Search Results
Abstract
The i-butyldodecylsulfoxide (BDSO) was synthesized. The extraction of uranium(VI) has been carried out with BDSO in toluene from various HNO3 concentrations. It was found that the distribution ratio increases with increasing nitric acid concentration up to 3.0 mol/l and then decreases. The distribution ratios also increase with increasing extractant concentration. The extracted species appears to be UO2(NO3)2·2BDSO and the equilibrium constant value is 15.2. The influence of temperature, sodium nitrate and oxalate concentrations on the extraction was also investigated, and the thermodynamic functions of the extraction reaction were obtained.
Abstract
Synthetic enstatite MgSiO3 was crystallized from a melt, quenched into water, and then annealed at 873 K. The product is the monoclinic polymorph with the unit cell parameters of a=0.9619(7), b=0.8832(3), c=0.5177(4) nm, β=108.27(5)°. Heat capacity was measured from 6 to 305 K using an adiabatic vacuum calorimeter. Thermodynamic functions for clinoenstatite differ by about 5% from those predicted after a thermodynamic model in the literature, but are very close to those measured for orthorhombic enstatite.
Abstract
Heat capacity of stoichiometric homogeneous spinel MgFe2O4 was measured from 5 to 305 K and thermodynamic functions were derived for temperatures up to 725 K using our previous high-temperature experimental data for the same sample. Anomaly in C p was found at very low temperatures. Experimental data below 20 K contain large (up to 25% near 5 K) error arising from the difference in the thermal history between the experimental series. Magnetic contribution to the low-temperature heat capacity was tested, and the linear function was found to fit experimental data better than the three-halves power derived from the spin-wave theory.
Abstract
A new extractant, N-octanoyl-2-methylpiperidine (OMPPD) has been synthesized. The extraction of U(VI) with N-octanoyl-2-methylpiperidine (OMPPD) in nitric acid has been studied. The dependence of the partition reaction of U(VI) on the concentrations of nitric acid, extractant, salting-out agent LiNO3, and temperature has been studied. In the light of the results, the extraction mechanism is discussed. The synergistic extracted complexes may be presented as UO2(NO3)2(OMPPD)2 . The related thermodynamic functions were calculated.
Abstract
The temperature dependence of the molar heat capacities of the tellurites PbTeO3, Pb2Te3O8 and Ge(TeO3)2 are determined. By statistical manipulation of the values obtained, the parameters in the equations for the corresponding compounds showing this dependence are determined using the least-squares method. These equations and the standard molar entropies are used to determine the thermodynamic functions Δ0 T S m 0, ΔT T H m 0 and (Φm 0+Δ0 T H m 0/T) for T′=298.15 K.
Abstract
The temperature dependence of the molar heat capacities of the tellurites Fe2(TeO3)3, Fe2TeO5 and Fe2Te4O11 were determined. By statistical manipulation of the values obtained, the parameters in the equations for the corresponding compounds showing this dependence were determined using the least-squares method. These equations together with the standard molar entropies were used to determine the thermodynamic functions Δ0 T S m 0, ΔT T,H m 0 and (Φm 0 + Δ0 T’ H m 0 / T) for T’=298.15 K.
Abstract
The results of recent developments on modelling of supramolecular ordering and physicochemical properties of molecular mixtures have been reviewed. The main attention is paid to the unified approach based on a generalized quasichemical model for a set of thermodynamic, dielectric and optical properties of mixtures, self-organized by specific bonding. Interrelations between thermodynamic, as well as dielectric, and optical properties of liquid mixtures, reflecting different molecular parameters, and the characteristics of quasichemical processes are presented. Applications for thermodynamic functions of mixing, permittivity, coefficients Rayleigh light scattering in molecular mixtures are considered. Data on thermodynamics of aggregation in mixtures have been obtained.
Abstract
The thermodynamic functions for the extraction of Sc3+ by liquid cation exchangers HD and HDEHP are determined radiometrically by the temperature coefficient method. The role of diluent dielectric constant on the extraction of Sc3+ by HD is also studied. The thermodynamic parameters determined indicated that the free energy variation for the extraction of Sc3+ by HD is mainly determined by the entropic terms arising from the hydration—dehydration process of the exchanged ions. In the case of HDEHP as extractant, the free energy variations are determined mainly by the entalpic terms of the system.
Summary
The sorption of 60Co2+, 115mCd2+ and 203Hg2+ from diluted solutions (as analogues for radioactive waste waters) on ETS-4 microporous titanosilicate was studied at 277, 293, 313 and 333 K by measuring the sorption kinetics using a batch-method. The sorption of these radiocations was compared by means of the distribution coefficient and of the sorption capacity. The maximum sorption capacities follow the order: 203Hg2+>115mCd2+³60Co2+. The thermodynamic functions of the sorption processes have been estimated. The increase of the absolute value of DG° with increasing temperatures shows that higher temperatures favor ionic exchange.
Abstract
The extraction coefficients for the actinyl ions extracted with tri-n-butyl phosphate (TBP) from 2.0M CH3 COOH, CH2 ClCOOH and CCl3 COOH in various temperatures have been measured. Distinct discontinuities of the lnD vs. 1/T plots were interpreted as a proof for the extraction mechanism changes. Results obtained were used to calculate the thermodynamic functions of the actinyl complexation in the aqueous phase and of the partition process. It is proposed that the inner-sphere complex formation increases in the order acetates < chloroacetates < trichloroacetates.
