Liquid Membrane Extraction Research Articles

Three liquid phase membrane extraction method based on the electro-migration assisted by high-performance liquid chromatography for the analysis of carcinogenic heterocyclic aromatic amines in steak samples

A combination of microwave digestion and three-phase hollow fiber electromembrane extraction (HF-EME) with high-performance liquid chromatography (HPLC) was designed to determine carcinogenic heterocyclic aromatic amines (HAAs) in steak samples. The recorded fingers of merit (LOD: 1.4–1.6 ng/g, LOQ: 4.5–5.2 ng/g, RSD: 6.1–7.2 %, recovery: 91–95 % and EF: 107–112) underlines the adequacy of the proposed technique. The total of 2-amino-3-methylimidazo[4,5-f] quinoline (IQ), 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx), 2-amino-3,4 dimethylimidazo[4,5-f] quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4′5-b] pyridine (PhIP) in steak samples were 93.46 ± 4.93–174.52 ± 10.91 ng/g, 31.65 ± 1.87–877.97 ± 56.19 ng/g, 10.08 ± 1.01–535.73 ± 18.93 ng/g, and 62.56 ± 1.89–341.23 ± 41.45 ng/g, respectively. Lamb steak contain highest amount of MeIQx (877.97 ± 56.19 ng/g) and beef steak showed lowest concentration of MeIQ (10.08 ± 1.07 ng/g). In conclusion, several interesting features such as great recovery, suitable enrichment factor, very low sample amount and organic solvent requirement and short extraction time make this novel method appropriate for the analysis of the negligible levels of HAAs in complex food matrices.

Emulsion liquid membrane technique for optimal separation of Ni (II) and Sm (III) using response surface methodology and Box–Behnken experimental setup

ABSTRACT This study evaluated the reliability of the emulsified liquid membrane (ELM) extraction technique for recovering and separating metals, focusing on Nickel (Ni(II)) and Samarium (Sm(III)), both used in electrochemical devices. Key contributions include determining optimal conditions for creating a stable water-in-oil (W/O) emulsion. The optimal conditions were found to be a 5-minute emulsification time, 4 wt.% Span 80 surfactant concentration, a 1.6 volume ratio of the internal phase to the organic phase, 1 M H2SO4 concentration for the internal phase, a 40/160 volume ratio of the emulsion to the external phase, and kerosene as the diluent. Factors affecting the separation of Ni(II) and Sm(III) included the concentrations of the internal aqueous phase, surfactant, and extractant. Under these conditions, an equimolar mixture of Ni(II) and Sm(III) was extracted within 15 min. The study emphasized the importance of phase volume ratio and surfactant concentration for emulsion stability and extraction efficiency. The response surface method (RSM) and Box–Behnken design were used to optimize influential factors, with a modified quadratic model predicting extraction yields of 83.81% for Sm(III) and 15% for Ni(II). The study demonstrates that effective separation of Ni(II) and Sm(III) ions is achievable using this technique, providing valuable insights into efficient and selective metal ion extraction, contributing to the broader field of metal recovery and recycling technologies.

Interfacial effect of coexisting salt cations on extraction of erbium using gas bubble-supported organic liquid membrane

The conventional understanding about the specific ion effect from the coexisting electrolyte salts on the extraction and separation of target metal ions during liquid-liquid solvent extraction cannot explain some abnormal phenomena when more than one kind of background ions coexisting in the aqueous feed solutions to be separated. In this work, the specific ion effect of coexisting ions, Mg2+ and Al3+ as the example here, on extraction of Er3+ ion was investigated using gas bubble-supported organic liquid membrane. A very interesting phenomenon was noticed that, the difference in Er3+ extraction percentage was only 11.7 % in the Er-Mg solution system with addition of Al3+ ions or not, while it could reach 18.0 % in that of Er-Al with addition of Mg2+ ions or not. When Mg2+ and Al3+ coexisted simultaneously in the feed solutions, their specific ion effect on improving the extraction percentage of Er3+ was not equal to the sum of that when only single Mg2+ or Al3+ exists, respectively. Furthermore, a thinner organic liquid membrane supported by gas bubbles was in favor of enhanced interfacial enrichment of Er3+ and its diffusion mass transfer near the interface. During gas bubble-supported organic liquid membrane extraction, Mg2+ ions exhibited more obvious specific ion effect due to a weaker interaction with P507 molecules. However, a stronger hydration ability of Al3+ than Mg2+ ions induces a stronger competition of Al3+ with P507 molecules. Therefore, the coexistence of Mg2+ and Al3+ ions could play a synergistic role in enhancing enrichment of Er3+ on the basis of the mutual interference from the synergistic specific ion effect of coexisting Al3+ and Mg2+ ions. The research helps thoroughly understand the regulation mechanism on the synergistic specific ion effect for selective extraction of specified ions from the complex solutions containing multiple coexisting background ions.

Fatty Alcohol-Assisted Electro-Driven Liquid Membrane Multi-Stage Extraction Technology for Selective Separation and Purification of 3,4-Dihydroxybenzaldehyde from Salvia miltiorrhiza Bge.

3,4-Dihydroxybenzaldehyde (DHB) is a highly effective water-soluble compound in the traditional Chinese medicine Salvia miltiorrhiza Bge. Which demonstrates clear therapeutic effects against a variety of diseases. Therefore, the development of a selective approach for the separation of 3,4-dihydroxybenzaldehyde is of great significance. In this study, electro-driven extraction combined with multi-stage extraction technology was employed for the first time to separate 3,4-dihydroxybenzaldehyde from S. miltiorrhiza Bge. Decoction (Recovery ≥ 46.09%). Five long-chain fatty alcohols were selected as the supported liquid membrane (SLM) in the electro-driven extraction. Factors influencing extraction efficiency, including pH, voltage, and extraction time, were optimized using a design of experiments. Under the optimal conditions, the linearity of 3,4-dihydroxybenzaldehyde ranged from 0.01 to 100 μg·mL−1), with limits of detection (LOD) and quantification (LOQ) of 5 and 17 ng·mL−1, respectively. The precision of electro-driven liquid membrane extraction for 3,4-dihydroxybenzaldehyde was below 8.42%. This paper reports novel electro-driven liquid membrane extraction for selectively isolating 3,4-dihydroxybenzaldehyde from S. miltiorrhiza Bge.

Solvent-free parallel artificial liquid membrane extraction for drugs of abuse in plasma samples using LC-MS/MS

BackgroundParallel artificial liquid membrane extraction (PALME) is a 96-well plate setup variant of liquid-phase microextraction. Basic or acidic analytes are extracted in neutral form from the sample, through a supported liquid membrane (SLM), and into aqueous acceptor. PALME is already considered a green extraction technique, but in the current conceptual work, we sought to make it even greener by replacing the use of organic solvents with essential oils (EO). PALME was combined with LC-MS/MS for analysis of plasma samples and multiple drugs of abuse with toxicological relevance (amphetamines, phenethylamines, synthetic cathinones, designer benzodiazepines, ayahuasca alkaloids, lysergic acid diethylamide, and ketamine). ResultsFourteen EO were compared to organic solvents frequently used in PALME. The EO termed smart & sassy yielded the best analyte recovery for all drugs studied and was thus selected as SLM. Then, factorial screening and Box-Behnken were employed to optimize the technique. The extraction time, concentration of base, sample volume, and percentage of trioctylamine significantly impacted analyte recovery. The optimum values were defined as 120 min, 10 mmol/L of NaOH, 150 μL, and 0%, respectively. Once optimized, validation parameters were 1–100 ng mL-1 as linear range, accuracy ±16.4%, precision >83%, 1 ng mL-1 as limit of quantitation, 0.1–0.75 ng mL-1 as limit of detection, matrix effect <20%, and recovery 20–106%. Additionally, EO purchased from different production batches were tested and achieved acceptable reproducibility. Data were in compliance with requirements set by internationally accepted validation guidelines and the applicability of the technique was proven using authentic samples. SignificanceIn this study, the use of an EO provided a solvent-free sample preparation technique suited to extract different classes of drugs of abuse from plasma samples, dismissing the use of hazardous organic solvents. The method also provided excellent sample clean-up, thus being a simple and efficient tool for toxicological applications that is in agreement with the principles of sustainable chemistry.

Extraction of Alpha-cypermethrin Pesticides from Aqueous Solution by Emulsion Liquid Membrane

This research examines the emulsion liquid membrane (ELM) extraction efficiency and stability to abstraction of alpha-cypermethrin pesticides from aqueous solution when blended surfactants are used in the liquid membrane composition. The stability of the membrane was examined in the aspect of the emulsion breakdown time and distribution of droplet size. The ingredients employed in ELM were Span80 (sorbitan monooleate) and Tween80 (polyoxyethylene sorbitan monooleate) as surfactants and a mixture of kerosene, sunflower oil (3:7) as diluents and stripping agent was used sodium hydroxide (NaOH). Some parameters were assessed, including the value of Hydrophilic Lipophilic Balance (HLB), blended surfactant concentration, homogenizer speed, emulsification time, and NaOH concentration as a stripping agent. According to the results, a stable emulsion was created at HLB (5.37), blended surfactant 3 % (w/v), 12,700 rpm of homogenizer speed, 9 min of emulsification time, and 0.05 N of NaOH. Under these circumstances, 89.2 % of the alpha-cypermethrin was extracted with 1.8 % emulsion breakage. As a result, the combinations of (Span80 with Tween80) have enormous potential as surfactants and they can improve the stability of the emulsion. Additionally, completed was mass transfer investigation and extraction kinetics

Extraction of acid orange 7 from water by emulsion liquid membrane using Tri-dodecyl-amine as extractant

The main objective of this study was to investigate the feasibility of extracting Acid Orange 7 (AO7), a complex reactive dye, from aqueous solutions using a stabilized emulsion liquid membrane (ELM) technique. The ELM formulation comprised tri-dodecylamine (TDA) as the extracting agent, kerosene as the diluting medium, and SPAN 80 as the surfactant. We systematically examined various experimental variables that affect the extraction of AO7. These variables included the concentrations of the extractant and surfactant, internal phase concentrations, the ratio of the membrane phase to the internal phase, the choice of diluting medium and its grade, stirring speed, treatment ratio, and the initial concentration of AO7. Furthermore, we investigated the impact of sodium chloride concentration in the external phase. Our research findings indicate that the optimal conditions for AO7 extraction using the ELM method were as follows: a TDA concentration of 3% (w/w), a SPAN 80 concentration of 9% (w/w), an oil-to-aqueous phase ratio (O/A) of 1:1, kerosene as the diluting medium, H2SO4 as the internal phase, a stirring speed of 200 rpm, a treatment ratio of 1:10, and an initial AO7 concentration of 10 mg/L. Under these precise conditions, an exceptional extraction efficiency of 98.49% was achieved in just 15 min. Under these carefully controlled conditions, an exceptional extraction efficiency of 98.49% was achieved in just 15 min. Consequently, the emulsified liquid membrane extraction process demonstrates significant potential as an advanced separation technique for removing hazardous dyes, particularly in dilute solutions.

Extraction/transportation of Co2+ metal ions with bis(2-ethylhexyl) phosphate dissolved in kerosene using a multidropped liquid membrane technique.

The transport properties of Co2+ ions from the aqueous donor phase to aqueous acceptor phase with the recently developed multidroplet liquid membrane (MDLM) extraction system were studied. This system serves as a continuous process for the transportation of ions and requires fewer reagents for starting and conducting the procedure. Moreover, the procedure results in fewer waste chemicals and mixtures in comparison to traditional extraction methods. During extraction, bis(2-ethylhexyl) phosphate (D2EHPA) was used as a carrier material and 5% potassium thiocyanate (KSCN) solution was used to obtain a colored complex for UV-Vis detection. By means of several experiments, the optimum D2EHPA concentration, pH range for both donor and acceptor phases, and temperature range effect on transport kinetics were investigated. In the extraction of cobalt ions with the MDLM system, the activation energy was calculated as Ea = 13.80 kcal mol-1, and it was found that the extraction was chemically controlled since it was greater than 10 kcal mol-1.

Parallel artificial liquid membrane extraction coupled with UPLC-ESI-MS/MS method for high-throughput quantitation of repaglinide in diabetic patients

A high-throughput therapeutic monitoring method was developed for repaglinide (RPG) in diabetic patients, combining parallel artificial liquid membrane extraction (PALME) with ultraperformance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). PALME was performed using a 96-well donor plate comprising a donor solution containing a plasma sample, 50 mM phosphate buffer (pH = 8.0), and cetirizine (CTZ) as internal standard. A polypropylene (PP) porous membrane served as a selective support for the liquid membrane (SLM), preventing nonspecific binding produced by other membranes. The extraction was accomplished across SLM made of PP membrane with dodecyl acetate and 1 % trioctylamine (w/w), and the acceptor solution comprised DMSO and 200 mM formic acid (50:50, v/v). The simple workflow for PALME provided analyte enrichment, highly efficient sample cleanup, high throughput analysis, and excellent reproducibility. Method validation met FDA criteria, with a linear plasma calibration range (0.1–100 ng mL−1, r = 0.9995) and a lower limit of quantitation (LLOQ) of 0.1 ng mL−1. Recovery results at 98.9 % affirmed method reliability. The ability to analyze 198 samples per hour, coupled with a reduced amount of solvents, underscores the method's high throughput and eco-friendly profile. The PALME-UPLC-ESI-MS/MS method was successfully applied to therapeutic drug monitoring of RPG in diabetic patients following 2 mg RPG tablet administration, establishing its effectiveness.

Ultrasound-assisted leaching and supported liquid membrane extraction of waste liquid crystal displays for indium recovery

Indium recovery from waste liquid crystal displays (LCDs) was carried out by using ultrasound-assisted leaching (UAL) and supported liquid membrane (SLM) extraction. The leaching efficiency and purity of indium were approximately 97% and 94%, respectively, when using 0.75 M of sulfuric acid and 300 W of ultrasound power level. The highest extraction efficiency of indium was approximately 82%, obtained by using 20 vol% of D2EHPA fraction, 2 M of HCl concentration in the stripping solution and pH 3 of feed solution. The permeability coefficient, initial flux and reaction rate constant substantially increased with increasing D2EHPA fraction and feed solution pH, but HCl concentration provided little effect. If there is a synergistic effect occurring between the feed solution pH and the D2EHPA fraction, the permeability coefficient will be as high as 5.5 μm/s when using pH 3 of feed solution and 20 vol% of D2EHPA fraction. The overall recovery rate of indium can be close to 80%, and the indium purity of the final product solution can be almost 100%. If indium can be completely recovered in the extraction process, the final recovery rate of indium will be higher than 97%. Based on the findings of this study, indium can be efficiently recovered from waste LCDs by using the UAL and the SLM extraction methods.

Liquid-phase microextraction of aromatic amines: hollow fiber–liquid-phase microextraction and parallel artificial liquid membrane extraction comparison

Aromatic amines (AA) are carcinogenic compounds that can enter the human body through many sources, one of the most important being tobacco smoke. They are excreted with the urine, from which they can be extracted and measured. To that end, hollow fiber-liquid-phase microextraction (HF-LPME) and parallel artificial liquid membrane extraction (PALME) were optimized for the analysis of representative aromatic amines, as alternatives to liquid–liquid extraction (LLE). Relevant extraction parameters, namely organic solvent, extraction time, agitation speed, and acceptor solution pH, were studied, and the two optimized techniques—HF-LPME: dihexyl ether, 45 min, 250 rpm, and pH 1; PALME: undecane, 20 min, 250 rpm and pH 1—were compared. Comparison of the optimized methods showed that significantly higher recoveries could be obtained with PALME than with HF-LPME. Therefore, PALME was further validated. The results were successful for nine different AA, with regression coefficients (R2) of at least 0.991, limits of detection (LOD) of 45–75 ng/L, and repeatability and peak area relative standard deviations (RSD) below 20%. Furthermore, two urine samples from smokers were measured as proof of concept, and 2-methylaniline was successfully quantified in one of them. These results show that PALME is a great green alternative to LLE. Not only does it use much smaller volumes of toxic organic solvents, and sample—enabling the study of samples with limited available volumes—but it is also less time consuming and labor intensive, and it can be automated.Graphical

Optimization and Prediction of Stability of Emulsified Liquid Membrane (ELM): Artificial Neural Network

In this work, the emulsified liquid membrane (ELM) extraction process was studied as a technique for separating different pollutants from an aqueous solution. The emulsified liquid membrane used consisted of Sorbitan mono-oleate (Span 80) as a surfactant with n-hexane (C6H14) as a diluent; the internal phase used was nitric acid (HNO3). The major constraint in the implementation of the extraction process by an emulsified liquid membrane (ELM) is the stability of the emulsion. However, this study focused first on controlling the stability of the emulsion by optimizing many operational factors, which have a direct impact on the stability of the membrane. Among the important parameters that cause membrane breakage, the surfactant concentration, the emulsification time, and the stirring speed were demonstrated. The optimization results obtained showed that the rupture rate (Tr) decreased until reaching a minimum value of 0.07% at 2% of weight/weight of Span 80 concentration with an emulsification time of 3 min and a stirring speed of 250 rpm. On the other hand, the volume of the inner phase leaking into the outer phase was predicted using an artificial neural network (ANN). The evaluation criteria of the ANN model in terms of statistical coefficient and RMSE error revealed very interesting results and the performance of the model since the statistical coefficients were very high and close to 1 in the four phases (R_training = 0.99724; R_validation = 0.99802; R_test = 0.99852; R_all data = 0.99772), and also, statistical errors of RMSE were minimal (RMSE_training= 0.0378; RMSE_validation = 0.0420; RMSE_test = 0.0509; RMSE_all data = 0.0406).

Environmentally Friendly Strategy for Treating In Situ Leaching Solutions of Ion-Adsorption Type Yttrium-Rich Heavy Rare-Earth Ore by a Bubble-Supported Organic Liquid Membrane

A novel environmentally friendly strategy based upon bubble-supported organic liquid membrane (BSOLM) extraction using saponified naphthenic acid as extractant is proposed in the present work for treating the in situ leaching solutions of ion-adsorption type yttrium-rich heavy rare-earth ores in South China. It was revealed that selectively preferential separation of non-yttrium rare earths from yttrium can be achieved, while the electrolyte aluminum salt can be retained in the raffinates for subsequent return as the leaching reagent for performing in situ leaching of ion-adsorption type heavy rare-earth ores. The BSOLM extraction exhibits an obvious advantage over conventional extraction in promoting the competitive mass transfer and separation of coexisting rare earths from yttrium and other non-rare-earth impurity ions. Using erbium as a representative of heavy rare earths, it was found that the differences in diffusive mass transfer rate of Er3+, Y3+, and Al3+ ions in the boundary layer of laminar flow near the surface of the extractant liquid membrane result in their enhanced separation. The BSOLM extraction prevents the convective disturbance along the normal vertical direction of the interface due to the irregular movement of dispersed oil droplets in the conventional extraction and therefore inhibit the co-extraction of Al3+ ions. The effects of Al3+ ion concentrations in aqueous feed solutions, initial aqueous pHs, concentrations of naphthenic acid, and its saponification degree on the separation efficiency were investigated. Experimental results confirmed that competitive hydration and adsorption of Al3+ ions at the interface play an important role in increasing the difference in concentration distribution of Er3+ and Y3+ ions near the interface during BSOLM extraction; therefore, the separation of rare earths from yttrium can be controllable.

Separation of Rare-Earth Elements Using Supported Liquid Membrane Extraction in Pilot Scale

Separation of Rare-Earth Elements Using Supported Liquid Membrane Extraction in Pilot Scale

Performance and mechanism study on surfactant-stabilized oil microdroplets extraction from oily wastewater

Petrochemical, coal chemical, and metal smelting industries generate substantial amounts of oily wastewater. The major obstacle in treating these wastewaters is surfactant-stabilized oil microdroplets. Solvent extraction has shown significant application potential in this kind of oil microdroplet removal due to its high-efficiency, economy, and environmental friendliness. However, mechanistic study and other in-depth investigation are still needed to support the more high-performance extractant screening and process design. In this study, in terms of the surfactant-stabilized oil microdroplet extraction from oily wastewater, the mechanism was analyzed by characterizing the compositions and properties of the intermediate layer and extractant phase. It was demonstrated that, unlike conventional liquid–liquid extraction system containing molecular solutes, the extraction of surfactant-stabilized oil microdroplets is accomplished by the mass transfer of extractant from the exterior to the interior of the oil microdroplets and the rise of extractant-containing oil droplets in the aqueous phase with critical influences. This behavior of mass transfer and droplet rise is supported by the mechanism of the emulsion liquid membrane extraction technique and the Stokes’ law. In addition, we illustrated the positive or negative effects of several factors (e.g. molecular extractant type, extractant dosage, stirring time, stirring speed and so on) on extraction efficiency. This confirmed the mechanism proposed above. And multistage extraction experiments showed that this solvent extraction technology was able to treat oily wastewater to discharge standards. Finally, by combining with the feasibility analysis of extractant regeneration, non-polar extractants were considered as the more suitable extractant than polar extractant because of the realizability of regeneration, lower costs for regeneration and better extraction performance.

Potential Role of Phytochemical Extract from Saffron in Development of Functional Foods and Protection of Brain-Related Disorders.

The present review is designed to measure the effects of saffron extract in functional foods and its pharmacological properties against various disorders. Saffron is a traditional medicinal plant used as a food additive. The stigma of saffron has bioactive compounds such as safranal, crocin, crocetin, picrocrocin, kaempferol, and flavonoid. These bioactive compounds can be extracted using conventional (maceration, solvent extraction, soxhlet extraction, and vapor or hydrodistillation) and novel techniques (emulsion liquid membrane extraction, ultrasound-assisted extraction, enzyme-associated extraction, pulsed electric field extraction, microwave-assisted extraction, and supercritical fluid extraction). Saffron is used as a functional ingredient, natural colorant, shelf-life enhancer, and fortifying agent in developing different food products. The demand for saffron has been increasing in the pharma industry due to its protection against cardiovascular and Alzheimer disease and its antioxidant, anti-inflammatory, antitumor, and antidepressant properties. Conclusively, the phytochemical compounds of saffron improve the nutrition value of products and protect humans against various disorders.

Determination of nerve agent biomarkers in human urine by a natural hydrophobic deep eutectic solvent-parallel artificial liquid membrane extraction technique

Alkyl methyl phosphonic acids (AMPAs) are the major metabolites of organophosphorus nerve agents. A method based on the use of natural hydrophobic deep eutectic solvents as supported liquid membrane in parallel artificial liquid microextraction (PALME) combined with LC-MS/MS analysis was developed and applied to their extraction from urine samples.PALME is a miniaturized liquid-phase extraction method performed in a multiwell plate format where the aqueous sample and the aqueous acceptor phase are separated by a flat membrane impregnated with an organic solvent. In this study, we investigated the possibility of replacing the harmful conventional organic solvent by an emerging green solvent, a coumarin/thymol-based deep eutectic solvent, in ordered to raise the greenness of the sample preparation method.Linear response was obtained in an interval of 0.5, 5 or 10–100 ng/ml depending on the AMPAs with a determination coefficients (R2s) ranging from 0.9751 to 0.9989 for their determination in not treated urine samples. Enrichment factors (EFs) up to 12.65 were obtained, and repeatability was within 8.90–16.28% RSD (n = 12). The limit of quantifications (LOQs: S/N ≥ 10) of the whole analytical procedure were in the range from 0.04 to 5.35 ng/ml. In addition to its good sensitivity, the presented method permitted the treatment of 192 samples in 120 min (equivalent to 37.5 s/sample), which places it as one of the most powerful preparation technique for biomonitoring of civilian or military people exposed to nerve agents in case of public health emergency. Indeed, the developed procedure combined sensitivity, high-throughput, greenness, simplicity and practicality for the determination of five acidic polar AMPAs in urine samples.

Controllable enhancement of mass transfer kinetics related with the thickness of organic thin-layer liquid membrane on surface of gas bubble

Gas bubble supported organic thin-layer liquid membrane extraction is a unique mode of gas-liquid-liquid three phase extraction for enrichment and enhanced separation of low-concentration target metal ions from various complex aqueous solutions. We found that the extraction rate of metal ions has a close relationship with the thickness of organic liquid membrane on the surface of gas bubble. Further, the thickness of organic liquid membrane could be easily controlled by changing the ratios of the volume flowrate of gas versus organic phase pumped into the extraction column. Therefore, the reaction behavior of target metal ions can be controlled purposefully by adjusting the thickness of organic membrane for enhanced kinetic separation of different co-existing metal ions. In present work, extraction of low-concentration rare-earth ions from the in-situ leaching solutions of ion-adsorbing type rare-earth ores was suggested as an example to detect such a surprising phenomenon. A quantitative relationship of the extraction rate of rare-earth ions with the thickness of organic liquid membrane was obtained. Accordingly, a theoretical prediction of the extraction efficiency of the gas bubble supported organic thin-layer liquid membrane was possible. Experiments were performed to demonstrate the validity of the suggested kinetic equations.

Simulation of the enhancement of Dean flow on the liquid–liquid extraction in membrane contactors

Dean vortices generated through the curved paths have been demonstrated to be beneficial to enhance gas–liquid mass transfer in membrane contactors. However, the effect of Dean vortices in liquid–liquid membrane extraction was seldom studied. This work implemented a numerical model describing the liquid–liquid extraction process in curved membrane contactors with the software of COMSOL. The liquid–liquid extraction experiments were first performed verifying the applicability of the simulation. Firstly, the discussion about the role of membrane resistance revealed the fact that enhancement provided by Dean flows would be more pronounced for systems with lower membrane resistance. A parametric study was then conducted including geometric parameters and physical properties of the fluid, which indicated smaller pitch, smaller curvature diameter, and less viscous fluid led to a better enhancement. The intensification factor was in the range of 1 ∼ 1.8, corresponding to the Dean number range of 5 ∼ 30. Considering the energy consumption, the values of modified intensification factors were lower than 1 only when the Dean numbers were smaller than 8. Finally, the performance of four curved geometries: helically-wound, 90-degree bend, meander-shaped, knotted were compared. The presented model yielded new insights into the liquid–liquid exaction enhancement in the curved membrane contactors.

Enhanced interfacial salt effect on extraction and separation of Er(III) from Mg(II), Al(III), Fe(III) sulfate aqueous solutions using bubble-supported organic liquid membrane

Understanding the essence of specific salt effect on mass transfer of metal ions acrossing liquid–liquid interface is of crucial importance to intensify extraction and separation of target metal ions. In present work, the effect from various typical coexisting electrolyte salt cations, Mg(II), Al(III), Fe(III) cations, in the in-situ leaching solutions of ion-adsorption type rare earth ores on extraction and separation of heavy rare earths (Er(III) ions as a representative) by our previously suggested new method, bubble-supported organic liquid membrane (BSOLM) extraction, was investigated. It is found that extraction and separation of low concentration Er(III) ions can be significantly enhanced, even when the concentrations of Mg(II), Al(III) and Fe(III) cations are low enough. It cannot be explained by the traditional salt effect theory. Experiments revealed that BSOLM extraction results in an enhanced interfacial salt effect due to its essence of mass transfer only occurring on the surface of thin-layer organic extractant liquid membrane. It is benefit for intensifying the interfacial competitive adsorption of coexisting salt cations. The competitive hydration of those salt cations at interface promotes the extraction of low concentration Er(III) ions, whereas their competitive adsorption is unfavorable of the separation of Er(III). The present work highlights the microscopic nature of specific interfacial effect of various coexisting electrolyte salt cations on extraction of target rare-earth ions. It is benefit for development of new methods to intensify extraction and selective separation of low concentration rare-earth ions from the electrolyte salt in-situ leaching solutions of ion-adsorption type rare earth ores.