Dibutyl Phosphoric Acid Research Articles

Effect of di-butyl phosphate on the distribution behavior of uranyl ions in PUREX solvent

ABSTRACT Di-butyl phosphoric acid (HDBP) is one of the major hydrolytic and radiolytic degradation product of tri-n-butyl phosphate (TBP) employed for the extraction of U(VI) and Pu (IV) from the spent nuclear fuel dissolver solution. The presence of HDBP in the solvent phase limits the recovery of actinides during stripping. In view of this, the extraction and stripping behavior of uranyl nitrate in 1.1 M TBP in n-dodecane (n-DD) was studied in presence of di-butyl phosphate (HDBP). The distribution ratio (D) of uranium (VI) in HDBP/n-DD was negligible and the D value increased gradually with an increase in HDBP content in the organic phase. An alternate method was developed for estimation of HDBP in TBP/n-DD system based on uranium metal retention in organic phase. Based on the results it was found that 1 M HDBP in 1.1 M TBP/n-DD retained about 0.63 M of uranium (VI) in the organic phase during stripping. The results were further validated using irradiated solvent. FT-IR spectroscopic investigation also revealed the retention of U(VI) in 1.1 M TBP/n-DD containing HDBP even after several stripping with 0.01 M HNO3.

Structural Investigation of Technetium Dibutylphosphate Species Using X-ray Absorption Fine Structure Spectroscopy.

The speciation of Tc after the extraction of Tc(IV) from H2O and 1 M HNO3 by dibutylphosphoric acid (HDBP) in dodecane has been studied by X-ray absorption fine structure (XAFS) spectroscopy. Results show the formation of dimeric species with Tc2O2 and Tc2O units, and the formulas [Tc2O2(DBP·HDBP)4] (1) and [Tc2O(NO3)2(DBP)2(DBP·HDBP)2] (2) were, respectively, proposed for the species extracted from H2O and 1 M HNO3. The interatomic Tc-Tc distances found in the Tc2O2 and Tc2O units [2.55(3) and 3.57(4) Å, respectively] are similar to the ones found in Tc(IV) dinuclear species. It is likely that the speciation of Tc(IV) in dodecane is due to the extraction of a species with a Tc2O unit for (2) and to the redissolution of a Tc(IV)-DBP solid for (1). The XAFS results for (1) and (2) were compared to that obtained for the extraction of Tc(IV) with TBP/HDBP/dodecane from 0.5 M HNO3, (3) which highlight the formation of Tc mononuclear nitrate species {i.e., [Tc(NO3)3(DBP)] or [Tc(NO3)2(DBP·HDBP)]}. These results confirm the importance of the preparation and speciation of the Tc(IV) aqueous solutions prior to extraction and how much this influences and drives the final Tc speciation in organic extraction. These studies outline the complexity of Tc separation chemistry and provide insights into the behavior of Tc during the reprocessing of used nuclear fuel.

Separation of REE(III) and Am(III) by Extraction with Compounds of Zirconium and Dibutyl Phosphoric Acid from Solutions of Nitric and Hydrochloric Acids

Separation of REE(III) and Am(III) by Extraction with Compounds of Zirconium and Dibutyl Phosphoric Acid from Solutions of Nitric and Hydrochloric Acids

A Study of the Radiolysis Products of the Tri-n-Butyl-Phosphate–Isopar-M–HNO3 System before and after Regeneration with Carbonates of Organic Bases

By measuring the hydrodynamic characteristics (viscosity, density of extraction mixture, and interfacial tension) and determining the composition of degradation products by the IR, CMS, and nuclear magnetic resonance methods, the efficiency of using solutions of methylamine and guanidine carbonates at the stage of intracycle regeneration was evaluated. It has been experimentally proven that, when using these solutions, the same efficiency is achieved as when using a sodium bicarbonate solution. The main products of radiation destruction of the 30% Tri-n-butyl-phosphate in Isopar-M extraction mixture irradiated after saturation with nitric acid are determined: dibutyl phosphoric and monobutyl phosphoric acids, carboxylic acids, ketones, carbonyl compounds, and hydrocarbons.

Synthesis of 3-Deoxy-d-manno-oct-2-ulosonic Acid (KDO) and Pseudaminic Acid C-Glycosides.

The preparation of glycosyl dibutyl phosphates in the 3-deoxy-d-manno-oct-2-ulosonic acid (KDO) and pseudaminic acid series and their application to the formation of C-glycosides are described. Both donors were obtained from the corresponding thioglycosides by treatment with dibutylphosphoric acid and N-iodosuccinimide. As with the thioglycosides, both donors adopted very predominantly the strongly electron-withdrawing tg conformation of their side chains, which is reflected in the excellent equatorial selectivity of both donors in the formation of exemplary O-glycosides. With respect to C-glycoside formation on the other hand, contrasting results were observed: the KDO donor was either relatively unselective or selective for the formation of the axial C-glycoside, while the pseudaminic acid donor was selective for the formation of the equatorial C-glycoside. These observations are rationalized in terms of the greater electron-withdrawing ability of the azides in the pseudaminic acid donor compared to the corresponding acetoxy groups in the KDO series, resulting in a reaction through tighter ion pairs even at the SN1 end of the general glycosylation mechanism. The contrast in the axial versus the equatorial selectivity between C- and O-glycosylation cautions against the extrapolation of models for SN1-type glycosylation with weak nucleophiles for the explanation of O-glycosylation.

Molecular Dynamics Investigations of Dibutyl-phosphoric Acid-Parameterization and Dimerization.

A reparameterized molecular dynamics force field for dibutyl-phosphoric acid (HDBP) has been developed. Parameterization was done using the general Amber force field, as a starting point. The density and dipole moment of bulk phase simulations compare well to that of known experimental values, and the heat of vaporization is comparable to an estimated empirical value. All values have been optimized to within 4%. The newly optimized force field was validated against the self-diffusion coefficient, matching experimental data to within 18%, which is a significant improvement compared to the nonoptimized force field. Further, a potential of mean force study was carried out to understand the behavior of hydrogen bonds in HDBP dimers. This required the determination of hydrogen bonding criteria that captures the behavior of the HDBP dimer and is reported in this work as well.

The hydrophobic mechanism of di(2-ethylhexyl) phosphoric acid to hemimorphite flotation

In this paper, the flotation separation of hemimorphite from quartz was investigated by using di(2-ethylhexyl) phosphoric acid (DEHPA) as a collector. The results elucidated that DEHPA exhibited better flotation performances to hemimorphite than dibutyl phosphoric acid (DBP), tributyl phosphate (TBP), octanoic acid (OA) and palmitic acid (PA). And DEHPA also possessed good selectivity against quartz flotation and could realize the effective flotation separation of hemimorphite from quartz under pH 6.0–10.0. The adsorption and contact angle findings clearly indicated that DEHPA selectively adsorbed on hemimorphite, hardly on quartz. After DEHPA treatment, the hydrophobicity of hemimorphite was dramatically improved. Zeta potential suggested that DEHPA anion anchored on hemimorphite surfaces mainly through chemical bonds. FTIR inferred that DEHPA chemisorbed on to hemimorphite surfaces by formation of the ZnO bonds between the O atoms of the P(O)(OH) group and the surface zinc atoms, simultaneously with splitting the OH bonds of the POH group. XPS gave clear evidences that the adsorbed DEHPA combined with Zn(II) species on hemimorphite surfaces to generate the Zn(II)-DEHPA surface complexes.

Selective Crystallization of Phosphoester Coordination Polymer for the Separation of Neodymium and Dysprosium: A Thermodynamic Approach.

Thermodynamics of the formation of coordination polymers (CPs) or metal-organic frameworks (MOFs) has not been focused on, whereas many CPs or MOFs have been synthesized in a solution. With a view of separating Nd3+ and Dy3+ in an aqueous solution, we demonstrate that crystallization of the CPs of Nd3+ and Dy3+ based on dibutyl phosphoric acid (Hdbp) can be thermodynamically described; crystallization yields of [Ln(dbp)3] (Ln = Nd or Dy) complex are predicted well using a simple calculation, which takes the apparent solubility products (Kspa) for [Ln(dbp)3] and the acid dissociation constant of Hdbp into account. The Kspa values of [Nd(dbp)3] and [Dy(dbp)3] are experimentally determined to be (1.3 ± 0.1) × 10-14 and (2.9 ± 0.4) × 10-18 M4, respectively, at 20 °C. The ratio of these Kspa values, that is, ca. 4500, is significantly larger than the ratio of the solubility products for inorganic salts of Nd3+ and Dy3+. Therefore, Nd3+ and Dy3+ are selectively crystallized in an aqueous solution via the formation of CPs. Under optimized conditions, Dy3+ crystallization is preferable, whereas Nd3+ remains in the solution phase, where the ratio of the Dy molar content to the total metal content (i.e., Nd + Dy) in the crystal is higher than 0.9. The use of acids, such as HCl or HNO3, has no practical impact on the separation in an aqueous solution.

Extraction and Preconcentration of dissolved dibutyl phosphoric acid (HDBP) from aqueous uranyl nitrate solutions for gas chromatographic analysis

With a view to mitigate the complexities associated with aqueous solubility of Organophosphorous solvent, accurate estimation of dissolved organic in aque- ous streams assumes great importance. Present method employs solvent extraction using 10 % (v/v) mixture of benzyl alcohol-benzene (BBA) for selective enrichment/ extraction of dissolved Dibutyl phosphosphoric acid (HDBP), the target analyte, in presence of tributyl phos- phate from nitric acid solutions containing bulk amount of uranyl ions. The extracted HDBP after methylation is subjected to gas chromatographic analysis using thermal conductivity detector. A calibration plot of HDBP esti- mation in the concentration range of 10-100 ppm, yields a precision with RSD of ± 5% . Graphical Abstract

Fluorescence studies of metal complexes in synergistic extraction systems combining dibutyl phosphoric acid and tri-n-butyl phosphate

The extraction of lanthanides using a combination of tri-n-butyl phosphate (TBP) and dibutyl phosphoric acid (HDBP) was found to display characteristics of microemulsion aggregates, which may be related to synergistic effects. We studied the extraction of lanthanides and actinides, in our case dysprosium, europium, and uranium, with TBP and HDBP in conjunction with 2D fluorescence spectrometry. The results presented indicate that the coordination environment around the metal ion in the organic phase changes as the ratio between TBP and HDBP changes. This suggests the presence of mixed complexes of M:TBP:HDBP but does not rule out the presence of reverse micelles.

Radiolysis of Tributyl Phosphate by Particles of High Linear Energy Transfer

Tributyl Phosphate (TBP), used in chemical separation processes for used nuclear fuel, is susceptible to radiolysis causing losses in process performance. We have studied its degradation by exposing dry 1M TBP/n-dodecane solutions to gamma radiation from a cesium-137 source and in a mix of low and high linear energy transfer (LET) radiation by irradiating samples in the UC Irvine TRIGA® reactor and utilizing the 10B(n,α)7Li reaction. In a 1 M solution of TBP in n-dodecane the degradation of TBP (G−TBP) was found to be 0.36 and 0.14 μmol/J for low and high LET radiation, respectively. The formation of dibutyl phosphoric acid, DBP, (G+DBP) in this solution was found to be 0.18 and 0.047 μmol/J for low and high LET radiation, respectively. In samples exposed to low LET as well as a mix of low and high LET a variety of TBP degradation products containing phosphorus were observed indicating that other degradation products than DBP and the monobutyl diacid (MBP) were formed. Our results for both low and high LET radiation compare well with previous studies on these systems indicating that high LET degrades TBP to a lesser extent than gamma radiation. Available data for high LET is not as abundant as for low LET making such comparisons challenging. Nevertheless, our method yields a value for G+DBP that agrees well with previous alpha radiolysis studies indicating that our method shows promise for studying high LET radiolysis in liquid-liquid extraction systems.

Fourier Transform Infrared Spectroscopy and Multivariate Analysis for Online Monitoring of Dibutyl Phosphate Degradation Product in Tributyl Phosphate/n-Dodecane/Nitric Acid Solvent

In liquid–liquid extraction separation processes, accumulation of organic solvent degradation products is detrimental to the process robustness, and frequent solvent analysis is warranted. Our research explores the feasibility of online monitoring of the organic solvents relevant to used nuclear fuel reprocessing. This paper describes the first phase of developing a system for monitoring the tributyl phosphate (TBP)/n-dodecane solvent commonly used to separate used nuclear fuel. In this investigation, the effect of extraction of nitric acid from aqueous solutions of variable concentrations on the quantification of TBP and its major degradation product dibutylphosphoric acid (HDBP) was assessed. Fourier transform infrared (FTIR) spectroscopy was used to discriminate between HDBP and TBP in the nitric acid-containing TBP/n-dodecane solvent. Multivariate analysis of the spectral data facilitated the development of regression models for HDBP and TBP quantification in real time, enabling online implementation of the monitoring system. The predictive regression models were validated using TBP/n-dodecane solvent samples subjected to high-dose external γ-irradiation. The predictive models were translated to flow conditions using a hollow fiber FTIR probe installed in a centrifugal contactor extraction apparatus, demonstrating the applicability of the FTIR technique coupled with multivariate analysis for the online monitoring of the organic solvent degradation products.

Synergistic Extraction of Dysprosium and Aggregate Formation in Solvent Extraction Systems Combining TBP and HDBP

During treatment of nuclear fuel in the Plutonium/URanium EXtraction (PUREX) process, the extractant tri-n-butyl phosphate (TBP) is known to degrade to dibutylphosphoric acid (HDBP), which increases the extraction of metal ions, thereby inhibiting their stripping from the organic phase. To better understand this phenomenon, we investigated how mixtures of TBP and HDBP influenced the extraction of metal, nitric acid, and water, and correlated the results to aggregated structures in the organic phase. The mole ratios of TBP-HDBP mixtures had a non-linear effect on the extraction of Dy3+ and water from 0.2 M HNO3, indicating synergism. In 2 M HNO3, the TBP:HDBP mole ratio had a more linear relation to Dy3+ and water extraction, so the synergistic effect was less pronounced than in the low acid system. The extraction of nitric acid showed no synergistic effect and follows closely what would be expected in a system using TBP only. The small-angle X-ray scattering (SAXS) data of the 0.2 M acid system showed maximum contrast at a TBP:HDBP mole ratio of 0.25, so that the synergistic mixture is also the most aggregated at 0.2 M acid. The 2 M acid system also showed that the mixed system is more aggregated than the end members, although this does not result in peak extraction. Previous studies of synergistic extraction of metal cations explain the enhanced extraction by increased dehydration of the metal ion. Although our data do not rule out the formation of mixed complexes according to the classical mechanism of synergism, our evidence of increased water extraction and aggregate formation in systems combining TBP and HDBP are complementary to the metal-centric dehydration aspects of the process. The findings in this study give insights into the complex chemistry of solvent extraction, providing a possible link between formation of aggregates in the organic phase and synergistic extraction.

Enantioselective Allylic Thioetherification: The Effect of Phosphoric Acid Diester on Iridium‐Catalyzed Enantioconvergent Transformations

You'll take the high road and I'll take the low road: Enantioenriched allylic thioethers have been synthesized from chiral racemic allylic alcohols. The combination of an Ir-(P,alkene) complex and dibutyl phosphoric acid are required to attain high selectivities. Mechanistic studies uncover an enantioconvergent transformation in which substrate enantiomers react along different pathways to give the same product (see scheme; cod=1,5-cyclooctadiene).

Mechanism of Synergistic Extraction of Samarium Using Alkylphosphoric Acid as Main Extractant

The synergistic extraction of samarium (Sm(III)) using two different main extractants and three organic phosphine oxides as synergist was examined. A synergistic effect was observed when dibutylmonothiophosphoric acid (DBTPA) was used with tri-n-butylphosphine oxide (TBPO) or dibutylphosphate (DBOBPO). The order of extractability was TBPO > DBOBPO. On the other hand, the extractability of samarium in the DBTPA + tri-n-butylphosphate (TBOPO) system was not significantly greater than the extractability of samarium in the DBTPA system. An antagonistic effect was observed when dibutylphosphoric acid (DBPA) was used as the main extractant and TBPO as the synergist. The extractability of samarium in the DBOBPO/TBOPO system was almost the same as that of samarium in the TBPO system. This difference in the extractabilities observed when using different synergists with the two main extractants probably resulted from the balance between the association abilities of the synergist and the main extractant. This could be explained by the basicity of the oxygen atom in the synergists and the coordination ability of the synergist with the samarium/main extractant complex. This was in turn due to the coordination number of the aforementioned complex.

Dibutyl phosphoric acid and its acid zirconium salt as an extractant for the separation of transplutonium elements and rare earths and for their partitioning

Acid Zr salt of dibutyl phosphoric acid (ZS HDBP) dissolved in 30% TBP with isoparaffines was investigated and successfully tested on “hot” rigs as TBP-compatible solvents for TPE and RE recovery from simulated and real HLW, containing 1–3 mol/L HNO3, and for their partitioning with DTPA in formic media. Mo was also separated. The possibility of the use of 1–1.5 mol/L HDBP solutions in meta-nitrobenzotrifluoride (F-3) for these purposes is demonstrated as well. Addition of chlorinated cobalt dicarbollide (CCD) to ZS HDBP solution in F-3 gives rise to synergetic effect during extraction and, in combination with PEG, allows to extract Cs and Sr along with TPE and RE from HLW of mentioned acidity, and to separate the elements to fractions by their valence.

Separation of Precipitate-forming Elements during High Level Waste Treatment Using Acidic Zirconium Salt of Dibutyl Phosphoric Acid

Iron extraction and the limits of iron dibutyl phosphate precipitation were investigated for use in TPE/RE recovery and partitioning with the use of the acidic Zr salt of dibutyl phosphoric acid (ZS HDBP, Zr:HDBP = 1:9), dissolved in 30% TBP with Isopar-L. The presence of Mo and the solvent loading with RE affected the Fe extraction in the opposite ways. Slow kinetics and process irreversibility were found for the Fe extraction with the ZS HDBP solution. To increase acceptable Fe concentration in a HLW, reduction of Fe(III) by ascorbic acid (AA) was studied to be carried out continuously in the feed flow, just before entering the head contactor of the partitioning extraction cycle. The Mo extraction is of the same order as that of TPE and RE; so its selective stripping prior to the TPE/RE separation is required. This can be done using the DTPA or H2O2 solution in diluted nitric acid. The effectiveness of the process was verified by laboratory scale trials on the centrifugal contactor rig using simulated HLW. The Zr-to-HDBP ratio of 1:6 was found to be useful to decrease the Fe and Mo extractability for their better backwashing with complexants.

Separation of Precipitate-forming Elements during High Level Waste Treatment Using Acidic Zirconium Salt of Dibutyl Phosphoric Acid

Separation of Precipitate-forming Elements during High Level Waste Treatment Using Acidic Zirconium Salt of Dibutyl Phosphoric Acid

The influence of tributyl phosphate on molybdenum extraction with solutions of dibutyl phosphoric acid

The influence of tributyl phosphate on molybdenum extraction with solutions of dibutyl phosphoric acid

The influence of dibutyl phosphoric acid on zirconium extraction with diluted tributyl phosphate and the role of uranyl nitrate

Distribution coefficients of zirconium (DZr) in the 30% TBP — aqueous HNO3 solution extraction system rise 1000–2000 times with the increase of the dibutyl phosphoric acid (HDBP) concentration from 0 to 0.01–0.08 mol/L. A solvate with the molar ratio Zr: HDBP = 1 was found by IR spectroscopy and analytic methods in the initial range of HDBP concentration. In the presence of U(VI) DZr decreases with the growing U concentration, however, the ratio of Zr distribution coefficient in the presence of HDBP (DAZr) to DZr determined in its absence, RZr = DAzr/DZr, is rather high. Function of enhancement (F) was introduced for the evaluation of simultaneous influence of U and HDBP on Zr extraction. An increase of the U concentration resulted first in the decrease in FZr, and then in its increase. The rising part of the FZr curve was more noticeable at a molar excess of Zr over HDBP. The mechanism of Zr extraction by 30% TBP solution in the presence of HDBP when Zr is in excess to HDBP indicates the formation of the solvate with the ratio Zr: HDBP = 1; in the presence of U(VI) the complex with the same ratio is formed by the HDBP interaction with U in the system with a great excess of both HDBP and Zr.