Mono 2-ethylhexyl Phosphoric Acid Research Articles

Pertraction of Vanadium(V) from Dilute Acidic Media by an Emulsion Liquid Membrane Containing a Commercial Extractant

AbstractEmulsion liquid membrane (ELM) pertraction of VV ions from dilute acidic solution by using a mixture of di(2‐ethylhexyl)phosphoric acid (D2EHPA) and mono(2‐ethylhexyl)phosphoric acid (M2EHPA) was studied. First, solvent extraction of VV from an aqueous medium was performed, and the optimum feed pH and extractant concentration were obtained. Tributyl phosphate was used as modifier to increase membrane stability and decrease membrane swelling. The effects of diluent type, extractant concentration of the emulsifier concentration, stripping reagent concentration (sulfuric acid), organic phase/stripping phase volume ratio, emulsification time and speed, feed initial pH, agitation speed, temperature, and contact time on VV extraction efficiency and ELM stability were considered.

Extraction and permeation of cadmium ions through supported liquid membrane impregnated with mixtures of D2EHPA and M2EHPA

The use of an organic carrier consisting of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and mono-(2-ethylhexyl) phosphoric acid (M2EHPA), diluted in kerosene, for separation of cadmium through a supported liquid membrane (SLM) was investigated. The extraction percentage of cadmium and permeability coefficients rose by increasing M2EHPA and feed phase concentration. By increasing the volume percentage of M2EHPA, the permeability coefficient of cadmium increased to a maximum value of 8 cm s−1 at 1·5 vol.-% declining at higher volume percentages. The permeability of cadmium ions through the SLM decreased with time. The permeation coefficient increased as the initial cadmium concentration increased.On a étudié l’utilisation d’un support organique consistant d’acide phosphorique di-(2-éthylhexyle) (D2EHPA) et mono-(2-éthylhexyle) (M2EHPA), dilué dans du kérosène, pour la séparation du cadmium à travers une membrane liquide supportée (SLM). Le pourcentage d’extraction du cadmium et les coefficients de perméabilité s’élevaient avec l’augmentation du M2EHPA et de la concentration de la phase d’alimentation. En augmentant le % de volume de M2EHPA, le coefficient de perméabilité du cadmium augmentait à une valeur maximale de 8 cm s−1 à un volume de 1·5% et déclinait à des % plus élevés du volume. La perméabilité des ions de cadmium à travers la SLM diminuait avec le temps. Le coefficient de perméation augmentait avec l’augmentation de la concentration initiale de cadmium.

Effects of Ligand Structure on Reactive Vapor−Liquid Distribution Ratio and Selectivity for C6-Olefin Isomers

Vapor−liquid equilibrium experiments are performed to evaluate the suitability of π-complexing silver of various phosphoric and sulfonic acids for application as functionalized solvents in Reactive Extractive Distillation to separate 1-hexene from other C6-olefin isomers. The effect of solvent structure is investigated by testing five different ligands, di (2-ethylhexyl) phosphoric acid (D2EHPA), di (butyl) phosphoric acid (DBPA), mono (2-ethylhexyl) phosphoric acid (MEHPA), di (nonyl) naphthalene sulfonic acid (DNNSA), and dodecyl benzene sulfonic acid (DBSA), for a variety of C6-olefin isomers (1-hexene, 2-methyl-1-pentene, n-hexane, 1,5-hexadiene, trans-2-hexene). The introduction of silver in the solvent increases the solvent selectivity for 1-hexene. At equal silver concentration the ligand size does not influence the selectivity of chemically similar components (1-hexene/2-methyl-1-pentene) but increases that of chemically different components (1-hexene/n-hexane). A lower pressure, a higher silver concentration, or higher solvent-to-feed (S/F) ratio are beneficial for the 1-hexene selectivity. The highest selectivity is obtained for Ag−DBPA (20 wt % Ag, S/F-ratio of 3): 1.23 for 2-methyl-1-pentene and 1.42 for n-hexane, relative to 1.04−1.06 for unreactive solvents.

Synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA

Simultaneous extraction of zinc and cadmium by a mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) and mono-2-ethyl hexyl phosphoric acid (MEHPA), and the synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA have been investigated. It was shown that the extraction of zinc and cadmium by DEHPA and/or MEHPA can be increased by an increase of pH. The results also illustrate that the pH0.5 of zinc, by increase in MEHPA from 0.1 to 8 vol%, did not vary significantly while that of cadmium varies from 0.63 to 2.4. In other words MEHPA prevents selective extraction of zinc from aqueous media containing both zinc and cadmium. Studies on the selective separation parameter βZn/Cd show that it was reduced 50 to 13 times by an increase in MEHPA from 0.1 to 8.0 vol%. In this paper, the effects of DEHPA and MEHPA concentration on co-extraction of zinc and cadmium have been investigated.

Determination of Radiolysis Products in Zirconium Salt of Di‐(2‐Ethylhexyl) Phosphoric Acid by High Performance Liquid Chromatography/Mass Spectrometry

A liquid chromatography with an electrospray ionization‐mass spectrometry (LC‐ESI‐MS) method is described for the quantitative measurement of di‐(2‐ethylhexyl) phosphoric acid (D2EHPA), mono‐(2‐ethylhexyl) phosphoric acid (M2EHPA) in zirconium salt of di‐(2‐ethylhexyl) phosphoric acid (Zr‐D2EHPA). During the solvent extraction process of radioactive waste, the Zr‐D2EHPA extractant may be degraded to D2EHPA, M2EHPA, and PO4 −3 etc. Amounts of D2EHPA and M2EHPA in Zr‐D2EHPA must be monitored because the production of these compounds means degradation, which leads to a decrease in the extraction yield. Retention behavior for D2EHPA and M2EHPA is studied with a Phenomenex LUNA‐C18 (4.6 mm × 25 cm) analytical column and methanol/H2O (50 mmol CH3COONH4) by LC. Optimum conditions of eluent for the determination of D2EHPA and M2EHPA irradiated with 60Co γ‐rays of Zr‐D2EHPA are methanol:H2O (50 mmol CH3COONH4) = 80:20 ratio in the SCAN mode of the MS for D2EHPA and Methanol:H2O (50 mmol CH3COONH4) = 75:25 ratio in the SIM mode of the MS for M2EHPA. Di‐(2‐ethylhexyl) phosphoric acid and M2EHPA compounds are well separated within 10 min. Dynamic ranges are 10–100 µg mL−1 for D2EHPA and 10–200 µg mL−1 for M2EHPA, respectively. The detection limits are 1 µg mL−1 in the SCAN mode of the MS for D2EHPA and 1 µg mL−1 in the SIM mode of the MS for M2EHPA in this system with a 20 µL sample loop.

The solubility and stability of organophosphoric acid extractants in H 2SO 4 and HCl media

The solubility and stability of several organophosphoric acid extractants is investigated in light of the selection of suitable extractants for iron(III) solvent extraction as a potential iron rejection route in zinc processing. Specifically, the effects were studied of acid medium (HCl and H 2SO 4), metal-salt presence (Fe 2(SO 4) 3 and FeCl 2,3), and temperature (20 and 50 °C) on extractant solubility and degradation. Aqueous entrainment was not considered. Tests were performed on three organophosphoric acid extractant candidates: OPAP (equimolar mixture of mono- and di-octylphenyl acid phosphates); D2EHPA (di-(2-ethylhexyl) phosphoric acid); and M2EHPA (mono-2-ethylhexyl phosphoric acid). With regard to simple H 2SO 4 and HCl acid solutions, the order of solubility and degradation followed was M2EHPA≫OPAP>D2EHPA. The presence of metal-salts reversed the observed order of degradation, H 2SO 4(aq)>HCl (aq), increasing degradation in the latter medium. To explain the degradation behaviour in HCl strip medium, a mechanism that considers iron(III) metal-catalyzed ester hydrolysis is postulated.

Kinetic Study on the Extraction of Aluminum and Beryllium by Mono(2-ethylhexyl)phosphoric Acid.

The kinetics of aluminum and beryllium extraction by mono(2-ethylhexyl)phosphoric acid (M2EHPA) is studied using a stirred transfer cell. M2EHPA has high surface activity and forms reverse micelles in the organic phase. The formation of a 1:1 complex of the metal ion and the dissociated M2EHPA anion in the aqueous phase is found to be rate-determining. The formation of reverse micelles does not affect the extraction rate, and rapid attainment of the extraction equilibria observed otherwise in the shaking experiments is considered to be caused by the large interfacial area due to the lowering of interfacial tension.

Radiation effects on the extraction of americium(III) with di(2-ethylhexyl) phosphoric acid

Radiation effects on the extraction of Am(III) with di (2-ethylhexyl) phosphoric acid (DEHPA) was studied by exposing DEHPA to gamma rays under various conditions. Gamma irradiation of undiluted DEHPA causes an enhancement of extraction of Am(III) due to the formation of mono (2-ethylhexyl) phosphoric acid (MEHPA) similarly to that of Nd(III). The presence of diluent during irradiation brought about a slight difference from the results in the absence of a diluent. The marked change occurred in Df when the organic solvent was exposed to γ-ray while being mixed with nitric acid solution. An initial slight increase of Df for Am(III) and Nd(III) was followed by a subsequent decrease beyond an absorbed dose of approximately 200 Wh·1−1. This phenomenon was explained by the enhanced decomposition of DEHPA and the subsequent strong hydrolytic and radiolytic decomposition of MEHPA to H3PO4 in the aqueous phase, and the complex forming nature of H3PO4 with Am(III) and Nd(III).

Extraction of selected metallic cations by di-acidic phosphorus-based extractants, XPO(OH) 2, in a ketone diluent

Isopiestic measurements in dry methyl isobutyl ketone (Hexone), with tri 2-ethyl hexyl phosphoric acid as monomeric standard, show both mono 2-ethyl hexyl phosphoric acid, ( C 2 H 5· C 8 H 12 O) PO( OH) 2, H 2 MEHP, and 2-ethyl hexyl phosphonic acid, ( C 2 H 5· C 6 H 12 O) PO( OH) 2, H 2[ EHP] to be essentially dimeric, the respective number of formula weights per aggregate being measured as 2·4 and 2·3. Assuming the extractants to be dimeric under extraction conditions (wet Hexone) the extraction of Am(III), Eu(III) and Tm(III), as representatives of M 3+, and of Ca(II) and U(VI) i.e. UO 2 2+, as of M 2+, in the H 2Y (Hexone) vs. HCl system may be presented as: H 2 Y is H 2 MEHP: M δ 3+ + 2·5( H 2 Y) 2 o ⇌ M( HY)( H 2 Y 2) 2 o + 3 H δ+ H 2 Y is H 2[ EHP]: M δ 3+ + 3( H 2 Y) 2 o ⇌ M( H 2 Y 2) 2 o + 3 H δ+ H 2 Y is H 2 MEHP or H 2[ EHP]: M δ 3+ + 2( H 2 Y) 2 o ⇌ M( H 2 Y 2) 2 o + 2 H δ+ In H 2MEHP (diluent) vs. HCl systems, comparison of extractant dependency of the K for Eu(III) is made for toluene (non hydrogen bonding), Hexone (hydrogen bond acceptor) and n-decanol (hydrogen bond donor and acceptor) as diluent. The variation of log K with Z for lanthanides(III) in 0·30 F extractant (Hexone) vs. 0·0625 F HCl shows H 2[EHP] to be the more promising extracting for mutual separation of lanthanides (III).

Applicability of certain organo phosphorus extractants to environmental and biological radioactivity surveys

The applicability of certain organo phosphorus extractants to environmental and biological radioactivity surveys has been demonstrated. Specifically, a solution of mono 2-ethyl hexyl phosphoric acid, H 2MEHP, in a hydrocarbon and/or chlorinated hydrocarbon diluent has been shown to extract radioactive Ce(III), Pm(III), Y(III), Am(III), Pu(III), Th(IV), Np(IV), Pu(IV) and U(VI) from acidified human urine with sufficiently high K values to permit basing a scheme of analysis for such radioelements upon liquid-liquid extraction. The specific K value is strongly dependent upon the valence of the element, permitting a partial mutual separation of the above set of elements through use of the H 2MEHP (hydrocarbon and/or chlorinated hydrocarbon) vs. HCl system. These separation possibilities are multiplied by introduction of negative synergist, specifically 2-ethyl hexanol-1, which serves to progressively inactivate H 2MEHP. Consequently, under certain conditions, M(III) may be scrubbed from an extract leaving M(IV) and M(VI) in the organic phase; but under another set of conditions involving a greater relative concentration of negative synergist, M(VI) may be scrubbed from the extract leaving M(IV) in the organic phase. Further mutual separation is accomplished by means of extraction with di 2-ethyl hexyl phosphoric acid, HDEHP, this extractant serving to separate Y from Pm, Ce(III) and Am and to separate Ce(IV) from Pm and Am. Finally, extraction with tri n-octyl phosphine oxide, TOPO, is utilized in the separation of U(VI) from Pu(III). Through use of selected diluents of different densities, the organic phase has been made the upper or lower phase in accordance with maximum ease of manipulation. Flow sheets have been devised and tested. Advantages of the techniques are discussed, and other areas of application are suggested.

Synergistic effects in the extraction of selected metallic cations by mono (2-ethyl hexyl) phosphoric acid

The effect of synergistic agents upon the extraction of M(III) lanthanides, Y(III), Am(III), Cm(III), Th(IV), and U(VI) by H 2MEHP, mono 2-ethyl hexyl phosphoric acid, in a carrier diluent from aqueous HCl has been investigated as a function of carrier diluent, synergistic agent, concentration of H 2MEHP and Z of M(III) lanthanides. It was found that a plot of log K vs log ( r−0·5) or log ( r−2), depending upon the synergist, is more meaningful than a plot of log K vs F or log F of the synergist, where r is the ratio, ( F of synergist/ F of H 2MEHP). For some elements as r increases from zero, K rises to a maximum (region of positive synergism); in others no positive synergism is noted. In each instance in which a maximum is found, the maximum becomes progressively more pronounced as the synergist is varied from n-decanol to TBP, tri-n-butyl phosphate, to TOPO, tri-n-octyl phosphine oxide. In the negative synergism range, the limiting slope of the log K vs log ( r−0·5) plot for all of the M(III) examples studied (TBP synergist, cyclohexane and toluene diluents) is −3. Similarly, the limiting slope of the log K vs log ( r−2) plot (n-decanol synergist, cyclohexane diluent) is −3 for M(III), −4 for Th(IV) and −2 for U(VI). The extractant dependency for Eu(III) and Am(III) by H 2MEHP in the absence of synergist is shown to be first power in toluene diluent and third power in n-decanol diluent. Z-studies in the diluents toluene, cyclohexane and n-decanol are included. Tentative explanations of the negative synergistic effects are proposed in terms of assumed chemical interaction between synergist and H 2MEHP; and possible applications of these effects are suggested.