Feasibility of surfactant-free supported emulsion liquid membrane extraction

Supported emulsion liquid membrane (SELM) is an effective means of conducting liquid-liquid extraction. SELM extraction is particularly attractive for separation tasks in the microgravity environment where density difference between the solvent and the internal phase of the emulsion is inconsequential and a stable dispersion can be maintained without surfactant. In this research, dispersed two-phase flow in SELM extraction is modeled using the Lagrangian method. The results show that the SELM extraction process in the microgravity environment can be simulated on earth by matching the density of the solvent and the stripping phase. The feasibility of surfactant-free SELM (SFSELM) extraction is assessed by studying the coalescence behavior of the internal phase in the absence of the surfactant. Although the contacting area between the solvent and the internal phase in SFSELM extraction is significantly less than the area provided by regular emulsion due to drop coalescence, it is comparable to the area provided by a typical hollow-fiber membrane. Thus, the stripping process is highly unlikely to become the rate-limiting step in SFSELM extraction. SFSELM remains an effective way of achieving simultaneous extraction and stripping and is able to eliminate the equilibrium limitation in the typical solvent extraction processes. The SFSELM design is similar to the supported liquid membrane design in some aspects.     

Uranium extraction enhancement form phosphoric acid by emulsion liquid membrane

This work is mainly concerned with the uranium extraction from phosphoric acid commercially produced by Abu Zaabal Fertilizers and Chemical Co., Egypt. This target would realize a dual purpose where the phosphate ore is considered as an alternative source of uranium besides eliminating its environmental contamination. The applied procedures are that of the new technology of emulsion liquid membrane. Authors have indeed pointed out that the variables explored still leave open to question the roles of stripping at the internal interface as well as the bulk transfer of uranium in the internal phase. For this purpose, two reducing agents are studied as additives to two organic solvent systems; namely the organophosphorous synergistic mixture of D2EHPA/TOPO as well as the tridodecyl amine. The relevant factors have first been optimized upon synthetic uraniferous phosphoric acid solution followed by the application upon the commercial acid after purification. These factors include the concentration of solvent system and the used emulsifier, acid concentration of the external and internal phases besides the nature and concentration of the reductant added to the internal phase. In addition, the permeation time as well as the oxidation state of the external phase was studied. All these factors have indeed been studied under different mixing speeds ranging from 300 up to 1,000 rpm. Ascorbic acid concentration, 1 % as an additive to the internal phosphoric acid phase (40 % P₂O₅) resulted in 95 % uranium extraction efficiency at the lower speed of 600 rpm.     

Simplified model for extraction of rare-earth ions using emulsion liquid membrane

By considering the resistances of rare-earth ions in both the external and membrane phases, the interfacial reaction and the membrane breakage, a mathematical model for the extraction of rare-earth ions by batch emulsion liquid membrane process is established. Further, two simplified mass transfer equations are also derived from the proposed model in each of the specified cases. The validity of both the model and the resulting equations are tested by batch extraction of Sm³⁺ with emulsion liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier in kerosene. The experimental results show that both the proposed model and the resulting equations can simulate mass transfer process satisfactorily.     

Mathematical modeling of silver extraction by an emulsion liquid membrane process

A general physical model of a typical batch extraction system employing an emulsion liquid membrane process for the extraction of silver has been developed. The model takes into account the extraction reaction between the silver ion and the carrier molecules at the external interface, the diffusion of the complex in the membrane phase, the stripping reaction at the internal interface and the reaction of silver ion with the reagent, HCL, in the internal phase to yield silver chloride incapable of permeating through the membrane phase. In addition, the leakage of the internal aqueous phase to the external aqueous phase due to membrane breakage has been incorporated in this model. The batch extraction of silver using D2EHPA as a carrier has been carried out under various experimental conditions. The experimental data can be well explained by the present model.     

Synchronized extraction and purification of L-lactic acid from fermentation broth by emulsion liquid membrane technique

This study aims to investigate the recovery of L-lactic acid from fermentation broth by an emulsion liquid membrane (ELM), made up of sunflower oil as the diluent, Sorbitan monooleate (Span 80) as the surfactant, Aliquat 336 as the carrier, and sodium hydroxide (NaOH) solution as the internal aqueous phase. Particularly, the ELM process was properly set up, through the identification of the optimal ELM operating parameters on the final extraction efficiency of L-lactic acid, including Span 80 concentration, NaOH concentration, Aliquat 336 concentration, stirring speed, phase ratio, and treatment ratio. The obtained results showed that the extraction efficiency of L-lactic acid reached up to 99% under the following optimal conditions: 10 minutes after contact time, 4% w/w Span 80, 3% w/w Aliquat 336, 0.1?N solution of NaOH, stirring speed of 300?rpm, phase ratio 1, and treatment ratio 0.25. A stable system without considerable emulsion swelling and breakage was monitored using a dynamic light scattering (DLS) apparatus for the selected optimal ELM operating parameters.     

Studies on extraction of chromium (VI) from acidic solutions containing various metal ions by emulsion liquid membrane using Alamine 336 as extractant

The extraction of chromium (VI) ions from acidic solutions containing various metal ions by emulsion liquid membrane (ELM) was studied. Liquid membrane consists of a diluent, a surfactant, and an extractant. 0.5 M ammonium carbonate solution was used as stripping solution. Effects of acid concentration in feed solution, type and concentration of stripping solution, mixing speed, surfactant concentration, phase ratio and the influence of membrane characteristics were studied and optimum conditions were determined. Under the optimum conditions, extraction of chromium (VI) was tested and it was possible to selectively extract 99% of chromium from the acidic feed solution. This study also examined the effect of extractant concentration and acid type in the feed solution on the extraction of Cr (VI) ions and almost all of Cr (VI) from the acidic feed solution containing 500 mg/L from each of Co (II), Ni (II), Cd (II), Zn (II), and Cu (II) ions, and 100–500 mg/L Cr (VI) was extracted within 5–10 min.     

Direct uranium extraction from dihydrate and hemi-dihydrate wet process phosphoric acids by liquid emulsion membrane

A new liquid emulsion membrane (LEM) process for uranium extraction from either dihydrate 28-30% P₂O₅ (DH) or hemi-dihydrate 42-45% P₂O₅ (HDH) wet process phosphoric acid is proposed. In this process, the organic component of the LEM is composed of a synergistic mixture of 0.1M di-2-ethyl hexyl phosphoric acid (DEHPA) and 0.025M trioctyl phosphine oxide (TOPO) with 4% Span 80. The internal or the strip acid phase is composed of 0.5M citric acid. The prepared LEM was proved to be stable in 42-45% P₂O₅ acid concentration range and can, therefore, be applied to the phosphoric acid produced by the hemi-dihydrate process. After breakdown of the loaded emulsion, the uranyl citrate in the internal strip phase is separated by adding methanol followed by its calcination to the orange oxide. Most of the reagents used are recycled. The proposed process is characterized by simplicity, practically closed operation cycle in addition to lower capital and operating costs.     

乳状液膜法分离水中的铬

乳状液膜法由于其独特的物理化学性质,已广泛用于金属离子的萃取分离[1～3]。本文以span80-煤油-NaOH液膜体系分离水中铬。不加流动载体,利用内、外相中被分离物的浓度梯度实现物质迁移。当Cr2O2-7进入内相时,与内相的NaOH发生反应,在内相高浓度的NaOH存在下,可保持Cr2O2-7在液膜两侧有最大的浓度梯度,促使Cr2O2-7的迁移,实现Cr2O2-7与外相溶液的分离。1　实验部分1 1　仪器与试剂D40-1型电动搅拌器(杭州仪表电机厂),78-1型磁力加热搅拌器(江苏金坛新一佳仪器厂),721型分光光度计(上海第三分析仪器厂)。铬标准溶液(100ml/L):准…     

Mathematical modeling of penicillin G extraction in an emulsion liquid membrane system containing only a surfactant in the membrane phase

An extraction experiment of penicillin G was performed in an emulsion liquid membrane system in which only ECA 4360J exists in the organic membrane phase without a predominant carrier, Amberlite LA-2, used in our previous works and it functions as a carrier as well as a surfactant. A permeation model for the present system has been developed as a primary study to examine the transport mechanism of penicillin G in the previous batch and continuous systems with two carriers of Amberlite LA-2 and ECA 4360J. The model takes into account the mass transfer in the external aqueous film, the extraction reaction between penicillin G and ECA 4360J at the external interface, the diffusion of penicillin G in the emulsion phase, the stripping reaction at the internal interface and the pH change of internal aqueous solution containing Na₂CO₃ with penicillin G transported into the internal phase. The experimental data were well fitted with the present model. Also, an expression for the reaction of penicillin G with ECA 4360J was obtained through a series of equilibrium measurements in liquid–liquid extraction system.     

Effect of volume ratio of internal aqueous phase to organic membrane phase (w/o ratio) of water-in-oil emulsion on penicillin G extraction by emulsion liquid membrane

The batch extraction of penicillin G from a model media was studied so as to obtain the optimal w/o ratio in an emulsion liquid membrane (ELM) system with the help of our previous works. First of all, the effects of organic solvents or surfactants in membrane phase on apparent degree of its extraction at various w/o ratios were investigated. The organic solvents and surfactants were kerosene/n-butyl acetate and Span 80/PARABAR 9551, respectively. The optimal composition between two surfactants for the highest apparent degree of extraction was obtained at each w/o ratio.With the optimal surfactant composition at each w/o ratio, citrate buffer solutions of three different concentrations having about pH 4.8 were selected as the external aqueous phase. The mass of Na₂CO₃ in the internal phase was kept constant for every w/o ratio in order to investigate the effects of w/o ratio on the degree of extraction under the same trapping mass of Na₂CO₃ for penicillin G. The highest possible concentration of Na₂CO₃ in the internal phase was chosen using balance equations and equilibrium expressions. In consequence, the highest actual degree of extraction of 98.2% and the lowest percentage of swelling of 36.0 were obtained in the specific ELM system with 0.41 M citrate buffer solution, 0.175 M Na₂CO₃ and w/o ratio of 1/1.     

Separation study of cadmium through an emulsion liquid membrane

A study of the transport of Cd(2+) ions through a tri-ndashoctylamine(TOA)-sorbital monooleate (Span 80)-oxylene liquid membrane has been performed with varying concentrations of HCl, KI, TOA, Span 80 and NaOH in the feed, membrane and stripping solutions. Maximum transport was observed at 0.01 M KI, 0.025 M HCl, 0.015 M TOA, 3% (w/v) Span 80 and 0.025 M NaOH. With this system, cadmium could be completely separated from Zn(2+), Fe(2+), Co(2+), Ni(2+), Cr(3+) and Mn(2+). The transport mechanism of this metal ions through the membrane has been discussed.     

Stability analysis of environmentally benign green emulsion liquid membrane

A new stable green emulsion liquid membrane (GELM) was formulated by selecting the environmentally benign vegetable oils. The rice bran oil (RBO) based GELM has shown better stability in comparison to that obtained from other oils. GELM was prepared using 10?mL RBO, 0.25 [M] NaOH concentration, 2 (v/v, %) surfactant concentration, 0.4 (v/v) phase ratio, 2000?rpm emulsification speed, and 20?min emulsification time. Under these optimum conditions, GELM has been found to be stable for 120?±?2?min (no significant phase change) and has shown complete phase separation after 4 hours. Therefore, RBO as a green solvent has high potential to be applied in several ELM process applications.     

Separation study of mercury through an emulsion liquid membrane

A study of the transport of Hg(II) ions through a tri-n-octylamine (TOA) - sorbital monooleate (Span 80) -toluene liquid membrane has been performed with varying concentrations of HCl, KCl, TOA, Span 80 and NaOH in the feed, membrane and stripping solutions. Maximum transport was observed with 0.01 M KCl, 2.5 x 10(-2) M HCl, 1.5 x 10(-2) M TOA, 3% (w/v) Span 80 and 0.05 M NaOH. With this system, mercury could be completely separated from Cu, Zn, Fe, Co, Ni, Pb, Mn and Cd. The transport mechanism of this metal ion through the membrane is based on the association of metal anions (HgCl(4)(2)) with protonated TOA molecules at the feedside interface, diffusion through the membrane, decomposition of the complex at the strip-solution-side membrane interface under alkaline conditions, and backdiffusion of TOA molecules. Transport with the membrane is dependent on the concentration gradient but in the surrounding solutions it is inversely related to the concentration gradient.     

Extraction of strontium ions with emulsion liquid membrane technique

The aims of this study are to form a liquid membrane suitable for the extraction of strontium ions from aqueous solutions and to determine the factors influencing the stability of the membrane, the extraction efficiency and the rate of transport. The suggested membrane is composed of kerosene, Span 80 and D2EHPA. It has been observed that the extraction efficiency and the rate of transport increase with increasing ratio of emulsion to outer phase volume, stirring rate and D2EHPA concentration and decreasing pH of the inner phase. As the strontium ion concentration in the outer phase increases, the transport rate increases but the separation efficiency decreases. The maximum separation efficiency achieved in the experiments was 92%.     

铜在乳状液膜体系中的迁移行为

近年来膜分离技术在环境治理方面得到广泛应用。本文研究了铜在span80-TBP（磷酸三丁酯）-煤油-NH3液膜分离体系中的迁移行为。用TBP作为载体,在溶液中迁移时,在外相与膜相界面上形成中性络合物后穿过膜相,在膜相与内相界面上络合物再与NH3反应,生成铜氨络离子,释放出来的TBP又返回膜相。     

Ligand-accelerated liquid membrane extraction of metal ions

A method has been developed to enhance the liquid membrane extraction of heavy metals such as cobalt, copper and nickel. The method consists of introducing anion ligands, such as acetate, to the aqueous solution containing metal ions. In the absence of a ligand in the aqueous phase, it takes about 15 min for a 80% cobalt recovery, while only 2 min are needed for a 95% recovery with the addition of 0.1 M acetate in the feed solution. The ligand effects on liquid membrane extraction are rationalized in terms of the labile nature of the ligand—metal complexes, the distribution coefficients of the metal ions, the interfacial and surface tensions, and by the nuclear magnetic r̀esonance (NMR) spectra of the metal—organic complexes.     

Photometric extraction method for determination of cephalexin

Summary A photometric extraction method is developed for determination of cephalexin. Cephalexin is hydrolysed for 5 min in sulphuric acid medium on a steam-bath, the hydrolytic product forming a coloured compound with ninhydrin in 25% H₂SO₄. This compound is extracted with CHCl₃ and its absorbance measured at 520 nm. The reaction is selective — it is negative for the initial reagents in the cephalexin synthesis and for most other antibiotics. The only two antibiotics giving a similar reaction — ampicillin and cephalotin — do not interfere in the determination of cephalexin. The method is rather simple and permits rapid determination of cephalexin with satisfactory precision and accuracy — coefficient of variation 0.91–1,36%, relative error of the determination 0.66–1,19% (95% confidence limits).

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Zusammenfassung Eine extraktions-photometrische Bestimmungsmethode für Cephalexin wurde ausgearbeitet. Die Substanz wird 5 min auf dem Wasserbad in schwefelsaurem Milieu hydrolysiert. Das hydrolysierte Produkt bildet mit Ninhydrin in 25%iger Schwefelsäure eine gefärbte Verbindung. Diese wird mit Chloroform extrahiert und bei 520 nm gemessen. Die Reaktion ist selektiv; sie verläuft negativ bei den Ausgangsprodukten der CephalexinSynthese und bei den meisten anderen Antibioticis. Die einzigen beiden Antibiotika, die eine ähnliche Reaktion geben — Ampicillin und Cephalotin — stören die Bestimmung von Cephalexin nicht. Die Methode ist ziemlich einfach und ermöglicht die rasche Bestimmung von Cephalexin mit hinreichender Genauigkeit: der Variationskoeffizient beträgt 0,91–1,36%, der relative Fehler 0,66—1,19% (bei einer Vertrauensgrenze von 95%).

     

On-line automated sample preparation for liquid chromatography using parallel supported liquid membrane extraction and microporous membrane liquid-liquid extraction

An automated system was developed for analysis of non-polar and polar ionisable compounds at trace levels in natural water. Sample work-up was performed in a flow system using two parallel membrane extraction units. This system was connected on-line to a reversed-phase HPLC system for final determination. One of the membrane units was used for supported liquid membrane (SLM) extraction, which is suitable for ionisable or permanently charged compounds. The other unit was used for microporous membrane liquid-liquid extraction (MMLLE) suitable for uncharged compounds. The fungicide thiophanate methyl and its polar metabolites carbendazim and 2-aminobenzimidazole were used as model compounds. The whole system was controlled by means of four syringe pumps. While extracting one part of the sample using the SLM technique. the extract from the MMLLE extraction was analysed and vice versa. This gave a total analysis time of 63 min for each sample resulting in a sample throughput of 22 samples per 24 h.     

Inclusion extraction of alkali metals by emulsion liquid membranes bearing nano-baskets

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty and significance of this study is application of nano-baskets of calixarene in the selective and efficient separation of alkali metals, as both carrier and surfactant. For this aim, four derivatives of p-tert-calix[4]arene bearing different sulfonamide moieties were synthesized and their inclusion-extraction parameters were optimized. Maximum extraction was achieved using calixarene scaffold 03 (3.45 × 10^?2 M) as carrier/demulsifier, commercial kerosene as diluent in membrane, sulphonic acid (0.2 M) and ammonium carbonate (0.4 M) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300 rpm), and initial solute concentration (100 mg/L). The selectivity of membrane over more than ten interfering cations was examined and the results reveled that under the optimized operating conditions, the extraction percent of alkali metals was 98–99 %.     

Span80-TBP-NaOH体系破乳方法及膜内反应研究

采用Span80-TBP-NaOH体系乳状液膜法提取红土矿浸出液中的镍,对提取分离后的乳液进行破乳实验,经过加热-离心联合破乳法,破乳率可达90%.通过比较提取镍前后,乳液的红外光谱图,证明了膜内反应的发生;通过比较原始油相和破乳后油相的红外光谱图,证明了破乳后油相的重复利用性.