Mixtures Of Tri-n-butyl Phosphate Research Articles

Solvent extraction of intra-lanthanides using a mixture of TBP and TODGA in ionic liquid

The recovery and separation of trivalent lanthanides into individual elements is difficult owing to their similar chemical behaviours. In this study, the solvent extraction of trivalent lanthanide ions from nitric acid solutions in an organic phase comprising a mixture of two electrically neutral extractants, viz. tri(n-butyl)phosphate (TBP) and N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA), is investigated. The hydrophobic room-temperature ionic liquid (IL), 1-methyl-3-butyl-imidazolium bis(trifluoromethanesulfonyl)imide, is employed as a more environmentally benign diluent compared to the conventional molecular solvents. The results reveal that the addition of TBP as a co-extractant with TODGA not only significantly enhances the metal ion extraction but also affords high intra-lanthanide ion selectivity. This is attributed to the formation of complex lanthanide species with both TBP and TODGA. In addition, when IL is used as a diluent, the cationic exchange between metal–organic ligand species and IL cations, as well as neutral complex extraction result in a more efficient extraction. Moreover, the hydrophobic anionic IL entities can also be involved in the extraction mechanism, affording lipophilic metal–organic ligand complexes. The synergistic solvent combination of TODGA, TBP, and IL can afford an excellent separation of the lanthanide(III) ions.

Synergistic extraction and separation of Fe(III) and Zn(II) using TBP and D2EHPA

ABSTRACTWaste chloride pickle liquors from hot-dip galvanizing plants, steel plants and flue dust contain reasonable amounts of heavy metals such as Zn, Cr, Ni, etc. Iron is invariably associated with most of these materials and comes into solution during leaching. Thus, the synergistic extraction of zinc(II) and iron(III) from leach solutions in tri-n-butyl phosphate (TBP)–di(2-ethylhexyl) phosphoric acid (D2EHPA) system diluted in kerosene was investigated. The Zn and Fe concentrations in the leach liquor used in the present study were 2 g/L. Experiments were carried out in the pH range of 0.5–4.0, temperature of 25°C, using sole D2EHPA, sole TBP and D2EHPA–TBP mixtures at different ratios. Results showed that the co-extraction of zinc(II) and iron(III) increased with increasing equilibrium pH using D2EHPA. It is demonstrated that the mixtures of TBP and D2EHPA are more efficient and selective than D2EHPA alone. At low pH values, the separation factor is low when pure D2EHPA is used as an extractant; however, using TBP as a synergist, the separation factor increases and results in a better separation of zinc from iron. Increasing TBP to D2EHPA ratios in the organic phase caused a slight shift to the right in the extraction isotherm of iron and a marked shift to the right in the extraction isotherm of zinc, and the maximum separation factor of 13.3 × 103 was achieved at a TBP to D2EHPA volume ratio of 4:1 (0.58 M TBP: 0.12 M D2EHPA). Furthermore, the effect of equilibrium pH, organic to aqueous phase ratio and Cl− concentration on the selective extraction was investigated. Using two extraction stages at the O/A ratio of 2:1 and pHe (equilibrium pH) of 3 and 1 for zinc and iron, respectively, 99% of zinc(II) and 96.25% of iron(III) were extracted.

Stoichiometry and structural studies of Fe(III) and Zn(II) solvent extraction using D2EHPA/TBP

Abstract The extraction equilibrium of Zn(II) and Fe(III) from chloride solution by the mixture of TBP (tri-n-butyl phosphate) and D2EHPA (di(2-ethylhexyl) phosphoric acid), diluted in kerosene was studied. The results show that in TBP to D2EHPA volume ratio of 3:1 (0.55 M TBP:0.15 M D2EHPA) ΔpH0.5 increased to about 2.5 and Fe(III) and Zn(II) extracted separately with the percentage extraction of 99% and 80%, respectively. The Fourier transform infrared (FTIR) measurements were used in order to find the possible structural functionalities of extracted species in the organic phase. Moreover, the FTIR measurements indicated that there was a hydrogen bond between TBP and D2EHPA molecules. According to FTIR studies and slope analysis method, the reaction between TBP, D2EHPA and zinc was determined and the FTIR-ATR (attenuated total reflectance) method was also employed to verify the stoichiometry of Zn(II) - organic complexes in the organic phase. Both FTIR-ATR and slope analysis methods provided the same results that the ZnA2AH·TBP was probably the extracted specie in the organic phase.

Comparative Molecular Dynamics Study on Tri-n-butyl Phosphate in Organic and Aqueous Environments and Its Relevance to Nuclear Extraction Processes.

A refined model for tri-n-butyl phosphate (TBP), which uses a new set of partial charges generated from our ab initio density functional theory calculations, has been proposed in this study. Molecular dynamics simulations are conducted to determine the thermodynamic properties, transport properties, and the microscopic structures of liquid TBP, TBP/water mixtures, and TBP/n-alkane mixtures. These results are compared with those obtained from four other TBP models, previously described in the literature. We conclude that our refined TBP model appears to be the only TBP model from this set that, with reasonable accuracy, can simultaneously predict the properties of TBP in bulk TBP, in organic diluents, and in aqueous solution. The other models only work well for two of the three systems mentioned above. This new TBP model is thus appropriate for the simulation of liquid-liquid extraction systems in the nuclear extraction process, where one needs to simultaneously model TBP in both aqueous and organic phases. It is also promising for the investigation of the microscopic structure of the organic phase in these processes and for the characterization of third-phase formation, where TBP again interacts simultaneously with both polar and nonpolar molecules. Because the proposed TBP model uses OPLS-2005 Lennard-Jones parameters, it may be used with confidence to model mixtures of TBP with other species whose parameters are given by the OPLS-2005 force field.

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.

Synergistic extraction of uranium(VI) with tri-n-butyl phosphate and i-butyldodecylsulfoxide

The synergistic extraction of uranium(VI) from aqueous nitric acid solution with a mixture of tri-n-butyl phosphate (TBP) and i-butyldodecylsulfoxide (BDSO) in toluene was investigated. The effects of the concentrations of extractant, nitric acid, sodium nitrate and sodium oxalate on the distribution ratios of uranium(VI) have been studied. The values of enthalpy change for the extraction reactions with BDSO, TBP and a mixture of TBP and BDSO in toluene were -23.2±0.8 kJ/mol, -29.2±1.4 kJ/mol and -30.6±0.6 kJ/mol, respectively. It has been found that the maximum synergistic extraction effect occurs when the molar ratio of TBP to BDSO is close to 1. The composition of the complex of the synergistic extraction is UO2(NO3)2 . BDSO . TBP.

Solvent extraction of Tc(VII) by the mixture of TBP and 2-nitrophenyl octyl ether

The extraction of Tc(VII) by the mixture of tri-n-butyl phosphate (TBP) and 2-nitrophenyl octyl ether (NPOE) has been studied. 0.2M NPOE-TBP can extract Tc(VII) effectively from 1M HNO3 and 1M NaOH solutions with distribution ratios of 57.1 and 12.3, respectively. The distribution ratio of Tc(VII) decreases with increasing (>0.5M) HNO3 concentration but increases with the increase of NaOH concentration. A pH 9 NaOH solution has proven to be suitable for Tc(VII) stripping. A simple extraction-stripping cycle can remove Tc(VII) from a sodium hydroxide solution. A more sophisticated extraction process is proposed to remove Tc(VII) from nitric acid solution because the co-extracted HNO3 prevents the direct stripping of Tc(VII) by NaOH solution of pH 9.

Viscosities and densities of binary liquid mixtures of TBP with benzene, toluene and ortho-xylene

Abstract Viscosities and densities of binary mixtures of tri-n-butyl phosphate (TBP) with benzene, toluene and o-xylene were measured at 30, 35, 40 °C. The non-idealities reflected in mixture viscosities are expressed in terms of excess viscosities. A Redlich-Kister-type equation was fitted to the binary η-X-T data for each system.

Synergistic extraction of iron(III) at higher concentrations in D2EHPA-TBP mixed solvent systems

The extraction of iron(III) from chloride solutions at macrolevel concentration by different solvents such as tri-n-butyl phosphate (TBP), di(2-ethylhexyl) phosphoric acid (D2EHPA), and their mixture in various proportions has been investigated at different acid concentrations. The synergistic extraction of iron(III) with a mixture of TBP and D2EHPA was studied and the results were compared with that of the extraction by individual solvent alone. An increase in the concentration of the synergist, TBP, in the D2EHPA-TBP solvent system resulted in an increase in the synergistic co-efficient value. The experimental data are treated graphically to explain the formation of organic phase extracted species, and the equilibrium extraction constants for the species are determined. It is found that a maximum of two molecules of TBP are adducted to the extracted species of the corresponding nonsynergistic system. Stripping of iron(III) with hydrochloric acid from loaded D2EHPA was found to increase with an increase in acid concentration. In the case of D2EHPA-TBP mixtures, stripping efficiency was increased with an increase in acid concentration up to a certain level and then it was decreased. The experimental results indicate that an iron exchange reaction between loaded D2EHPA and TBP proceeds during stripping at a higher concentration of hydrochloric acid (from mixed loaded solvent system). A plausible mechanism for iron(III) extraction and stripping has been discussed.

Evaluation of Excess Correlation Factor in Dilute Binary Mixtures of Tri-N-Butyl Phosphate (TBP) in Nonpolar Solvents

Abstract Excess correlation factor δg in dilute binary mixtures of TBP in nonpolar solvents like tetrach-loromethane, n–hexane, n–heptane, benzene, p–xyiene, carbon disulphide and cyclohexane has been calculated. δg is found to be positive in binary mixtures of TBP–p–xylene, TBP–carbon disulphide and negative in TBP–n–hexane, TBP-benzene, TBP–cyclohexane mixtures. δg changes its sign from negative to positive in TBP–tetrachloromethane and TBP–n heptane. A sharp peak observed in TBP–carbon–disulphide indicates possibility of complexation.

Thermal Decomposition of Nitrated Tributyl Phosphate

Extended contact between heated mixtures of trin-butyl phosphate (TBP) and aqueous solutions of nitric acid and/or heavy metal nitrate salts at elevated temperatures can lead to exothermic reactions of explosive violence. Most solvent extraction operations (e.g., Purex) are conducted at ambient conditions without heating TBP and have been performed safely for decades, but several explosions involving TBP have occurred in the United States, Canada, and the former Soviet Union. This investigation was undertaken to characterize the products of thermal decomposition of both single- and two-phase mixtures of TBP, nitric acid, and water under a variety of conditions. The data indicate that the extent of reaction and the rate of gaseous product formation are affected by the presence of Zr4+, distillation compared with reflux conditions, temperature, water/HNO3 and HNO3/TBP ratios, and whether the decomposition occurs under constant pressure or constant volume conditions. Higher reaction temperatures accelerate the rate of decomposition, but the extent of decomposition, as measured by the quantity of gaseous products, was greater at lower temperatures when the decomposition was performed under distillation conditions. Higher gas production occurs under reflux conditions, lower H2O/HNO3 ratios, and when a separate water-HNO3 phase is initially present. The major gaseous products include N2, CO, CO2, NO, and N2O. Measurable amounts of NO2 were not present in the final product mixture, although an orange color suggesting the presence of NO2 was observed in the early stages of decomposition. The major liquid products were dibutyl phosphoric acid, butyl nitrate, and water. Small amounts of C1-C4 carboxylic acids were also present. Because of the small sample sizes that were employed and the isothermal conditions of the decomposition, runaway reactions were not observed. Some possible reaction pathways are considered.

Nuclear magnetic resonances of tri- n-butyl phosphate-diluent mixtures

Hydrogen and phosphorus magnetic resonance measurements have been obtained for mixtures of tri- n-butyl phosphate (TBP) + chloroform, TBP + benzene, TBP + water, and TBP + 1-butanol at 295.15 K, and phosphorus magnetic resonance measurements for the binary mixture of TBP + n-heptane at 293.15 K. These results suggest that both solvation and aggregation occur in TBP mixtures.

Molecular Interaction in Binary Mixtures of Tri-N-Butyl Phosphate (TBP) and Aliphatic Alcohols-Effect of Free Volume and Internal Pressure

Abstract The ultrasonic velocity, density and viscosity in binary mixtures of TBP with a number of aliphatic primary alcohols viz. methanol, ethanol, 1-hexanol, 1-heptanol, 1-octanol and 1-decanol have been measured at frequency 3 MHz and at temperature 303.16 K. The data are used to compute excess internal pressure and excess enthalpy in these mixtures. The results corroborate the findings of these authors from dielectric studies that the interaction is maximum in 1 heptanol-TBP system and microheterogeneous β-clusters with antiparaliel orientation of dissimilar molecules predominate in it.

Physical properties of the NO‐absorbing system cupric chloride‐tributyl phosphate

AbstractFor pure tri‐n‐butyl phosphate (TBP) as well as solutions of cupric chloride in TBP and for mixtures of TBP with n‐decane or solutions of cupric chloride therein, the density, viscosity, physical solubility of nitric oxide (NO) and its diffusion coefficient have been determined and a discussion is presented

The extraction behavior of titanium(IV) in concentrated hydrochloric acid with tri- n-butyl phosphate and β-diketones

Solvent extraction of titanium(IV) from concentrated hydrochloric acid (11.6 mol dm −3) with tri- n-butyl phosphate (TBP), 2-thenoyltirfluoroacetone (TTA), and benzoylacetone (BA), or a mixture of TBP and of the β-diketones into chloroform, was studied at 298 K. From the relation between the distribution ratio and hydrogen-ion or ligand concentration, the numbers of moles of the extractants in extracted species were computed. It was concluded that titanium(IV) mono- and disolvates with TBP, disolvates with β-diketone, 1:1 and 1:2 mixed solvates with TBP and β-diketone were extracted. It was also concluded that the β-diketones must be associated with titanium(IV) in their undissociated form and that the mixed disolvates were more stable than the statistically expected values from individual solvates.