Tri-iso-amyl Phosphate Research Articles

Solvent extraction studies with some fission product elements from nitric acid media employing tri-iso-amyl phosphate and tri-n-butyl phosphate as extractants

Tri-iso-amyl phosphate (TiAP) has been identified as an alternate extractant to tri-n-butyl phosphate (TBP) for the reprocessing of fast reactor fuels. In the present work, extraction behaviour of some fission product elements such as Zr(IV), RuNO(III), \( {\text{TcO}}_{ 4}^{ - } \), La(III), Ce(III) and Nd(III) along with Am(III) has been investigated with 1.1 M solutions of TiAP and TBP in n-alkane diluents from nitric acid medium. The extraction of Zr(IV) has been evaluated with unirradiated and gamma irradiated solvents as a function of organic phase uranium(VI) loading. The influence of degradation products of TiAP and TBP on the extraction behaviour of fission products has also been examined. The effect of diluent degradation products and effect of alkali wash on the extraction of Zr(IV) is discussed. The formation of interfacial deposits during the washing of gamma irradiated solvents with alkali solution is also discussed.

Separation of U(VI) and Pu(IV) from Am(III) and Trivalent Lanthanides with Tri-iso-amyl Phosphate (TiAP) as the Extractant by Using an Ejector Mixer-Settler

Counter-current solvent extraction runs have been carried out to develop a suitable flow sheet for fast reactor fuel reprocessing with 1.1M Tri-iso-amyl Phosphate (TiAP)/Heavy Normal Paraffin (HNP) as the solvent by using an ejector mixer-settler facility. A spent solvent of 1.1M TiAP/HNP used for earlier runs has been employed in the present study after the regeneration. Separation of U(VI) and Pu(IV) from Am(III) and lanthanides such as La(III), Pr(III), Nd(III), Sm(III), and Eu(III) as fission product representatives with the above solvent has been investigated with an optimized flow sheet. Stage profile data generated for the extraction and strip runs for the above separation have been reported. Overall and stage-wise mass balance data for the above runs are also discussed.

Extraction kinetics of Uranium(VI) and Thorium(IV) with Tri-iso-amyl phosphate from nitric acid using a Lewis Cell

The extraction kinetics of uranium(VI) and thorium(IV) with Tri-iso-amyl phosphate (TiAP) from nitric acid medium has been investigated using a Lewis Cell. Especially, dependences of the extraction rate on stirring speed, temperature, interfacial area were firstly measured to elucidate the extraction kinetics regimes. The experimental results demonstrated that extraction kinetic of U(VI) is governed by chemical reactions at interface with an activation energy, Ea, of 43.41 kJ/mol, while the rate of Th(IV) extraction is proved to be intermediate controlled, of which the Ea is 23.20 kJ/mol. Reaction orders with respect to the influencing parameters of the extraction rate are determined, and the rate equations of U(VI) and Th(IV) at 293 K have been proposed as $$ {\text{r}} = - {\text{dcUO}}_{ 2} \left( {{\text{NO}}_{ 3} } \right)_{ 2} /{\text{dt}} = 1. 80 \times 10^{ - 3} \left[ {{\text{UO}}_{ 2} \left( {{\text{NO}}_{ 3} } \right)_{ 2} } \right]^{ 1.0 1} \left[ {\text{TiAP}} \right]^{0. 5 5} , $$ $$ {\text{r}} = - {\text{dcTh }}\left( {{\text{NO}}_{ 3} } \right)_{ 4} /{\text{dt}} = 1. 8 8\times 10^{ - 3} \left[ {{\text{Th }}\left( {{\text{NO}}_{ 3} } \right)_{ 4} } \right]^{ 1.0 4} \left[ {\text{TiAP}} \right]^{ 1. 7 7} \left[ {{\text{HNO}}_{ 3} } \right]^{0. 3 8} , $$ respectively.

Third Phase Formation in the Extraction of Th(NO3)4 by Tri-n-Butyl Phosphate and Tri-iso-Amyl Phosphate in n-Dodecane and n-Tetradecane from Nitric Acid Media

Binary solutions of tri-n-butyl phosphate (TBP) or tri-iso-amyl phosphate (TiAP) in n-dodecane or n-tetradecane (1.1 M) as diluents have been investigated for third phase formation in the extraction of Th(NO3)4 from its solutions with 1 M or 5 M HNO3 as a function of equilibrium aqueous phase Th(IV) concentration ([Th(IV)]aq,eq) at 303 K. Extraction isotherms for the extraction of Th(IV) and HNO3 have been generated with respect to [Th(IV)]aq,eq. The difference in density between the third phase and the diluent-rich phase as well as the diluent-rich phase and the pure diluent, ratio of volume of the diluent-rich phase to that of the third phase have also been determined over a wide range of [Th(IV)]aq,eq in the triphasic region. An attempt has also been made to determine the extractant concentrations in the third phase and the diluent-rich phase in the extraction of Th(NO3)4 by the above solvents from its saturated solutions with 1 M and 5 M HNO3.

Extraction and stripping behaviour of tri-iso-amyl phosphate and tri-n-butyl phosphate in n-dodecane with U(VI) in nitric acid media

Abstract Batch extraction of U(VI) by 1.1 M solution of tri-iso-amyl phosphate (TiAP) in n-dodecane (n-DD) from uranyl nitrate solutions in nitric acid media has been investigated as a function of metal loading and equilibrium aqueous phase acidity at 303 K. A method adopted for free acidity determination by using a mixture of potassium oxalate and sodium fluoride for complexing U(VI) has been validated by comparing the data generated in the present study with literature data available for tri-n-butyl phosphate (TBP) under identical conditions. Extraction and stripping behaviour of 1.1 M TiAP/n-DD-U(VI)/HNO3 and 1.1 M TBP/n-DD-U(VI)/HNO3 systems have been compared by carrying out extraction, scrubbing and a series of stripping in cross-current mode. Stripping behaviour of both the solvents loaded with U(VI) and HNO3 has also been investigated as a function of time to understand the effects of nitric acid induced degradation on stripping.

Density, Viscosity, and Interfacial Tension of Binary Mixture of Tri-iso-amyl Phosphate (TiAP) and n-Dodecane: Effect of Compositions and Gamma Absorbed Doses

The changes in interfacial tension against water, density, and coefficient of viscosity of a binary mixture of tri-iso-amyl phosphate (TiAP) and n-dodecane have been measured before and after gamma radiolysis. Density, viscosity, and interfacial tension of binary mixtures are additive functions of mole fractions of TiAP and gamma absorbed dose, which respectively form a plane in three-dimensional plots of linear–linear–linear, loge–loge–linear, and loge–loge–linear scales. Logarithmic interfacial tension also forms a three-dimensional plane with density and viscosity in loge–linear–linear plot. Redlich–Kister type equations (RK-eq) have been introduced to model excess properties of binary mixtures, where a second independent variable is the absorbed dose. The parametric coefficients of RK-eqs pertaining to excess molar volume, viscosity deviations, and interfacial tension deviations of the mixtures are linear functions of the absorbed dose. Molecular interactions between solute–solute and solute–solvent have also been quantified in terms of apparent molar volume at infinite dilution, among others.

Studies on Third Phase Formation in the Extraction of Th(NO3)4 by Tri-iso-amyl Phosphate in n-alkane Diluents

Third phase formation in the extraction of Th(NO3)4 from its solution with near-zero free acidity by 1.1 M solutions of tri-iso-amyl phosphate (TiAP) in n-dodecane, n-tetradecane, n-hexadecane, and n-octadecane has been investigated as a function of equilibrium aqueous phase Th(IV) concentration at 303 K. Distribution of Th(NO3)4 between organic and aqueous phases as well as the variation of densities of organic phases in biphasic and triphasic regions for its extraction by the above-mentioned solvents have been investigated with respect to equilibrium aqueous phase Th(IV) concentration under the above experimental conditions. Data on the ratio of volume of the diluent-rich phase to that of third phase for various TiAP/n-alkane-Th(NO3)4-303 K systems have also been generated in the present study. The results obtained are compared with literature data available for tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) systems which were experimented under identical conditions.

Thermal decomposition characteristics of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide-tri n-butyl phosphate–nitric acid systems

Thermal stability of neat octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (OΦD[IB]CMPO) and TRUEX solvent composition (0.2M OΦD[IB]CMPO-1.2M tri n-butyl phosphate-in n-dodecane) in the presence and absence of nitric acid has been studied in ambient air in a closed vessel, employing an adiabatic calorimeter. Enthalpies and kinetic parameters for the decomposition reaction were derived wherever possible and are reported for the first time. Neat OΦD[IB]CMPO was found to be thermally stable up to 633 K and exhibited an exothermic decomposition later. It decomposed at lower temperatures (376–386 K) depending on the nitric acid concentration. The exothermic rise in temperature and pressure increased exponentially, while activation energies exhibited exponential decrease for the decomposition reactions with increase in nitric acid content. TRUEX solvent was found to be stable up to 661 K in the absence of nitric acid while in the presence of 8 and 4M HNO3, it decomposed between 387 and 413 K. All these samples on decomposition formed incompressible gases and viscous black liquids. The results also indicate that the neat OΦD[IB]CMPO and the TRUEX solvent are thermally more stable than neat tri n-butyl phosphate (TBP), PUREX solvent (1.1M TBP/n-DD), neat diamyl amyl phosphonate (DAAP) and 1.1M DAAP/n-DD, triisoamyl phosphate (TiAP) and 1.1M TiAP/n-DD.

Extraction and thermodynamic behavior of U(VI) and Th(IV) from nitric acid solution with tri-isoamyl phosphate

The extraction behavior of U(VI) and Th(IV) with tri-isoamyl phosphate–kerosene (TiAP–KO) from nitric acid medium was investigated in detail using the batch extraction method as a function of aqueous-phase acidity, TiAP concentration and temperature, then the thermodynamic parameters associated with the extraction were derived by the second-law method. It could be noted that the distribution ratios of U(VI) or Th(IV) increased with increasing HNO3 concentration until 6 or 5 M from 0.1 M. However, a good separation factor (D U(VI)/D Th(IV)) of 88.25 was achieved at 6 M HNO3, and the stripping of U(VI) from TiAP–KO with deionized water or diluted nitric acid was easier than that of Th(IV). The probable extracted species were deduced by log D-log c plot at different temperatures as UO2(NO3)2·(TiAP)(1–2) and Th(NO3)4·(TiAP)(2–3), respectively. Additionally, △H, △G and △S for the extraction of U(VI) and Th(IV) revealed that the extraction of U(VI) by TiAP was an exothermic process and was counteracted by entropy change, while the extraction of Th(IV) was an endothermic process and was driven by entropy change.

Synthesis and characterization of red-oil from tri iso-amyl phosphate/n-dodecane/nitric acid mixtures at elevated temperature

Red-oil is a mixture of nonspecific composition consisting of extractant, degradation products, nitrated solvent and unidentified red-coloured nitro-organics. Red-oil formation is coupled with decomposition of extractant and diluent into gases of explosive nature. If ignited or incinerated, these gases may cause rapid pressurization and endanger the integrity of containment. Such an event occurred at Tomsk-7 facility in 1993. To ensure safe operation, red-oil formation has to be avoided in the fuel cycle facilities by a careful combination of several independent measures like strict control over temperature, limiting organic entrainment in the aqueous streams (which are to be concentrated by evaporation) and control over acidity of aqueous phases. Since tri-iso amyl phosphate (TiAP) has much lower aqueous solubility as compared to TBP, it is visualized as alternate solvent for PUREX process. In this work, TiAP red-oil was synthesized and characterized.

Calorimetric studies on thermal decomposition of tri isoamyl phosphate–nitric acid systems

The thermal decomposition of tri isoamyl phosphate (TiAP), nitric acid-solvates namely, TiAP·1.1HNO3 and TiAP·2.2HNO3, solutions of TiAP in n-dodecane (n-DD) and in pentamethylheptane (PMH) with nitric acid were studied using an adiabatic calorimeter in air under closed and opened conditions employing heat-wait-search mode. Neat TiAP was found to be stable up to 535K and decompose above this temperature. The acid-solvates were found to decompose exothermically at 384 and 365K, respectively and caused high rise in temperature and pressure, producing non-condensable gasses such as N2O, CO2 and CO and a blackish residue. Decomposition enthalpies for TiAP·1.1HNO3 and TiAP·2.2HNO3 were derived and found to be −465.1±2.4 and −937.0±6.2kJmol−1, respectively. Kinetic parameters have been derived wherever possible. Heat capacities of acid-solvates have been measured at constant pressure in the temperature range 305–340K using heat flux type differential scanning calorimeter and are reported in this paper.

Experimental measurement and correlation of flash point of alternate PUREX/UREX solvent (36% TiAP) in C8–C16 diluents

Flash point of a chemical characterizes its operating safety envelope. Tri-isoamyl phosphate (TiAP) is being proposed as an alternate to conventional nuclear solvent tri-n-butyl phosphate but flash point of TiAP containing organic solutions are not available in literature. Flash points of C8–C16n-alkanes and 36% TiAP/C8–C16n-alkane solutions were experimentally measured and correlated by means of empirical correlations. This paper is probably the first reported work in the literature on flash points of TiAP containing solutions.

Measurement of dispersion numbers for 36 and 100% tri-isoamyl phosphate solvents equilibrated with aqueous nitric acid solutions

Dispersion number is a direct indication of the settling and coalescing property of solvent with the given aqueous system. By dispersion number measurement, suitability of solvent can be characterized for post-mixing settling operations during solvent extraction. Tri-isoamyl phosphate (TiAP) is being proposed as extractant, alternate to conventional extractant TBP for nuclear solvent extraction processes. In this work, TiAP is characterized by measuring the dispersion numbers for 36% TiAP in n-dodecane and 100% TiAP solutions, equilibrated with aqueous nitric acid solutions of varying concentrations.

Thermophysical properties of 36% and 100% TiAP solvents at 298.15 K

Thermophysical properties of alternate PUREX/UREX extractant tri-iso-amyl phosphate (TiAP) in different diluents are not available in literature. In this study, density, viscosity and refractive indices of 36% v/v TiAP solutions (~1.1 M) in C6–C16n-alkanes, benzene, toluene, carbon tetrachloride and iso-octane at 298.15 K and 0.1 MPa have been measured experimentally. In the case of n-alkanes, these properties were correlated by empirical functions of carbon number of diluents. In addition, for 36% TiAP and 100% TiAP solutions, nitric acid extraction studies were also performed and acid uptakes as well as thermophysical properties of equilibrated phases were also measured. Compositions of solvates in equilibrated organic phases were also proposed.

Note: Effect of Temperature in the Extraction of Uranium and Plutonium by Triisoamyl Phosphate

The extraction of uranium(VI) by triisoamyl phosphate (TiAP) has been studied to derive the thermodynamic parameters such as entropy change and the free-energy change. The extraction of U(VI) and Pu(IV) has also been studied with 1.1 M solutions of tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP), and TiAP as a function of temperature. While the enthalpy of U(VI) extraction was found to be exothermic, the enthalpy for the extraction of Pu(IV) was always found to be endothermic. The temperature at which the distribution ratios of U(VI) and Pu(IV) cross each other (the temperature of inversion) has been derived for TBP, TAP, and TiAP, and the results reveal the lowest temperature of inversion occurs for TiAP. The results indicate the advantage of TiAP as an extractant in avoiding plutonium reflux during the PUREX process involving high plutonium feed solutions, in addition to lower aqueous solubility, freedom from the third-phase formation problem, lower degradation, and better economics.

Pressurization studies in a sealed autoclave for thermal decomposition of nitrated TBP and TiAP

Study of runaway reaction between tri-n-butyl phosphate (TBP) and nitric acid resulting in red-oil formation (and related problems) in the process evaporators of reprocessing plants has been a major safety concern since last 50 years. Thermal decomposition of nitrated TBP results in rapid pressurization and in close-vent condition it may lead to failure of process vessel and containment. Thermal decomposition of nitrated TBP is reported in the literature but corresponding studies for alternate PUREX/UREX solvent tri-iso-amyl phosphate (TiAP) are not available. In this work, comparative study of the thermal decomposition of nitrated solvents (TBP as well as TiAP) under adiabatic conditions in a sealed autoclave is presented. Experimental results indicate much lesser pressurization in the case of TiAP as compared to TBP.

Effect of temperature on the extraction of uranium by TiAP/n-dodecane

The effect of temperature on the extraction of uranium by tri isoamyl phosphate (TiAP) has been studied as a function of nitric acid concentration, temperature and TiAP concentration. The resultant data has been used to derive the enthalpy of extraction of uranyl nitrate using “second law” method. The results are compared with those of tri n-butyl phosphate (TBP) system carried out under identical conditions. The results indicate that the enthalpy of extraction are also exothermic as observed in the TBP system but are distinctly more exothermic in TiAP systems at the acidities measured, while exhibiting similar enthalpies for 0.55M TiAP solutions.

Parameters Influencing Third‐Phase Formation in the Extraction of Th(NO3)4 by some Trialkyl Phosphates

Third‐phase formation in the extraction of Th(IV) by trialkyl phosphates (TalP) such as tri‐n‐butyl phosphate (TBP), tri‐iso‐butyl phosphate (TiBP), tri‐sec‐butyl phosphate (TsBP), tri‐n‐amyl phosphate (TAP), tri‐2‐methylbutyl phosphate (T2MBP), tri‐iso‐amyl phosphate (TiAP), tri‐sec‐amyl phosphate (TsAP), and tri‐cyclo‐amyl phosphate (TcyAP) has been investigated under various conditions. Formation of a third phase in the extraction of Th(IV) by TBP/n‐dodecane as a function of TBP concentration at 303 K was studied. Measurements were also carried out on the extraction of Th(IV) from its solution with near‐zero free acidity by various phosphate/diluent binary solutions (1.1 M) as a function of temperature. Third‐phase formation in the extraction of Th(IV) by 1.1 M TalP in various diluents from nitric acid media has also been studied as a function of equilibrium aqueous‐phase acidity at 303 K. Empirical equations to predict limiting organic concentration with respect to various parameters for third‐phase formation in the extraction of Th(IV) by TBP and TAP from nitric acid media have been derived. Some of the above phosphates have been investigated for the distribution of Th(NO3)4 between the “diluent‐rich phase” (DP) and “third‐phase” (TP) in the extraction of Th(IV) by 1.1 M TalP in various diluents from its saturated solution with near‐zero free acidity at 303 K. Results of the above studies are presented in this paper. Based on these studies, the effects of extractant concentration, the temperature, the nature of the diluent, the equilibrium aqueous‐phase acidity, and the structure of the extractant on third‐phase formation behavior of trialkyl phosphates are described in this paper.

Extraction of oxalic acid from solutions of electrolyte mixture

Extraction of oxalic acid with tributyl phosphate and triisoamyl phosphate from solutions of its mixtures with nitric, phosphoric, sulfuric, and hydrochloric acid and with ammonium nitrate and chloride was studied. In the extractability series, oxalic acid occupies the position between nitric and phosphoric acids, with sulfuric and hydrochloric acids acting as strong salting-out agents. Nitric acid salts drastically decrease the distribution ratios of oxalic acid.

Measurement of enthalpies of vaporization of trialkyl phosphates using correlation gas chromatography

The enthalpies of vaporization of several trialkyl phosphates such as, tri- n-butyl phosphate (TBP), triisobutyl phosphate (TiBP), tri-secondary butyl phosphate (TsBP), tri- n-amyl phosphate (TAP), triisoamyl phosphate (TiAP), Tri-2-methyl butyl phosphate (T2MBP), tri-secondary amyl phosphate (TsAP), and trihexyl phosphate (THP) have been measured for the first time using correlation gas-chromatographic technique. Normal paraffin hydrocarbons have been used as references after demonstrating the suitability of them by determining the enthalpies of vaporization of trimethyl phosphate (TMP) and triethyl phosphate (TEP) for which data is available in the literature. The vaporization enthalpies were correlated to structural parameters characterizing the compounds studied. Solvent accessible surface area (SAS), among the parameters, was found to exhibit excellent correlation to the enthalpies of vaporization of trialkyl phosphates as well as the normal paraffin hydrocarbons used as the reference. The Hildebrand's solubility parameters for the trialkyl phosphates were derived from the values of enthalpy of vaporization at 298.15 K.