Di(2-ethylhexyl)phosphoric Acid Concentration Research Articles

Extraction of lutetium(III) from aqueous solutions by employing a single fibre-supported liquid membrane

Transport behaviour of Lu(III) across a polypropylene hollow fibre-supported liquid membrane containing di(2-ethylhexyl)phosphoric acid (DEHPA) in dihexyl ether as a carrier has been studied. The donor phase was LuCl(3) in the buffer solution consisting of 0.2 M sodium acetate at pH 2.5-5.0. A miniaturised system with a single hollow fibre has been operated in a batch mode. The concentration of Lu(III) was determined by indirect voltammetric method using Zn-EDTA complex. The effect of pH and volume of the donor phase, DEHPA concentration in the organic (liquid membrane) phase, the time of extraction and the content of the acceptor phase on the Lu(III) extraction and stripping behaviour was investigated. The results were discussed in terms of the pertraction and removal efficiency, the memory effect and the mean flux of Lu(III). The optimal conditions for the removal of (177)Lu(III) from labelled (177)Lu-radiopharmaceuticals were discussed and identified. The removal efficiency of Lu(III) greater than 99% was achieved at pH of the donor phase between 3.5 and 5.0 using DEHPA concentration in the organic phase of 0.47 M and the ratio of the donor to the acceptor phase of 182.

Transport Study of Cu(II) Through Hollow Fiber Supported Liquid Membrane

The transport of Cu(II) from aqueous solutions containing buffer media through hollow fiber supported liquid membrane (HFSLM) using di(2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in kerosene as membrane phase and hydrochloric acid as striping phase was investigated. A set of factors were studied, including tube side velocity, shell side velocity, pH of the feed phase, Cu(II) concentration in the feed phase, buffer media concentration and D2EHPA concentration in the membrane phase. Experimental results indicate that the mass transfer coefficient increases with increasing both carrier concentration in the organic phase and flow rates on the tube side and shell side, and decreases with increasing initial Cu(II) concentration in the feed phase. With increasing pH value and acetate concentration in the feed phase, the mass transfer coefficient reaches a maximum value then decreases. The optimal operating conditions are obtained at pH value of 4.44 and 0.1 mol·L −1 acetic ion concentration in feed phase, and carrier volume fraction of around 10% in kerosene as organic phase. A mathematical model of the transport mechanism through HFSLM is developed. The modeled results agree well with the experimental ones.

Extraction and recovery of rhodamine B, methyl violet and methylene blue from industrial wastewater using D2EHPA as an extractant

The extraction behavior of cationic dyes namely rhodamine B (RB), methyl violet (MV) and methylene blue (MB) from industrial wastewater has been investigated using di-(2-ethylhexyl) phosphoric acid (D2EHPA) in hexane as a carrier. The extraction of cationic dyes increases with decreasing feed phase pH and increasing D2EHPA concentration in organic phase. The stripping percentage of dyes using acetic acid as the stripping agent from loaded D2EHPA was found to increase with increasing acid concentration. 98% stripping efficiency of dyes was achieved with 8.5 mol/L acetic acid solution at an organic:aqueous phase ratio (O/A) of 2:1. Parameters examined include D2EHPA concentration, effect of diluents, effect of pH, effect of initial dye concentration, equilibration time, and various stripping agents, aqueous to organic phase ratio in extraction and organic to aqueous phase ratio in stripping.

Enantioselective Extraction of Racemic Mandelic Acid by Di(2‐ethylhexyl) Phosphoric Acid and Tartaric Acid Derivatives as Mixed Complex Chiral Selectors

The distribution behavior of mandelic acid (MA) enantiomers was examined in a two‐phase system containing di(2‐ethylhexyl) phosphoric acid (D2EHPA) with two tartaric acid derivatives as complex chiral selectors in n‐octanol. Factors affecting the extraction were investigated, including the structure and concentration of tartaric acid as well as the concentration of D2EHPA and D,L‐MA. The results showed that both the distribution ratio and enantioselectivity were greatly improved by using a complex chiral selector rather than using the tartaric acid derivative by itself. Finally, it was found that the formation of mixed complex chiral selectors by mixing two tartaric acid derivatives with D2EHPA can improve the capacity of enantioselective extraction.

Separation of l-lysine by solvent sublation

Solvent sublation was used to separate the low concentration l-lysine from the aqueous solution by using dodecylbenzenesulforic acid (DBSA) as the surfactant, di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant, n-heptane as the extraction solvent. Especially the effects of initial pH, D2EHPA concentration in the organic phase, DBSA and NaCl concentration in the aqueous phase and air flow rate on the separation efficiency were investigated. The results showed that the optimum conditions of initial pH, D2EHPA concentration in the organic phase, DBSA and NaCl concentration in the aqueous phase and air flow rate were 7, 30%, 0.2 g/l, 0 mol/l and 250 ml/min, respectively, under room temperature and the enrichment ratio and recovery ratio were 13.26 and 79.57%, respectively. The separation efficiency of solvent sublation was higher than that of the traditional foam floatation and solvent extraction. Furthermore, the separation mechanism of solvent sublation was also discussed.

Extractive Resolution of racemic mandelic acid through a bulk liquid membrane containing binary chiral carrier

A method of bulk liquid membrane (BLM) using complex of di(2-ethylhexyl) phosphoric acid (D2EHPA) and O,O'-dibenzoyl-(2R, 3R)-tartaric acid (L-(-)-DBTA) was developed for the extractive resolution of racemic mandelic acid (rac MA). The effects of resolution time, concentration of D2EHPA in the organic phase, concentration of rac MA in the feed phase, stirring speed and temperature on extractive resolution were studied. The experimental results have shown that the greatest separation factor (α) 2.74 and the enantiomeric excess value (ee, %) 46.47% were obtained when the resolution time was about 4 h, the molar concentration ratio of rac MA, D2EHPA and L-(-)-DBTA 0.05:0.2:0.3, the stirring speed 400 r min-1 and the temperature 35 ºC. The developed method is helpful for optimizing the transport of BLM systems and for large-scale production of pure enantiomer.

Facilitated transport of Cr(III) through polymer inclusion membrane with di(2-ethylhexyl)phosphoric acid (DEHPA)

In this study, transport of Cr(III) through polymer inclusion membrane (PIM) with di(2-ethylhexyl)phosphoric acid (DEHPA) as carrier was reported. First, PIM was characterized by using FTIR and atomic force microscopy (AFM) techniques and contact angle measurements. Then, the effects of Cr(III) (in feed phase), HCl (in stripping phase) and DEHPA (in membrane) concentrations on the transport were investigated. DEHPA concentration varies from 0.25 to 0.5 M and it was determined that the transport of Cr(III) increased with the carrier concentration up to 0.4 M. It was also observed that the transport of Cr(III) through the PIM tended to increase with Cr(III) and HCl concentrations. According to the competitive transport of Cr(III), Cu(II) and Ni(II) through the PIM, the transport selectivity order was found as Cr(III) ≈ Cu(II) > Ni(II). The result from the transport of Cr(III) mixed with Cr(VI) also showed that flux of Cr(III) was not influenced by the presence of Cr(VI) in feed phase and no Cr(VI) transport through the PIM was determined. PIM had lower experimental Cr(III) flux than those of supported liquid membrane (SLM) and activated composite membrane (ACM) under the same experimental conditions. However, long-term stability of PIM and small difference between normalized flux for PIM and experimental SLM flux indicated that PIM could replace SLM for practical applications.

Adsorption of lanthanides(III) from aqueous solutions by fullerene black modified with di(2-ethylhexyl)phosphoric acid

AbstractFullerene black (FB) - a product of electric arc graphite vaporization after extraction of fullerenes - was modified with the di(2-ethylhexyl)phosphoric acid (D2EHPA). The distribution of D2EHPA between FB and aqueous HNO3 solutions has been studied. The effect of HNO3 concentration in the aqueous phase and that of D2EHPA concentration in the sorbent phase on the adsorption of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates from HNO3 solutions by D2EHPA-modified FB are considered. The stoichiometry of the sorbed complexes has been determined by the slope analysis method. The efficiency of lanthanides’ adsorption increases with an increase in the element atomic number. A considerable synergistic effect has been observed upon the addition of the neutral bidentate tetraphenylmethylenediphosphine dioxide ligand to D2EHPA in the sorbent phase.

Facilitated transport of Cr(III) through activated composite membrane containing di-(2-ethylhexyl)phosphoric acid (DEHPA) as carrier agent

The facilitated transport of chromium(III) through activated composite membrane (ACM) containing di-(2-ethylhexyl) phosphoric acid (DEHPA) was investigated. DEHPA was immobilised by interfacial polymerisation on polysulfone layer which was deposited on non-woven fabric by using spin coater. Then, ACM was characterised by using scanning electron microscopy (SEM), contact angle measurements and atomic force microscopy (AFM). Initially, batch experiments of liquid–liquid distribution of Cr(III) and the extractant (DEHPA) were carried out to determine the appropriate pH of the feed phase and the results showed that maximum extraction of Cr(III) was achieved at a pH of 4. It was also found that Cr(III) and DEHPA reacted in 1/1 molar ratio. The effects of Cr(III) (in feed phase), HCl (in stripping phase) and DEHPA (in ACM) concentrations were investigated. DEHPA concentration varies from 0.1 to 1.0 M and it was determined that the transport of Cr(III) increased with the carrier concentration up to 0.8 M. It was also observed that the transport of Cr(III) through the ACM tended to increase with Cr(III) and HCl concentrations. The stability of ACM was also confirmed with replicate experiments.

Recovery of zinc from an industrial zinc leach residue by solvent extraction using D2EHPA

A hydrometallurgical treatment involving solvent extraction of zinc using di-2-ethylhexyl phosphoric acid (D2EHPA) has been investigated to recover zinc from an industrial leach residue. The residue was leached with sulfuric acid producing leach liquor which was subjected to solvent extraction for enrichment of zinc and removal of impurities. Operating variables, such as pH, D2EHPA concentration, temperature, aqueous/organic (A/O) phase ratio, tri-butyl phosphate (TBP) concentration and sodium sulfate (Na 2SO 4) concentration in aqueous phase were studied. Practically, all zinc was extracted from the aqueous solution at pH 2.5 with 20% w/w D2EHPA in kerosene. Increasing either TBP concentration up to 5%, or Na 2SO 4 concentration up to 0.2 M, increased the zinc extraction. Zinc could be extracted at one theoretical stage at A/O of 1/1, as calculated by McCabe–Thiele method.

Zinc and Copper Separation through an Emulsion Liquid Membrane Containing Di‐(2‐Ethylhexyl) Phosphoric Acid as a Carrier

AbstractThe separation of zinc and copper ions from sulfuric acid solutions by an emulsion liquid membrane (ELM), using di‐(2‐ethylhexyl) phosphoric acid (D2EHPA) as a carrier, has been investigated. The batch extraction of zinc and copper was carried out while varying a selection of experimental conditions, i.e., stirring speed, treatment ratio, concentrations of metal ions in the feed phase, carrier and Span 80 concentration in the membrane, and internal phase concentration. The results obtained demonstrate the effectiveness of D2EHPA as a carrier for the separation of zinc and copper from sulfuric acid media using an ELM. An increase of the D2EHPA concentration beyond 2 vol.‐% does not result in the improved extraction of zinc because the viscosities of the membrane and emulsion have a trend to increase for higher carrier concentrations. It was found that the extraction rate of copper was affected by the carrier concentration in the liquid membrane and by the pH and metal content in the external phase. A 3 vol.‐% concentration of surfactant in the organic phase was required to stabilize the emulsion. The number of stages required for the extraction of zinc and copper by an ELM was determined from McCabe‐Thiele plots.

Di(2-ethylhexyl)phosphoric acid-coconut oil supported liquid membrane for the separation of copper ions from copper plating wastewater

Permeation of Cu(II) from its aqueous solution through a supported liquid membrane (SLM) containing di(2-ethylhexyl)phosphoric acid (D2EHPA) carrier dissolved in coconut oil has been studied. The effects of Cu(II), pH (in feed), H 2SO 4 (stripping) and D2EHPA (in membrane) concentrations have been investigated. The stability of the D2EHPA-coconut oil has also been evaluated. High Cu(II) concentration in the feed leads to an increase in flux from 4.1 × 10 −9 to 8.9 × 10 −9 mol/(m2·s) within the Cu(II) concentration range 7.8×10 −4 −78.6×10 −4 mol/L at pH of 4.0 in the feed and 12.4 × 10 −4 mol/L D2EHPA in the membrane phase. Increase in H 2SO 4 concentration in strip solution leads to an increase in copper ions flux up to 0.25 mol/LH 2SO 4, providing a maximum flux of 7.4 × 10 −9 mol/(m 2·s). The optimum conditions for Cu(II) transport are, pH of feed 4.0, 0.25 mol/LH 2SO 4 in strip phase and 12.4 × 10 −4 mol/L D2EHPA (membrane) in 0.5 μm pore size polytetrafluoroethylene (PTFE) membrane. It has been observed that Cu(II) flux across the membrane tends to increase with the concentration of copper ions. Application of the method developed to copper plating bath rinse solutions has been found to be successful in the recovery of Cu(II).

Chemically Driven Tension Fluctuation and Motion of Interface with Divalent Cation and Di(2-ethylhexyl)phosphoric Acid

Abstract Fluctuation in the interfacial tension in an oil/water interface composed of di(2-ethylhexyl)phosphoric acid (DEHPA) and divalent cations (Mg2+, Ca2+, Sr2+, and Ba2+) were investigated. Only a combination of Ca2+ and DEHPA caused noticeable tension fluctuation and spontaneous interfacial flow. Light-scattering experiments and the extraction of cations with DEHPA indicated that both a high reactivity between cation and DEHPA, of which only Ca2+ had a high reactivity, and strong attractive interactions between M(DEHP)2 molecules were required for fluctuation. These may induce a collective desorption of Ca(DEHP)2. This was supported by the observation of alternating pH-change with m-Cresol Purple. An N-shape dependency of interfacial pressure on the DEHPA concentration was observed only for Ca-containing interface. Due to this dependency, there was a DEHPA concentration range in the interfacial pressure vs the concentration curve, which satisfies two different conditions. First, the dependency of the interfacial pressure on the concentration is negative, and second, there are other two concentrations with the same interfacial pressure value. The DEHPA concentration range involving tension fluctuation almost agreed with the concentration range, which is discussed. The interface may be a chemical generator predicted by Vedove and Sanfeld.

Recovery of zinc sulphate from industrial effluents by liquid–liquid extraction using D2EHPA (di-2-ethylhexyl phosphoric acid)

The liquid–liquid extraction of zinc using D2EHPA as extractant has been investigated in this paper in order to recover zinc sulphate from an industrial effluent produced by Votorantim Co. (Brazil) which contains several metallic species such as cadmium, cobalt, iron, lead, calcium, magnesium, manganese and nickel. The study was carried out in two main steps: (1) extraction and stripping laboratory scale tests in order to assess adequate operational conditions for the favourable recovery of zinc from the effluent and (2) continuous pilot scale tests using a mixer-settler battery aiming to reproduce the bench results. In the laboratory scale experiments, operating variables such as the pH of the aqueous effluent (0.5–5.0), concentration of D2EHPA (5–50%,w/w) and aqueous/organic volumetric phase ratio (1/5–5/1) were investigated for the zinc extraction process; for the zinc stripping process, the organic/aqueous volumetric phase ratio (1/1–10/1) was studied by contacting a metal loaded organic phase with an industrial acid solution produced by the company in the electrolysis of zinc. The continuous mixer-settler tests have shown that zinc can be selectively and quantitatively removed from the effluent (around 98%) using 3 extraction stages (pH 2.5, [D2EHPA] = 20% (w/w) and A/O = 1), and other 3 stripping stages (O/A = 4). A final solution containing 125.7 g/L of zinc was obtained that could be sent directly to electrowinning.

Preparation and characterization of fine silver powder with colloidal emulsion aphrons

Colloidal emulsion aphrons (CEAs) can be considered as the micrometer-sized water-in-oil emulsion cores encapsulated by a “soapy shell” consisting of multi-layer surfactant molecules. The emulsion core sizes of CEA dispersion are roughly in 10–100 μm, whereas the sizes of inner phase are in 1–5 μm. CEAs can be used as a microreactor to synthesize fine powder materials. Silver powders with various sizes and shapes were prepared with di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the mobile carrier in membrane phase, ascorbic acid ( V c) as reducing agent in inner phase and cyclohexane as the membrane of CEAs. The linear silver particles were formed under low mobile carrier concentration in membrane phase or low ascorbic acid concentration in inner phase, whereas the granular silver particles with comparatively small sizes were obtained under the high mobile carrier concentration or high ascorbic acid concentration, and also silver powder of “nano-porous microsphere” was prepared with CEAs by adjusting the D2EHPA concentration in membrane phase, ascorbic acid concentration in inner phase and the molar ratio of silver ion to ascorbic acid ( n A g + / V c ). Compared with emulsion liquid membrane (ELM) method, the silver powder prepared with CEAs was usually in granular form with smaller sizes because of the higher transfer rate, but for that prepared with ELMs was only in linear form. Two kinds of silver powder samples with typical shapes, one is the “nano-porous microsphere” prepared with CEAs and the other is the linear silver powder prepared with ELMs, were characterized by thermogravimetry (TG)–differential thermal analysis (DTA), X-ray powder diffraction analysis and field emission scanning electron microscope (FESEM).

Extraction equilibria and separation of phenylalanine and aspartic acid from water with di(2‐ethylhexyl)phosphoric acid

AbstractThe distribution equilibria of single and binary L‐phenylalanine and L‐aspartic acid between water and a kerosene solution of di(2‐ethylhexyl)phosphoric acid (D2EHPA) were studied. It was shown that the distribution ratios of phenylalanine generally increased with increasing aqueous pH (2–5) in the D2EHPA concentration range 0.1–0.5 mol dm−3, but those of aspartic acid decreased with increasing solution pH. Different reaction stoichiometries were proposed for the extraction of phenylalanine and aspartic acid under the conditions studied. The extraction equilibrium constants were obtained. Competitive extraction in binary systems was more apparent in the pH range where the cationic form of amino acids was not predominant. The present results indicated that selective separation of phenylalanine to aspartic acid was possible with this cationic extractant when they were extracted at higher pH and stripped using higher acidity of HCl solution. Copyright © 2006 Society of Chemical Industry

Mass-transfer characteristics of a spiral-channel SLM module in pertraction of phenylalanine

Transport of phenylalanine (Phe) through a supported liquid membrane (SLM) containing di-(2-ethylhexyl) phosphoric acid (DEHPA) as carrier in a spiral-channel module was studied. The value of the molar flux of Phe through SLM increases with the velocity of the feed phase in the channel. However, soon at a velocity of about 1.5–4 cm.s−1, the maximum value is achieved. With increasing initial concentration of Phe in the feed phase, the transport rate increases. An increase in the concentration of DEHPA in the solvent did not result in an increase of the transport rate despite the fact that the value of the distribution coefficient increased proportionally. This is related to the slower kinetics of decomposition of the complex on the stripping interface. An analysis of mass-transfer resistances of Phe in pertraction through SLM showed that decisive resistances are based on the kinetics of chemical reactions of complex formation and decomposition, and their share in the overall resistance is about 25 and 35%, respectively. The lifetime of SLM with DEHPA as the carrier is less than 1 day for dilute aqueous feeds unsaturated with the membrane phase. It increases with the concentration of DEHPA that is connected with a relatively high solubility of DEHPA in diluted aqueous solutions. The spiral-channel module can be used for testing solvents for pertraction and membrane-based solvent extraction under defined hydrodynamic conditions.

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.

Uranium extraction from partially neutralised and diluted phosphoric acid using a synergistic organophosphorous solvent mixture

A process is described for the separation of uranium from partially neutralised and diluted phosphoric acid (PNDA) which is generated in fertiliser plants when phosphoric acid is used to scrub ammoniacal vapours from the neutralisation reactors. The separation process is based on solvent extraction using a synergistic mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) with tri- n-alkyl phosphine oxide (TAPO). The effects of process parameters including concentration of DEHPA and TAPO, temperature and degree of neutralisation of acid have been investigated. Laboratory scale and pilot plant scale tests have been carried out. The extraction reaction is found to be exothermic with enthalpy effect of 30 kJ/mol. Tests on stripping of extracted uranium and recovery of uranium have been carried out and results are reported. Analysis of data indicates significant differences in the mechanism of uranium extraction from PNDA and the mechanism reported in literature for extraction of uranium from weak phosphoric acid using a similar solvent mixture.

Study of salt effects on the kinetics of extraction of cobalt(II) and zinc(II) at trace level by D2EHPA in n-dodecane

The effects of a salt on the extraction kinetics of metal cations Co 2+ and Zn 2+ by di(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in n-dodecane have been studied using the rotating membrane cell (RMC) technique. The kinetics were investigated for tracer amounts of radiolabelled metal ions (2×10 −8 M Co(II) and 10 −4 M Zn(II)) and D2EHPA concentration in the range 0.02–0.5 M. A “pre-equilibrated” nitric acid (PENA) solution was used for some experiments. This solution was prepared by contacting a HNO 3 solution with a 0.2 M D2EHPA organic phase. First, the effect of the nature of the anion (acetate, Cl −, ClO 4 −, NO 3 −) was investigated at pH 3 and 5. The results were compared with those using the D2EHPA-saturated PENA solution. For Co(II), acetate and PENA solutions led to kinetics that were faster than with the other anions. For Zn(II), the kinetics were fast with all anions. For Co(II) with acetate ion and for Zn(II) with acetate, nitrate and perchlorate ions, the results indicate that the reaction cannot be strictly interfacial. The faster kinetics observed with acetate were attributed to the formation of a complex with the metal ion and to a subsequent reaction between this complex and extractant in the aqueous bulk. Next, the effect of adding various amounts of NaClO 4 and KNO 3 has been studied at pH 3 for salt concentrations between 0 and 1 M. On the assumption of a slow reaction between the metal and the extractant in the aqueous phase, the results for cobalt could be described by a primary electrolyte effect on this reaction.