Liquid Membrane Type Research Articles

FTIR and ESEM Analysis of soil moisture Microscopic conservation feature with liquid membrane

Liquid membrane applied in soil has a good soil moisture conservation and evaporation suppression performance. Application of spectrum analysis technology to understand its structure and micro morphological characteristics will be help to reveal the soil moisture conservation mechanism of liquid membrane. In this paper, we used the three types of liquid membrane as the research object based on the laboratory preparation, with infrared spectrometer (FTIR) and environmental scanning electron microscope (ESEM) as the means, analysis the soil moisture mechanism of liquid membrane. The results showed that the -OH between the CMC and PVA generated intermolecular hydrogen bonds, the formation of hydrogen bonds between molecules of the two components strengthened the two-phase’s compatibility, increasing the liquid membrane’s effective groups and forming a dense mesh structure.ESEM observation showed that liquid membrane can effectively cementing soil particles, generating the soil-membrane structure, reducing soil moisture to evaporate, improve soil moisture conservation performance.

Types of bulk liquid membrane and its membrane resistance in heavy metal removal and recovery from wastewater

Bulk liquid membrane (BLM) is one of the simplest types of liquid membrane that shows superior membrane stability but inferior solute fluxes. The inferior solute fluxes of BLM are caused by its small interfacial area per unit volume, long transportation path, and high membrane resistance. The interfacial area and transportation path of BLM are influenced by its configurations, whereas the membrane resistance is governed by its membrane phase viscosity, stirring speed, and operating temperature. Hence, this paper aims to outline the different types of BLM and discuss the various factors affecting the membrane resistance of BLM in heavy metal removal and recovery from wastewater. Major challenges and future prospects toward the utilization of BLM as a prospective separation technique for large-scale industrial applications are also highlighted and discussed.

Bulk liquid pertraction of NaCl from aqueous solution using carrier-mediated transport

In the present work, removal of NaCl using the bulk liquid membrane (BLM) technique has been investigated, using a simple apparatus for conducting the experiments. Variables investigated were volume ratio of donor phase (DP) to receptor phase (RP), presence of sequestering agent (SA) in RP, type of organic liquid membrane (LM), quantity of mobile carrier (MC) in the LM. Stirring speed and volume of LM were kept constant at 100 rpm and 130 ml, respectively. The mass transfer of NaCl was analysed based on kinetic laws of two consecutive irreversible first-order reactions, and kinetic parameters (k1d, k2m, k2r, , tmax, , and ) for the transport of NaCl were investigated. The values obtained demonstrate that the process is diffusionally controlled. Results indicate that the membrane entrance and exit rate constants (k1, k2) increase with decreasing DP:RP ratio and with decrease in quantity of MC, and quantity of SA, and the presence of dichloroethane (DCE) is preferred to chloroform (CF) as LM.

The simultaneous stripping of arsenic and selenium from wastewaters using hollow-fibre supported liquid membranes.

The extraction of total arsenic and selenium using hollow-fibre supported liquid membranes (HFSLMs), with specific interest in the optimal conditions for the extraction in wastewater, is reported. The extraction time, type of liquid membrane, sample and donor pH and stirring rate were optimised, and thereafter, the developed method was tested in real wastewater samples. The optimal HFSLMs adopted, after optimisation tests, comprised of Aliquat 336, 0.8M NaOH, 200rpm and 80min as the extractant, stripping phase, stirring rate and reaction time, respectively. The developed method had reasonable-to-high extraction efficiencies in real wastewater samples with the final effluent recording as high as 73 and 78% removal efficiencies for Se and As, respectively. Considering the initial concentrations found in the samples, use of this developed method could bring down the concentrations to levels admissible by the United States Environmental Protection Agency (US-EPA) and World Health Organisation (WHO).

The research and application of liquid membrane

By the serious soil “white pollution”, the research and application of liquid membrane for the prevention of soil pollution caused by plastic mulch is of great significance. The article reviews the development process of the liquid membrane materials, summarizes the application effects of different liquid membranes on soil improvement and water use, points out limitations of liquid membrane and the future development trend. With natural biodegradable materials (especially the industrial and agricultural waste) as raw material to develop new type of multifunctional biodegradable liquid membrane is a hotspot of current research of liquid membrane. Past research is mainly for agricultural water saving and moisture conservation, the future research should strengthen the study of soil degradation, soil and water conservation and the control of degradation rate.

Low voltage electrically stimulated lab-on-a-chip device followed by red-green-blue analysis: a simple and efficient design for complicated matrices.

In the present work, a simple and portable analysis device was designed for the first time for the determination of lead ions as the model analyte. The basis of the lead analysis is its extraction and pre-concentration in an acceptor droplet via the application of an electrical field. The acceptor droplet is a KI solution and therefore, the formation of a yellow precipitation of PbI2 was a sign of the presence of lead ion in the solution. Following this, digital picture of the final acceptor droplet was analyzed by investigating its Red-Green-Blue (RGB) components. The results show that the RGB intensities of the acceptor phase are proportionate to the lead concentration in the sample solution. Also, a 9.0 V battery was used to apply the electrical field, and other effective parameters, such as the type of organic liquid membrane, pH of the sample solution, and the extraction time, were considered to obtain the optimal conditions. The model analyte was determined by extracting it from a 100 μL sample solution across a thin layer of 1-octanol, immobilized in the pores of a polypropylene membrane sheet, and into the acceptor droplet via applying a 9.0 V electrical potential for 20 min. The device is capable of determining lead ions down to 20.0 ng mL(-1), with admissible repeatability and reproducibility (the intra- and inter-assay precision ranged between 3.8-7.0% and 9.8-11.9%, respectively). Also, we calculated error% for the model analyte in the range of -8.5 to +4.5, which suggests that the chip offers acceptable accuracy for the analysis of lead ions. The linearity was studied in the range of 50.0-1500 ng mL(-1), with a correlation coefficient of 0.9994. Finally, the designed device was used for the analysis of lead in real samples.

Mini-Review on the Use of Liquid Membranes in the Extraction of Platinum Group Metals from Mining and Metal Refinery Wastewaters/Side-Streams

The current mini-review focuses on the use of liquid membranes in the platinum group metal (PGM/PGMs) extraction from various types of wastewaters to prevent environmental pollution; and for the metal recovery to address the scarcity of the PGMs in the industrial cycles. The bulk liquid membranes have been used to the extracted PGMs from the (acidic) aqueous media with recoveries of up to 96.3 ± 2.5% of the original PGM amount. The extraction time generally ranges from 2 to 24 hours. The bulk membrane liquid in the PGM extraction will depend on the covalent structure of the extractant, the feed phase PGM concentration and the complex of the PGM in question that is actually extracted from the aqueous environment. The advantages of this type of liquid membrane include its operational simplicity, but the disadvantages include limited possibility to improve the extraction performance of the system. Literature data are encouraging as they indicate that extraction of PGMs from mining and metal-refinery side-streams does not suffer from interference from metal contaminants that are commonly found in the mining and metal refinery side-streams, e.g. iron. Thus further research should focus on the application of ELM to extraction of PGMs from said wastewaters and major research drive should focus on the use of the Taylorvortex column and the non-Newtonian ELMs. With the supported liquid membranes, 78-82% of the original PGM content could be recovered from model side-streams. The selectivity of the extraction for individual PGMs can be controlled by the extractant used.

Separation of Two Amino Acids by Microemulsion Bulk Liquid Membrane

In this research work the potentialities of microemulsion bulk liquid membrane for the selective transport of L-tryptophan (L-Trp) and L-tyrosine (L-Tyr) are investigated at 298.15 K. Reversed micelle formed by sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in dichloroethane, was used as mobile carrier to transport amino acids between a source and a receiving aqueous phase. The effects of pH, surfactant concentration and initial amino acid concentration on the extraction efficiency and transfer rate of the amino acids were studied. It is verified that for a mixture of two amino acids, L-Trp can be extracted selectively by using this type of the bulk liquid membrane with optimized condition.

Liquid membrane-based CO 2 reduction in a breathing apparatus

Hydrophilic porous hollow fiber membranes were used to study appropriate immobilized liquid membranes (ILMs) for selective separation of carbon dioxide from anesthesia breathing circuit gas mixture containing nitrous oxide (N 2O), carbon dioxide (CO 2), oxygen (O 2) and halogenated hydrocarbons (HHCs). The pores in these hollow fibers were impregnated with the following liquids: Na-glycinate–glycerol solution; K-glycinate–glycerol solution and Na-glycinate–PEG 400–glycerol solution. Halogenated hydrocarbon liquids (HHCs) used in the permeation study were halothane, enflurane, sevoflurane and desflurane. Separation of CO 2–N 2O–O 2–HHC mixtures was studied using a variety of hollow fiber support membranes and modules and at temperatures between 25 and 37 °C. Relatively low separation factors between CO 2/N 2O were observed in the case of the immobilized Na-glycinate–glycerol solution or K-glycinate–glycerol solution due to similar physicochemical characteristics of carbon dioxide and nitrous oxide. Highest CO 2 permeances achieved using 5%CO 2 inlet feed concentration at 37 °C with hydrophilic microporous polyethersulfone (PES) membranes immobilized either with 3 M-Na/K-glycinate–glycerol or 2 M-Na-glycinate in 50/50 glycerol/PEG 400 solution were in the order of 100–490 GPU (1GPU = 10 −6 scc/cm 2-s-cmHg). Observed HHC permeances were in the range of 0.02–2.6 GPU depending on the type of liquid membrane, carrier, temperature and hollow fiber used during this study. Reasonably high selectivity for CO 2/HHC was observed at room and elevated temperatures (37 °C). A module having larger membrane area achieved considerable CO 2 removal from the feed breathing gas mixtures at higher sweep gas flow rates (100–450 cm 3/min) while using 5%CO 2 inlet feed gas concentration. The highest carbon dioxide permeance of 1600 GPU was achieved with the breathing gas mixture containing 2%CO 2 at the elevated temperature of 37 °C, where 5%CO 2/70%N 2O/O 2 balance yielded a CO 2 permeance of 490 GPU at 37 °C. An ultrathin hydrophobic porous coating on the outside surface of the PES hollow fibers prevented flooding of the liquid membrane by moisture condensation or flowing water on the outside of the fiber.

Chromium removal by emulsion liquid membrane using [BMIM] +[NTf 2] − as stabilizer and TOMAC as extractant

A new type of emulsion liquid membrane (ELM) has been prepared to separate and concentrate chromium (Cr) from waste water. A hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM] +[NTf 2] −) is used in the membrane phase as a stabilizer to provide sufficient stability and a second ionic liquid Tri-n-octylmethylammonium chloride (TOMAC) as a carrier. The other components to prepare emulsion are kerosene as solvent, span 80 as surfactant and NaOH as an internal reagent. In the present experimental investigation, the effects of various parameters such as homogenization speed, carrier concentration, internal phase concentration, agitation speed, treat ratio, internal to membrane phase ratio, surfactant concentration, pH of the feed phase and ([BMIM] +[NTf 2] − concentration on the % removal of Cr have been reported. At an optimum condition, 97% percentage of Cr could be extracted. Results showed that the stabilizing effect of [BMIM] +[NTf 2] − keeps on decreasing as the extraction proceeds. However, the provided stability by the combination of [BMIM] +[NTf 2] − and span 80 has been found to be sufficient during the extraction process.

Development of supported liquid membrane techniques for the monitoring of trace levels of organic pollutants in wastewaters and water purification systems

The supported liquid membrane (SLM) extraction technique has been developed and successfully used for the monitoring of trace quantities of ionisable organic contaminants, including 17β-estradiol and its metabolites, testosterones and their methyl ester derivatives, benzimidazole anthelmintic antibiotics and sulphonamides in aquatic systems. A number of parameters which control the mass transfer in the supported liquid membrane extraction process such as donor and acceptor pH, extraction time and the type of organic liquid membrane were optimised to enhance the efficiency of the liquid membrane in the removal of these compounds. The method developed gave very low detection limits (0.3ng/l to 2.4ng/l for 17β-estradiol and its metabolites; between 1μg/l and 20μg/l for sulphonamides; and between 0.1ng/l and 10ng/l for benzimidazole anthelmintic compounds). The SLM method showed good linearity, reproducibility and repeatability values and is therefore suitable for routine monitoring of such compounds in water and wastewater systems.

Analysis of Extraction of Cu(II) by Strip Dispersion Hybrid Liquid Membrane (SDHLM) using PMBP as Carrier

A liquid membrane system, denoted a strip dispersion hybrid liquid membrane (SDHLM) containing 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazolone –5 as carrier in xylene, was reported for the transport and separation of Cu(II) from Zn (II) ions. The effects of various factors on the transport of copper(II) ions through SDHLM were systematically investigated by orthogonal tests. The optimum transport conditions of copper ions were summarized. In the overall mass transfer process the mass transfer resistance due to the aqueous boundary layer diffusion and diffusion in the microporous membrane is dominant. The accumulation of the Cu(II)‐carrier coordination compound in the membrane shows that the transfer in SDHLM possesses the characteristic of nonequlibrium mass transfer in this study. The rheologic experiments verified that the organic phase in the SDHLM system was the non‐Newtonian fluid and the organic phase after transport of 6 hr was a system of thixotropy in our experimental conditions. The lag ring experiments proved that the thixotropy of the organic phase in the SDHLM system was relevant to the composition of the membrane. In the experimental comparison of two types of liquid membrane, SDHLM has superiority over SLM in respect of transport flux, permeability coefficient, recovery percentage or concentration of solute in the stripping solution, efficiency of uphill transport, loss of membrane solution, and the separation efficiency of the membrane.

Use of Highly Hydrophobic Ionic Liquids for Ion-selective Electrodes of the Liquid Membrane Type

The phase-boundary potential at the interface between an aqueous KCl solution (W) and a hydrophobic room-temperature ionic liquid (RTIL), trioctylmethylammonium bis(nonafluorobutylsulfonyl)imide ([TOMA(+)][C(4)C(4)N(-)]), containing dicyclohexano-18-crown-6 (DCH18C6), shows the nernstian response to K(+) in W within a polarized potential window of 500 mV between [TOMA(+)][C(4)C(4)N(-)] and W, demonstrating that hydrophobic RTILs can be used as a nonvolatile ionic medium for liquid-membrane ion-selective electrodes. The complex formation constant of K(+) with DCH18C6 in [TOMA(+)][C(4)C(4)N(-)] is estimated to be on the order of 10(9) from the upper detection limit using a partition equilibrium model in the presence of a neutral ionophore. The response time of the phase-boundary potential is approximately 20 min. Gelled [TOMA(+)][C(4)C(4)N(-)] also shows the nernstian response to K(+), although the upper limit is lower probably due to a change in the solvent properties from the non-gelled [TOMA(+)][C(4)C(4)N(-)]. The response time of the gelled [TOMA(+)][C(4)C(4)N(-)] is approximately 5 min, shorter than that of the non-gelled [TOMA(+)][C(4)C(4)N(-)].

Simultaneous removal and recovery of cadmium (II) and CN − from simulated electroplating rinse wastewater by a strip dispersion hybrid liquid membrane (SDHLM) containing double carrier

A novel liquid membrane system, denoted strip dispersion hybrid liquid membrane (SDHLM) with a double carrier (TRPO, trialkyl-phosphine oxide, and D2EHPA, di-(2-ethylhexyl) phosphoric acid) membrane phase, basic stripping aqueous phase and weak acidic waste water phase, was reported for the simultaneous removal and recovery of Cd(II) and CN − from simulated electroplating rinse wastewater. The basic stripping solution containing the concentrated Cd(CN) 4 2− could be again used in the electroplating tanks. The experiments verified that CN − was more quickly transported from the feed phase into the stripping solution than cadmium (II) when the organic phase only contains TRPO. In order to reach the same transport rate for CN − and Cd(II) D2EHPA was added in the organic phase only containing TRPO. Effect of various factors on the transport of CN − and Cd(II) were systematically investigated by orthogonal test of the extraction or membrane transport. The analysis of mass transfer resistances in SDHLM indicates that the mass transfer resistance due to the membrane-phase diffusion is dominant in the overall mass transfer process. The accumulation of coordination compound of CN −-carrier or Cd(II)-carrier in membrane for SDHLM shows that the transfer in SDHLM possesses the characteristic of nonequlibrium mass transfer in this study. According to the optimized condition, after the transport of 6 h for SDHLM the content of CN − or Cd(II) in the feed phase is 0.05 and 0.02 mg/L, respectively. The uptake of membrane solution into an adjacent aqueous phase for SLM is 2.1–2.6 times as high as that in SDHLM. In the experimental comparison of permeability coefficient, recovery percentage or concentration of solute in stripping solution, loss of membrane solution, the accumulation of coordination compound between CN −-carrier or Cd(II)-carrier in membrane, and transport efficiency of membrane for the two types of liquid membrane, SDHLM has superiority over SLM.

25,000-fold pre-concentration in a single step with liquid-phase microextraction

Hollow fiber protected liquid-phase microextraction (LPME) was developed for large sample volume extractions in a single step, with special emphasis on extraction of basic drugs from environmental waters. Five antidepressant drugs were extracted from 1100 or 100 mL water samples, through approximately 50 μL of dihexyl ether immobilized in the pores in the wall of a porous hollow fiber (liquid membrane), and into 20 μL of 10 mM HCl or HCOOH as the acceptor solution. Extractions were performed for 60 or 120 min supported by magnetic stirring at 800 rpm, and hereafter the acceptor solution was directly injected in HPLC-UV or HPLC-MS. Compared with earlier work on LPME from small sample volumes, both closing the hollow fiber and the type of liquid membrane was found to be critical for large volume extractions. The hollow fibers were carefully closed with a small piece of metal wire, dihexyl ether was used as the liquid membrane, and pH in the sample was adjusted to 11.8 with NaOH. Recoveries from 1100 mL samples were in the range 33–49%, and enrichments were in the range 18,000–27,000 after 120 min of extraction. With HPLC-MS, the drugs were detected down to the 5–30 pg L −1 level. Within-day precision was within 12.4–20.6% R.S.D. ( n = 6), whereas between-day precision was within 17.6 and 37.2% R.S.D. Linearity was obtained in the range 1–500 ng L −1 with r 2-values between 0.982 and 0.994. The proposed LPME system was utilized to detect the five antidepressants in wastewater from the city of Tromsø in Northern Norway.

Study of transport and separation of Zn(II) by a combined supported liquid membrane/strip dispersion process containing D2EHPA in kerosene as the carrier

The transport of Zn(II) ions through a combined supported liquid membrane/strip dispersion system was studied as a function of membrane area, fluxes, membrane composition, and pH in the feed phase. The experiments demonstrate that the transport of Zn(II) ions is coupled by the counter-flow of H +, and zinc(II) ions can be quickly separated from Cu(II) ions by the new form of a liquid membrane. The experiments verify that the new type of liquid membrane exhibits great feasibility in hydrometallurgy and the treatment of wastewater. The experiments show that the uptake of carriers out of the membrane phase into the feed phase increases with an increase of pH value in the feed phase.

Comparison of transport and separation of Cd(II) between strip dispersion hybrid liquid membrane (SDHLM) and supported liquid membrane (SLM) using tri- n-octylamine as carrier

A novel liquid membrane system, denoted strip dispersion hybrid liquid membrane (SDHLM) containing tri- n-octylamine-secondary octanol in kerosene, was reported for the transport and separation of Cd(II) from Zn(II) ions. The experiments show that Cd(II) can be efficiently transported into stripping solution with SDHLM. In the experimental comparison of transport flux, permeability coefficient, recovery percentage or concentration of solute in stripping solution, efficiency of uphill transport, loss of membrane solution, and separation efficiency of membrane for two types of liquid membrane, SDHLM has superiority over SLM.

Behaviour of nucleotides and oligonucleotides in potentiometric HPLC detection

Potentiometric HPLC detection was studied of mononucleotides (UMP, AMP, UDP, ADP, CTP, UTP, GTP, ATP) and oligonucleotides (a synthetic mixture d(T) 12–18 5′OH, a mixed 21-mer, 33-mer, and 60-mer). Coated-wire electrodes were used. The coatings were of the liquid membrane type containing PVC, DOS and synthetic macrocyclic amine- and podand ureum receptors. Electrodes based on these receptors gave very sensitive responses to triphosphate nucleotides and to oligonucleotides. The molar response of the oligonucleotides was related to their molar mass. The HPLC system consisted of a reversed phase column eluted with a phosphate buffer, triethylammoniumacetate (TEAA), and an acetonitrile gradient. The sensitive potentiometric response of these highly charged ions is discussed.

Development of Chemical Sensors and Their Application to Flow Analysis Systems

Flow analysis has many advantages concerning sensitivity, accuracy, repeatability and analytical throughput etc, compared with a batchwise analysis. The flow-based method makes the involved analytical processes automatic and rapid. Therefore, the combination of a chemical sensor with the flow method enhances the performances of the chemical sensor. Especially, potentiometric detection using ion-selective electrodes has been widely used in flow analysis due to its features, simplicity in analytical operation and wide dynamic range in analysis. This paper reports on several chemical sensors applied to flow systems that we have engaged so far concerning: (1) Liquid membrane type ion-selective electrodes, such as nitrate, vitamin B1, tetrafluoroborate and surfactants sensitive electrodes based on an oleophilic anion exchange resin membrane and a hydrophobic ion exchanger. (2) Flow titration by using both a buffer solution and its corresponding electrode, such as a pH glass electrode with a pH buffer, a cupper(II) ion-selective electrode with a metal ion buffer solution and a redox electrode with a potential buffer solution. (3) Surface plasmon resonance sensors for succarides and some endocrine disrupting chemicals based on a boronic acid polymer membrane and antigen or antibody immobilized membrane. (4) Sequential injection analysis combined with beads injection technique for vitellogenin as biomarker for assessing the pollution of environment in hydrosphere.

Designing Potentiometric Sensor Materials for the Determination of Organic Ionizable Substances in HPLC

AbstractThis article provides a model to explain the response of liquid membrane type potentiometric electrodes towards organic ions in HPLC systems. The model is a synthesis of data from 7 recent articles from our group on the determination of several classes of compounds (organic acids, amines, beta‐blockers, clenbuterol, mucolytic drugs and aminoalcohols) with potentiometric detection in HPLC. The presented model uses the difference in chemical potential of the analyte ion in the eluent and in the membrane phase as the sensitivity determining factor. Methods used to estimate this difference in chemical potential are compared. For liquid membrane coatings containing no selectively interacting (complex forming) ionophores, this difference could be estimated from calculated log P (lipophilicity) and P (polarizability) values for the analyte ions. If complex forming agents are present, the extra interaction of the analyte ion with the complex forming agent can be estimated via a solvation parameter model. In the latter case, molecular modeling may also be useful.