HDEHP Concentration Research Articles

Purification of 89Sr from FBTR irradiated Yttria target by extraction chromatography using HDEHP impregnated XAD-7 resin

Abstract 89Sr is used in bone pain palliative care of cancer patients and the same is being produced presently via the 89Y(n, p)89Sr reaction by irradiating yttria target in Fast Breeder Test Reactor (FBTR). An efficient separation method was standardized for the removal of bulk yttrium target by extraction chromatography using di(2-ethylhexyl) phosphoric acid (HDEHP) impregnated on XAD-7 resin. In the present paper, the extraction behavior of Sr(II) and Y(III) was studied as a function of the concentration of nitric acid in the aqueous phase and concentration of HDEHP in the resin phase. The separation of Sr(II) and Y(III) was standardized using the above resins and the method was subsequently applied satisfactorily for the removal of yttrium from the dissolver solution of FBTR irradiated yttria pellet towards the purification of 89Sr. A baseline separation of 89Sr and Y was achieved. Leaching and breakthrough capacity studies were evaluated for the resins and it was established that the stability and capacity of the resins were satisfactory. The breakthrough capacity was found to be 12 mg Y(III) per gram of the HDHEP resin whereas the leaching studies established that the resins are stable for multiple cycle of operations.

A rapid impregnation method for loading desired amounts of extractant on prepacked reversed-phase columns for high performance liquid chromatographic separation of metal ions

A time-efficient impregnation method for loading extractant onto reversed-phase columns was developed, using di-(2-ethylhexyl) phosphoric acid (HDEHP) as a model extractant. The optimal loading conditions for the impregnation process of a standard analytical scale column was achieved by dissolving an appropriate amount of HDEHP (per void volume) in n-pentane, flushing the column with two void volumes (5mL) of impregnation solution and heating the column for a short time to remove the solvent. The process takes about one hour, a significant time reduction compared to commonly used impregnation methods (17–23h). The chromatographic traits for separation of the lighter lanthanides (La-Gd) using columns impregnated under different conditions were evaluated; heating for short period of time gave improved column performance most likely due to the presence of n-pentane in the pores of the support material. A linear relation was found (R2=0.9934) for the amount of HDEHP loaded as a function of HDEHP concentration in the impregnation solution. The coated amounts of HDEHP were in the range of 0.29–2.25mmol per column by flushing with 5mL of impregnation solution containing 0.3–5.0mmol of HDEHP per void volume. This ‘flush-evaporate’ impregnation method allowed for loading a pre-determined amount of extractant and produces very small amounts of organic waste. An overview of the various impregnation approaches previously used for extractant coating on prepacked columns and bulk support materials is also presented.

Extraction of Water and Speciation of Trivalent Lanthanides and Americium in Organophosphorus Extractants.

Complexes of the trivalent lanthanides and Am with di-2-ethylhexylphosphoric acid (HDEHP) dissolved in an aliphatic diluent were probed with UV-vis, X-ray absorption fine structure, and time-resolved fluorescence spectroscopy while the water concentration was determined by Karl Fischer titrations. In particular, our work focuses on the Nd-hypersensitive UV-vis absorbance region to identify the cause of changing absorbance values at 570 and 583 nm in relation to the pseudooctahedral Nd environment when coordinated with three HDEHP dimers. In contrast to recently reported interpretations, we establish that while impurities have an effect on this electronic transition band, a high water content can cause distortion of the pseudooctahedral symmetry of the six-coordinate Nd, resembling the reported spectra of the seven-coordinate Nd compounds. Extended X-ray absorption fine structure analysis of the Nd in high-concentration HDEHP solutions also points to an increase in the coordination number from 6 to 7. The spectral behavior of other lanthanides (Pr, Ho, Sm, and Er) and AmIII as a function of the HDEHP concentration suggests that water coordination with the metal likely depends on the metal's effective charge. Fluorescence data using lifetime studies and excitation and emission spectra support the inclusion of water in the Eu coordination sphere. Further, the role of the effective charge was confirmed by a comparison of the Gibbs free energies of six- and seven-coordinate La-HDEHP-H2O and Lu-HDEHP-H2O complexes using density functional theory. In contrast, HEH[EHP], the phosphonic acid analogue of HDEHP, exhibits a smaller capacity for water, and the electronic absorption spectra of Nd or Am appear to be unchanged, although the Pr spectra show a noticeable change in intensity as a function of the water content. Electronic absorption extinction coefficients of AmIII, NdIII, PrIII, SmIII, ErIII, and HoIII as a function of the HDEHP concentration are reported for the first time.

Extraction behaviour of Am(III) and Eu(III) from nitric acid medium in TEHDGA-HDEHP impregnated resins

Abstract The extraction behaviour of Am(III) and Eu(III) from nitric acid medium was studied in the solvent impregnated resins containing extractants such as tetra-bis(2-ethylhexyl)diglycolamide (TEHDGA) or bis-(2-ethylhexyl)phosphoric acid (HDEHP) or mixture of TEHDGA+HDEHP. The rate of extraction of Am(III) and Eu(III) from 1 M nitric acid and the effect of various parameters, such as the concentration of nitric acid in aqueous phase and concentration of TEHDGA and HDEHP in resin phase, on the distribution coefficient of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) in HDEHP-impregnated resin decreased and that in TEHDGA-impregnated resin increased, with increase in the concentration of nitric acid. However, in (TEHDGA+HDEHP) – impregnated resin, synergic extraction was observed at lower nitric acid concentration and antagonism at higher nitric acid concentration. The mechanism of Am(III) and Eu(III) extraction in the combined resin was investigated by slope analysis method. The extraction of various metal ions present in the fast reactor simulated high-level liquid waste was studied. The separation factor of Am(III) over Eu(III) was studied using citrate-buffered diethylenetriaminepentaacetic acid (DTPA) solution.

Extraction behaviour of Am(III) and Eu(III) from nitric acid medium in CMPO-HDEHP impregnated resins

Abstract Chromatographic resin containing extractants such as octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) or bis-(2-ethylhexyl)phosphoric acid (HDEHP) or mixture of extractants (CMPO + HDEHP) in an acrylic polymer matrix was prepared and studied for the extraction of Am(III) and Eu(III) over a range of nitric acid concentration. The effect of various parameters such as concentration of nitric acid in aqueous phase and the concentration of CMPO and HDEHP in the resin phase was studied. The distribution coefficient of Am(III) and Eu(III) in the impregnated resin increased with increased in the concentration of nitric acid for CMPO-impregnated resin, whereas a reverse trend was observed in HDEHP impregnated resin. In case of resin containing both the extractants, synergism was observed at low nitric acid concentration and antagonism at high nitric acid concentration. The mechanism of extraction was probed by slope analysis method at 0.01 and 2 M nitric acid concentrations. Citrate-buffered DTPA was used for the selective separation of Am(III), and a separation factor of 3–4 was obtained at pH 3.

Extraction equilibria and kinetics of Ti(IV) from leached chloride liquors of ilmenite

Extraction of titanium (IV) from real chloride leach liquor of ilmenite was carried out with 0.1 mol·L−1 di-(2-ethylhexyl) phosphoric acid (HDEHP) in kerosene. Equilibrium and kinetics studies for Ti(IV) were carried out in the presence of impurities that were leached with Ti(IV). Parameters affecting extraction rate of Ti(IV) from chloride media in the presence of Fe(III), Mg(II), and Al(III) were studied to evaluate the stoichiometry of extracted Ti(IV) species. It is found that the extraction rate of Ti(IV) is dependent on the extractant concentration and pH of solution. Under the optimum conditions, more than 95 % Ti(IV) can be extracted. On the basis of slope analysis method, the extracted species of Ti(IV) appears to be [TiO(H2A2)2]org, where H2A2 refers to HDEHP. Further, the kinetic studies of the extraction process of Ti(IV) and other metal ion impurities were carried out by a Lewis cell with a constant interfacial area of 16.7 cm2. Analysis of the experimental results suggests that TiO2+ extraction rate by HDEHP is the first with respect to hydrogen ion concentration and HDEHP concentration. The results are interpreted by a reaction mechanism where the extraction process is controlled by a diffusion process at the interface rather than in the bulk phase.

Impregnation and Characterization of High Performance Extraction Columns for Separation of Metal Ions

Impregnation behaviors of reverse-phase silica materials and C18-silica HPLC columns were studied using di-(2-ethylhexyl)phosphoric acid (HDEHP) as a model extractant. Initially, the adsorption efficiency of the ligand on different types of bulk particles was investigated using various concentration of HDEHP in different composition of methanol/water mixtures based on a batch technique. Subsequently, impregnation of HPLC columns was performed using the dynamic flow-through technique. The experimental data fitted well to the Langmuir model and the adsorption isotherms from the flow-through experiment were used to prepare extraction columns of different ligand densities. Finally, the impregnated columns were characterized and validated through HPLC separation of the lanthanides.

Study on a Novel Disphase Supplying Supported Liquid Membrane for Transport Behavior of Divalent Nickel Ions

A novel disphase supplying supported liquid membrane (DSSLM), containing supplying feed phase and supplying stripping phase for transport behavior of Ni(II), have been studied. The supplying supported feed phase included feed solution and di(2-ethyhexyl) phosphoric acid (HDEHP) as the carrier in kerosene, and supplying stripping phase included HDEHP as the carrier in kerosene and HCl as the stripping agent. The effects of volume ratio of membrane solution to feed solution (O/F), pH, initial concentration of Ni(II) and ionic strength in the feed solution, volume ratio of membrane solution to stripping solution (O/S), concentration of H2SO4 solution, HDEHP concentration in the supplying stripping phase on transport of Ni(II), the advantages of DSSLM compared to the traditional supported liquid membrane (SLM), the system stability, the∼reuse of∼membrane∼solution and the retention of membrane phase were studied. Experimental results indicated that the optimum transport of Ni(II) was obtained when H2SO4 concentration was 2.00 mol·L−1, HDEHP concentration was 0.120 mol·L−1, and O/S was 4: 1 in the supplying stripping phase, O/F was 1: 10 and pH was 5.20 in the supplying feed phase. The ionic strength in supplying feed phase had no obvious effect on transport of Ni(II). When initial Ni(II) concentration was 2.00×10−4 mol/L, the transport percentage of Ni(II) was up to 93.1 % in 250 min. The kinetic equation was deduced in terms of the law of mass diffusion and the interface chemistry.

Synthesis and characterization of neodymium phosphate powder resulted from neodymium loaded-HDEHP organic solutions by a stripping–precipitation process using a Lewis type cell

The solvent extraction process of neodymium(III) from aqueous solution by di(2-ethylhexyl) phosphoric acid (HDEHP) in kerosene has been performed as a first step to accomplish the homogeneous precipitation of neodymium phosphate by stripping from an organic metal loaded HDEHP solution using phosphoric acid solutions. In this study, stripping–precipitation approach was proposed to synthesize powders of neodymium phosphate using a modified Lewis cell. The effects of extractant, organic phase, neodymium concentration, stripping phase, phosphoric acid content and temperature were separately investigated. The neodymium precipitate was characterized by X-ray diffractometry, scanning electron microscopy, particle size measurement, thermogravimetric analysis and infrared spectroscopy. The results showed that the powder precipitated with 3 M H 3PO 4 showed more regular and slightly larger particles than those obtained by 5 M H 3PO 4 while the precipitate with 8 M H 3PO 4 gave highly agglomerated particles. Increasing the HDEHP concentration from 0.25 M to 0.75 M gave an increase of the particle size of the precipitate. As the temperature increases (10–45 °C), the formed particles appeared to be more crystalline and smaller in size.

RECOVERY OF NI2+ BY DI-(2-ETHYLHEXYL) PHOSPHORIC ACID (HDEHP)

This paper dealts with solvent and bulk liquid membrane extraction of Ni2+ from its chloride solutions by HDEHP in n-heptane. Effects of extraction time, initial pH and Ni2+ concentration in the feed as well as HDEHP concentration in the organic phase were investigated. Solvent extraction equilibrium was established within 10 minutes. Ni2+ showed to be extracted into the organic phase preferentially as Ni(DEHP), complexes. The Ni2+ extraction yield decreased with increasing initial Ni2+ concentration, with decreasing pH and/or HDEHP concentration. The later is not only due to shifting equilibrium of Nils extraction reaction, but also due to concurent extraction of HCI. Results of bulk liquid membrane extraction could be described by the kinetics of interfacial pseudo-first order reactions. Observed rate constants were determined ⁓ 2,30.10-2 ⁒ 2,68.10-2 min-1 for concentration range [Ni2+]0 ⁓ 10-3 ⁒ 10-2 mol/l.

Transport of U(VI), Th(IV) and lanthanides through cation exchange membrane impregnated with HDEHP-kerosene using electric field

Summary Electrodialysis has been investigated as a method to enhance the transport of U(VI), Th(IV) and lanthanides through Nafion cation exchange membrane I and impregnated with HDEHP-kerosene II. The recovery factor of U(VI) through Nafion cation exchange membrane with and without the applied electric field was 0.8 and 0.14, respectively. The transport process of U(VI) through ion exchange membrane was studied as a function of variation of nitric acid concentration in the feed solution, HDEHP concentration in the membrane stripping solution concentration, pH of the feed solution and effect of electric field. From this study the cationic flux of U(VI) through Nafion I and impregnated with HDEHP-kerosene II was 5.2 × 10−8 and 8.7 × 10−8 g eq cm−1, respectively. The technique of electrodialysis is efficient in preconcentration of U(VI) to 2.8 fold of the initial concentration. The recovery factors of lanthanide elements La(III), Eu(III) and Er(III) through the systems I and II were 0.8 in system I and 0.86, 0.8 and 0.73 in system II, respectively. The recovery factors of La(III), Eu(III), Er(III) and U(VI) through the system II were 0.82, 0.75, 0.71 and 0.27, respectively. The recovery factor of Th(IV) and U(VI) at pH = 1.5 was found to be 0.99 and 0.3, respectively.

Separation and recovery of platinum and rhodium by supported liquid membranes using bis(2-ethylhexyl)phosphoric acid (HDEHP) as a mobile carrier

Transport of Pt and Rh ions from an aqueous 1 mol dm −3 HCl feed solution containing 20% stannous chloride into a stripping solution 8 mol dm −3 HCl through a supported liquid membrane (SLM) consisting of bis(2-ethylhexyl)phosphoric acid (HDEHP) in kerosene, supported on PVDF film, have been studied. Various parameters, such as concentration of HCl in feed and stripping solutions, concentration of HDEHP in the membrane, stirring time and concentration of SnCl 2 in 1 mol dm −3 HCl, have been investigated. Transport of Pt is independent whereas that of Rh increases with HDEHP concentration (0.003–2 mol dm −3) in the membrane phase. Mutual separation of Pt and Rh is achieved by preferential transport of Pt at low concentration of HDEHP (0.003 mol dm −3) and Rh left behind is recovered by transport at high concentration of HDEHP (2 mol dm −3) in membrane. Selective recovery of Pt and Rh have been achieved from other platinum group metal ions, gold and other metal ions. The methods have been demonstrated to recover Pt and demonstrated to recover Pt and Rh selectively from industrial waste samples such as catalyst, anode slime and artificial mixtures.

Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di‐2‐ethylhexylphosphoric acid

AbstractThis paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm−3 HDEHP, 10−3 mol dm−3 HNO3 in the feed solution, 1 mol dm−3 HCl in compartment 2 and 1 mol dm−3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm−2 to reach a maximum value at 30 mA cm−2 (8 × 10−9 g eq cm−2 s−1). The transport percentages of 0.3 g dm−3 Th(IV) in the presence of 0.1 g dm−3 Eu(III) and 1 g dm−3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI).© 2001 Society of Chemical Industry

Extraction Kinetics of Uranium(VI) with di(2-ethylhexyl) Phosphoric Acid Using a Hollow Fiber Membrane Extractor

The kinetics of solvent extraction of U(VI) with di(2-ethylhexyl) phosphoric acid (HDEHP) using a microporous hydrophobic hollow fiber membrane extractor has been investigated. The effects of U(VI) and hydrogen ion concentrations in aqueous phase, HDEHP concentration in organic phase, flow velocities of aqueous and organic phase and temperature on extraction rate of U(VI) were examined. The experimental results suggest that the extraction rate of U(VI) is controlled by diffusion.

Lead Removal from Foundry Waste by Solvent Extraction

Solvent extraction is used to reduce lead concentrations from millpond wastewater solids, a type of foundry process waste. Toluene and toluene mixed with di-(2-ethyl-hexyl) phosphoric acid (HDEHP) have been tried as leaching solvents. Toluene is ineffective as a solvent in extracting lead, but the toluene-HDEHP mixture effectively removes lead from solid foundry waste. The effects of the HDEHP concentration, the contact time, and the amount of solvent used on lead extraction have been investigated. The mass transfer process is rapid: contact time of 1/2 hour has been found to be sufficient to accomplish the leaching process. The concentration of HDEHP significantly impacts lead removal. The optimum concentration of HDEHP is determined to range from 0.05 to 0.1 mol/l. The Toxicity Characteristic Leaching Procedure (TCLP) test of the treated samples gives leachable lead in much lower quantities than those found in the untreated samples. Thus the solvent extraction process appears to be an effective method to significantly reduce the lead content of millpond wastewater solids.

Permeation of Lanthanum through Supported Liquid Membranes

Abstract The mechanism of lanthanum transport through a supported liquid membrane is presented. The membrane consisted of a Teflon millipore membrane with a kerosene solution of di(2-ethylhexyl) phosphoric acid (HDEHP) as a mobile carrier held within the pores by capillary forces. Interposing the liquid membrane between two aqueous solutions with different pH values, lanthanum was transported and concentrated from the high pH solution to the low pH solution across the liquid membrane. The effects of HDEHP concentration in the membrane solution and of the lanthanum concentration and pH in the aqueous phases on the permeation rates of lanthanum were investigated. It was observed that the permeation rates decrease drastically by the addition of surfactant to the membrane phase. The permeation rates of lanthanum can be explained by a permeation model which includes the extraction and the stripping reaction at the membrane interfaces and the diffusion process of the complex formed between lanthanum and HDEHP t...

Extraction of Selected Lanthanoids and Scandium with Bis(2-ethylhexyl)hydrogenphosphate in 1,1,2,2-Tetrachlorodifluoroethane

A study was made of the extraction of Ce, Pm, Eu, Tm and Sc(III) from aqueous into organic medium of 1,1,2,2-tetrachlorodifluoroethane (CFC-112) using bis(2-ethylhexyl)hydrogenphosphate (HDEHP) as extracting reagent. On the basis of earlier work which demonstrated the usefulness of using this type of solvent for extractions with dibutylhydrogenphosphate (HDBP) and also the possibility of using CFC-112 for converting the metal chelates formed to the solid phase, the work was concentrated particularly on the dependence of the extraction of selected lanthanoids on the analytical concentration of HDEHP and also on the [H+] concentration. In addition the dimerization and distribution constants were determined for this reagent in a mixture of CFC-112 with benzene and the extraction constants were determined for the individual metals.

Complexes of cadmium with phosphoric acid

We have investigated the behaviour of109Cd, in two-phase systems: (HDEHP−C6 H6/ H3 PO4−HClO4−LiOH, μ=0.2), as a function of the independent equilibrium parameters which define the system: pH, equilibrium concentration of H3 PO4 and total concentration of HDEHP in the organic phase. The data have been interpreted in terms of the existence of phosphoric complexes characterized by their order 1 with regard to H3 PO4 and their charge z. The l and z. values are: 0<1<2, z=−2, 0, 1, 2 for the following ranges: 0.7<pH<2.7 and CH3 PO4<4M. Stability constants of the predominant complexes have been obtained. Finally, a formulation of these complexes has been proposed on the basis of partial charge of the atoms. Some complexes, could be formulated as hydroxy-phosphoric species, resulting from competition between hydroxy and dihydrogenophosphate anions. In concentrated phosphoric acid (CH3 PO4=4M), complexation of cadmium is not more than 25%.

Extraction Chromatographic Performance of Uranium Using XAD-4 Loaded with Di-2-ethylhexylphosphoric Acid and Nitrate Solutions

Chromatographic extraction of uranium from nitrate medium using di-2-ethythexylphosphoric acid (HDEHP) loaded on XAD-4 (macroporous styrene divinylbenzene) is investigated. Parameters affecting column performance including flow rate, HDEHP concentration and column dimensions are studied in terms of height equivalent to theoretical plate and break-through capacity. The experimental results are analysed based on Van Deemter equation. The different constants representing the longitudinal diffusion of the solute in the mobile phase, packing irregularities of the column and rate of transfer of solute between the stationary and aqueous phases are evaluated and discussed. Optimum conditions for uranium removal from comparable simulated high active waste nitrate solution are studied.

Extraction of cadmium(II) by mixtures of organophosphorus compounds

The extraction of cadmium(II) by mixtures of di(2-ethylhexyl)phosphoric acid (HDEHP) and trioctylphosphine oxide (TOPO) dissolved in tetradecane from aqueous chloride solution has been studied at 25°C. The distribution of metal has been determined as a function of both HDEHP and TOPO concentration. Distribution data have been treated numerically using the program LETAGROP-DISTR, and the composition of the extracted species into the organic phase has been determined. The extraction constants for these species are given.