HDBP Concentration Research Articles

Removal Effectiveness for Washing Ce(IV), U(VI), and Zr(IV) Ions from Contaminated Purex Solvent by Hydrazine Carbonate

The contaminated solvent from the Purex process is washed with alkaline detergents such as sodium carbonate, which generates a large amount of secondary wastes. Therefore, hydrazine carbonate as a salt-free reagent deserves to be studied in depth. In this study, the Ce(IV), U(VI), and Zr(IV) metal ions in organic phases containing dibutyl phosphate (HDBP) of 30% tributyl phosphate (TBP)–dodecane were washed with hydrazine carbonate. The effects of the oscillation time (1 to 15 min); temperature (25°C to 85°C); cumulative number of washes (one to four times); mass fraction of hydrazine carbonate (0.1% to 20%); volume ratio of the aqueous phase to the organic phase (0.2 to 5); HDBP concentration (0 to 0.4 M); HNO3 concentration (0.05 to 8 M); and concentration of Ce(IV), U(VI), and Zr(IV) metal ions on the removal percentages of Ce(IV), U(VI), and Zr(IV) metal ions in polluted solvents were studied. The results showed that when the organic phase containing 0.02 M HDBP was washed three times with 5% hydrazine carbonate at 25°C, the removal percentages of the Ce(IV), U(VI), and Zr(IV) ions were 96%, 98%, and 94%, respectively. Meanwhile, the retention concentrations of the three in the organic phase were 35, 28, and 78 mg/L, respectively. The increase of the mass fraction of hydrazine carbonate enhances the removal of the metal ions from the organic phase into the aqueous phase. High acid is not conducive to alkaline washing of metal ions. The increase of HDBP concentration not only promotes extraction but also increases the retention capacity of the organic phase and has the most significant effect on Zr(IV). U(VI) promotes the preferential washing of Zr(IV) while Ce(IV) increases the metal retention concentration of Zr(IV) in the organic phase.

Extraction of molybdenum from nitric acid solutions with solutions of dibutyl hydrogen phosphate zirconium salt

The extraction of Mo with a solution of dibutyl hydrogen phosphate (HDBP) zirconium salt (ZS) in xylene and in TBP-xylene and TBP-decane mixtures was studied in comparison with the Mo extraction in similar systems without Zr. The Mo extraction is enhanced to the largest extent (by a factor of 7 with 1.5 M HNO3) at the HDBP: Zr ratio of 12, but the majority of experiments were performed at the ratio HDBP: Zr = 9, characteristic of the extraction of TPE and REE. The plots of D Mo vs. HNO3 concentration in all the cases pass through a minimum at ∼3 M HNO3, and the minimum is the deeper, the higher the TBP concentration. At the same time, in the system with HDBP ZS at the TBP concentration in the solvent exceeding 50%, further decrease in D Mo is not observed. The dependence of the Mo distribution ratio D Mo on the HDBP concentration at a fixed ratio HDBP: Zr = 9, the composition of the saturated systems, and the spectra of the saturated and unsaturated (with respect to Mo) systems suggest formation of mixed HDBP-Zr-Mo complexes. Assumptions concerning their composition and structure were made. According to the IR data, in these complexes in the absence of TBP the nitrate ion is not coordinated to the Mo atom. Bridged structures Mo-O-Mo are not formed either. Addition of TBP leads to a decrease in D Mo in the extraction with HDBP ZS, but, at the same time, the slope of the dependence of D Mo on the HDBP concentration increases, and the limiting capacity of the solvent for Mo also somewhat increases. These effects are primarily attributed to an increase in the HNO3 concentration in the organic phase in the presence of TBP.

Extraction of long-lived radionuclides from nitric acid solutions using an extractant based on dibutyl hydrogen phosphate and chlorinated cobalt dicarbollide

Chlorinated cobalt dicarbollide (CCD), when added to concentrations of 0.25 M to a solution of dibutyl hydrogen phosphate (HDBP) in m-nitrobenzotrifluoride (MNBTF), increases the distribution ratios of trace amounts of Eu and Am without changing the slope (tan α ∼ 2) of their dependences on HDBP concentration in the 0–1.5 M range. At [CCD]/([CCD] + DBPA]) = 0.2–0.22, the synergistic effect is observed in the entire range of HDBP concentrations in extraction of these elements from 1.0 and 2.5 M HNO3. In this case, HDBP suppresses the extraction of Cs with CCD in the area below the synergistic maximum, where antagonism is observed in the extraction of Cs. Polyethylene glycol (PEG, Slovafol-909) was added to the extraction mixture to improve the extraction of Sr. The extremum is attained at its concentration in the solvent with HDBP of ∼0.033–0.065 M, which is smaller than that in the absence of HDBP by a factor of 1.5–2.5. With increasing concentration of HDBP in the HDBP-CCD-PEG-MNBTF extraction system, the slopes for Eu and Am are 1.3 and 0.6, whereas the slopes for Cs and Sr decrease nonlinearly and amount to −1.8 and −1.3, respectively. With increasing concentration of HNO3, D for Eu, Am, and Cm decreases in proportion to the HNO3 concentration to the power of −3 irrespective of the PEG concentration, and for Cs and Sr, to the power of −2 in the presence of PEG, whereas in the PEG-free systems the dependences are nonlinear. The synergistic extractant is characterized by higher (by an order of magnitude) solubility of metal solvates as compared to the HDBP-MNBTF system (concentration of Eu in the extractant >0.163 M). The extractant containing HDBP (1.1 M), CCD (0.23 M), and Slovafol-90 (0.065 M) in MNBTF is suggested for combined recovery of rareearth (REE) and transplutonium elements (TPE) and of Cs and Sr from high-level waste (HLW) after reprocessing of spent nuclear fuel (SNF) with high burn-up.

Distribution of HDBP in two-phase systems consisting of aqueous nitric acid, organic diluent (with or without TBP), and HDBP or its zirconium salt

The distribution of HDBP between 0–5 M aqueous HNO3 and various solvents or solutions of acidic zirconium salt of HDBP (HDBP ZS, HDBP : Zr ratio 6–18) in the same solvents [decane, xylene, CCl4, m-nitrobenzotrifluoride (F-3), 30 vol % TBP in decane and xylene] was studied. The HDBP concentration in aqueous solutions decreases with an increase in the HNO3 concentration. At HDBP concentrations in the organic phase below 0.1 M, its distribution follows the Nernst equation; in the range 0.1–0.4 M, its concentration in the aqueous phase at a constant acidity is approximately constant; and with a further increase in the HDBP concentration in the organic phase, its concentration in the aqueous phase starts to grow again. When the organic solvent is TBP in diluent, the HDBP concentration in more concentrated HNO3 solutions decreases by almost an order of magnitude compared to the systems without TBP, whereas with water and dilute HNO3 solutions the difference from the TBP-free systems is insignificant. The presence of Zr somewhat increases the HDBP distribution ratio. The extraction of HNO3 with a solution of HDBP in xylene and CCl4 apparently involves the HDBP dimer. A mathematical description of the HDBP and HNO3 distribution between aqueous nitric acid solutions and xylene or CCl4, based on equations of chemical reactions between the components, was suggested.

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.

Extraction of HNO3 with solutions of zirconium salt of dibutyl hydrogen phosphate in 30% tributyl phosphate and in xylene

Zirconium salt of dibutyl hydrogen phosphate (ZS HDBP) dissolved in xylene or 30% tributyl phosphate (TBP) + xylene mixture extracts noticeable amounts of HNO3 at its low concentrations in the aqueous phase, when extraction of HNO3 with straight HDBP itself is not observed. IR data show that DBP− and NO 3 − ions compete for coordination to Zr, which also adds from 2 to 4 HDBP molecules. With a further increase in the HDBP concentration, the HDBP and HNO3 molecules compete for coordination in the outer coordination sphere of zirconium. Inflections in the S-shaped dependence of the HNO3 concentration in the organic phase on the [Zr]:[HDBP] molar ratio lie within the interval from 1:8 to 1:12, which corresponds to filling of the Zr outer sphere with HDBP molecules. In the presence of TBP, these curves become smooth and have no apparent inflection.

Extraction of Ce, Pm, Eu, Tm and Sc Using Di-n-butylhydrogenphosphate in 1,1,2,2-Tetrachlorodifluoroethane

A study was carried out of the extraction of Ce, Pm, Eu, Tm and Sc from aqueous HNO3 medium into an organic phase 1,1,2,2-tetrachlorodifluoroethane (CFC-112, Ledon-112) using di-n-butylhydrogenphosphate (HDBP) as extracting reagent. The organic solvent was studied from the point of view of some of its interesting properties that can be utilized in practical applications of liquid extraction. Especially the dependence of the extraction of selected lanthanoids on the HDBP concentration and pH was studied and constants K2 and KD(HA) were found for this reagent in CFC-112 and mixtures of this solvent with benzene.

“The Third Phase” of Extraction Processes in Fuel Reprocessing, (I)

Formation conditions, compositions and structures of precipitates or “the third phase” were systematically examined in the systems of Zr and radiation depleted products of TBP, such as HDBP, H2MBP, H3PO4, by means of elemental analysis, X-ray diffraction, infrared spectra and 1H-NMR. It was confirmed that one of the most important origins for the third phase is a complexation between Zr ion and the depleted products of TBP. Followings were also elucidated: (1) When the depleted products co-exist with each other, the cooperative effects on the precipitate formation appear in low acid solutions. (2) Precipitate formation depends on the mole ratio of HDBP/Zr. The amount of precipitate reaches the maximum at the mole ratio of approximately 2 and decreases with increasing concentration of HDBP and finally disappears at approximately 10. (3) Precipitate formed at the mole ratio of approximately 2 has the chemical formula, Zr (NO3)2 (HDBP)2 (OH)2. (4) Precipitates of the Zr-H2MBP system begin to appear at the co...

"The thrid phase" of extraction processes in fuel reprocessing. (I). Formation conditions, compositions and structures of precipitates in Zr-degradation products of TBP systems.

Formation conditions, compositions and structures of precipitates or “the third phase” were systematically examined in the systems of Zr and radiation depleted products of TBP, such as HDBP, H2MBP, H3PO4, by means of elemental analysis, X-ray diffraction, infrared spectra and 1H-NMR. It was confirmed that one of the most important origins for the third phase is a complexation between Zr ion and the depleted products of TBP. Followings were also elucidated: (1) When the depleted products co-exist with each other, the cooperative effects on the precipitate formation appear in low acid solutions. (2) Precipitate formation depends on the mole ratio of HDBP/Zr. The amount of precipitate reaches the maximum at the mole ratio of approximately 2 and decreases with increasing concentration of HDBP and finally disappears at approximately 10. (3) Precipitate formed at the mole ratio of approximately 2 has the chemical formula, Zr (NO3)2 (HDBP)2 (OH)2. (4) Precipitates of the Zr-H2MBP system begin to appear at the co...

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.

Kinetics and mechanism of di-n-butylphosphoric acid transfer between toluene and aqueous phases

The rate of inter-phase distribution of di-n-butylphosphoric acid (HDBP) between toluene and dilute aqueous acid or alkali has been studied, using a quiescent interface, stirred mass-transfer cell. The initial rate of organic to aqueous (o → a) partition is first order with respect to total initial organic phase HDBP concentration; the order with respect to initial aqueous phase hydrogen ion activity ({H+}a, i) changes from zero at low {H+}a, i to –1.0 at high {H+}a, i. A mechanism is proposed in which the rate controlling process is diffusion of the singly ionized HDBP dimer (HD–2) from the interface into the aqueous phase; consistency with initial rate laws is demonstrated and information is obtained on the state of interfacially adsorbed HDBP species. In the absence of mineral acid the initial aqueous to organic (a → o) transfer rate is third order with respect to total initial aqueous phase HDBP concentration (Ca, i). Variation of {H+}a, i at constant Ca i showed the order with respect to {H+}a, i to be 1.0. A mechanism, consistent with experiment, is proposed in which the interfacial formation of (HD–2) is the rate-controlling process.Initial rate data are used for the first time in liquid-liquid extraction to predict successfully equilibrium distribution ratios. The correlation shows that transfer mechanisms remain the same under equilibrium and non-equilibrium conditions. A treatment was developed for derivation of “absolute” extraction rates and it is shown that under certain conditions during net o → a transfer, the mechanism of a → o transfer changes from the observed for initial rates.

Studies on mono- and di- n-butylphosphoric acids—V : The extraction of nitric acid from aqueous solution by di- n-butylphosphoric acid and further results on the distribution of di- n-butylphosphoric acid in aqueous-organic solvent systems

The distribution of 32P-labelled di- n-butylphosphoric acid (HDBP) between toluene and aqueous nitric acid has been measured as a function of (i) the concentration of HNO 3 from 0·5–12 M for 0·01, 0·05 and 0·5 M HDBP, and (ii) the concentration of HDBP from 10 −5-0·5 M for 1, 6 and 10 M HNO 3. The dimerization constant and monomer distribution coefficient for HDBP in toluene-1 M HNO 3 correspond to log K 2 = 5·09 and log K d = 0·70. The amount of HNO 3 extracted by a 0·5 M solution of HDBP in toluene can be expressed by the relation C HNO 3(org) = 0·051 C HNO 3(unionized, aq) up to 12 M HNO 3 in the aqueous phase; approximately 20 per cent of the uncomplexed HDBP and 40 per cent of the HDBP·HNO 3 complex are hydrated. A third phase forms in the 0·5 M HDBP-kerosene-HNO 3 system at >4 M HNO 3 in the aqueous phase; at 12 M HNO 3 the third phase has the empirical formula HDBP·HNO 3·H 2O.

Studies on mono- and di- n-butylphosphoric acids—II The solubility and distribution of mono- and di- n-butylphosphoric acids in aqueous-organic solvent systems

The solubilities of mono- and di- n-butylphosphoric acid (H 2MBP and HDBP respectively) at 25°C in water, aqueous nitric acid, odourless kerosene and benzene have been measured using 32P-labelled acids. The net distribution coefficient ( D HDBP) for HDBP has been measured as a function of the concentration of HDBP for 1. (i) a number of organic solvents in contact with 1 M HNO 3, 2. (ii) chloroform in contact with 0·1 and 1 M perchloric acid, and 3. (iii) the kerosene-HNO 3 system from 0 to 15 M HNO 3 In TBP-kerosene-HNO 3 systems, D HDBP and D H 2MBP have been measured as functions of the concentrations of HDBP, H 2MBP, TBP, and HNO 3, and TBP has been shown to associate with both HDBP and H 2MBP. The data can be applied to the calculation of equilibrium distribution coefficients for HDBP and H 2MBP in TBP-HNO 3 systems over a range of [TBP] from 0·1–100% v/v in the diluent, of [HNO 3] from 0 to 15 M, and of [HDBP] and [H 2MBP] either separately or together in the range 10 −6 M-0·05 M. The solubility and distribution data for HDBP are qualitatively interpreted in terms of 1. (i) a series of equations for the dissociation of HDBP, the dimerization of HDBP in both aqueous and organic phases, the association of HDBP with TBP and with HNO 3, and the association of TBP with HNO 3, and 2. (ii) the distribution of the HDBP monomer and dimer, and the HDBP·HNO 3 species, between the phases. The dimerization constants of HDBP in various organic solvents, the distribution constants of the monomer and the dimer in aqueous-organic solvent systems, and the association constant between TBP and HDBP in kerosene have been calculated.