S. B. Koganti

Salt effect model for aqueous solubility of TBP in a 5 to 100% TBP/N-dodecane-nitric acid-water biphasic system at 298.2 K

Abstract The solubilities of nonelectrolytes in aqueous electrolyte solutions have traditionally been modeled by using the Setschenow equation for salt effect. The aqueous solubility of tri-n-butyl phosphate (TBP) during operating conditions of the Purex process is an important parameter for safety considerations. Use of the Setschenow equation for aqueous solubility of TBP under limited conditions has been reported in the literature. However, there is no general model available to account for the presence of the diluent and for the case of multicomponent electrolyte solutions in which only some electrolytes are solvated and extracted by TBP. An extended salt effect model is proposed for predicting the aqueous solubility of TBP in a 5 to 100% TBP/n-dodecane-nitric acid-water biphasic system at 298.2 K. The literature data on TBP solubility were correlated to aqueous acid concentration, diluent concentration in the solvents, and an interaction parameter for electrolytic solutes (extracted or not extracted by TBP).

Adsorption Kinetics and Breakthrough Behaviour of Tri-n-butyl Phosphate on Amberlite XAD-4 Resin

Adsorption behaviour of tri-n-butyl phosphate (TBP) from aqueous solution (dilute HNO3) on Amberlite XAD-4 has been investigated experimentally. Factors affecting the adsorption rates and breakthrough curves have been studied in batchwise and semicontinuous fixed bed adsorber. The adsorption isotherm of TBP on Amberlite XAD-4 resin have also been determined and the Freundlich model of adsorption is used to describe adsorption equilibrium. For the case of nonlinear equilibrium a simplified method proposed by Chi Tein is used to estimate intraparticle diffusion coefficient. The intraparticle diffusion coefficient is found to be in the range of 10−8 cm2·s−1. Results of fixed bed column are used to estimate mass transfer zone (MTZ) length, length of unused bed (LUB), breakthrough capacity corresponding to fixed value of effluent concentration (5 mg/l of TBP) and degree of saturation of bed at breakthrough. The MTZ length was found to vary from 21.8 cm to 37.3cm when flow rate changed from 13.5 ml/min to 52 ml...

An extended Setschenow model for Pu(IV) third phase formation in 20% tri-n-butyl phosphate based nuclear solvent extraction system

Abstract Formation of a third phase during liquid–liquid extraction is observed when solvate concentration in the organic phase exceeds its solubility limit in the diluent. This phenomenon is also observed in certain reaction systems like phase‐transfer catalysis. Although this phenomenon has been known since the early fifties, quantitative models have not been reported in the open literature. Recently, a Setschenow type model for Pu(IV) third phase formation in BESO/diluent system has been proposed. In the present work, the salt‐effect model is extended to cover Pu(IV) third phase formation in 20% TBP/diluent based nuclear solvent extraction system. Since it is an extended form of the Setschenow model for salting, it provides a basic understanding of salting‐in/out during third phase formation and related phenomena.

Speciation Studies in Third Phase Formation: U(IV), Pu(IV), and Th(IV) Third Phases in TBP Systems

Abstract Conventionally, composition of the actinide‐tributylphosphate (TBP) solvate is assumed to be the same in the unpartitioned organic phase and the formed third phase. For example, if a 1:2 solvate has formed during extraction, the solvate is expected to be in the same state even during the third phase condition. However contemporary analysis, based on the spectroscopy, has indicated the presence of an extended solvate. In this study, a possible mechanism is described and validated using the published data on U(IV), Pu(IV), and Th(IV) third phase in TBP systems. The proposed mechanism can be readily extended to speciation in U(VI) third phase formation in TBP systems.

Prediction of Liquid Mixture Viscosity for Dry and Water-Saturated TBP/[italic]n[roman]-Dodecane Solutions

Accuracy of earlier reported models for predicting liquid mixture viscosity for dry and water-saturated tri-n-butyl phosphate (TBP)/n-dodecane solutions is stated to be ±20%. Interaction parameters...

An Empirical Correlation for Pu(III) Distribution Coefficients in 30% TBP/n‐Dodecane PUREX System in the Presence of U(VI), U(IV), Pu(IV), Pu(III), and Hydrazine Nitrate

Abstract For modeling and simulation of the partitioning step (either chemical or electrochemical) of the PUREX process, distribution coefficients of the involved species are needed. In this contribution, reported experimental data on Pu(III) extraction under PUREX conditions have been analyzed, and an empirical model is reported. The model reported here is considered more reliable than the model currently available in the literature.

An empirical equation for vapor pressure of tri-n-butyl phosphate in the temperature range of 273.15 to 562.15 K

Tri-n-butyl phosphate (TBP) is an excellent industrial solvent for metal extraction in the nuclear chemical industry. It is also being used as a major constituent of hydraulic fluids in the aircraft industry and other industrial applications. Risk assessment studies demand limiting of airborne concentration of TBP during normal as well as accidental exposure to humans, as the toxicity index for TBP is quite high. Published data on TBP vapor pressure has been analyzed, and an empirical equation is reported for the temperature range of 273.15 to 562.15 K. The performance of the reported equation is compared with the correlations available in the literature.

A Numerical Model for Prediction of Boundary Acid Concentration for Prevention of Polymerization at Macro Pu Concentrations

Under low aqueous acidity conditions, Pu(IV) hydrolysis and subsequent polymerization can cause severe problems during aqueous reprocessing of spent nuclear fuel. Thus knowledge of formation mechanism and proper identification of conditions leading to polymere formation is important for efficient design of reprocessing flowsheets

Empirical Modeling of U(IV) Distribution in a Nitric Acid-Water-30% TBP/ n -Dodecane Biphasic System in the Presence of U(VI), Pu(III), and Hydrazine Nitrate

In current salt-free flow sheets, U(IV) is used as a reductant in reductive partitioning of U-Pu. Because U(IV)-tri-n-butylphosphate (TBP) solvate has a low solubility in the organic phase, quantitative knowledge of U(IV) distribution behavior is important. Published data on U(IV) distribution between an aqueous nitric acid and 30% TBP/n-dodecane biphasic system at 298.15K is analyzed, and an empirical model is reported. Performance of this model is compared with one earlier published model.