Determination of radiocerium in fission products by extraction chromatography using di-(2-ethylhexyl)phosphoric acid

An extraction chromatographic method is described for the determination of cerium in a fission product mixture. Cerium(IV) is separated on a column of siliconized kieselguhr saturated with di-(2-ethylhexyl)phosphoric acid (HDEHPA). After washing the column with a mixture of sodium bromate and nitric acid, cerium is eluted by a mixture of 5M HNO₃ and 0.1M ascorbic acid. The optimum conditions for the quantitative sorption and elution of cerium were found, and the reproducibility of the yield was verified. The influence of other fission and corrosion products (Mg, Fe, Al, U) on the sorption and elution of cerium was studied. The method has been successfully applied for the determination of cerium in artificial and natural mixtures of fission products.     

Effect of radiolysis products of di-(2-ethylhexyl)phosphoric acid upon the extraction of lanthanides

In order to clarify the influence of radiation degradation of DEHPA upon the extraction of lanthanides, the extraction of neodymium(III) was studied using DEHPA, MEHPA, 2-ethylhexanol and γ-ray irradiated DEHPA. The most significant effect of DEHPA radiolysis on the extraction was found to be the enhacement of extraction capability mainly due to the primary radiolysis product MEHPA. 2-Ethylhexanol, another radiolysis product, showed a depressant effect on DEHPA-Nd(III) extraction. However, the mixture of MEHPA and 2-ethylhexanol improved the extraction. The mixed solvent DEHPA-MEHPA was found to be more effective than the individual components for lanthanide extraction.     

Extraction recovery of vanadium(IV) from acid sulfate solutions with di-(2-ethylhexyl)phosphoric acid

Extraction of vanadium(IV) with di-(2-ethylhexyl)phosphoric acid from acid sulfate solutions in the presence of sodium sulfate was studied. The composition of the complex being extracted was found, and the equation of the extraction reaction was determined. The equilibrium constant of the reaction by which vanadium(IV) is extracted with di-(2-ethylhexyl)phosphoric acid was found by taking into account the complexation of vanadium(IV) in acid sulfate solutions.     

Determination of cerium in fission products by extraction with di(2-ethylhexyl)phosphoric acid

Summary The extraction of cerium, oxidized to the tetravalent state, from nitric acid medium by di(2-ethylhexyl)phosphoric acid in hexane was studied. The effect of nitric acid concentration, agent concentration, oxidizer amount, and carrier concentration on the yield of cerium extraction was investigated and the optimum conditions of the extraction were found. Under these conditions, the reproducibility of the method was determined and the extraction of other fission products (Sr, Cs, Zr, and Ru) was also tested. The procedure was verified by the determination of cerium in artificial and real mixtures of fission products.

---

Zusammenfassung Es wurden Untersuchungen angestellt über die Extraktion von vierwertigem Cer aus salpetersaurer Lösung mit Hilfe von Di-(2-äthylhexyl)-phosphorsäure in Hexan. Im einzelnen wurde der Einfluß der Konzentration an Salpetersäure, Reagens, Oxydationsmittel und Träger auf die Extraktionsausbeute geprüft und die optimalen Bedingungen festgelegt. Weiterhin wurde die Reproduzierbarkeit des Verfahrens bestimmt und bei der Anwendung auf künstliche und natürliche Gemische von Spaltprodukten das Verhalten der anderen Elemente (Sr, Cs, Zr, Ru) untersucht.

     

Kinetic studies on the extraction of uranium(VI) from phosphoric acid medium by bulk liquid membrane containing di-2-ethylhexyl phosphoric acid

To go through the first stage of industrial solvent extraction process in order to recover uranium from phosphate rocks by liquid membrane techniques, as a simple model, the kinetics of facilitated transport of uranium(VI) from a dilute phosphoric acid medium into more concentrated phosphoric acid media as a receiving phase through a bulk liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier was studied. The influence of phosphoric acid concentration in the source and receiving phases, carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (k _e, k _s, t _max, J _max) were calculated for the interface reactions assuming two consecutive, irreversible first-order reactions. The activation energy values were calculated as 29.40 and 19.51 kJ mol^?1 for extraction and stripping, respectively. The values of calculated activation energy indicated that both the extraction and stripping processes were controlled by mixed regime (both kinetic and diffusion). In addition, the influence of adding trioctyl-phosphine oxide into the membrane phase as a synergic agent on the transport kinetics was determined.     

Solvent extraction of Fe(III) by di-(2-ethylhexyl)phosphoric acid from phosphoric acid solutions

The extraction of iron(III) from aqueous phosphoric acid was studied using di-(2-ethylhexyl)phosphoric acid and trioctylphosphine oxide in nonaromatic hydrocarbon diluent. Distribution ratios have been investigated as a function of concentration of iron(III), phosphoric acid concentration, extractant concentration and extraction temperature. The apparent enthalpy change for the extraction reaction has been calculated from the temperature dependence data. It was found that the extractant dependency for iron(III) is first power indicating hydrolysis of iron(III) in the aqueous phase.     

Extraction chromatography with bis(2-ethylhexyl)phosphoric acid for separation of tin(IV)

Tin is extracted from 0.01M hydrochloric acid on a silica-gel column impregnated with bis(2-ethylhexyl)phosphoric acid, stripped with 5M hydrochloric acid, and then determined spectrophotometrically as its Pyrocatechol Violet complex at 555 nm. Tin has been separated from several multicomponent mixtures containing arsenic, antimony, bismuth, lead and copper, and determined in various alloys.     

Mass spectrometric study of the radiolysis of di-(2-ethylhexyl)phosphoric acid

A mass spectrometric study on DEHPA was carried out and compared with radiolysis data on DEHPA for γ-irradiation in the liquid phase. The mass spectra of DEHPA show an extremely low intensity of parent ion and the presence of double rearrangement ions of (RO)P(OH) ₃ ⁺ and P(OH) ₄ ⁺ , where R is the 2-ethylhexyl group. The appearance potentials of the principal ions in the mass spectrum were determined and the dissociation processes of DEHPA in the phase discussed. The fragment ions show good agreement with the results in the liquid phase where the mono-ester, orthophosphoric acid, octane and heptane were formed by the dealkylation, however, the peak intensities of some fragment ions in the mass spectrum differ from the radiolytic yields of the corresponding products. These differences imply the significant role of neutralization and recombination reactions in the liquid phase radiolysis.     

Extraction of rare-earth elements with solutions of di-(2-ethylhexyl)phosphoric acid in flow-through system under local vibrational treatment

Results obtained in a study of the influence exerted by the vibrational treatment in the dynamic interfacial layer on the extraction of rare-earth elements with solutions of di-(2-ethylhexyl)phosphoric acid in a diluent in a flow-through system are presented. It was shown that the coefficient of extraction acceleration under a local vibrational treatment of the dynamic interfacial layer is smaller than that in the static system and is determined by the nature of an element being extracted and a solvent, frequency and amplitude of oscillations of the vibration element, and fluid flow rate. The degree of extraction of rare-earth elements in a certain time is noticeably higher and can reach a double excess if there is a local vibrational treatment of the dynamic interfacial layer. In this case, the accumulation of a lanthanide in the dynamic interfacial layer is substantially lower, and it does not exceed 10% of the total amount of rare-earth elements in the system.     

Reversed phase partition chromatographic separation of antimony (III) with bis(2-ethylhexyl) phosphoric acid

A new method is proposed for the extractive Chromatographic separation of antimony. Antimony is extracted from 0.001–0.5M hydrochloric acid by a silica gel column coated with bis (2-ethylhexyl) phosphoric acid stripped with 2–8M hydrochloric, nitric or sulphuric acid, and determined spectrophotometrically at 555 nm as its complex with phenylfluorone. Antimony can thus be separated from a large number of elements, including iron, manganese, copper and thallium. Arsenic, antimony, bismuth and tin can be sequentially separated.     

The intensity of spontaneous surface convection in di-(2-ethylhexyl)phosphoric acid systems

The dependence of the rate of the arising and evolution of spontaneous surface convection (SSC) on various effects during the extraction of rare-earth metals (REMs) with heptane (or toluene) solutions of di-(2-ethylhexyl)phosphoric acid (D2EHPA) (HA) was studied. The intensity of SSC in heptane was higher than in toluene systems. In the same solvent, it was higher for the elements from the cerium subgroup. At low concentrations of a REM salt in the starting aqueous solution, the modulus of the surface rate of liquid flow in the dynamic interphase layer (DIL) was high because low-solubility salt particles experienced sedimentation, and the interphase surface was renewed. It was concluded that, at higher REM concentrations in the aqueous phase, the modulus of the surface flow rate was considerably higher because of the accumulation of LnA₃ and structure formation in the interphase layer. For comparison, we give the moduli of surface flow rates of liquids during the re-extraction of acids in a toluene, HNO₃/water system, in which the rate is higher than in aqueous REM(III) salt/D2EHPA solution in an organic diluent. Original Russian Text ? N.F. Kizim, E.N. Golubina, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 7, pp. 1384–1390.     

Zn(II), Cd(II) and Cu(II) separation through organic–inorganic Hybrid Membranes containing di-(2-ethylhexyl) phosphoric acid or di-(2-ethylhexyl) dithiophosphoric acid as a carrier

A membrane process for metal recovery from aqueous solutions was studied. Metal ions diffused from the feed solution to the stripping phase through an Hybrid Membrane containing di-(2-ethylhexyl) phosphoric acid (D2EHPA) and/or di-(2-ethylhexyl) dithiophosphoric acid (D2EHDTPA) as a carrier. Such membranes were prepared by a sol–gel route including cellulose triacetate and polysiloxanes. Transport behaviour was evaluated for both carriers under similar experimental conditions. The transport experiments reported here concerned transport at different cycles and selectivity towards different metal ions. Using D2EHPA the membrane provided a selective transport of zinc to the stripping compartment of the membrane cell, while copper and cadmium remained in the feed compartment. Whereas, using D2EHDTPA as carrier the transport rate increased and the selectivity profiles were inverted in relation with those of D2EHPA. With a mixture of both extracting agents it was observed an intermediate behaviour in selective transport, being possible to modulate it.     

Atomic absorption determination of indium after extraction with di-(2-ethylhexyl)phosphoric acid

The equilibrium data show that indium can be quickly extracted from acidic aqueous solutions by di-(2-ethylhexyl)phosphoric acid in methyl isobutyl ketone. In this polar solvent the species ML₃·HL is extracted. The overall extraction constant is higher than that for other tervalent metals. The extraction process can be combined with AAS determination of the indium. The method is fast because stripping is not necessary, and the organic phase can be analysed directly by AAS. Use of a 51 v/v aqueous: organic phase ratio increases the sensitivity. In the pH-range used the method has good selectivity.     

Solvent extraction of neodymium,europium and thulium by di-(2-ethylhexyl)phosphoric acid

The extraction of Na³⁺, Eu³⁺ and Tm³⁺ by di-(2-ethylhexyl)phosphoric acid, HDEHP has been studied from various aqueous acidic solutions. The extraction of these elements is inversely proportional to the third power of the hydrogen ion concentration. Antagonistic effects were observed when the extraction was studied by mixtures of HDEHP and tributyl phosphate, TBP, or trioctylphosphine oxide, TOPO. The presence of water-miscible alcohols and acetone generally increases the extraction of these three elements from HCl solutions. Reaction mechanisms have been suggested and discussed in the light of the data obtained.     

Extraction of certain actinide and lanthanide elements from different acid media by polyurethane foams loaded with di-(2-ethylhexyl)phosphoric acid (HDEHP)

The effect of added TBP on the extraction of uranium(VI) with a solution of di-(2-ethylhexyl)-phosphoric acid (HDEHP) in o-dichlorobenzene from nitric acid solutions has been investigated at varying concentrations of nitric acid, HDEHP, TBP and uranium(VI). The mechanism of the synergistic effect of TBP is discussed on the basis of the results and can be summarized in the following equation: UO _2(aq) ²⁺ +0.67(HX)_3(o)+2TBP_(o)UO₂X₂·2TBP_(o)+2H _(aq) ⁺ where HX denotes HDEHP and the HDEHP loaded on the foam is trimerized.     

Reversed-phase column extractive separation of germanium with bis(2-ethylhexyl)phosphoric acid

Germanium was quantitatively extracted from 6–10 M hydrochloric acid on a silica gel column coated with bis(2-ethylhexyl)phosphoric acid and stripped with various acids. Germanium was then determined spectrophotometrically as its complex with phenylfluorone. Germanium was effectively separated from large numbers of main group and transition elements. The determination of germanium in fly ash by the proposed method is reported.     

Determination of phthalic acid, mono-(2-ethylhexyl) phthalate and di-(2-ethylhexyl) phthalate in human plasma and in blood products

Pretreatment for the determination of phthalic acid, mono-(2-ethylhexyl) phthalate (MEHP) and di-(2-ethylhexyl) phthalate (DEHP) in human serum or plasma, and the determination of these compounds in blood products by high-performance liquid chromatography was studied. The amount of phthalic acid, MEHP and DEHP, migrated into blood products from a flexible bag, was studied. About 0.1% of DEHP in a flexible bag was found to have migrated into human platelet plasma. Most of the MEHP and phthalic acid detected in human platelet plasma was not derived from the flexible bag but was produced by enzymatic hydrolysis of the migrated DEHP. The amount of DEHP eluted into blood products from the flexible bag differed, depending upon storage time, storage temperature, etc.