2 (N-base)2.
Abstract
The heat capacities of selected inorganic binary and ternary alkali metal compounds are determined using differential scanning calorimetry (DSC). As part of an ongoing research program at Battelle Memorial Institute since 1983, the heat capacities of cesium and rubidium chalcogenides, aluminates, silicates and uranates in the temperature range 310 to 800 K have been added to the series of compounds. The measured data is to be combined with the standard enthalpies of formation and low temperature heat capacities to obtain reliable thermodynamic data on the alkali metal compounds to high temperatures.
Abstract
Differential thermal analysis has been used for quantitative determination of heats of aluminothermic redox reaction of MnO2 and V2O5 over a wide range of temperatures. Heat of reaction V2O5−Al and MnO2−Al systems have been determined using the calibration plot established. The experimentally determined values compare well with those predicted from thermodynamic data available in the literature. It has been found that V2O5−Al system involves a higher heat of reaction in comparison to the MnO2−Al system.
Polycaprolactone (PCL) is a new material used in orthopedics. It is characterized by an endothermic melting peak at about 61‡C, an endothermic decomposition peak at about 380‡C and an exothermic peak at about 453‡C. These three observed phenomena and the corresponding thermodynamic data made it easily possible to identify PCL among the other polymers previously examined with Differential Thermal Analysis (DTA).
Immobilization of ethylenesulfide on silica surface using acid and base catalysts
Adsorption and thermodynamic data
Abstract
The reaction of cyclic ethylene sulfide with 3-aminopropyltrimethoxysilane resulted in a new silylating agent, which was anchored onto a silica surface via the sol-gel procedure using hydrochloric acid or ammonium hydroxide as acid or base catalysts, respectively. Both organofunctionalized surfaces have the ability to adsorb divalent cations from aqueous nitrate solution. Through calorimetric titrations, the thermodynamic data of cation-basic center interactions were obtained. Exothermic enthalpy values were obtained for all interaction processes. The calculated free Gibbs energy is in agreement with the spontaneity of the reactions and the positive entropy values for all reactions are favorable for these systems.
Abstract
Polar n-alkylmonoamines of general formula H3C(CH2) n NH2 (n = 1, 3, 5) interacted with layered silicate vermiculite at the solid/liquid interface. The maximum amount of amine intercalated (N f ) inside the interlamellar space were 0.62, 0.46, and 0.38 mmol g−1, to give the following order of intercalation ethyl → butyl → hexylamines. The layered vermiculite solid was suspended in deionized water and calorimetrically titrated with this series of amines, to give favorable thermodynamic data, such as exothermic enthalpy, negative Gibbs free energy and positive entropy data.
Abstract
Synergistic extraction of hexavalent uranium and plutonium as well as trivalent americium was studied in HNO3 with thenoyl, trifluoro-acetone (HTTA)/1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutral donors viz, DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as dileunt. A linear correlation was observed when the equilibrium constant log Ks for the organic phase synergistic reaction of both U(VI) and Pu(VI) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of the donor (both mono- and bi-functional) indicating bi-functional donors also behave as mono-functional. This was supported by the thermodynamic data (
G
0,
H
0,
S
0) obtained for these systems. The organic phase adduct formation reactions were identified for the above systems from the thermodynamic data. In the Am(III) HTTA system log K
s
values of bi-functional donors were found to be very high and deviate from the linear plot (log K
s
vs. log K
h
) obtained for mono-functional donors, indicating that they function as bi-functional for the Am(III)/HTTA system studied. This was supported by high +ve
S
0 values obtained for this system.
Abstract
The influence of H2O–EtOH and H2O–Acetone mixed solvents at various compositions on the thermodynamics of complex formation reaction between crown ether 18-crown-6 (18C6) and glycine (Gly) was studied. The standard thermodynamic parameters of the complex [Gly18C6] (log K°, Δr H°, Δr S°) were calculated from thermochemical data at 298.15 K obtained by titration calorimetry. The complex stability and its formation enthalpy increase with increasing the non aqueous component concentration in both mixed solvents. The thermodynamic data were discussed on the basis of the solvation thermodynamic approach and the solvation contributions of the reagents and of the complex to the complex stability were analyzed.
