Trioctylphosphine Oxide Concentration Research Articles

Investigation of thorium(IV) separation from cerium(IV) on a silica gel column coated with tri-octylphosphine oxide

The parameters effecting the efficiency of thorium extraction on silica gel coated with Tri-octylphosphine oxide(TOPO) such as; HNO 3 concentration, thorium concentration, TOPO concentration, flow rate and nature of diluent were studied and optimum conditions were determined. Various elution reagents were tried to elute thorium from the column. High recovery was obtained with 0.5 M H 2SO 4, 0.5 M HCl solutions. Extraction data have been used to separation thorium from iron(III) and Ce(IV). The solution that contains Fe(III), Ce(IV) and Th(IV) in nitric media was passed through the TOPO/silica gel column, whilst Th(IV) and Ce(IV) were extracted by TOPO, Fe(III) was not. Firstly Th(IV) was eluted with H 2SO 4 then Ce(IV) was eluted with HCl. As a result, optimum conditions are here reported for the separation of thorium from cerium(IV).

Rate of Association of 2-Thenolytrifluoroacetone and Trioctylphosphine Oxide in Carbon Tetrachloride-Aqueous Solution Systems and Its Effect on the Solvent Extraction of Copper(II)

By spectrophotometry and by a liquid-liquid distribution method, the rate and equilibrium of the association of 2- thenoyltrifluoroacetone (Htta) with trioctylphosphine oxide (TOPO) in carbon tetrachloride-aqueous 0.1mol dm-3 perchlorate solution systems were studied. The effect of this association on the rate and equilibrium of the solvent extraction of copper(II) in the liquid-liquid system containing these extractants was examined. The associate of these reagents in carbon tetrachloride at equilibrium was concluded to contain one TOPO, one water, and one keto form Htta molecule. The change in the distribution ratio of Htta during the two-phase agitation was larger in the presence of TOPO. The extraction of copper(II) from the aqueous phase with Htta in the presence of TOPO was higher just after the start of two-phase agitation and it decreased gradually until the equilibrium was reached. The rate of this decrease of copper(II) extraction was explained in terms of the rate of decrease in the Htta and TOPO concentrations due to their association in the organic phase.

Equilibrium and Kinetic Studies on the Separation of Uranium and Thorium from Nitric Acid Medium by Liquid Emulsion Membrane Based on Trioctylphosphine Oxide Extractant.

It was found that the extraction percent (E%) values of U(VI), Th, Zr and Fe(III) from 0. 1 mol dm−3 (M) HNO3 solution by 0. 1 M TOPO in cyclohexane solution are 98, 78, 85 and 85%, respectively. Among these elements, only U(VI) and Th were found to be stripped from their organic phase by 0. 1 M sodium citrate solution. Cerium, copper and cadmium were not extracted by trioctylphosphine oxide (TOPO) under similar conditions. Based on these equilibrium results, a liquid emulsion membrane (LEM) was prepared from TOPO/Span 80/sodium citrate and the factors affecting its stability were studied. Permeation of U(VI) into this membrane was kinetically studied in detail. Its forward permeation rate was found to be mainly dependent on TOPO concentration and slightly dependent on U(VI) and HNO3 concentration of the external phase. Permeation results showed that it is possible to recover 98% of U(VI) and 82% of Th from 0. 1 M HNO3 solution containing Ce, Zr, Fe(III), Cd, and Cu by the membrane. The recovered U(VI) and Th were contaminated with less than 2% of Fe(III).

Solvent Extraction of Seven Trivalent Metal Ions in Aqueous Perchlorate Solutions with Trioctylphosphine Oxide in Hexane and Rapid Extraction of Chromium(III)

Solvent extraction of scandium(III), yttrium(III), lanthanum(III), europium(III), gallium(III), indium(III), and chromium(III) in weakly acidified 1 mol dm−3 NaCIO4 solutions with trioctylphosphine oxide (TOPO) in hexane was studied. The extraction equilibrium was established by the two phase agitation for within 3 min and the extracted species except chromium(III) were found to be M(TOPO)43+(CIO4−)3. The extraction of chromium(III) was also achieved by the two phase agitation for only a short time but, from the dependence of the extraction on the TOPO concentration, the extracted species was assumed to be Cr(TOPO)63+(C104−)3. Since the inert Cr(H2O)63+ was so rapidly extracted and the solvation number was higher than that of the other metal ions, the TOPO molecules were assumed to combine with the hydrating water molecules by hydrogen bonds which can be formed in a short time even when the metal ion was inert. The chromium(III) was also extracted rapidly from 1 mol dm−3 NaSCN, NaNO3, NaBr, and NaCl solutions with TOPO in hexane and the extraction was better from NaSCN solution than from NaC104 solution but it was not effective from the solutions of other salts.

Reduction of Manganese(III) in Tris(benzoyltrifluoroacetonato)Mn(III) in Carbon Tetrachloride in the Presence of Trioctylphosphine Oxide

Abstract An addition of trioctylphosphine oxide (TOPO) enhanced the rate of back extraction of manganese in tris(benzoyltrifluoroacetonato)Mn(III) from carbon tetrachloride containing benzoyltrifluoroacetone (4,4,4-trifluoro-1-phenyl-1,3-butanedione, Hbfa) into acid aqueous solutions due to reduction of manganese(III) in this complex in the organic phase. It was found by spectrometry that manganese(III) in this complex in water- and air-saturated carbon tetrachloride was stable for a long time in the absence of TOPO but its reduction occurred in the presence of TOPO. The rate of reduction was first order with respect to the TOPO concentration and inverse first order with respect to the Hbfa concentration. This was explained as follows: An addition of TOPO to the metal ion in the complex promoted the dissociation of one of the bfa− ions in the complex and the leaving bfa− ion gave an electron to the manganese(III). On the other hand, a bfa− ion from the coexisting Hbfa in the solution should exchange with the bfa− in the MnIII(bfa)3 complex but it does not cause reduction of manganese(III) and this was assumed to compete with the addition of TOPO and to cause the inverse first order dependence of the rate of reduction on the Hbfa concentration.

Studies on mixed ligand complexes of samarium(III), europium(III) and dysprosium(III) with 1-nitroso-2-naphthol and trioctylphosphine oxide

The extraction behavior of Sm(III), Eu(III) and Dy(III) with 1-nitroso-2-naphthol (HA) and trioctylphosphine oxide (TOPO) in methyl isobutyl ketone (MIBK) from aqueous NaClO4 solutions in the pH range 4–9 at 0.1M ionic strength has been studied. The equilibrium concentrations of Sm and Dy were measured using their short-lived neutron activation products,155Sm and165mDy, respectively. In the case of Eu, the concentrations were assayed through the152,154Eu radiotracer. The distribution ratios of these elements were determined as a function of pH, 1-nitroso-2-naphthol and TOPO concentrations. The extractions of Sm, Eu and Dy were found to be quantitative with MIBK solutions in the pH range 5.9–7.5, 5.6–7.5 and 5.8–7.5, respectively. Quantitative extraction of Eu was also obtained between pH 5.8 and 8.8 with chloroform solutions. The results show that these lanthanides (Ln) are extracted as LnA3 chelates with 1-nitroso-2-naphthol alone, and in the presence of TOPO as LnA3(TOPO) and LnA3(TOPO)2 adducts. The extraction constants and the adduct formation constants of these complexes have been calculated.

Recovery of fatty acids by immobilized solvent extraction

AbstractThe use of silicone rubber tubes swollen with solutions of TOPO (trioctyl phosphine oxide) in kerosene as membranes for the recovery of fatty acids from anaerobic digesters was investigated. The flux of acetic and propionic acids was found to increase with the concentration of TOPO when the concentration was low. At very high TOPO concentrations, the flux decreased indicating the existence of an optimum TOPO concentration. The relationship between the flux and concentration of unionized propionic acid did not agree with that expected for pure diffusion. This was due to the reversible reaction between TOPO and propionic acid in the membrane. The flux of propionic acid was measured as a function of time for new membranes and for membranes removed from storage. Rather long times, 70 to 300 hours, were required to achieve steady acid fluxes. This time was required to fully develop the concentration profiles within the membranes.

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.

Selective extraction of the transplutonium and rare-earth elements by trioctylphosphine oxide

In the studies of nuclear reactions of heavy ions with heavy nuclei it is often necessary to determine the yields of TPE. Trioctylphosphine oxide (TOPO) has high selectivity with respect to trivalent TPE and rare earths. The possibility of using target or catcher materials as salting-out agents in the extraction of TPE with TOPO from solutions containing DTPA and lactic acid was investigated. The influence of the concentration of Pb, Bi, Cu, Ni, nitric acid and TOPO on the distribution coefficients was established. The advantages of application of the method for the extraction chromatographic separation of TPE and rare earths from the other elements produced in the interaction of ions with heavy elements are shown.

A Study of the Mechanism for the Extraction of Uranium, Water, and Nitric Acid with Trioctylphosphine Oxide Using a Binary Molten Mixture of Biphenyl and Naphthalene as the Solvent

Abstract Liquid-liquid distribution with trioctylphosphine oxide (TOPO) and a binary molten mixture of biphenyl and naphthalene (weight ratio=3:1) has been examined for the extraction of uranium from a 0.1 mol kg−1 nitric acid solution. The stoichiometry of the TOPO complex of uranyl nitrate in the molten biphenyl–naphthalene phase was established to be UO2(NO3)2(TOPO)2. The extracted species of water and nitric acid are H2·TOPO and H3O+·TOPO·NO3− at concentrations of TOPO of less than 0.1 mol kg−1. The thermodynamic quantities (ΔH°, ΔG°, and ΔS°) were obtained for the extraction of uranyl nitrate, nitric acid, and water into TOPO–bi-phenyl–naphthalene and TOPO–cyclohexane solutions from the temperature dependence of the extraction constants. More exothermic enthalpy and smaller entropy changes were observed for the binary molten mixture; these differences were attributed to the aromatic and viscous properties of the solvent.

Studies on the Solvent Extraction of Metal Perchlorates III. Extraction Equilibria of Alkaline Earth Ions with Trioctylphosphine Oxide as Perchlorate and Thiocyanate

Abstract Solvent extraction of alkaline earth metal ions in 1 mol dm−3 sodium perchlorate or thiocyanate aqueous solution with trioctylphosphine oxide (TOPO) in hexane was studied at 25 °C. The extraction in both systems improved in the order: beryllium(II)>calcium(II)>strontium(II)\simeqmagnesium(II)\simeqbarium(II). When the TOPO concentration was the same, the extraction of beryllium or calcium thiocyanate was better than that of the perchlorate, that of magnesium or strontium thiocyanate was nearly similar to that of the perchlorate, while barium perchlorate was extracted better than its thiocyanate. From these results it was concluded that these five perchlorates and strontium and barium thiocyanates were extracted as ion-pairs, [M(topo)4]2+(X−)2, (X−=ClO4− or SCN−), while beryllium thiocyanate was extracted as solvates of noncharged complexes, M(SCN)2(topo)n, (n=2 and 3), and that magnesium and calcium thiocyanates in the organic phase (n=3 and 4) should have both ionic and coordinative properties. The poor extraction of magnesium salts was assumed to be due to their strong hydration.

The Extraction of the Chromium(III) Ion from Trichloroacetate Solutions to Inert Solvents Containing Trioctylphosphine Oxide

Abstract Chromium(III) has been extracted with 0.1 mol dm−3 trioctylphosphine oxide(TOPO) in various inert solvents from a 0.1 mol dm−3 trichloroacetate(TCA−) buffer solution of pH 3.5 to 6.0. As diluents of TOPO, hexane and cyclohexane are most effective, while chloroform is quite ineffective. The extraction mechanism has been clarified by analyzing separately the distribution of water, trichloroacetic acid(HTCA), and the Cr(III) ion between the aqueous and organic phases. Water and HTCA are present in the cyclohexane phase as H2O·TOPO and HTCA·TOPO respectively. Chromium(III) is extracted with TOPO into cyclohexane as an ionassociation complex like Cr(H2O)63+(TCA−)3·3TOPO, and the extraction constant is 107.68. It is concluded that the hexahydrated Cr(III) ion is solvated by three molecules of TOPO, forming an ion pair with three trichloroacetate anions. The extractability of Cr(III) in the present system depends most effectively on the concentration of HTCA-free TOPO in the organic phase.

Solvent extraction equilibria of acids—II: Extraction of phosphoric acid from various aqueous solutions with trioctylphosphine oxide

Solvent extraction equilibria of phosphoric acid with trioctylphosphine oxide (TOPO) has been studied at 25°C. When the diluent was hexane, a trisolvate with TOPO was extracted but when it was benzene or carbon tetrachloride, both a trisolvate and a disolvate were extracted. Extraction into hexane was slightly enhanced by hydrochloric acid and greatly impaired by perchloric or nitric acid in the aqueous phase and the impairment was found to be due to a decrease in the free TOPO concentration caused by the extraction of the strong acid. It is concluded after the correction for this decrease in the free TOPO concentration that these strong acids enhanced the net extraction of phosphoric acid by forming a mixed acid species, H 3PO 4·HX·(TOPO) 3 (where HX is a strong acid), which is assumed to have a hydrogen-bond between the phosphoryl oxygen of the phosphoric acid and HX, and that the order of enhancement is HClO 4 > HNO 3 > HCl. The constants for the above extraction equilibria were determined.

Kinetic studies of solvent extraction of metal complexes—VI: Equilibrium and rate of solvent extraction of iron(III) perchlorate with trioctylphosphine oxide in hexane

The equilibrium and rate of solvent extraction of iron(III) in 4 M aqueous perchlorate media with trioctylphosphine oxide (TOPO) in hexane have been studied at 25°C. Although the distribution ratio of iron(III) was apparently dependent on the hydrogen-ion concentration, the extracted species was found to be Fe(ClO 4) 3(TOPO) 4 after correction for the decrease in the free TOPO concentration caused by extraction of perchloric acid. The rate was found to be first order with respect to TOPO and inverse first order with respect to hydrogen-ion, and the controlling reaction was assumed to be association of FeOH 2+ with TOPO in the aqueous phase. The extraction was accelerated by chloride, bromide, or nitrate ions (X −) and this was explained by another extraction mechanism controlled by association of FeX 2+ with TOPO in the aqueous phase. It was concluded that the rate of association with TOPO increases in the order of FeOH 2+FeNO 3 2+ > FeBr 2+ > FeCl 2+.

Synergistic extraction of radium using 2-thenoyltrifluoroacetone and tributyl phosphate or trioctylphosphine oxide

The extraction of radium into a mixture of 2-thenoyltrifluoroacetone (HTTA) and tributyl phosphate (TBP) or trioctylphosphine oxide (TOPO) in n-hexane or cyclohexane has been investigated with regard to the dependence on pH, and TBP and TOPO concentrations. It has been found that the formation of mixed complexes of the type Ra(TTA)2 (TBP)2 and Ra(TTA)2(TOPO)2 occurs and the overall extraction constants of both complexes were calculated. With the systems described, very high distribution ratios of radium have been attained; these may advantageously be used for the separation and concentration of traces of radium.

Synergistic extraction of radium and barium using 1-phenyl-3-methyl-4-benzoylpyrazol-5-one and trioctylphosphine oxide

The extraction of radium and barium into a mixture of 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPy) and trioctylphosphine oxide (TOPO) in n-hexane or cyclohexane was investigated as a function of pH and TOPO concentration. It was found that the synergistic enhancement of the extraction is caused by the formation of mixed complexes of type M(Py)2 (TOPO)3 and the overall extraction constants of both complexes were calculated.

The Solvent Extraction of Zinc(II) in Sodium Perchlorate-halide Solutions with Trioctylphosphine Oxide

Abstract The solvent extraction of zinc(II) in 1m sodium perchlorate ionic media containing chloride, bromide, or iodide ions at 25°C was determined as a function of the halide-ion (X−) concentration by using the zinc-65 tracer. From the extraction data with isopropyltropolone (IPT) in chloroform, the formation of the ZnX+ complex was observed, but the stability constants of these complexes were not large (ZnCl+: β1 is 100.00, ZnBr+: β1 is less than 10−0.5and the formation of ZnI+ is negligible), and the higher complexes were negligible in all cases. The extraction of zinc(II) from these media with methylisobutylketone (MIBK) was not effective, although the extracted species could be identified as ZnX2. The extraction with trioctylphosphine oxide (TOPO) in hexane, on the other hand, was much better than that with MIBK. From the distribution ratio determined as a function of the halide and TOPO concentrations, the extracted species were concluded to be Zn(ClO4)2(TOPO)4, ZnX(ClO4)(TOPO)3, and ZnX2-(TOPO)2. The extraction constants for these species were determined by a graphic analysis of the data, and it was concluded that the extractabilities are larger in the order: iodide>bromide>chloride. From these data, it is clear that, if a suitable and effective neutral extractant is employed, the extractions of the above complexes are possible, even from aqueous solutions in which practically no complex is formed.