Self-association and association of tri-n-butyl phosphate (TBP) in different diluents

The interact ion of tri-n-butyl phosphate (TBP) with diluents and its self-association have been investigated. The corresponding equilibrium constants were determined and used to calculate the concentration of TBP monomer. The calculated TBP monomer concentrations correspond to the TBP activities published in the literature

Solvent extraction of thorium nitrate with tri-n-butyl phosphate. A chemical model

The chemical model presented is founded on the prediction of all chemical reactions taking place in a solvent extraction system. Starting from equilibrium constant expressions of these chemical reactions the corresponding mathematical formulae for calculation of the concentrations of distributing species are derived. If the required chemical reactions in the organic phase are involved, the model fits the experimental data and enables the calculation of the concentrations of distributing species in the organic phase within the concentration range in which the distribution of reacting species was measured. The model is used to describe the extraction of thorium nitrate with tri-n-butyl phosphate (TBP). It characterises the distribution data by formation of disolvate and trisolvate of thorium nitrate with TBP, in addition to the dimerization of TBP. The diluent induced variations of the extraction constants values have been correlated by means of the empirical solvent polarity parameter, E(T), The activity coefficients of TBP, not included in solvation of thorium nitrate, are also calculated

A chemical model of the solvent extraction system: Nitric acid uranyl nitrate water tri-n-butyl phosphate (TBP)-diluent

A mathematical model founded on the equilibrium constants expressions has been developed for the simultaneous extraction of nitric acid and uranyl nitrate with TBP in alkane diluents. The model uses chemical activities of nitric acid and uranyl nitrate in the aqueous phase and the stoichiometric concentrations of their TBP solvates in the organic phase. The apparent formation constants of the species (TBP)(2), (TBP)(2) . HNO3, TBP . HNO3 and UO2(NO)(3) . 2TBP, present in the organic phase, have been established. The model fits well the distribution results over the whole concentration range of the extraction isotherms, and extractant concentrations 5-100% TBP. The starting data are the chemical activities of nitric acid and uranyl nitrate in the aqueous phase and their stoichiometric concentrations in the organic phase

Self-association and association of tri-n-butyl phosphate (TBP) in different diluents

The interact ion of tri-n-butyl phosphate (TBP) with diluents and its self-association have been investigated. The corresponding equilibrium constants were determined and used to calculate the concentration of TBP monomer. The calculated TBP monomer concentrations correspond to the TBP activities published in the literature

Self-association and association of tri-n-butyl phosphate (TBP) in different diluents

The interaction of tri-n-butyl phosphate (TBP) with diluents and its self-association have been investigated. The corresponding equilibrium constants were determined and used to calculate the concentration of TBP monomer. The calculated TBP monomer concentrations correspond to the TBP activities published in the literature

Modeling of the simultaneous extraction of nitric acid and uranyl nitrate with tri-n-butyl phosphate. Application to extraction operation

A mathematical model developed for the equilibrium HNO3-UO2(NO3)(2)-tri-n-butyl phosphate (TBP)-diluent is the basis of the computation of distribution isotherms. The isotherms are used to study the influence of TBP concentration on two chosen operation parameters, distribution coefficients and number of theoretical stages, for the selected flow sheets. It is established that an increase in TBP concentration leads to a decrease in the number of theoretical stages for the extraction flow sheets but to their increase for the stripping flow sheets. Given diagrams can be used to determine the efficiency of extraction processes. Agreement with available literature calculations on the number of theoretical stages supports the use of our model in the computation of distribution isotherms, of the system quoted above, in a wide range of nitric acid, uranyl nitrate, and TBP concentrations

Influence of pyridine and urea on the rat brain ATPase activity

The neurotoxicity of pyridine and urea was investigated in respect to their ability to alter the activity of synaptosomal membrane Na+/K+-ATPase and Mg2+-ATPase. In vitro treatment with pyridine and urea stimulated Na+/K+-ATPase activity in a dose-dependent manner up to 40% and 60%, respectively. Mg2+-ATPase activity increased up to 40% after pyridine treatment, while urea had no effect at all. The neuroactive potencies of pyridine and urea were evaluated by estimating parameters K-m and Delta V-max for enzyme stimulation, as well as Hill coefficient to estimate the levels of cooperativity for pyridine and urea binding. The results suggest that pyridine stimulates both enzymes, probably by interacting with some neuronal membrane components, and altering the lipid micro-environment of the ATPases. In contrast, urea stimulates the Na+/K+-ATPase only, assumingly by acting on it directly or via some other regulatory mechanism. Stimulation of Na+/K+-ATPase and Mg2+-ATPase by the substances tested and subsequent alteration of neuronal cell functioning could contribute to the CNS dysfunction upon chronic exposure to pyridine and urea