Liquid Membrane Extraction Research Articles

Extraction of Silver Ions from Aqueous Solutions by Emulsion Liquid Membrane

A comprehensive study pertaining to the emulsion liquid membrane (ELM) extraction process to enrich dilute aqueous solutions of silver salt is presented. The study has highlighted the importance and influence of membrane composition for maximizing the extraction of Ag+ ions. The liquid membrane was made up of Cyanex-302 as an extractant and the industrial solvent mainly consists of paraffinic and naphthenic hydrocarbons (C10-C14) as a diluent, Montane®-80 (sorbitan monooleate) as the surfactant and nitric acid solution as the stripping solution. The selection of the extractant (Cyanex-302) and the stripper (HNO3) was based on conventional liquid–liquid extraction studies. The role of pH as an important parameter in the LEM process for extraction of Ag+ was studied. Extraction of Ag+ increased with an increase in strip phase and carrier concentration. The fundamental parameters (emulsion stability, pH of the feed aqueous solution, agitation speed, surfactant concentration, strip phase concentration, carrier concentration, surfactant concentrations and treatment ratio) affecting the separation of Ag+ through the ELM were investigated to select the best combination of process parameters. The maximum extraction of Ag+ (about 99%) was achieved at a Montane®-80 concentration of 5% (v/v), strip phase concentration of 0.4M nitric acid and a phase ratio of 1:1.

Determination of isoquinoline alkaloids in extracts of Chelidonium majus L. using emulsion liquid membrane extraction and GC/MS

Determination of isoquinoline alkaloids in extracts of Chelidonium majus L. using emulsion liquid membrane extraction and GC/MS

Speciation Analysis of Labile and Total Silver(I) in Nanosilver Dispersions and Environmental Waters by Hollow Fiber Supported Liquid Membrane Extraction.

Hollow fiber supported liquid membrane (HFSLM) extraction was coupled with ICP-MS for speciation analysis of labile Ag(I) and total Ag(I) in dispersions of silver nanoparticles (AgNPs) and environmental waters. Ag(I) in aqueous samples was extracted into the HFSLM of 5%(m/v) tri-n-octylphosphine oxide in n-undecane, and stripped in the acceptor of 10 mM Na2S2O3 and 1 mM Cu(NO3)2 prepared in 5 mM NaH2PO4-Na2HPO4 buffer (pH 7.5). Negligible depletion and exhaustive extraction were conducted under static and 250 rpm shaking to extract the labile Ag(I) and total Ag(I), respectively. The extraction equilibration was reached in 8 h for both extraction modes. The extraction efficiency and detection limit were (2.97 ± 0.25)% and 0.1 μg/L for labile Ag(I), and (82.3 ± 2.0)% and 0.5 μg/L for total Ag(I) detection, respectively. The proposed method was applied to determine labile Ag(I) and total Ag(I) in different sized AgNP dispersions and real environmental waters, with spiked recoveries of total Ag(I) in the range of 74.0-98.1%. With the capability of distinguishing labile and total Ag(I), our method offers a new approach for evaluating the bioavailability and understanding the fate and toxicity of AgNPs in aquatic systems.

Bulk liquid membrane extraction of silver(I) with 2-mercaptobenzothiazole as a carrier: Kinetic approach

The transport and separation of silver(I) ions across a bulk liquid membrane by 2-mercaptobenzothiazole (MBT) as carrier were investigated. The efficiency of Ag(I) transport was studied as a function of different parameters. The maximum of Ag(I) recovery was 85% in the presence of thiourea 0.1 M at pH 1, as complexing agent in the receiving phase, for a short extraction time of 4 h. A selective separation between Ag(I) and Mn(II) ions from equimolar mixture Ag–Cu–Mn solutions was performed. Besides, we have applied the kinetic model involving two consecutive irreversible first-order reactions to calculate the pseudo-first-order apparent membrane entrance and exit rate constants ke and ks, respectively. Under optimal conditions, the kinetic model curves of time dependence of silver concentrations (R) in the feed, membrane and receiving phases showed a good agreement with the experimental results. The apparent rate constants values were 6.93 × 10−3 min−1 for ke and 6.81 × 10−2 min−1 for ks. The transport of silver(I) is mainly controlled by the slow reaction of the formation of Ag–MBT complex at the membrane entrance.

Removal of chromium(VI) from aqueous solutions using a novel hybrid liquid membrane—electrodialysis process

Chromium(VI) is one of the most toxic metals, and the removal of this metal ion from effluents and waste waters is a problem of great significance. A novel hybrid process of electrodialysis and liquid membrane extraction is proposed for chromium(VI) removal from aqueous solutions. Transport through bulk liquid membranes was found to be effective for chromium(VI) anions removal from chloride acidic solutions during galvanostatic electrodialysis. Solutions of tri-n-octylamine with admixtures of di(2-ethylhexyl) phosphoric acid in 1,2-dichloroethane were used as the liquid membranes. Effects of current density, chromium(VI) and hydrochloric acid concentration in the feed solution, carrier and admixture concentration in the liquid membrane were studied, and optimal conditions were determined. It is demonstrated that a practically complete removal of chromium(VI) from the feed solution is achieved during 1.0–4.0h of electrodialysis. A maximal stripping degree of ∼90% is obtained under the optimal conditions. A possibility of effective single-stage removal of chromium(VI) into dilute solutions of hydrochloric, sulphuric, perchloric, phosphoric acids and water is demonstrated.

Comparison of solvent extraction and LEM extraction in static mixer for recovery of Mo(VI) from dilute aqueous solution

In this paper, the liquid emulsion membrane extraction of molybdenum(VI) has been conducted in static mixer. The performance in LEM mode is compared to a conventional solvent extraction mode. The rate of extraction in LEM mode is found to be significantly higher than conventional solvent extraction. Study reveals that the optimum residence time, height of the static mixer and optimum surfactant concentration are the deciding parameters of the performance of static mixer. The effect of various parameters such as superficial velocity of aqueous phase and organic phase, residence time, initial Mo(VI) concentration in feed phase, height of column, and surfactant concentration on rate of extraction has been investigated. A mathematical model is developed to predict volumetric mass transfer coefficient (kLa) in a static mixer. The kLa value is reduced from 0.045s−1 to 0.015s−1 when height of the mixer was increased from 31cm to 93cm respectively under the same hydrodynamic conditions. This anomalous decrease of kLa with increase in height is due to acid extraction by TBP which reduces driving force for extraction of Mo(VI). HTU for solvent extraction and LEM extraction are estimated as 0.67m and 0.15m respectively which indicates less mass transfer resistance in LEM.

Recovery of kraft lignin from pulping wastewater via emulsion liquid membrane process.

Kraft lignin (KL) is a renewable source of many valuable intermediate biochemical products currently derived from petroleum. An excessive of lignin comes from pulping wastewater caused an adverse pollution problems hence affecting human and aquatic life. A comprehensive study pertaining to emulsion liquid membrane (ELM) extraction of lignin from pulping wastewater was presented. ELM formulation contains Aliquat 336 as carrier, kerosene as diluent, sodium bicarbonate (NaHCO3 ) as stripping agent and Span 80 as surfactant. The emulsion stability was investigated at different surfactant concentrations, homogenizer speed and emulsification time. Modifier (2-ethyl-1-hexanol) was added to avoid segregation of third phase while improving the emulsion stability. At optimum conditions, 95% and 56% of lignin were extracted and recovered, respectively at 10 min of extraction time, 0.007 M of Aliquat 336, 0.1 M of NaHCO3 and 1:5 of treat ratio. Additional of modifier was contributed to highest recovery up to 98%. The ELM process was found to be equally feasible and quite effective in the recovery of KL from real pulping wastewater. Therefore, ELM process provides a promising alternative technology to recover KL from pulping wastewater while solving the environmental problems simultaneously.

A Process Concept for High-Purity Production of Amines by Transaminase-Catalyzed Asymmetric Synthesis: Combining Enzyme Cascade and Membrane-Assisted ISPR

For the amine transaminase (ATA)-catalyzed synthesis of chiral amines, the choice of donor substrate is of high importance for reaction and process design. Alanine was investigated as an amine donor for the reductive amination of a poorly water-soluble ketone (4-phenyl-2-butanone) in a combined in situ product removal (ISPR) approach using liquid-membrane extraction together with an enzyme cascade. This ISPR strategy facilitates very high (>98%) product purity with an integrated enrichment step and eliminates product as well as coproduct inhibition. In the presented proof-of-concept alanine shows the following advantages over the other frequently employed amine donor isopropyl amine: (i) nonextractability of alanine affords high product purity without any additional downstream step and no losses via coextraction, (ii) higher maximum reaction rates, and (iii) broader acceptance among ATAs.

Novel 90Sr–90Y generator system based on a pertraction through supported liquid membrane in hollow fiber contactor

Separation of yttrium(III) from strontium(II) with 15% (v/v) di(2-ethylhexyl)phosphoric acid (DEHPA) in dodecane was carried out in a hollow fiber supported liquid membrane (SLM) extraction system operated under closed-loop recirculation of the donor and acceptor phase. The donor phase was a mixture of 5.7mmoldm−3 of Sr(II) and 0.23mmoldm−3 of Y(III) in 0.1moldm−3 HCl, the acceptor solution was 3moldm−3 HCl, and the donor to acceptor phase volume ratio was 6.2. At the donor flow rate of 4.7cm3min−1 and the acceptor flow rate of 0.8cm3min−1, the yield of Y(III) in the acceptor phase (in the form suitable for radiopharmaceutical preparation) reached 60% after 360min with a molar ratio of Y(III) to Sr(II) in the acceptor of 250:1, as compared to 1:25 in the donor phase. The yield of Y(III) was 72% at the acceptor flow rate to 1.9cm3min−1, but a breakthrough of Sr(II) through liquid membrane increased from 0.02 to 0.2%.

Separation of Co(II) and Li(I) with Cyanex 272 using hollow fiber supported liquid membrane: A comparison with flat sheet supported liquid membrane and dispersive solvent extraction process

Separation of Co(II) and Li(I) by non-dispersive solvent extraction using a hollow fiber supported liquid membrane has been investigated. Separation of both the metals by flat sheet supported liquid membrane and dispersive solvent extraction technique has also been investigated and compared. The parameters for the three processes were optimized to achieve quantitative separation of Co(II) over Li(I) with Cyanex 272 diluted with kerosene. The feasibility to produce pure metal salt solutions was established by controlling the process parameters like pH of the feed solution, extractant concentration, metal ion concentration and acid concentration for selective stripping. For both the hollow fiber and the flat sheet supported liquid membrane processes, the aqueous feed pH of 6.0 and 750mol/m3 of Cyanex 272 in the membrane phase were the best conditions for extraction, whereas the best stripping results were obtained with 100 and 25mol/m3 H2SO4, respectively. In the case of dispersive solvent extraction process, the quantitative separation of the metals was achieved by extraction at equilibrium pH of 5.50 using 100mol/m3 of Cyanex 272, and stripping with 10mol/m3 H2SO4 solution. Under the optimum conditions, the separation factor was found to be 18, 178 and 180 for hollow fiber supported liquid membrane, flat sheet supported liquid membrane, and dispersive solvent extraction, respectively. Suitable mathematical models for the quantitative extraction of the metal in dispersive solvent extraction and mass-transfer coefficient in non-dispersive solvent extraction were proposed and validity of the models was verified. Proposed models and the mathematical analyses revealed that both dispersive solvent extraction and non-dispersive solvent extraction process followed cation-exchange reaction mechanism with similar kind of stoichiometry.

Sensitivity enhancement in direct coupling of supported liquid membrane extractions to capillary electrophoresis by means of transient isotachophoresis and large electrokinetic injections

Enhanced sensitivity for determination of basic drugs in body fluids was achieved by in-line coupling of extraction across supported liquid membrane (SLM) to large electrokinetic injection and transient isotachophoresis-capillary zone electrophoresis (tITP-CZE) in commercial CZE instrument. Twelve cm long tITP plug of 300mM ammonium acetate was formed in the separation capillary just before the electrokinetic injection of acceptor solution containing nortriptyline, haloperidol and loperamide extracted across the SLM. The tITP plug ensured efficient stacking and preconcentration of the injected basic drugs due to the tITP action of ammonium and the drugs were then separated by CZE using 5.2M acetic acid as background electrolyte. No interferences were observed from highly-abundant body fluid species (NaCl and human serum albumin) due to the excellent clean-up properties of SLMs and analytical sensitivity increased up to 340 times compared to SLM extractions coupled in-line to CZE with standard hydrodynamic injections. The SLM-tITP-CZE method was characterized by good repeatability (RSDs of peak areas below 7.8%), linearity over two orders of magnitude (r2 better than 0.994) and limits of detection (defined as 3×S/N) between 3 and 45μg/L. Interfacing of SLM extractions to CZE instrumentation was achieved by low-cost, disposable micro-extraction devices, which can be routinely prepared in every analytical laboratory. These devices eliminated sample carry-over, minimized the need for manual sample handling and ensured fully automated determination (including extraction, injection, preconcentration and separation) of the three basic drugs in 20μL of untreated body fluids.

Hollow fiber supported liquid membrane coupled with high performance liquid chromatography for highly sensitive determination of bisphenols in environmental water samples

Hollow fiber supported liquid membrane (HFSLM) extraction provides a high enrichment factor and easy sample clean-up for bisphenols in environmental waters.

Liquid membranes for extraction

Types and peculiarities of liquid membrane extraction are surveyed. The properties of bulk, supported, and emulsion liquid membranes are given. The basic principles of liquid membrane extraction, the types of carriers, and the stability of systems in the course of processes are considered. The use of liquid membranes for the separation of gas mixtures is demonstrated. The advantage of membrane extraction is the possibility of achieving high degrees of extraction and concentration in a single stage. At the same time, the organization of a membrane extraction process is more complicated than that of traditional processes.

On the application of bulk-supported liquid membrane techniques in hydrometallurgy

A theory of bulk-supported liquid membrane extraction has been developed. The process is performed sequentially in a series of three-phase mass-transfer stages. In each stage the extractant circulates in a closed circuit and alternately contacts a donor (feed) phase and an acceptor (stripping) phase. Special cases have been analyzed in which the phases in the chambers move countercurrently in plug-flow mode; contact chambers represent perfectly-mixed cells; contact chambers consist of a series of theoretical stages; each contact chamber represents a theoretical stage. Experimental and computational studies on extraction and separation of lanthanide chlorides have been carried out using two schemes of a cascade of mixer-settlers: (1) connected in the usual way with external circulation of the extractant (the extractant first passes through all the stages of extraction and then through all the stripping stages) and (2) based on a bulk-supported liquid membrane (the extractant recycles between each pair of extraction and stripping stages). The effectiveness of the bulk-supported liquid membrane extraction scheme was considerably greater than that of the conventional scheme. Experiments on the extraction of lanthanide chlorides from neutral aqueous solutions in the system involving methyltrioctylammonium di(2-ethylhexyl)phosphate were carried out. The experimental results are in satisfactory agreement with the data calculated, which confirms the agreement between theory and experiment. The bulk-supported liquid membrane extraction can be applied to other systems and heavy metals as well.

Hydrophilic nanoporous ion-exchange membranes as a stabilizing barrier for liquid–liquid membrane extraction of lithium ions

Stability of supported liquid membrane (SLM) has been a key issue in the application of high efficiency liquid membranes. In this paper, a nanoporous ion exchange membrane, prepared by blending polyethersulfone (PES) with sulfonated poly (phenyl ether ketone, SPPESK), was utilized as the stabilizing barrier for the extraction of lithium ion based on liquid–liquid membrane extraction. The membrane was prepared via immersion precipitation and the ratio between PES and SPPESK was varied in order to obtain a membrane with the best performance. It was found that at a PES/SPPESK ratio of 6/4 and a polymer concentration of 30wt%, the membrane showed a Li+ flux of 1.67×10−8molcm−2s−1 at a Li+ feed concentration of 0.13mol/L. The membrane demonstrated nearly unchanged stress but a slight decline in elongation after 50 days in contact with the organic extractant, indicating the potential solvent resistance. Using tributylphosphate (TBP) as the extractant and kerosene as the diluent, lithium extraction and stripping were demonstrated in both single-staged and sandwiched membrane extraction contactor systems. The preliminary results on using SPPESK/PES barrier membrane for stabilizing the liquid membrane will lead to a new scientific and technology development in lithium mining from brine and seawater in the near future.

Removal of thiols from model jet-fuel streams assisted by ionic liquid membrane extraction

This work focuses on the use of ionic liquids as alternative solvents for the removal of thiols, at room-temperature, from n-dodecane used as jet fuel model stream. The model extraction system composed by a selected ionic liquid, the thiol to be removed and an alkane representative of the jet-fuel, show high selectivities and low distribution ratios, which makes unfeasible the use of conventional liquid–liquid extraction processes due to the high volume of ionic liquid required. This works evaluates the use of supported ionic liquid membranes (SILMs) for the selective removal of thiols applying vacuum in the downstream side. This approach consists in the incorporation of the ionic liquid inside the membrane pores, while due to the vacuum applied, the thiol compound is scrubbed. To study the target solute transport from the feed to the ionic liquid, extraction experiments were carried out using different 1-ethyl-3-methylimidazlium cation-based ionic liquids. The mass transfer resistance was found to be higher in the ionic liquid phase, which results mainly from the high ionic liquid viscosities, hindering the thiol transport. The SILMs stability was investigated by evaluating different membrane supports, with the various ionic liquids selected for study. The results obtained show that the ionic liquids were properly incorporated inside the pores of the membrane support. However, and despite the negligible mutual solubility between n-dodecane and the studied ionic liquids, n-dodecane permeation through the membrane support was found to be undesirably high. This problem was solved by using a membrane contactor with polypropylene hollow fibre membranes, not wetted by the ionic liquid, which receives the thiol compound transported. Under these conditions, n-dodecane was not detected in the receiving ionic liquid phase.

Removal of the Selected Pesticides from a Water Solution by Applying Hollow Fiber Liquid–Liquid Membrane Extraction

A supported liquid membrane extraction of different pesticides (acetamiprid, dimethoate, imidacloprid, linuron, and tebufenozide) from an aqueous solution containing 20 mg dm–3 of each pesticide by 5% TOPO (tri-n-octylphosphine oxide) in DHE (di-n-hexyl ether) has been investigated in a hollow fiber contactor having an aqueous feed/organic interfacial area of 15.4 cm2. In a single-pass operation, the maximum removal efficiency of 95% was achieved for the most nonpolar (log P = 4.38) pesticide tebufenozide at the feed flow rate of 0.5 cm3 min–1. The diffusion through the boundary layer of the feed stream was a rate-controlling step in the extraction of nonpolar pesticides (linuron and tebufenozide) with a mass-transfer coefficient in the feed stream being proportional to the feed flow rate raised to the power of 0.51–0.57. The maximum overall mass-transfer coefficient based on the feed phase of KF = 0.18 cm min–1 was obtained for tebufenozide at the feed flow rate of 1.8 cm3 min–1. The organic phase entrapped in the membrane pores offered a major resistance to the mass transfer of polar pesticides (log P < 1) and accounted for 85% of the overall mass-transfer resistance for imidacloprid at 1.8 cm3 min–1. The pesticides removed from the feed solution were almost completely accumulated in the organic phase but were recovered from the membrane pores to a large extent (50–90%) by rinsing the membrane with methanol after extraction.

Supported Liquid Membrane Extraction of Reactive Dye Using Fabricated Polypropylene Membrane

This study investigates the transport of dye ions across a supported liquid membrane (SLM) by using tridodecylamine as a carrier and sodium hydroxide (NaOH) as a stripping agent. A microporous polypropylene membrane was used as a membrane support and prepared by the thermal induced phase separation (TIPS) technique. Two different TIPS techniques were used when preparing membranes: solidification and without solidification with polymer concentrations varied at 10, 15 and 20%. The results revealed that both techniques produced membranes with similar morphologies, but different pore size structures. The membrane with 15% polymer concentration which was prepared by the solidification technique produced a microporous membrane with a symmetric structure, defined pore size and high stability, and thus is feasible as the support material. The fabricated membrane was tested and the results revealed that 100% of reactive dyes was succesfully removed with 58% recovery from an aqueous solution. The fabricated membrane also exhibited high stability up to 25.5 h of extraction, thereby demonstrating an improved method for the separation of reactive dyes using a SLM.

High-throughput analysis of drugs in biological fluids by desorption electrospray ionizationmass spectrometry coupled with thin liquid membrane extraction

Biological fluids such as urine, saliva and whole blood were analyzed for contents of drugs by a new combination of desorption electrospray ionization mass spectrometry (DESI-MS) and thin liquid membrane extraction (TLME). Analytes from the sample were extracted into a thin liquid membrane of hexadecane deposited on a porous Teflon membrane, from which they were subsequently analyzed directly by DESI. The total analysis time was 15 minutes for analysis of several samples with a potential analysis time of less than a minute per sample. Thanks to the pre-concentration and sample clean-up built into the method, methadone was detected in urine in full-scan mode with an LOD of 4 ng mL(-1), while amitriptyline, nortriptyline and pethidine showed LODs of 17 ng mL(-1). Quantification was possible for several basic drugs using one common internal standard, providing relative accuracies in the range of 10-30%. A reliability test was performed on 20 samples with methadone, amitriptyline, nortriptyline and pethidine in urine, showing that none of the samples having concentrations above the LOD were missed and no false positives were found. Diphenhydramine and one of its metabolites were detected in authentic samples of urine and saliva, and methadone was detected from a whole-blood sample spiked to a concentration of 100 ng mL(-1). The method has several advantages, such as extremely low price in consumables, the possibility of fast analysis of very crude biofluids such as whole blood and the potential for a very high sample throughput.

Reverse Micelle Mediated Bulk Liquid Membrane Separation of Platinum Gold and Silver From Real Samples

Simple and selective reverse micelle mediated bulk liquid membrane extraction procedure is developed for the separation and simultaneous pre-concentration of precious metals from valuable wastes like spent auto mobile catalytic converters and gold jewelry washings. Quantification has been carried out using inductively coupled plasma optical emission spectrometry (ICP-OES). Tri octyl methyl ammonium chloride (TOAC), a cationic hydrophobic surfactant, forms reverse micelles after dissolution in trichloroethylene facilitating the extraction of platinum, gold and silver ions into the bulk liquid membrane. The procedure is based on the formation of extractable hydrophobic ion-associates between TOAC cationic reverse micelles and anionic metal ions. These hydrophobic ion-associates which are transported into the bulk organic membrane from an aqueous feed phase are subsequently stripped into a receiving solution in a unitary process. Optimum conditions for the overall transport efficiency of precious metals have been evaluated. The accuracy of the procedure was validated by analyzing GBWAu-18 ore from faulted zone and PTM-1a nickel-copper sulphide matte certified reference materials. The procedure has been applied to spent catalytic converters and jewellery washings. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.