TBP In Dodecane Research Articles

Sorption decontamination of aqueous and organic media from TBP and acidic products of its decomposition

The processes of sorption decontaminationof aqueous solutions from TBP on the polymeric sorbent Polysorb-1,as well as of a 70% solution of TBP indodecane from butylphosphoric acids using layered double oxides and Mg-Alhydroxides were studied. It has been established that the useof the polymeric sorbent Polysorb-1 makes it possible to decontaminateaqueous solutions from TBP in static and dynamic modes, andthe use of the LDH-Mg-Al-CD-OH sorbent allows the decontamination ofTBP solutions in dodecane from acid products of decomposition andhydrolysis of TBP.

Assessment of metallic membrane-based counter-current micro-contactor for non-dispersive solvent extraction: Experimental studies and modelling

Non-dispersive solvent extraction (NDSX) in a micro-contactor eliminates the need of phase separator. Thus, NDSX is an approach to achieve intensification of solvent extraction process. The interface between the two phases which flow counter-currently is stabilized by metallic membrane (stainless steel mesh). However, the use of counter-current flow puts hydrodynamic limitations on stability of the interface and hence on the operation of the contactor. In this study, a theoretical model to estimate the maximum stability length and corresponding extraction is reported and validated with the experimental data of nitric acid extraction using 30% (v/v) TBP in dodecane as the solvent. The model is further used to perform parametric analysis to understand the effect of various parameters on maximum stability length and corresponding extraction. The model is also used for assessing feasibility of using metallic membrane-based counter-current micro-contactor for non-dispersive solvent extraction of uranium from nitric acid medium.

Liquid-liquid dispersion in pulsed disc and doughnut column and pulsed sieve plate column: A comparative study

Pulsed disc and doughnut columns (PDDCs) and pulsed sieve plate columns (PSPCs) are widely used for liquid-liquid extraction processes in nuclear fuel cycle. In this study, experiments are performed to understand the effects of operating parameters (continuous phase velocity, dispersed phase velocity and pulsing velocity) on Sauter mean diameter and drop size distribution in PDDC and PSPC. Experiments are conducted in aqueous continuous mode of operation using 3N nitric acid as the aqueous phase and 30% TBP in dodecane as the organic phase. Previously reported correlations for estimating drop diameter in PSPC and PDDC are evaluated with the experimental data of this study. Correlations based on modification of previously reported correlations are proposed for estimating Sauter mean drop diameter in PSPC and PDDC.

Effect of operating and geometric parameters on dispersed phase holdup in Pulsed Disc and Doughnut and Pulsed Sieve Plate Columns: A comparative study

A detailed experimental study is performed to understand the effects of different operating and geometrical parameters on dispersed phase holdup in Pulsed Disc and Doughnut Columns (PDDCs) and Pulsed Sieve Plate Columns (PSPCs). The phase system used in the experiments consists of mutually saturated water as the aqueous phase and 30% TBP in dodecane as the organic phase. The experiments are conducted in aqueous continuous mode. The operating parameters that have been varied are the superficial velocities (flow rates) of the continuous and dispersed phase and pulsing velocity. The geometrical parameters are plate spacing or disc spacing and column diameter. Previously reported correlations for dispersed phase holdup are evaluated with the experimental data generated in this study. New correlations, based on modification of previously reported correlations, are proposed.

Direct dissolution of g-level U metal and U-6 % Zr alloy bits by TBP-nitric acid adduct and in situ extraction at ambient pressures

A study on direct dissolution of g-level metallic U and U-6 % Zr alloy bits by TBP-nitric acid adduct followed by in situ extraction at ambient pressures under batch and dynamic conditions was performed. The product organic solution was adjusted to 30 % TBP in dodecane and from it, U(VI) could be stripped quantitatively with 0.01 N nitric acid. Experimental results of the study are presented in this paper.

Single-stage micro-scale extraction: Studies with single microbore tubes and scale-up

Abstract The study focuses on single-stage solvent extraction of HNO 3 from 3 M HNO 3 using 30% TBP in dodecane in microbore tubes. The objective of the study is to identify a configuration that ensures high stage efficiency (⩾90%), quick settling and low pressure drop (⩽2 bar) and to demonstrate this configuration at a total throughput of 1 LPH using parallel paths. To find out the right configuration, experiments with single microbore tubes are conducted to observe the effects of flow rate, diameter and length of microbore tube on stage efficiency, pressure drop and settling behavior. The experiments show that the configuration consisting of a Y-junction of 750 μm diameter having a single microbore tube of 800 μm diameter and 300 cm length on its downstream side is capable of handling total flow rate of 0.5 LPH with high stage efficiency, quick settling and low pressure drop. Two such configurations are used in parallel to achieve total flow rate of 1 LPH. Specific extraction rate achieved in the contactor based on microbore tubes is compared with the specific extraction rate estimated for a mixer-settler. The comparison shows that the use of microbore tube contactor leads to process intensification.

The redox chemistry of neptunium in γ-irradiated aqueous nitric acid in the presence of an organic phase

The radiolytic changes in oxidation state for solutions of initially Np(V) and/or Np(VI) were investigated by gamma-irradiation in conjunction with UV/Vis spectroscopy of the aqueous phase. Samples were irradiated in varying concentrations of nitric acid, and with or without the presence of 30 % TBP in dodecane. At short irradiation times Np(V) was oxidized to Np(VI), even in the presence of the organic phase. Upon the radiolytic production of sufficient amounts of nitrous acid, reduction of Np(VI) to Np(V) occurred in both phases. This was accompanied by stripping of the previously extracted Np(VI). Nitric acid concentrations of 6 M mitigated this reduction.

Solvent extraction in microbore tubes with UNPS–TBP in dodecane system

Solvent extraction of uranium from 500ppm uranyl nitrate pure solution (UNPS) into an organic phase containing 30% TBP in dodecane has been studied. An opposed T-type microfluidic junction having microbore tube on the downstream side has been used in experiments. Effects of contact time and O/A ratio on stage efficiency and overall volumetric mass transfer coefficient have been studied. Effects of microbore tube diameter and method of varying the contact time on stage efficiency and overall volumetric mass transfer coefficient have also been investigated. Liquid–liquid two-phase flow patterns of the same phase system sans uranium, observed in transparent microbore tubes, are used to explain some of the experimental trends. Numerical simulations to visualize liquid–liquid two-phase flow patterns at the microfluidic junction are also carried out to support the explanations of some of the experimental trends.

Contribution of extraction isotherms modeling based on the Mikulin–Sergievskii–Dannus approach to the speciation of plutonium(IV) in TBP 30 %/dodecane

Abstract In this study, a thermodynamic model based on Mikulin and Sergievskii–Dannus equations to calculate activity coefficients in both organic and aqueous phases was used to model plutonium(IV), nitric acid and water extraction by 30% TBP in dodecane. The speciation of Pu(IV) in the organic phase was determined via extraction isotherms modeling. The best agreement between experimental and calculated plutonium distribution ratios was obtained by considering two Pu(IV) complexes in the organic phase: Pu(NO3)4(TBP)2 and Pu(NO3)4(TBP)3.

Extraction of americium(VI) by a neutral phosphonate ligand

Recently the use of the more unusual hexavalent oxidation state of americium has been receiving increased attention for the purpose of developing an efficient Am/Cm or Am/lanthanide separation system. We have already demonstrated the feasibility of performing this separation with 30% TBP in dodecane, and are now looking at different extractants to increase Am(VI) distribution ratios. Following on from this the extraction of bismuth oxidized americium from nitric acid solutions by dibutyl butyl phosphonate has been studied. The results of this study indicate that increasing the basicity of the extractant molecule has significantly improved the extraction efficiency.

Extracting Acetic Acid from Acidic Solutions

In the UREX + process, acetic acid must be removed from the raffinate stream to avoid interference with the recovery and recycle of nitric acid solutions. Solvent extraction was selected to be the most promising approach to accomplish this cleanup. Acetic acid partitioning into pure diluents used in the UREX + process were found to be too low for an effective separation. Of the solvents tested, the most promising solvents for the extraction of acetic acid were found to be TBP in dodecane and TBP in FS-13.

Synergic extraction for recovery of americium from waste solution containing an excess of uranium

A method based on synergic extraction has been evolved for the recovery of tens of milligrams of americium from analytical wastes in 7-8M HNO3 medium containing excess uranium as a two step procedure viz., (1) separation of uranium by contacting with TBP in dodecane and (2) recovery of americium by an extraction-cum-strip cycle using a synergic mixture of PMBP-TBP in dodecane after decreasing the acidity of the solution. Other transition metals such as iron found in significant proportion were separated from Am by using the difference in the kinetics of extraction of iron and americium into HPMBP-TBP-dodecane mixture by short duration contacts. About 99% of Am could be recovered into about 20% of its initial volume.

Thermochemical Oxidation of Components of Extraction Solutions and Boundary Conditions of Thermal Explosion: 6. Thermal Stability of Two-Phase Systems TBP-HNO3and TBP-Dodecane-HNO3in Sealed Vessels

Thermochemical degradation of two-phase systems TBP-HNO3 and 30% TBP in dodecane-HNO3 (HNO3 concentration 1.5-10 M) on heating in a sealed vessel to 130-170°C is studied. Heating to 130-150°C promotes exothermic oxidation of the organic phase, resulting in its self-heating. The oxidation rate (self-heating and specific volume of gaseous products) increases with increasing HNO3 concentration in the aqueous phase. Irradiation of the organic phase decreases the thermal resistance of the systems, which is reflected in a decrease in the onset temperature of exothermic reactions. In the organic phase 30% TBP in dodecane, irradiated to doses of 1.5-2.4 MGy, in contact with 14 M HNO3, exothermic reactions start at 85-95°C.

Stripping of actinides, fission and corrosion products from loaded TRUEX solvent (0.2M CMPO+1.2M TBP in dodecane) phase using potassium ferrocyanide

Stripping of the nuclides U, Np, Pu, Am, Eu, Zr, Ru and Fe from the loaded TRUEX solvent (0.2M CMPO+1.2M TBP in dodecane) has been carried out with a potassium ferrocyanide solution. In four contacts, 98% or more of U, Pu, Am and Eu could be stripped whereas Zr and Ru recoveries were 94% and 92%, respectively. Further, the co-precipitation of Am, Pu, U and Eu on ferric ferrocyanide precipitate from the CMPO phase has shown high recovery of Am, Pu and Eu but lower for U.

Extraction of U(IV) and U(VI) with 30% Tributyl Phosphate under Conditions of Formation of the Second Organic Phase

Extraction of U(IV) and U(VI) from nitric acid solutions with 30% TBP in dodecane under conditions of formation of two organic phases was studied. With respect to uranium recovery, this extraction system substantially differs from the similar system with 30% TBP in hexachlorbutadiene in which only one organic phase is formed. The study of the electronic spectra showed that the U(IV) and U(VI) solvates formed in light and heavy organic phases are different.

Thermochemical Oxidation of Components of Extraction Solutions and Threshold Conditions of Thermal Explosion: 4. Kinetics of Reaction of TBP Solutions in Dodecane with Nitric Acid

The reaction of 30% solutions of TBP in dodecane with HNO3 at the initial concentration of the acid of 1.4 M was studied in the temperature range 75-150°C. The kinetic parameters of acid consumption, gas evolution, and accumulation of liquid-phase products were determined. The effect of γ-preirradiation on the kinetics of oxidation processes was studied. From the kinetic data the threshold temperature conditions for transformation of oxidation processes into the thermal explosion were estimated and the presumable mechanism of initiation and development of oxidation reactions was discussed.

Separation and Recovery of Uranium and Plutonium from Oxalate Supernatant

The separation of uranium and plutonium from oxalate supernatant, obtained after precipitating plutonium oxalate, containing ~10 g/l uranium and 30–100 mg/l plutonium in 3M HNO3 and 0.10–0.18M oxalic acid solution has been carried out. In one extraction step with 30% TBP in dodecane: ~92% of uranium and ~7% of Pu is extracted. The raffinate containing the remaining U and Pu is extracted with 0.2M CMPO+1.2 M TBP in dodecane and near complete extraction of both the metal ions is achieved. The metal ions are back extracted from organic phases using suitable stripping agents. The recovery of both the metal ions separately is >99%. The uranium species extracted into the TBP phase from the HNO3+oxalic acid medium was identified as UO2(NO3)2·2TBP.

Distribution of Pu(VI) from nitric acid to tri-n-butyl phosphate saturated with uranium(VI)

Solvent extraction of plutonium(VI) from nitric acid (1 to 5M) into 20% and 30% TBP in dodecane saturated with uranium(VI) (0% to 80%) has been studied. For a particular nitric acid concentration, the distribution coefficient (K d ) is found to decrease with the increase in saturation of organic phase with uranium(VI). At a fixed organic phase the saturationK d increased with increase in nitric acid concentration, however, the magnitude of this increase inK d decreased with the increase in saturation.

Recovery of plutonium and americium from laboratory acidic waste solutions using tri- n-octylamine and octylphenyl- N- N- diisobutylcarbamoylmethylphosphine oxide

Plutonium from acidic waste solutions has been recovered quantitatively using tri- n-octylamine (TnOA) in xylene and americium using a mixture of octylphenyl- N- N- diisobutylcarbamoylmethylphosphine oxide (CMPO) and TBP in dodecane by extraction and extraction chromatographic methods. The Pu( IV) TnOA species extracted into the organic phase from higher nitric acid concentrations has been confirmed as (R 3NH) 2Pu(NO 3) 6 (where R 3N = TnOA by employing slope analysis as well as spectrophotometric studies.

Recovery of plutonium from assorted laboratory wastes

Almost quantitative recovery of plutonium from assorted non-recoverable aqueous acidic and organic waste solutions originating from solvent extraction studies and synthesis of solid plutonium compounds has been achieved by using combined solvent extraction and extraction chromatographic techniques. During solvent extraction a mixture of 0.2M CMPO+1.2M TBP in dodecane was used as the extractant while in extraction chromatography a small column of CMPO adsorbed on Chromosorb-102 (CAC) was utilised. The activities could finally be recovered from the loaded organic phase as well as the CAC column. The effluent after the combined operation was almost alpha-free. About 3 g of plutonium was recovered from about 19 litres of different wastes.