Di(2-ethylhexyl)phosphoric Acid Concentration Research Articles

Effect of di-(2-ethylhexyl)phosphoric acid on microstructure, cloud point and uranyl ion binding competence of Triton X-100 micelles

The incorporation of an extracting agent di-(2-ethylhexyl)phosphoric acid (D2EHPA) into non-ionic surfactant, Triton X-100 (TX-100) micelles was investigated by monitoring the microstructural changes using light scattering (LS) and small angle neutron scattering (SANS) techniques. Dynamic light scattering (DLS) studies indicate a gradual increase in the apparent diffusion coefficient (Da) of the micelles upon addition of D2EHPA, suggesting the incorporation of D2EHPA molecules into TX-100 micelles. Quantitative analysis of the SANS data for D2EHPA containing micelles indicates that the effective surface charge on the micelles increases with increasing concentration of D2EHPA, while the dimensions of the micelles remain almost same. Thus, the observed increase in Da of the micelles is attributed to the changes in the intermicellar interactions. The increase in repulsive interaction with addition of D2EHPA is also evident from an increase in the cloud point of the micellar solutions. The microstructural and cloud point changes occurred in D2EHPA containing micelles in the presence of an inorganic salt, sodium chloride (NaCl) further support the inclusion of D2EHPA molecules into TX-100 micelles. The binding of uranyl ions (UO22+) to TX-100–D2EHPA mixed micelles was ensured by monitoring a decrease in the intermicellar repulsion upon addition of uranyl nitrate hexahydrate and a subsequent decrease in the cloud point of the micelles. A red-shift in the absorption peaks of uranyl nitrate hexahydrate in the presence of TX-100–D2EHPA mixed micelles also confirms the binding of UO22+ to mixed micelles. The quantitative estimation of UO22+ bound to TX-100–D2EHPA mixed micelles was carried by cloud point extraction (CPE) method followed by spectrophotometric determination.

Dysprosium pertraction through facilitated supported liquid membrane using D2EHPA as carrier

AbstractThe pertraction of dysprosium (Dy) through a supported liquid membrane (SLM) system consisting of PTFE (polytetrafluoroethylene) support, D2EHPA (di-2-ethylhexyl phosphoric acid) dissolved in kerosene as membrane solution, and HNO3 solution as stripping solution, was studied. The experiments were designed by the Taguchi method in order to investigate the effects of initial Dy concentration, feed phase pH, different stripping solution concentration, and D2EHPA concentration in the membrane phase on Dy pertraction. Optimal experimental conditions for Dy pertraction were obtained using an analysis of variance (ANOVA) (feed concentration: 130 mg L

Solvent Extraction of Light Rare Earth Ions Using D2EHPA from Nitric Acid and Sulphuric Acid Solutions

A study on solvent extraction of a mixture of light rare earths ions (La (III), Nd (III) and Ce (IV)) from nitric and sulphuric acid solutions with di-(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene as an extractant has been carried out. The influences of D2EHPA and acid concentrations on the extraction efficiency of rare earth metal ions were evaluated. It was found that the extraction percentage of La, Nd and Ce decreased as the acids concentrations increased. On the contrary, the extraction efficiency of these ions increased as D2EHPA concentration increased. The utmost extraction percentage of La, Nd and Ce (99.4%, 99.7% and 100% respectively) was extracted from 0.1 M HNO3using 1.0 M D2EHPA. The order of extraction ability of the studied rare earth elements by D2EHPA decreased in the series of Ce (IV)>Nd (III)>La (III).

Properties of the material spontaneously formed in interfacial layer of system at extraction of rare-earth elements

The wetting ability of the material formed spontaneously in the interface layer of an aqueous solution of a rare-earth element (REE) salt/solution of di-(2-ethylhexyl)phosphoric acid (D2EHPA) extraction system adhered onto a glass plate is investigated. It is found that its properties depend on the natures of the REE and the solvent, and the initial concentrations of the REE and the extracting reactant. It is shown that the material formed at the interface and adhered onto a glass plate has controlled wetting ability. The difference between the properties of interface REE formations for yttrium and cerium subgroups is established. The electric conductivity of interphase formations in the same systems is measured and shown to display an extreme dependence on time in systems with heptane but a monotonically increasing one in systems with toluene. It is shown that the electric conductivity of interphase formations diminishes sharply with an increase in the ratio of the initial concentrations of REE salt and D2EHPA. It is concluded that an increase in the relative gain of the average molar mass of interphase formations indicates coagulation and the formation of polymers.

Optimization of nickel removal using liquid–liquid extraction and response surface methodology

The nickel extraction efficiency by means of liquid–liquid extraction (LLE) method was studied using response surface methodology; six parameters were identified as influential factors on nickel removal efficiency as the response. However, on screening experiments, only two factors were selected: pH and di-(2-ethylhexyl) phosphoric acid (D2EHPA) concentration. Face-centered composite design (FCCD) was applied in order to determine the optimum conditions for nickel removal by LLE. The results of FCCD showed that a second-order model described the relationship between the factors and nickel removal properly. Results showed that the optimum conditions are pH 1.1 and D2EHPA concentration 0.2 M, where 95.57% of nickel removal was achieved.

Transport of cobalt(II) through a hollow fiber supported liquid membrane containing di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the carrier

This work presents experimental, modeling and simulation studies for Co2+ ion extraction using hollow fiber supported liquid membrane (HFSLM) operated in a recycling mode. Extractant di-(2-ethylhexyl) phosphoric acid (D2EHPA) diluted with kerosene has been used as the membrane phase. The Co2+ ion concentration in the aqueous feed phase was varied in the range of 1–3mM. Also, D2EHPA concentration was varied in the range of 10–30% (v/v). A mass transfer model has been developed considering the complexation and de-complexation reactions to be fast and at equilibrium. Equations for extractant mass balance and counter-ion (H+) transport have also been incorporated in the model. Extraction equilibrium constant (Kex) for cobalt–D2EHPA system has been estimated from equilibration experiments and found to be 3.48×10−6. It was observed that the model results are in good agreement with the experimental data when diffusivity of metal-complex (Dm) through the membrane phase is 1.5×10−10m2/s. Feed phase pH and strip phase acidity had negligible effect on the extraction profiles of Co2+ ions. An increase in D2EHPA concentration increased extraction rates of Co2+ ions. The membrane phase diffusion step was found to be the controlling resistance to mass transfer.

Recovery of copper(II) through polymer inclusion membrane with di (2-ethylhexyl) phosphoric acid as carrier from e-waste

Abstract In this study, permeation of copper ions through polymer inclusion membrane (PIM) containing di (2-ethylhexyl) phosphoric acid (D2EHPA) as carrier, cellulose triacetate (CTA) as polymer and di-octyl phthalate (DOP) as plasticizer has been investigated. The effects of Cu(II) in feed phase, H 2 SO 4 in strip phase and D2EHPA (in membrane) concentrations on the transport were investigated. D2EHPA concentration varied from 0.6×10 –2 to 6×10 –2 mol/L and it was found that the transport of Cu(II) increased with the carrier concentration up to 4.8×10 –2 mol/L. High Cu(II) concentration in the feed phase leads to an increase in flux from 0.53×10 –6 to 4.48×10 –6 mol/(m 2 s) within the Cu(II) concentration range 0.79×10 –4 mol/L–31.47×10 –4 mol/L at pH of 4.5. Increase in H 2 SO 4 concentration in strip solution leads to an increase in copper ions flux. Studies on the transport kinetics of Cu(II) ions and the stability of the membranes were also carried out. The developed methodology was applied for digested e-waste samples and found to be successful for the recovery of Cu(II).

Enantioseparation of Racemic Mixtures Based on Solvent Sublation

A method of solvent sublation was developed for the enantioseparation of racemic ofloxacin (rac Oflx) and racemic tryptophan (rac Trp). In this method, dibenzoyl-L-tartaric acid (L-DBTA) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) and sodium lauryl sulfate (SDS) were used as chiral coextractants and foamer, respectively. Several important parameters influencing the separation performances, such as pH in aqueous phase, concentrations of rac mixtures, L-DBTA, D2EHPA, and SDS, were investigated. Under the optimal operation conditions, the enantiomeric excess and enantioselectivity were 60.08% and 5.58 for Oflx and 65.09% and 6.31 for Trp, respectively. The yields of D-enantiomer and L-enantiomer were 34.23% and 8.54% for Oflx and 18.59% and 3.93% for Trp, respectively. The results suggest that the enantioselectivities have been enhanced compared with the traditional chiral extraction. This technique is an efficient chiral separation method, with many advantages such as low expenditures of organic solvent, low consumption of chiral extractant, and easy realization of multistage operation.

Removal of Zn(II) from Aqueous Acetate Solution Using Di (2-Ethylhexyl) Phosphoric Acid & Tributylphosphate

The extraction of Zinc (II) in acetate medium with di (2-ethylhexyl) phosphoric acid (D2EHPA) in chloroform diluent was investigated under different experimental conditions, in order to have a better understanding of the extraction mechanism. The extraction yield was found to depend on the concentrations of Zinc (II) and D2EHPA, and the equilibrium pH. The effects of acetic acid and the salting-out agent were also studied. The nature of the extracted species was investigated by the slope analysis method. Graphs of log D vs. log [D2EHPA] and log D vs. pH were plotted for Zn (II), and the species extracted into the organic phase was found to have the composition (ZnCH3COO)R.HR. The best performance was reached (80%) with zinc concentrations lower than 5 mM in a neutral medium. The extraction yield of metals decreased as the acetic acid concentration increased with any given extractant concentration. The addition of sodium acetate to the aqueous phase strongly increased the zinc extraction yield (99.5%). A synergistic effect was observed by the addition of tributhylphosphate (TBP) with the organic phase.

Synergic Extraction of Folic Acid with Di(2-ethylhexyl) Phosphoric Acid and Amberlite LA-2

The influences of extractants concentrations and solvent polarity on the efficiency of folic acid separation by synergic extraction with Amberlite LA-2 and di(2-ethylhexyl) phosphoric acid (D2EHPA) mixture have been analyzed. The results indicated the formation of an interfacial compound which includes one molecule of folic acid and one of D2EHPA, the hydrophobicity of this compound being increased by solvation with Amberlite LA-2 molecules. The number of aminic molecules participating in the interfacial complex formation is controlled by solvent polarity and D2EHPA concentration, decreasing from 3 to 1 with the increase of these two parameters. The results indicated that the most important synergic effect corresponds to the extractants mixture dissolved n-heptane, at low D2EHPA concentration in the organic phase (5 g/l).

Uphill transport and mathematical model of Pb(II) from dilute synthetic lead-containing solutions across hollow fiber supported liquid membrane

This work presents an experimental investigation and mathematical model of Pb(II) separation and stripping from relatively low-level lead-containing synthetic solutions through a hollow fiber supported liquid membrane (HFSLM) by using di-2-ethylhexyl phosphoric acid (D2EHPA) in toluene as an extractant or carrier. The separation was studied on several variables: concentration of D2EHPA, types of stripping solutions (distilled water, HNO3, H2SO4 and HCl), concentration of the selected stripping solution, flow patterns of feed and stripping solutions, types of lead-containing solutions (Pb(NO3)2 and PbCl2), and flow rates of feed and stripping solutions. The results remarkably showed that HFSLM could successfully reduce a very low concentration of Pb(II) in feed solution to less than the regulatory discharge limit of 0.2mg/L issued by the Ministry of Industry and the Ministry of Natural Resource Environment, Thailand. The highest extraction and stripping results were achieved by using 0.03M D2EHPA, 0.9M HCl at equal flow rates of feed and stripping solutions of 100mL/min using a single-pass of feed solution and circulating of stripping solution. High percentages of extraction and stripping were observed from both Pb(NO3)2 and PbCl2 solutions. The kinetics of Pb(NO3)2 and PbCl2 separation were corresponded to second-order reaction with the rate constants of 1.49 and 1.51L/mgmin, respectively. The prediction of Pb(II) concentrations in the outlet Pb(NO3)2 and PbCl2 feed solutions obtaining from mathematical model were in good agreement with the experimental results at the average percent deviations of 4% for Pb(NO3)2 solution and 8% for PbCl2 solution.

Separation of zinc from lean sphalerite leached liquor in nitrate medium with D2EHPA using supported liquid membrane

Separation of zinc and lead from an aqueous nitrate medium using supported liquid membrane with di(2-ethylhexyl)phosphoric acid (D2EHPA) as mobile carrier was studied. Celgard-2500, a microporous polypropylene film, was used as the solid support for the liquid membrane with a plate and frame type of cell used for the experiments. The effects of different parameters such as pH of feed solution (1–3·5), D2EHPA concentration in the membrane phase (10–100 mol m−3), acid concentration in strip solution and flowrate of the aqueous solution on separation of lead and zinc were studied. It was observed that zinc flux across the membrane increased with pH of the feed solution up to 3·0 and thereafter decreased while zinc flux increased with the D2EHPA concentration in the membrane phase up to 75 mol m−3 and thereafter decreased. The flowrate of 100 mL min−1 was sufficient to reduce the resistances due to the aqueous boundary layer while 950 mol m−3 H2SO4 was found sufficient to strip the metals from the membrane phase in the strip phase. Under the study conditions, the copermeation of lead with zinc was observed to be negligible.

Study on a novel flat renewal supported liquid membrane with D2EHPA and hydrogen nitrate for neodymium extraction

The Nd(III) extraction in flat renewal supported liquid membrane (FRSLM), with polyvinylidene fluoride membrane and renewal solution including HNO3 solution as the stripping solution and di(2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in kerosene as the membrane solution, was investigated. The effects of pH in the feed phase, volume ratio of membrane solution to stripping solution, concentration of HNO3 solution and concentration of carrier in the renewal phase on extraction of Nd(III) were also studied, respectively. As a result, the optimum extraction conditions of Nd(III) were obtained when concentration of HNO3 solution was 4.00 mol/L, concentration of D2EHPA was 0.100 mol/L, and volume ratio of membrane solution to stripping solution was 1.00 in the renewal phase, and pH was 4.60 in the feed phase. When initial concentration of Nd(III) was 2.00×10−4 mol/L, the extraction percentage of Nd(III) was up to 92.9% in 75 min.

Extraction Equilibria of 4-Hydroxypyridine using Di (2-ethylhexyl) Phosphoric Acid

Extractions of 4-Hydroxpyridine (4HP) from aqueous solutions using Di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant in 1-octanol and kerosene were studied. The factors that affected the distribution coefficient (D), such as equilibrium pH, the concentration of D2EHPA, and the type of diluents were discussed. The interaction mechanism between 4HP and D2EHPA was validated by infrared spectroscopic analysis. D increased with the increase of the concentration of D2EHPA and peak values appeared at equilibrium pH = 3.6–5.0. D in the polar diluent (1-octanol) was much higher than those in the non-polar diluent (kerosene). The extraction reaction was found to be a proton-transfer process and D2EHPA mainly reacted through its –OH with –N– of 4HP. The apparent reactive extraction equilibrium constants K 11 and K 12 were obtained by fitting the experimental data of extraction equilibrium. By comparing calculated D values from the proposed model with the experimental ones, the accuracy of the proposed model was examined.

Three-Liquid-Phase Extraction: A New Approach for Simultaneous Enrichment and Separation of Cr(III) and Cr(VI)

A novel and simple three-liquid-phase extraction (TLPE) approach was developed for the simultaneous removal and separation of Cr(III) and Cr(VI) from aqueous solutions. The proposed three-liquid-phase system (TLPS) consists of di(2-ethylhexyl)phosphoric acid (D2EHPA), poly(ethylene glycol) (PEG) with a molecular weight of 2000, and (NH4)2SO4. The effects of various factors including the aqueous solution pH, amounts of (NH4)2SO4 and PEG, initial chromium amount, D2EHPA concentration, phase-mixing time, and diluent on the three-phase partitioning behavior of Cr(III) and Cr(VI) were evaluated. The distribution behavior of the two oxidation states of chromium was found to be highly pH-dependent. Cr(III) preferred the D2EHPA-rich top phase through a cation-exchange reaction, whereas Cr(VI) was enriched in the PEG-rich middle phase through ion-pair formation. By appropriate selection of the extraction conditions, nearly all of the Cr(III) was extracted into the D2EHPA top phase, and more than 90% of the Cr(VI) ...

Selection of design parameters and optimization of operating parameters of soybean oil-based bulk liquid membrane for Cu(II) removal and recovery from aqueous solutions

The objectives of this work were to select suitable design parameters and optimize the operating parameters of a soybean oil-based bulk liquid membrane (BLM) for Cu(II) removal and recovery from aqueous solutions. The soybean oil-based BLM consists of an aqueous feed phase (Cu(II) source), an organic membrane phase (soybean oil (diluent), di-2-ethylhexylphosphoric acid (D2EHPA) (carrier) and tributylphosphate (phase modifier)) and an aqueous stripping phase (sulfuric acid solution (H 2SO 4)). Effects of design parameters (stirring condition and stripping/membrane to feed/membrane interface area ratio) of soybean oil-based BLM on the Cu(II) removal and recovery from aqueous solutions were investigated and the suitable parameters were selected for further studies. Optimization of the operating parameters (D2EHPA concentration, H 2SO 4 concentration, stirring speed, temperature and operating time) of soybean oil-based BLM for maximum percentage (%) recovery of Cu(II) was then conducted using Response Surface Methodology and the optimum parameters were determined. A regression model for % recovery was developed and its adequacy was evaluated. The experimental % recovery obtained under the optimum operating conditions was compared with the predicted one and they were found to agree satisfactorily with each other.

A Liquid Membrane-Based Green Method for the Separation and Determination of Lead in Saline Waters

ABSTRACT In this work, the authors proposed a new liquid membrane-based method for the determination of lead in saline waters. In this case, the new method is based on lead quantification by inductively coupled plasma-mass spectrometry (ICP-MS) after a preconcentration step by means of a bulk liquid membrane (BLM) system. With no sample manipulation, the system transports and preconcentrates the analyte ions in the sample into the acidic receiving solution, by means of an organic membrane containing di-(2-ethylhexyl)-phosphoric acid (DEHPA) acting as a chemical carrier. The chemical variables controlling Pb2+ permeation through the membrane were studied by use of a modified simplex approach. The most appropriate preconcentration rates were found at sample pH 4.7, maintained with a 0.08-M acetate buffer solution, a 0.07-M DEHPA concentration, and a 0.23-M HNO3 receiving solution. Under these conditions, an extraction yield of 93.8 ± 0.1% and a preconcentration factor of 4.2 were obtained, thus allowing lead selective separation and accurate determination in real samples at environmental concentration levels. The system was tested with several real samples from the Gulf of Cádiz containing lead at the low ppb levels.

Liquid–liquid extraction of uranium from Egyptian phosphoric acid using a synergistic D2EHPA–DBBP mixture

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.

Separation of Eu(III) with supported dispersion liquid membrane system containing D2EHPA as carrier and HNO 3 solution as stripping solution

The Eu(III) separation in supported dispersion liquid membrane (SDLM), with polyvinylidene fluoride membrane (PVDF) as the support and dispersion solution containing HNO 3 solution as the stripping solution and Di(2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in kerosene as the membrane solution, was studied. The effects of pH value, initial concentration of Eu(III) and different ionic strengths in the feed phase, volume ratio of membrane solution and stripping solution, concentration of HNO 3 solution, concentration of carrier, different stripping agents in the dispersion phase on the separation of Eu(III) were also investigated, respectively. As a result, the optimum separation conditions of Eu(III) were obtained as the concentration of HNO 3 solution was 4.00 mol/L, concentration of D2EHPA was 0.160 mol/L, and volume ratio of membrane solution to stripping solution was 30:30 in the dispersion phase, and pH value was 5.00 in the feed phase. Ionic strength had no obvious effect on the separation of Eu(III). Under the optimum conditions studied, when initial concentration of Eu(III) was 1.00×10 −4 mol/L, the separation rate of Eu(III) was up to 94.2% during the separation period of 35 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The results were in good agreement with the literature data.

Optimizing extraction of Iron, Copper and Zinc from Cobalt-pregnant electrolyte by ph-based four-stage process

Optimization of recovery of iron (Fe), copper (Cu) and zinc (Zn) using di-2-ethylhexyl phosphoric acid (D2EHPA) was accomplished by pH-based four-stage extraction process, where NaOH, HCl, Shell-sol 3525 and H2SO4 were used as solvents. Laboratory tests were carried out on 8 samples collected from solvent-extraction unit at set pH values, feed concentration and flow rate, temperature, purity of cobalt (Co) solution and extractant concentration to optimize removal of Fe, Cu, and Zn from Co-pregnant solution. The samples used were 200 L of 150 g/L H2SO4, 200 L of 180 g/L HCl, 20 L of 30 g/L NaOH and 2 - 3.5 % concentrations of D2EHPA. The extraction of Fe3+ increased from 88 to 99 % when D2EHPA concentration was increased from 2 to 3 % (an increase of 11 %). The extraction of Zn2+ increased from 84 to 96 % in 3 days, and 84 to 100 % in 4 days when concentration of D2EPHA was increased by 1.5 % (increase of 12 % and 16 % respectively). A 1.5 % increase in concentration of D2EPHA produced 44 % increase of Cu2+ extraction efficiency in 3 days. The extraction efficiencies of Zn and Fe were twice that of Cu when D2EPHA in shell-sol 3525 was used as extractant at 3.5 % concentration D2EPHA.