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Abstract  

An emulsion liquid membrane (ELM) containing di-2-ethylhexylphosphoric acid (D2EHPA) as the carrier extractant and SPAN 80 as the surfactant was used to pre-concentrate Am3+ from dilute acid solutions. Effects of various factors such as: external phase pH, internal phase conditions, equilibration time, D2EHPA concentration, SPAN 80 concentration, etc. on Am3+ mass transfer were investigated. Emulsion was broken by the addition of solvents such as acetone and the actual mass transfer obtained after breaking the emulsion agreed well with that obtained by the difference method.

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Abstract  

This paper reports the results of an investigation into the solvent extraction of uranium from technical grade phosphoric acid using industrially available extractants as D2EHPA and TOPO diluted in technical grade kerosene. Preliminary tests showed that, the effect of different parameters such as uranium oxidation stage, temperature and the molar ratio of D2EHPA/TOPO on the uranium recovery was in good agreement with those of previous investigations. However, a detailed investigation into the effect of phosphoric acid concentration, organic concentration and acid/organic phase ratios suggested that the mechanism of D2EHPA/TOPO synergism was rather complex and it presented a different character depending on the acid concentration.

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Abstract  

The determination of uranium in liquid samples using energy dispersive X-ray fluorescence was investigated. The organic phase di-(2-ethyl hexyl) phosphoric acid and trioctyl phosphine oxide (D2EHPA-TOPO)/kerosene, which resulted from first and second cycles of uranium extraction from commercial phosphoric acid, was directly analyzed using 109Cd as a primary excitation source. Copper was used as an internal standard, which led to a linear relation between relative intensity of uranium and its concentration. Three calibration curves, 0–100, 100–1000 and 1000–6500 g· ml–1, according to uranium concentration in the studied samples, were constructed. The effect of different molarities of D2EHPA and TOPO was considered. The detection limit, precision and accuracy were 1.1 g · ml–1, 3% and 1.4%, respectively. The obtained results were compared with other techniques such as -ray spectroscopy, UV spectrometry and volumetry.

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Abstract  

Extraction of californium/III/ with di-/–2-ethylhexyl/ phosphoric acid /D2EHPA/ in heptane from pyrophosphate media is almost quantitative between pH 4 and 5. From tripolyphosphate media, however, two to three extractions are needed in the pH range of 3–5 to isolate Cf3+ completely. Reextraction experiments show that 1M H2SO4 can back-extract Cf3+ completely while two to three reextractions with 5M HNO3 can only separate californium/III/. Reverse phase partition chromatography experiments were performed to recover 300 g of californium/III/. From slope analysis of the extraction data the composition of the extracted species has been found to be Cf/H2P2O7/A.HA and Cf/H4P3O10/.A2.2HA from pyrophosphate and tripolyphosphate solutions, respectively, where D2EHPA is abbreviated as /HA/2.

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Abstract  

The effect of macroconcentration (Ma) lanthanide extraction on the microcomponent (Mi) extraction by D2EHPA was investigated. The investigation corroborated that the macrocomponent suppresses the microcomponent extraction. The extractability of Mi decreases with increasing Ma concentration and with increasing proton lanthanide number in macroconcentrations. Semi-empirical relations were derived describing lanthanide extraction in lanthanide macro- and microconcentrations as a function of the extraction of lanthanide macroconcentrations. Under the conditions discussed, these relations can be used to estimate for any lanthanide the distribution ratios for the lanthanide applied as a macrocomponent and for Eu applied as a microcomponent.

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Abstract  

This work concerns the extraction of U(VI) using supported liquid membrane (SLM) by di-(2-ethylhexyl) phosphoric acid (D2EHPA) and tri-n-octyl phosphine oxide (TOPO) with polyvinylidene difluoride (PVDF) as a membrane support. The influence of ionic strength (S), stirring rate (V) and extraction time (t) were studied. The effect of membrane thickness on the permeability and extraction yield of uranium was investigated. A comparative study was carried out using a 23 full factorial design between SLMs with one membrane and two membranes, and to achieve the best conditions of recovery procedure, obtaining the mutual interaction among variables and optimizing these variables. The recovery of U(VI) is almost quantitative, and the supported liquid membrane with two membranes in series is effective.

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Abstract  

The potentiometric estimation of D2EHPA containing M2EHPA of various samples in reagent grade acetone was studied. The differential plot of the results of analysis were determined using ORIGIN mathematical software for end point determination. Visual color indicators were also tested for estimation of D2EHPA and M2EHPA, but the accuracy of measurement was less than the endpoint determination by differential plots.

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Abstract  

A Sr ion transport study across D2EHPA-TBP kerosene oil based liquid membranes supported on microporous polypropylene film has been performed. The parameters studied were the effect of di(2-ethylhexyl)phosphoric acid (D2EHPA) and TBP concentration variation in the membrane liquid, HNO3 concentration variation in the stripping phase and citric acid concentration variation in the feed solution. The optimum conditions of transport are 0.3 mol/dm3 D2EHPA, 0.1 mol/dm3 TBP, 0.01 mol/dm3 citric acid in feed and 2 mol/dm3 HNO3 in the stripping phase. The mechanism of transport observed is counter-ion coupled transport. The coupling ions are protons. The maximum flux for Sr ion transport observed is 5.33·10–5 mol·m–2·s–1 and maximum permeability under optimum conditions observed is 8.08·10–11 m–2·s–1.

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Abstract  

Extraction of uranium from Egyptian phosphoric acid with synergistic mixture of di-2-ethylhexylphosphoric acid (D2EHPA) and di-butyl butyl phosphonate (DBBP) is reported in this paper. The influence of various factors such as D2EHPA concentration, DBBP concentration, phosphoric acid concentration, contact time, aqueous: organic phase’s ratio (aq:org) and temperature on the degree of extraction has been established. The data on the effect of temperature on the extraction showed that the enthalpy change is −23.12 kJ/mol. Uranium extracted by D2EHPA–DBBP is further subjected to a second cycle of extraction and scrubbing impurities. The uranium is finally converted to a high purity UO3 product using precipitation with hydrogen peroxide and heat treatment at 375 °C.

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Abstract  

The synergistic solvent extraction of Eu(III) and some other rare earth elements from nitrate solutions (HNO3+LiNO3) by a mixture of (TBP+D2EHPA) in n-hexane and cyclohexane has been investigated at 22 °C. Antagonism found in europium extraction from 0.1M HNO3 transforms into a synergistic effect. The synergistic effects existing for all investigated metals in extraction from 0.1M HNO3+3M LiNO3 were caused by formation of mixed complexes of the type Ln(D2EHPA)2nH2n–3+1(NO3)1TBPm, where 1=1 or 2. The selectivity of the extraction in a synergistic system is lower for the La–Yb pair than in the case of D2EHPA extraction under the same conditions. On the other hand, the application of the synergistic mixture is more suitable for Eu–Ho separation. Thus the synergistic effect can be used for the separation or refining of some lanthanides.

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