Mono 2-ethylhexyl Ester Research Articles

Separation of Gallium and Arsenic in Wafer Grinding Extraction Solution Using a Supported Liquid Membrane that Contains PC88A as a Carrier

Wafer grinding extraction solution was passed through a supported liquid membrane (SLM) that contained PC88A (2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester) as a carrier, to separate gallium from arsenic by selective permeation. The SLM separation process was conducted under various conditions. The kind of membrane supporter, the pH of the feed, the feed concentration, and the HCl content in the strip governed the concentration of gallium and arsenic in the strip phase. The conditions determined as optimal in the laboratory test were used to perform the pilot test. Well separation between gallium and arsenic was performed in both laboratory and pilot tests. Hydrophobic membrane polytetrafluoroethylene (PTFE) with 0.2 μm pores was the best of three membrane supporters. The most efficient separation was obtained using an acidic feed (pH at 1.8) with 1000 ppm gallium. Over a 12-h period of stripping, the striped Ga concentration increased with the HCl concentration from 0.5 to 2.0 M and then leveled off. The recovery rate in the pilot test exceeded that on the laboratory scale because the membrane area was greater. The pilot test yielded a high recovery percentage of gallium (at 91%) and a low recovery of arsenic (merely 1.3 ppm) in the strip over 72 h.

Separation of Copper and Zinc Ions by Hollow Fiber Supported Liquid Membrane Containing LIX84 and PC-88A

The separation of Cu 2 + and Zn 2 + in mixed solutions of zinc and copper sulfate has been studied using hollow fiber supported liquid membrane (HFSLM). The extractants for Cu 2 + and Zn 2 + were LIX84(anti-2-hydroxy-5-nonyl acetophenoneoxime) and PC-88A(2-ethylhexylphosphonic acid mono-2 ethylhexyl ester) which were diluted in kerosene, respectively. The effects of operational variables on the permeation rate and the separation factor of Cu 2 + and Zn 2 + were investigated. At metal concentrations in the feed solution between 1 to 200 mol.m - 3 under pH 2.0, the permeation rate of Cu 2 + by 10 mass% LIX84 HFSLM was I x 10 - 6 ∼5 × 10 - 6 mol.m - 2 .s - 1 while that of Zn 2 + with PC-88A was 10 - 6 ∼10 - 5 mol.m - 2 .s - 1 . By total recycle operation, copper sulfate solution with 99.6% purity and 99.9% pure zinc sulfate solution could he enriched from the dilute solution in which the concentrations of both Cu 2 + and Zn 2 + were 1 g/L. respectively.

Modeling on the Counteractive Facilitated Transport of Co in Co–Ni Mixtures by Hollow-Fiber Supported Liquid Membrane

The separation of cobalt from mixed solutions of cobalt and nickel sulfate through the hollow-fiber supported liquid membrane using 2-ethylhexylphosphonic acid mono-2 ethylhexyl ester as a carrier has been studied. A mathematical model was developed to analyze the permeation of cobalt in the competitive permeation of cobalt and nickel. The model was based on the continuity equation and considered not only the cotransport of cobalt and nickel, but also the counter-transport of hydrogen ions. The concentrations in the stripping solution were taken into account in the model as well as the concentrations in feed solution and liquid membrane. The experimental results were in good agreement with the model.

Use of organophosphorus extractants impregnated on silica gel for the extraction chromatographic separation of minor actinides from high level waste solutions

Silica-gel has been used as an inert support for the extraction chromatographic separation of actinides and lanthanides from HNO3 and synthetic high level waste (HLW) solutions. Silica-gel was impregnated with tri-butyl phosphate (TBP), to yield STBP; 2-ethylhexyl phosphonic acid, mono 2-ethylhexyl ester (KSM-17, equivalent to PC-88A), SKSM; octyl(phenyl)-N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO), SCMPO; and trialkylphosphine oxide (Cyanex-923), SCYN and sorption of Pu(IV), Am(III) and Eu(III) from HNO3 solutions was studied batchwise. Several parameters, like time of equilibration, HNO3 and Pu(IV) concentrations were varied. The uptake of Pu(IV) from 3.0M HNO3 followed the order SCMPO>SCYN>SKSM>STBP. With increasing HNO3 concentration, DPu increased up to 3.0M of HNO3 for STBP, SKSM and SCMPO and then decreased. In the case of Am and Eu with SCMPO, the D values initially increased between 0.5 to 1.0M of HNO3, remained constant up to 5.0M and then slightly decreased at 7.5M. Also, the effects of NaNO3, Nd(III) and U(VI) concentrations on the uptake of Am(III) from HNO3 solutions were evaluated. With increasing NaNO3 concentration up to 3.0M, DAm remained almost constant while it was observed that it decreases drastically by adding Nd(III) or U(VI). The uptake of Pu and Am from synthetic pressurized heavy water reactor high level waste (PHWR-HLW) in presence of high concentrations of uranium and after depleting the uranium content, and finally extraction chromatographic column separation of Pu and Am from U-depleted synthetic PHWR-HLW have been carried out. Using SCMPO, high sorption of Pu, Am and U was obtained from the U-depleted HLW solution. These metal ions were subsequently eluted using various reagents. The sorption results of the metal ions on silica-gel impregnated with several phosphorus based extractants have been compared. The uptake of Am, Pu and rare earths by SCMPO has been compared with those where CMPO was sorbed on Chromosorb-102, Amberchrom CG-71 and styrene divinylbenzene copolymer immobilized in porous silica particles.

Selective Extraction of Y from a Ho/Y/Er Mixture by Liquid−Liquid Extraction in the Presence of a Water-Soluble Complexing Agent

The selective extraction of Y from Ho/Y/Er solution by liquid−liquid extraction using (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester (EHPNA), in the presence of a water-soluble complexing agent (ethylenediaminetetraacetic acid, EDTA), has been investigated. The extraction behavior of the ternary system for Ho, Y, and Er, in the presence of EDTA can be expressed using extraction equilibrium formulations, applying for the EDTA free system and consistent with the assumption that the rare-earth metals, when complexed with EDTA, do not take part in the extraction (masking effect). The extraction of Ho and Er in the presence of EDTA is suppressed when compared to that of Y because of the masking effect, and the selective extraction of Y is enhanced. Simulation studies for the separation of Y from a Ho/Y/Er mixture, by the use of a countercurrent mixer−settler cascade, show that the separation is enhanced by the addition of EDTA in both extraction and scrubbing sections.

Mechanism of Photoreductive Stripping of Iron(III) in a Liquid−Liquid Extraction System and Its Application for a Hydrometallurgical Process

The mechanism of the photoreductive stripping of iron(III) in the liquid−liquid extraction process was investigated by employing (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester (EHPNA) and bis(2-ethylhexyl)phosphoric acid (D2EHPA) as extractants, n-dodecane and kerosene as diluents, and a xenon lamp as the light source. The photoreductive stripping of iron(III) progressed by photoirradiation following an initial induction period caused by dissolved oxygen in the extraction system. The iron(III)−extractant complex was photoexcited in the organic phase and photoreduced to the iron(II) complex by electron donation from the water at the aqueous/organic interface. A kinetic study of the photoreductive stripping of iron(III) revealed that the photochemical reduction of iron(III) was the rate-determining step. The removal of iron from a simulated zinc refinery residue solution by using liquid−liquid extraction combined with photochemical reduction of iron was also investigated, showing that the rare metals in the refinery residue, gallium and indium, were recovered effectively and leaving almost all iron(III) in the aqueous phase.

Solvent extraction separation of gallium(III) with 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (PC-88A)

A rapid method for the extraction separation of gallium(III) with PC-88A in toluene has been studied. The extraction of gallium(III) was found to be quantitative with 0.025 M PC-88A in toluene in the pH range 2.0–3.0. Gallium(III) extracted in the organic phase was stripped with 2.0 M HCl and was determined spectrophotometrically by the PAR method. Effects of parameters such as reagent concentration, time to achieve equilibrium, various diluent and diverse ions on the extraction of gallium(III) were also studied. The stoichiometry of the extracted species of gallium(III) was determined on the basis of slope analysis method. The extraction reaction proceeds via a cation exchange mechanism and the extracted species is in the GaL 33HL form. Temperature dependence of the extraction equilibrium constant was also examined to estimate the apparent thermodynamic functions Δ H, Δ G and Δ S for extraction reaction.

Solvent Extraction of Titanium(IV) with 2-Ethyl Hexyl Phosphonic Acid Mono 2-Ethyl Hexyl Ester(HEHEHP).

Liquid-liquid extraction of titanium(IV) from sulfuric acid solution using 2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester (PC-88A) in toluene has been studied. The extraction of titanium(IV) was found to be quantitative with 0.03 M PC-88A in toluene in the acidic range of 0.01–0.3 M and 12.0–14.0 M H2SO4. Titanium(IV) extracted in the organic phase was stripped with the mixture of 2.0–3.5 M H2SO4 and 3% H2O2. Effect of reagent concentration on the extraction of titanium(IV) was studied.The stoichiometry of the extracted species of titanium(IV) was determined on the basis of slope analysis method. The extraction reaction proceeds with cation exchange mechanism in the range of 0.01 M–0.3 M H2SO4 and the extracted species is in the TiOR2·2HR form and at higher acidty (12.0 M–14.0 M H2SO4) it proceeds by solvation, the extracted species is Ti(OH)3HSO4·4HR. Temperature dependence of the extraction equilibrium constants was examined to estimate the apparent thermodynamic functions (ΔH, ΔS and ΔG) for extraction reaction.

Liquid-liquid extraction separation of iron (III) with 2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester

Liquid-liquid extraction separation of iron(III) with 2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester (PC-88A) in toluene has been studied. Quantitative extraction of iron(III) with 5 × 10 −3 M PC-88A in toluene is observed in the pH range 0.75–2.5. From the extracted complex species in the organic phase iron(III) was stripped with 1–4 M HNO 3, 1.5–4 M H 2SO 4 and 1.5–4 M HCl, and later determined spectrophotometrically by thiocyanate method. Separation of iron(III) was carried out with some of the first transition metals in binary and multicomponent mixtures. This method was extended for the determination of iron in real samples.

MECHANISM OF THE EXTRACTANT LOSS IN LANTHANIDE EXTRACTION PROCESS WITH SAPONIFIED ORGANOPHOSPHORUS ACID EXTRACTION SYSTEMS — II: FORMATION OF AQUEOUS AGGREGATES

ABSTRACT Organophosphorus acids, including di(2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethyIhexyI phosphonic acid mono 2-ethylhexyl ester (PC88A), and di(2-ethylhexyl) phosphinic acid (P229) form reversed micelles (d=20-100A) or water-in-oil (w/o) microemulsions (d=100-2000 A) in n-heptane when they are saponified with concentrated alkalis, such as NaOH, KOH and NH3H2O. After equilibrating with water or solution containing europium, some extractant and diluent in the saponified organic phase transfers into the aqueous phase, and some water solubilized in the w/o microemulsion returns to the aqueous phase. Dynamic light scattering (DLS) results indicate that aggregates within the range of micelles or microemulsions are formed in the equilibrated aqueous phase. The normal micelle or o/w microemulsion has a non-polar core that solubilizes n-heptane. Therefore, the formation of aqueous aggregates leads to extractant and diluent loss in the extraction procedure. FT-IR spectra also confirm the presence of extr...

Effect of synthesized surfactants in the separation of rare earth metals by liquid surfactant membranes

Synthesized surfactants have been applied to the separation and concentration of rare earth metals by liquid surfactant membranes (LSMs). Using newly synthesized surfactants (nonionic dioleyl L-glutamate ribitol; cationic dioleyl L-glutamate quaternary ammonium chloride), extraction of lanthanum (La), praseodymium (Pr), and neodymium (Nd) by LSMs was carried out with (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester as a carrier. The effects of the synthesized surfactants on the extraction and separation of these metals were investigated. Rate constants in LSMs were obtained from the analysis with an interfacial reaction model for each rare earth metal. It was found that the surfactant strongly affects the extraction rate and separation of rare earth metals by LSMs. Among them, a cationic surfactant having two oleyl chains showed the best separation factor in the extraction of La, Pr, and Nd by LSMs. Further, the extraction rate of the cationic surfactant was about 40 times higher than that of a commercial surfactant such as Span 80

Extraction equilibrium of Ce(III), Pr(III) and Nd(III) with acidic organophosphorus extractants.

Solvent extraction has recently attracted major interest for industrial-scale separation of lanthanoids, alike ion exchange. It is well known that di(2-ethylhexyl)phosphoric acid (henceforth D2EHPA) is an effective extractant for the mutual separation of lanthanoids, because of its high separation factor. 2-Ethylhexylphosphonic acid mono2-ethylhexyl ester (henceforth EHPNA), which is similar in its chemical structure as D2EHPA, has a higher ability of back extraction at low acid concentration than D2EHPA. In this paper, the extraction equilibrium of cerium, praseodymium and neodymium by EHPNA was investigated and was compared with that by D2EHPA. It was found that the existence of two kinds of complexes should be considered in the region of high concentration of EHPNA, unlike the case of D2EHPA. The extraction of metals from the solution of mixed lanthanoids can be explained based on the extraction mechanism of individual elements.

THE KINETICS OF COBALT AND NICKEL EXTRACTION USING HEHEHP

ABSTRACT The kinetics of the extraction of cobalt and nickel using purified mono 2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester (HEHEHP) were studied using the Rotating Diffusion Cell (RDC) apparatus. The extraction of cobalt was Investigated over a wide range of cobalt concentration, extractant concentration, pH and temperature conditions. Nickel extraction was examined over a wide range of nickel concentrations. The kinetic data were treated according to both interfacial and mass transfer with chemical reaction (MTWCR) models. The MTWCR model adequately described the kinetic data for both the cobalt and nickel extraction experiments. No variation of an interfacial model was adequate to describe the data. In the MTWCR model, the extraction rate was shown to be controlled by a mechanism involving diffusion of the extractant into the aqueous phase boundary layer with subsequent reaction involving the addition of the first ligand to the cobalt or nickel ion. This extraction mechanism was substantiated by supplementary results including the activation energy determination which indicated mixed diffusion and chemical reaction control, the significant measured rate of partition of the extractant to the aqueous phase, and the values of the cobalt and nickel complex formation constants in the aqueous phase.