Dibutyl Phosphoric Acid Research Articles

RADIOLYSIS OF DIISODECYL PHOSPHORIC ACID AND ITS EFFECT ON THE EXTRACTION OF NEPTUNIUM

ABSTRACT Radiolysis of diisodecyl phosphoric acid (DIDPA) in n-dodecane containing tributyl phosphate (TBP) was examined by analyzing concentrations of acidic extractants and H3PO4, and its effect on the extraction of neptuniua was studied froi the aspect of the extraction rate. For the solvent containing 0.5 fi DIDPA and 0.1 1 TBP Irradiated in the absence of HNO3, G-values for degradation of DIDPA and for production of dibutyl phosphoric acid (DBP)were found to be 0.47 and 0.14, respectively. For the solvent irradiated in stationary contact with 0.5 M HNO3, G-value for DIDPA degradation was found to be 0.78, which ras 1.7 tines larger than the value for the solvent irradiated in the absence of HNO3.

Thin-layer chromatographic separation and determination of dibutylphosphoric acid in a mixture of monobutylphosphoric acid and tributyl phosphate

A thin-layer chromatographic (TLC) technique using a silica gel-cellullose plate has been developed for the separation of a mixture of monobutylphosphoric acid (H2MBP), dibutylphosphoric acid (HDBP) and tributyl phosphate (TBP) and for the determination of HDBP. The technique involves initial separation on a TLC plate followed by the determination of isolated HDBP by an indirect spectrophotometric method whereby the concentration of HDBP is measured by its ability to reduce the colour intensity of a thorium-thoron complex at 545 nm. Less than 1 µg of H2MBP and HDBP can be detected on the TLC plate. The method is suitable for the determination of 40–260 µg of HDBP.

Crystal structure of a solvent-extraction complex: Bis(dibutylphosphato)aquabarium-18-crown-6

A complex of barium with dibutylphosphoric acid (HDBP) and 18-crown-6 ether has been prepared and its crystal structure determined. Molecules of the complex contain an 18-crown-6 ring which has a Ba 2+ ion near its center and is capped on one side by a DBP − ion on the other by a DBP − ion and a H 2O molecule. Five of the O atoms of the crown are very nearly planar, while the sixth O atom and the Ba atom are 0.68 » and 0.61 » to one side, respectively. The H 2O molecule makes an intramolecular hydrogen bond to one phosphate group and an intermolecular hydrogen bond to another, by which it links the molecules into continuous chains. The shape of the crown as it adapts to the Ba 2+ ion is compared to the conformation it has in other complexes. Crystals of Ba[(C 4H 9O) 2· PO 2] 2·H 2O·(C 12O 6H 24) are triclinc, P 1 , with a = 13.79(1), b = 17.19(1), c = 9.488(6) », α = 105.78(5)°, β = 83.00(6)°, γ = 107.45(6)°, Z = 2.

Effect of temperature on the selectivity of the extraction of lanthanides with dibutylphosphoric acid from thiocyanate solution

Extraction coefficients and separation factors of all lanthanides were determined in the system: dibutylphosphoric acid /HDBP/ - 3M NH4NCS, in the temperature range of 15–50 °C. The values for the separation factors for such pairs as: Gd−Tb and Er−Tm, are higher than 4, those for the pair of Tb−Dy are higher than 3, and those for the La−Ce, Pm−Sm, Dy−Ho, Ho−Er and Tm−Yb pairs are higher than 2. The influence of temperature on the separation factors of light /La−Gd/ and heavy /Gd−Lu/ lanthanides is discussed and compared with that observed for the extraction from the nitric acid solutions. The results are also discussed in the light of the double-double effect and outer-, vs. inner-sphere complexation in the lanthanide series.

Zirconium behavior in the system HNO 3-30% tributyl phosphate-dodecane in the presence of monobutyl phosphoric acid

Dibutyl and monobutyl phosphoric acids result from the radiolytic degradation of tributyl phosphate in the solvent extraction processing of spent nuclear fuel. Information is needed about the interaction between zirconium and monobutyl phosphoric acid to assess the relative importance of this degradation product in terms of zirconium extraction, retention and solids formation. Monobutylphosphoric acid (H 2MBP) extracts zirconium from nitric acid to a similar extent as dibutyl phosphoric acid (HDBP). Zirconium extracts containing H 2MBP aged at low acidity, ≤0.1 M H +, undergo a reaction to produce a species that is retained by the solvent. There is no retention in the presence of HDBP alone. Gelatinous solids are formed in zirconium solutions in nitric acid by the addition of H 2MBP. Analyses of these solids correspond to the empirical formula Zr(MBP) 2·H 2O. In addition to this compound, an intermediate solid with a MBP Zr molar ratio of one is formed in 0.2 M HNO 3. The addition of H 2MBP to zirconium extracts in 1.09 M TBP in dodecane containing HDBP leads to a solid having a formula corresponding to Zr(OH) x (NO 3) y (DBP)-(MBP) where x + y = 1. Addition of H 2MBP to a zirconium extract in the absence of HDBP leads to a solid with a MBP Zr molar ratio of two. Solubility estimates of these solids show that the MBP compounds are more insoluble, by at least two orders of magnitude, than the corresponding DBP complexes. Extraction of zirconium in the system is mostly determined by HDBP while H 2MBP determines zirconium retention and precipitation.

Ion Chromatographic Determination of Dibutylphosphoric Acid in Nuclear Fuel Reprocessing Streams

Abstract A rapid method has been developed for the determination of dibutylphosphoric acid (DBP), a degradation product of tributylphosphate (TBP), which is used in a solvent extraction process for recovery of uranium. DBP along with any monobutylphosphoric acid (MBP) and phosphoric acid are extracted from the organic phase into dilute sodium hydroxide. DBP is separated from MBP and phosphoric acid by ion chromatography and is determined on a peak height ratio basis. The method requires only 30 minutes per analysis as compared to the conventional alumina column separation-colorimetric determination procedure which requires 8 h to complete. DBP has been quantified to a lower limit of 1.5 mg/L. Relative standard deviations ranging from 5.7% to 0.4% were obtained for DBP concentrations ranging from 1.5 to 500 mg/L, respectively.

Reply to “Comments on ‘Solvent Performance in THTR Nuclear Fuel Reprocessing. Part II: On the Formation of Dibutyl Phosphoric Acid by Radiolytic and Hydrolytic Degradation of the TBP-n-Paraffin Extractant’”

Reply to “Comments on ‘Solvent Performance in THTR Nuclear Fuel Reprocessing. Part II: On the Formation of Dibutyl Phosphoric Acid by Radiolytic and Hydrolytic Degradation of the TBP-<i>n</i>-Paraffin Extractant’”

Comments on “Solvent Performance in THTR Nuclear Fuel Reprocessing. Part II: On the Formation of Dibutyl Phosphoric Acid by Radiolytic and Hydrolytic Degradation of the TBP-n-Paraffin Extractant”

Comments on “Solvent Performance in THTR Nuclear Fuel Reprocessing. Part II: On the Formation of Dibutyl Phosphoric Acid by Radiolytic and Hydrolytic Degradation of the TBP-<i>n</i>-Paraffin Extractant”

Extraction of zirconium from nitric acid media by butyl lauryl phosphoric acid in dodecane

Butyl lauryl phosphoric acid (HBLP) was chosen as a model compound of secondary degradation products of Purex process solvent. The extent of zirconium complexation by this compound is similar to that of dibutyl phosphoric acid or bis(2 ethyl hexyl) phosphoric acid. The mechanism of zirconium extraction by HBLP was studied. The nature of the extracted species could not be unambiguously established. Tributyl phosphate has an antagonistic effect on the zirconium extraction by HBLP. Removal of HBLP from the solvent cannot be accomplished by alkaline washes representative of solvent clean-up procedures used in the Purex process. This could lead to a long term build-up of this type of compound under Purex processing conditions. The threshold HBLP concentration for an enhancement of zirconium extraction is 2 × 10 −4 M.

Solvent Performance in THTR Nuclear Fuel Reprocessing. Part II: On the Formation of Dibutyl Phosphoric Acid by Radiolytic and Hydrolytic Degradation of the TBP-n-Paraffin Extractant

Radiolysis and hydrolysis of tributylphosphate (TBP) in n-paraffin diluent were investigated under conditions simulating several parameters of the THOREX flowsheet for reprocessing thorium containing spent nuclear fuel. The solvent (30 vol% TBP-n-paraffin) was equilibrated with 0.25 to 3 molar nitric acid, and the organic phase was inspected by gas chromatography. Radiolysis in pure solvents (30 and 5 vol% TBP-n-paraffin) with doses from 0.5 to 13 Wh . l/sup -1/ produces HDBP with G values (TBP-based) of approx. 2 and approx. 6, slightly decreasing with higher doses. No H/sub 2/MBP was found. Radiolysis in solvent (30 vol% TBP-n-paraffin), equilibrated with 0.25 to 3 molar nitric acid at a constant dose of 7 Wh . l/sup -1/, leads to a considerably reduced radiolytic fraction of the total HDBP yield with a minimum of approx. 0.3 molar nitric acid in the organic phase (2 molar in the aqueous phase). Irradiating the solvent (30 vol% TBP-n-paraffin), equilibrated with 0.75 molar nitric acid (0.12 molar in the organic phase) with doses from 0.5 to 13 Wh . l/sup -1/, leads to a mixture of hydrolytically and radiolytically formed HDBP, the hydrolytic fraction of which raises the total HDBP yield over the radiolytic HDBP yield frommore » acid-free solvents up to doses of approx. 3 Wh . l/sup -1/. It is proposed to denominate TBP degradation product yields according to their origin, hydrolysis or radiolysis (G value), or just by a concentration value in case of mixed origin, valid for the experimental conditions.« less

Dosage de traces d'acide dibutylphosphorique par chromatographie en phase gazeuse

Trace determination of dibutyl phosphoric acid by gas chromatography The determination of traces of dibutyl phosphoric acid in mixtures of tributyl phosphate and technical grade dodecane was investigated by gas chromatography. A peak cutting technique involving the use of three columns and two different stationary phases for separation following methylation is presented. The calculated uncertainties in the results of the chromatographic analysis for three determinations are approximately: 16% for concentrations of about 10 -4 mol/1; 9% for concentrations of about 5·10 -4 mol/1; 1.5% for concentrations of about 5·10 -3 mol/1.

Acidic organophosphorus extractants—IX extraction of some lanthanides by means of dibutylphosphoric acid from strong acidic medium

The distribution of 141Ce, 152,154Eu, 160Tb and 168Tm between aqueous solution in perchloric, nitric or hydrochloric acids and dibutylphosphoric acid solution in benzene was studied. Beyond a certain limiting concentration of the mineral acid in the aqueous phase, a change of the extraction mechanism takes place, the Me X 3(HDBP) 3 complexes being extracted by the solvation mechanism ( X = ClO 4, NO 3, Cl). This extraction mechanism is independent on the initial concentration of hydrogen ions and on the atomic number of rare earth elements.

Acidic organophosphorus extractants — VIII: Extraction of cerium(IV) by dibutylphosphoric acid

The distribution of 141Ce between an aqueous solution of nitric, perchloric, or hydrochloric acids in the presence of NaBrO 3 and dibutylphosphoric acid solution in CCl 4 was studied. Ce is oxidized to the tetravalent state only in HNO 3 medium, the Ce(NO 3) 4(HDBP) 4 complex being extracted by the solvation mechanism. In the other two mineral acids, only Ce(III) is extracted, the D Ce(IV) D Ce(III) ratio achieving the value of even 10 5. When using a mixture of HNO 3 + HClO 4 acids, a synergic effect was observed.

Kinetics of precipitation of ferric dibutylphosphate from aqueous HNO 3 solutions

The kinetics of the precipitation of iron(III) dibutylphosphate in 1, 3, and 5 M HNO 3 were studied at an initial Fe 3+ concentration of 231 mg/l. (4·14 mM) and at initial dibutylphosphoric acid (HDBP) concentrations of 3·06 and 1·53 g/l. (14·56 and 7·28 mM). The experimental data on Fe 3+ concentration (C, moles/l.) were used to obtain the nonlinear parameters of the integrated form of the rate equation. dC/dt = - k (C - S Fe) n . This equation is obtained from a more general expression of the form dC/dt = -kk ′(C - S Fe) p (C D-S D) q , where C D and S D are, respectively, instantaneous and final (i.e. its solubility) concentrations of dibutylphosphate and S Fe is the final (solubility) concentration of Fe 3+. The assumed reaction, Fe 3++3 HDBP ⇌Fe (DBP) 3+3H +, appears to have a combined order n(= p+ q) of approximately 2; the rate constant (k) is of the order of 10 −3−10 −2 when time is expressed in minutes. The value of the solubility product increases from about 2 × 10 −13 to 2 × 10 −12 (moles/l.) 4 as the nitric acid concentration increases from 1 to 5 M.

The solvent extraction of hafnium(IV)—VI: Extraction of Hf(IV) by some dialkylphosphoric acids from chloride and nitrate media

The distribution of 175+181Hf(IV) between aqueous hydrochloric or nitric acid and (i) a solution of dibutylphosphoric acid in benzene and chloroform, (ii) di- n-amylphosphoric acid in toluene and (iii) diethylhexyl-and di- n-octylphosphoric acids in n-octane has been studied. In the range of concentrations of Hf used (up to 2 × 10 −6M), Hf is extracted from a hydrochloric acid medium up to C HCI of 3·5 M predominantly as HfClA 3(HA) 2, where HA is the dialkylphosphoric acid. In a medium of nitric acid at C HNO 3 ⩾ 1·5 M, or in one of hydrochloric acid at C HCI ⩾ 4·5 M, the initial ion-exchange reaction mechanism is replaced by an addition type of reaction with the formation of extractable complexes of Hf X 4(HA) y , where X = NO 3, Cl. At higher concentrations of HNO 3, an extractable HNO 3·HA complex is formed which results in a decrease in the distribution ratio of Hf.

The solvent extraction of hafnium(IV)—II extraction of Hf(IV) by some dialkylphosphoric acids from perchloric medium

The distribution of 175+181Hf(IV) was studied between aqueous solutions of perchloric acid and solutions of dibutyl-, diamyl-, diethylhexyl- and dioctylphosphoric acids (=HA) in benzene, chloroform, CCl 4, cyclohexane and n-octane. In the region of existence of mononuclear complexes (up to 1 × 10 −7 M Hf) Hf is extracted predominantly as Hf(ClO 4)A 3·(HA) 2. At higher initial concentration of Hf, polymeric complexes are formed in the aqueous phase, which cause a decrease in the value of the distribution ratio of the Hf (= D). In strongly acidic media (above 4 M HClO 4), the primary ion-exchange reaction mechanisms is replaced by an addition type of reaction, which results in the formation of very extractable complexes of Hf(ClO 4) 4(HA) 4. Consequently a considerable increase in the value of D occurs. When using diamyl- and dibutylphosphoric acids in this medium, the results are affected by adsorption of Hf on the walls. Addition of TBP caused a decrease in D. This antagonistic effect can be explained by the interaction of TBP with the HA.

Removal of Fission Products and Their Complexing Agents from Degraded Solvent by Ion Exchange Method

Removal of fission products and their complexing agents from chemically degraded TBP/kerosene and particularly from the kerosene diluent, was studied. With the use of column technique with mixed anion and cation exchange resins, more than 80% of the fission products and their complexing agents were removed. The carboxylic acids, which constitute one of the degradation products bringing about decrease of uranium extractability, were completely removed together with the complexing agents thereof by anion exchange resin. Removal was also obtained of monobutyl and dibutyl phosphoric acids (H2MBP and HDBP), which can retain fission products and which in actual practice are liable to be formed by hydrolysis of TBP under intensive irradiation with concentrated nitric acid and/or at the elevated temperatures.

Removal of Fission Products and Their Complexing Agents from Degraded Solvent by Ion Exchange Method

Removal of fission products and their complexing agents from chemically degraded TBP/kerosene and particularly from the kerosene diluent, was studied. With the use of column technique with mixed anion and cation exchange resins, more than 80% of the fission products and their complexing agents were removed. The carboxylic acids, which constitute one of the degradation products bringing about decrease of uranium extractability, were completely removed together with the complexing agents thereof by anion exchange resin. Removal was also obtained of monobutyl and dibutyl phosphoric acids (H2MBP and HDBP), which can retain fission products and which in actual practice are liable to be formed by hydrolysis of TBP under intensive irradiation with concentrated nitric acid and/or at the elevated temperatures.

Nitrosylruthenium-Organophosphorus Complexes

Nitrosylruthenium-dibutylphosphate complexes were prepared by the reaction of trinitrate-nitrosylruthenium with dibutylphosphoric acid and by the reaction of nitrosylruthenium hydroxide with dibuty...

Complex formation in the dilute uranyl nitrate-nitric acid-dibutyl phosphoric acid-tributyl phosphate-Amsco system

The re-extraction of uranium (VI) from TBP-Amsco solution into dilute nitric acid is hindered by the presence of dibutyl phosphoric acid. Attempts to correlate observed extraction coefficients with published equilibrium data established that the extraction coefficient of uranium is actually greater than calculated from the published data. The empirical formula of the previously undescribed complex is [UO 2(NO 3)(DBP)·TBP] x . Good agreement with the experimental data is obtained with x = 2. For this complex log K = 12·5. A characteristic set of six ultra-violet absorption peaks is associated with the complex.