Tributyl Phosphate System Research Articles

Mechanisms for the separation of Li+ and Mg2+ from salt lake brines using TBP and TOP systems

The tributyl phosphate (TBP)/FeCl3 system has been widely used for lithium extraction from high‑magnesium salt lakes. However, at high TBP concentrations, the Li/Mg selectivity is significantly lower. This study revealed that at high TBP concentrations, TBP alone extracted Mg2+ to form MgCl2·6TBP as the main product, thus affecting the extraction efficiency of Li+. On this basis, a neutral phosphate with long carbon chains, trioctyl phosphate (TOP), was used to replace TBP. The separation capacity and extraction mechanism of the TOP/FeCl3 system were studied, and density functional theory (DFT) calculations were employed to model the cationic complexes of the TOP and TBP systems. The results showed that in the presence of FeCl3, the extraction efficiency of Li+ (ELi) reached 91 %, and the Li/Mg separation factor (βLi/Mg) was 5688. In contrast, in the TBP/FeCl3 system with the same concentration, the ELi and βLi/Mg values were much lower at 74 % and 239, respectively. Furthermore, the TOP complex of Li+ had shorter Li − O bond lengths and a more negative binding energy, while that formed with Mg2+ had longer Mg − O bond lengths and the smallest HOMO–LUMO gap, indicating that TOP bonded more stably with Li+ and was less prone to Mg2+ extraction than TBP.

A selective hydrometallurgical method for scandium recovery from a real red mud leachate: A comparative study

The aim of this study was to recover Sc as the main product and Fe as a by-product from Hungarian bauxite residue/red mud (RM) waste material by solvent extraction (SX). Moreover, a new technique was developed for the selective separation of Sc and Fe from real RM leachates. The presence of high Fe content (∼38%) in RM makes it difficult to recover Sc because of the similarity of their physicochemical properties. Pyrometallurgical and hydrometallurgical methods were applied to remove the Fe prior to SX. Two protocols based on organophosphorus compounds (OPCs) were proposed, and the main extractants were evaluated: bis(2-ethylhexyl) phosphoric acid (D2EHPA/P204) and tributyl phosphate (TBP). The results showed that SX using diethyl ether and tri-n-octylamine (N235) was efficient in extracting Fe(III) from the HCl leachate as HFeC14. Over 97% of Sc was extracted by D2EHPA extractant under the following conditions; 0.05 mol/L of D2EHPA concentration, A/O phase ratio of 3:1, pH 0–1, 10 min of shaking time, and a temperature of 25 °C. Sc(OH)3 as a precipitate was efficiently obtained by stripping from the D2EHPA organic phase by 2.5 mol/L of NaOH with a stripping efficiency of 95%. In the TBP system, 99% of Sc was extracted under the following conditions: 12.5% vol of TBP, an A/O phase ratio of 3:1, 10 min of shaking time, and a temperature of 25 °C. The Sc contained in the TBP organic phase could be efficiently stripped by 1 mol/L of HCl with a stripping efficiency of 92.85%.

Dissolution of Palladium Metal in Solvent Leaching System with the Presence of Oxidizing Agent

Platinum group metals (PGMs) are important for the manufacture of advanced materials in the field of catalysts and electronic devices. Since the chemical properties of PGMs are very similar to each other, hydrometallurgical processes should be employed to recover PGMs with high purity from either ores or secondary resources. In hydrometallurgical processes for PGMs, the first step is the dissolution of PGMs. For this purpose, inorganic acid solutions with oxidizing agents are generally employed. In this work, nonaqueous solvent leaching systems with a relatively cheap price were employed to investigate the dissolution of pure palladium (Pd) metal. The solvent leaching systems consisted of concentrated hydrochloric acid solution and commercial extractants such as tributyl phosphate (TBP), 7-hydroxydodecan-6-one oxime (LIX 63), and di-n-octyl sulfide (DOS) in the presence of H2O2 as an oxidizing agent. Among the three systems, TBP showed the best efficiency for the dissolution of Pd. The effect of several parameters like TBP concentration, temperature, time, stirring speed and the weight ratio of Pd to TBP/HCl/H2O2 was explored. The dissolution percentage of Pd by the HCl–H2O2–TBP system was higher than by the HCl–H2O–H2O2 system at the same concentration of HCl and H2O2. The role of TBP in enhancing the dissolution of Pd was discussed on the basis of the interaction between HCl and TBP. Compared to aqueous systems, mass transfer is important in the dissolution of Pd metal by the solvent leaching system. Optimum conditions for the complete dissolution of Pd were obtained.

Effects of Impurity Ions on the Metastable Zone Width of Phosphoric Acid in Tributyl Phosphate

The solubility (from 0.95 °C to 19.11 °C) and metastable zone width of phosphoric acid in tributyl phosphate (TBP) have been measured using a laser method. The results show that the solubility curve is remarkably dependent on temperature in the experimental temperature range. A polynomial fitting of the solubility data was obtained. The metastable zone width increases directly with the increasing rate of cooling but decreases with the increasing concentration of phosphoric acid in TBP. An apparent secondary nucleation order m for phosphoric acid in the TBP system was calculated using Nývlt’s approach and revised using a modified linear regression method. The effects of typical impurity ions (Al3+, Mg2+, and Fe3+) on the metastable zone width for phosphoric acid in TBP were also investigated. The presence of impurity ions can enhance the metastable zone width for phosphoric acid in TBP.

Dynamic light scattering studies on the aggregation behavior of tributyl phosphate and straight chain dialkyl amides during thorium extraction

Dynamic light scattering (DLS) studies were carried out to investigate the aggregation behavior of 1.1M solutions of tributyl phosphate (TBP), N,N-dihexyl octanamide (DHOA) and of N,N-dihexyl decanamide (DHDA) in n-dodecane equilibrated with varying concentrations of nitric acid (0.1–6M) and of Th (10–200g/L). There was a gradual increase in thorium extraction with increased aqueous phase acidities. A significant enhancement in the aggregate sizes was observed with increasing concentration of thorium in the organic phase. The effect of 1-octanol as phase modifier was also investigated on the aggregation behavior of extracted species for TBP system.

Extraction properties of phthalic acid and aromatic polycarboxylic acids using various solvents

BACKGROUND: To explore the extraction properties of aromatic acids produced in the oxidation of coal, the extraction equilibrium of phthalic acid (as a typical product) was studied using three solvents, 1-octanol, 50% tributylphosphate (TBP)/kerosene, and 10% trialkylphosphine oxide (TRPO)/kerosene, and the feasibility of separating phthalic, [1,1′-biphenyl]-2,2′-dicarboxylic and trimellitic acids is discussed. RESULTS: Phthalic acid extraction followed the sequence: 10% TRPO > 50% TBP > 1-octanol, with recoveries from the TRPO and TBP systems being much larger than that for 1-octanol. The stoichiometry of formation of the complexes of TBP and TRPO with phthalic acid was 1:1. The apparent extraction equilibrium constant for TRPO is much larger than that for TBP. The distribution coefficient of [1,1′-biphenyl]-2,2′-dicarboxylic acid is much larger than that of the other two acids using 1-octanol as the extractant and this acid could be removed by 1-octanol from a mixture of the three acids. The extraction equilibrium correlations obtained for the individual acid component systems can be used to predict that of the acid mixture. CONCLUSION: The extent of phthalic acid extraction by the three solvents investigated is as follows: 10% TRPO > 50% TBP > 1-octanol. The stoichiometry of the complex formation of TBP or TRPO and phthalic acid is 1:1, and the apparent extraction equilibrium constant for TRPO is much larger than that for TBP. 1-octanol shows a good extractive selectivity for [1,1′-biphenyl]-2,2′-dicarboxylic acid as compared with phthalic and trimellitic acids. Copyright © 2011 Society of Chemical Industry

Alpha radiolytic degradation of N,N-dihexyl octanamide

The primary purpose of this study was to understand the alpha radiolytic degradation behavior of N,N-dihexyl octanamide (DHOA) vis a vis tributyl phos- phate (TBP) solutions in n-dodecane under plutonium loading conditions. These studies were carried out as a function of dose on different Pu loaded samples (contain- ing 0.002-10 g/L Pu) from 4 M HNO3 medium. These Pu loaded solutions were evaluated for stripping behavior by contacting with 0.5 M NH2OH at 0.5 M HNO3 solutions. Organic phase analysis was carried out by gas chroma- tography (GC) and by visible spectrophotometry. These studies clearly indicated that Pu stripping becomes difficult with increased dose in the case of TBP system. On the other hand, no such problem was observed in DHOA system during stripping of plutonium, thereby indicating that DHOA is a promising candidate for the reprocessing of high burn up Pu rich spent fuels.

Review of Physical and Chemical Properties of Tributyl Phosphate/Diluent/Nitric Acid Systems

Numerous publications have examined the chemical and physical aspects of tributyl phosphate (TBP), TBP/nitric acid, and TBP/diluent/nitric acid systems, but there are some discrepancies within the available data. There is also a lack of data on the physical properties of TBP at temperatures above 60°C. A review of more than 100 references, covering the physical and chemical properties of TBP and related systems will be presented. Data on solvent degradation and kinetics of the interactions occurring in these systems will be provided and compared. Also the existing data on TBP vapor pressure, solubility, and density will be discussed.

Studies on the Extraction of Actinides by Dibutylbutyl Phosphonate

Dibutylbutyl phosphonate (DBBP) was synthesized by the Michaelis Becker reaction, and was characterized by elemental analysis, IR, and 31P NMR. The extraction of U(VI), Th(IV), Pu(IV), Fe(III), and Am(III) by 1.1 M DBBP in n-dodecane as a function of nitric acid concentration was studied, and the results are compared with the extraction behavior of these ions with tributyl phosphate (TBP) and diamylamyl phosphonate (DAAP) in n-dodecane. The physical properties of the extractant such as the density, surface tension, viscosity, aqueous solubility, and phase-disengagement time with 1.1 M DBBP/n-dodecane have been measured and compared with those of 1.1 M TBP/n-dodecane and 1.1 M DAAP/n-dodecane. Studies on the third-phase formation behavior of 1.1 M DBBP/n-dodecane with U(VI) and Th(IV) nitrates in nitric acid medium have been carried out, and the results are compared with the TBP and DAAP systems. Studies were also carried out to study the U-Fe separation by DBBP impregnated on XAD-4 resin.

Structure and dynamics of binary and ternary lanthanide(iii) and actinide(iii) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) complexes. Part 2, the structure and dynamics of binary and ternary complexes in the Y(iii)/Eu(iii) –TTA – tributylphosphate (TBP) system in chloroform as studied by NMR spectroscopy

The stoichiometric reaction mechanisms, rate constants and activation parameters for inter- and intramolecular ligand exchange reactions in the binary Y/Eu(TTA)(3)(OH(2))(2)-HTTA and the ternary Y/Eu(TTA)(3)(OH(2))(2)-TBP systems have been studied in chloroform using (1)H and (31)P NMR methods. Most complexes contain coordinated water that is in very fast exchange with water in the chloroform solvent. The exchange reactions involving TTA/HTTA and TBP are also fast, but can be studied at lower temperature. The rate constant and activation parameters for the intramolecular exchange between two structure isomers in Y(TTA)(3)(OH(2))(2) and Y(TTA)(3)(TBP)(OH(2)) were determined from the line-broadening of the methine protons in coordinated TTA. The rate equations for the intermolecular exchange between coordinated TTA and free HTTA in both complexes are consistent with a two-step mechanism where the first step is a fast complex formation of HTTA, followed by a rate determining step involving proton transfer from coordinated HTTA to TTA. The rate constants for both the inter- and intramolecular exchange reactions are significantly smaller in the TBP system. The same is true for the activation parameters in the Y(TTA)(3)(OH(2))(2)-HTTA and the ternary Y/Eu(TTA)(3)(TBP)(OH(2))-HTTA systems, which are ΔH(≠) = 71.8 ± 2.8 kJ mol(-1), ΔS(≠) = 62.4 ± 10.3 J mol(-1) K(-1) and ΔH(≠) = 38.8 ± 0.6 kJ mol(-1), ΔS(≠) = -93.0 ± 3.3 J mol(-1) K(-1), respectively. The large difference in the activation parameters does not seem to be related to a difference in mechanism as judged by the rate equation; this point will be discussed in a following communication. The rate and mechanism for the exchange between free and coordinated TBP follows a two-step mechanism, involving the formation of Y(TTA)(3)(TBP)(2).

Preparation of Hematite Powders with Plate‐Like Morphology from Titania Wastes by Solvent Extraction Followed by Precipitation Stripping and Hydrothermal Synthesis

This paper embodies the results of the investigations carried out on the solvent extraction of iron(III), magnesium(II), aluminum(III), titanium(IV), vanadium(V), chromium(III), and manganese(II) from hydrochloric acid solutions using tributylphosphate (TBP) in kerosene as an extractant. The results demonstrate that iron(III) is extracted into kerosene as HFeCl4 · 2TBP. On the other hand, magnesium(II), aluminum(III), titanium(IV), vanadium(V), chromium(III) and manganese(II) were not extracted with TBP from 2.0 mol/dm3 hydrochloric acid solutions. The potential of the TBP system for the recovery of high purity ferric chloride from the simulated waste chloride liquors of the titanium minerals processing industry was assessed. Studies were also carried out to prepare hematite powders from titania wastes by solvent extraction combined with precipitation stripping and hydrothermal synthesis. The iron oxide powders were characterized by x‐ray diffraction (XRD), scanning electron microscopy (SEM) and particle size analysis. The recycling capacity of the TBP system was tested by both extraction and infrared (IR) spectral data.

A polymer NMR cell for the study of high-pressure and supercritical fluid solutions

Nuclear magnetic resonance (NMR) offers researchers unique, highly localized molecular information. The importance of this technique is well established in studies using chemical shift, spin coupling, and relaxation times providing detailed structural information, determining chemical equilibria and kinetics, and understanding molecular dynamic processes. However, the widespread application of NMR spectroscopy to high-pressure liquids and supercritical fluids has been limited due to the complexity of the necessary instrumentation. One approach to these studies is to build a dedicated high-pressure probe. Another involves the utilization of a high-pressure cell designed to fit in commercially available probes. Here we present the design and implementation of a simple, three-piece, high-pressure NMR cell constructed of high-performance polymers. The present cell has pressure capabilities of up to 400 bar; however, the ultimate temperature and pressure limits will be determined by the specific polymer chosen. High-resolution NMR spectra of methanol modified and tributyl phosphate (IBP) modified supercritical CO2 are presented. An example of supercritical fluid phase behavior monitored with NMR is demonstrated for the TBP system in which the chemical shift changes in the 31P nucleus as a function of density are indicative of solution phase separation. The multinuclear NMR data demonstrate the utility of this cell for studying supercritical fluid solution systems relevant to analytical separations and extractions.

Correlation between Extraction Equilibrium of Uranium(VI) and Density of CO2 Medium in a HNO3/Supercritical CO2−Tributyl Phosphate System

The extraction equilibrium of U(VI) between a nitric acid solution and a supercritical CO(2) phase containing tributyl phosphate (TBP) is formulated taking into account that (i) a distribution ratio of a metal extracted is a function of a distribution constant of each component involved in the extraction reaction, (ii) the distribution constant is defined as a ratio of solubilities of the component in both phases, and (iii) the solubility in the CO(2) phase is correlated with density of CO(2). A simple linear relationship between the distribution ratio, D(U), of U(VI) and density, ρ, of CO(2) is derived; log D(U) = a log ρ + A + B, in which a is a proportional constant implying the solvation characteristic of the solute in supercritical CO(2), A is a pressure-independent constant, and B is a variable determined by the distribution equilibrium of HNO(3). The equation derived was verified experimentally by the measurement of the distribution ratio of U(VI) and HNO(3) under various conditions of pressure and temperature. A novel concept of selective supercritical fluid extraction of metals by means of pressure-tuning or CO(2) density-tuning was proposed.

A solvent extraction process for the preparation of ultrahigh purity scandium oxide

The development of a solvent extraction process for the preparation of ultrahigh purity scandium oxide is described. The process consists of two solvent extraction circuits, viz. the removal of zirconium from the starting scandium oxide (purity about 99%) from a 6 M HClO 4 solution of scandium with 100% tributyl phosphate (TBP) in single stage at an O:A phase ration of 1:1 in the first extraction circuit and the separation from scandium of impurity elements such as calcium, aluminum, manganese, titanium, yttrium and lanthanides, from a 5.8 HCl solution containing scandium with a 40 vol% solution of di(1-methyl heptyl) methyl phosphate (P 350) in kerosene in three counter-current stages at an O:A ratio of 1.9:1 in the second extraction circuit. The scandium in the loaded organic phase is fully stripped in three stages using 1 M HCl at an O:A ratio of 1:1 for the TBP system and 2:1 for the P 350 system. The scandium is recovered as scandium oxide after precipitation with oxalic acid and calcination at 750–800°C. Experimental data show that the purity of the final scandium oxide product exceeds 99.995% under the selected conditions. The extraction yield of scandium was 99% for the first circuit and 98% for the second. The total recovery of scandium was found to be 93% or higher.

A Nuclear Magnetic Resonance Study on Ligand Exchange Reactions in U(VI) Nitrato Complexes with Ligands Containing Phosphoryl Group in Non-aqueous Solvents

The exchange reactions of tributyl phosphate (TBP) and dihexyl-N, N-diethylcarbamoylmethylphosphonate (CMP) in U(VI) nitrato complexes with TBP or CMP (abbreviated as U(VI)-TBP or U(VI)-CMP) have been studied by means of 31P NMR method in CD3COCD3 or CD2Cl2. The number of TBP coordinated to uranyl nitrate was directly determined to be 1 in CD3COCD3 and 2 in CD2Cl2 by the area integrations of 31P NMR signals of free and coordinated TBP. Similarly, the number of coordinated CMP was evaluated as 1 in CD3COCD3. The exchange rate constants of TBP and CMP in U(VI)-TBP and U(VI)-CMP complexes were calculated by the two-site exchange model. The exchange rate of TBP in U(VI)-TBP is independent of the free TBP concentrations ([TBP]f), while that in U(VI)-CMP is dependent on [CMP]f. From these results, the dissociative (D) and interchange (I) mechanisms were proposed for the exchange reactions of TBP in U(VI)-TBP and CMP in U(VI)-CMP, respectively. Kinetic parameters are as follows: rate constant (25°C), ΔH# (kJ·mo1−1), ΔS# (J·K−1·mol−1); 9.9×103s−1, 33.7, −55.4 (U(VI)-TBP system), 2.3×104 m−1·s−1 (apparent second-order), 25.2, −75.9 (U(VI)-CMP system).

Quantitative Equilibrium Constants between CO2and Lewis Bases from FTIR Spectroscopy

Equilibrium constants measured from the ν2 bending mode of CO2 by FTIR spectroscopy are reported for the electron donor−acceptor interactions of CO2 with three Lewis bases: triethylamine (TEA), pyridine (PYR), and tributyl phosphate (TBP). The average Kc values are 0.046 (CO2−TEA), 0.133 (CO2−PYR), and 1.29 (CO2−TBP) L/mol at 25 °C in the solvent pentane. For the CO2−TBP system, the average enthalpy of association, ΔH°, is −4.7 kcal/mol. Ab initio calculations indicate that steric repulsion of the ethyl groups in TEA cause the binding energy of the CO2−TEA complex to be weaker than that of the CO2−PYR complex by 1.34 kcal/mol, a trend that is in agreement with our spectroscopic data. The lattice fluid hydrogen bonding model was used in conjunction with the spectroscopically determined Kc values to predict bubble points for the CO2−TEA and CO2−TBP systems and CO2 sorption in a hypothetical polymer. These calculations indicate that these relatively weak specific interactions have a measurable effect on pha...

A modified program for computation of formation constants of synergetic extraction complexes with two-phase titrations by using the Marquardt-Fletcher algorithm

A modified computer program SCTPT for the computation of formation constants of extraction complexes with two-phase pH titration data by using the Marquardt-Fletcher algorithm is described. It can be used to deal with extraction systems which consist of a metal, an acidic extractant and a neutral synergistic reagent with no need of new subroutine. It has been applied successfully to the Pb-PMBP(1-phenyl-3-methyl-4-benzoyl-pyrazolone-5)-TBP (tributyl phosphate) system. The results obtained are in agreement with those published in the literature.

INFRARED AND NMR STUDIES INFRARED AND NMR STUDIES ON RHENIUM(VII) COMPLEXES WITH CMPO AND TBP

ABSTRACT The infrared and NMR studies have been carried out on Re(VII) (a stand-in for Tc(VII)) complexes with n-octyl(phenyl)-N,N-diisobutyl-carbamoylmethylphosphinc oxide (CMPO) and tributyl phosphate (TBP). In the IR study, changes in the absorption bands of the carbonyl and phosphoryl stretching regions were monitored when Re was extracted. The phosphoryl group was also investigated by using a phosphorus NMR. The spectra obtained in the mixed CMPO-TBP system were compared with those obtained in the CMPO or TBP system in order to discuss their bond-structures. It was found that CMPO showed semi-bidentate [1] and bidentate bonding and that TBP could extract HReO4 in the mixed CMPO-TBP system. The IR and NMR results showed evidence of enhancement in the Re (Tc) extraction in the mixed CMPO-TBP system.

Scavenger effects in the radiolysis of cyclohexane:4-methyl-4-phenyl-2-pentanone system and cyclohexane:Tributylphosphate system

Multiple scavenger effects have been used to investigate the radiolysis of cyclohexane. Using the excited siglet probes 4-methyl-4-phenyl-2-pentanone (MPP) and tributyl phosphate (TBP), we obtained the yields of the excited singlet state of benzene (1.4±0.2), cyclohexane (1.5±0.2), TBP (1.4±0.3), the yield of the thermal hydrogen atoms of cyclohexane (1.5), and the yield of the germinate ions of cyclohexane (3.8). The multiple scavenger effects of MPP and TBP were successfully used in the research of hydrogen atom transfer process in the radiolysis of cyclohexane.

Oscillator strengths of some lanthanide nitrates in tributylphosphate

Oscillator strengths for some lanthanide nitrates in tributylphosphate (TBP) are reported and interpreted by means of the Judd-Ofelt theory. The T λ parameters of the Judd-Ofelt theory are also reported. A comparison of relative intensity changes for the TBP systems compared to the aquo ions shows that some “non-hypersensitive” transitions may exhibit intensity changes as large as the changes shown by so-called “hypersensitive” transitions. This result is interpreted in terms of the relative effects of symmetry and covalency on the T λ parameters of the Judd-Ofelt theory.