A study on separation and extraction of four main alkaloids in Macleaya cordata (Willd) R. Br. with strip dispersion hybrid liquid membrane

A technique based on strip dispersion hybrid liquid membrane was developed for the separation and extraction of four main alkaloids from fruits of Macleaya cordata (Willd) R. Br. A microporous polypropylene membrane impregnated with an organic membrane solution comprised the heart of the strip dispersion hybrid liquid membrane system. The membrane solution was made by dissolving a cationic carrier, di‐(2‐ethylhexyl) phosphoric acid in an inexpensive, less toxic membrane solvent, kerosene. The transport of alkaloids from an aqueous feed solution through the membrane to a strip dispersion phase was driven by the concentration gradient of H⁺ and facilitated by di‐(2‐ethylhexyl) phosphoric acid. The effects of the extraction time and reuse times of the membrane, the strip solution composition, the carrier concentration, the volume ratio of the aqueous strip solution to the organic membrane solution, and the flow rates of the feed solution and the strip dispersion phase on the transport of alkaloids were investigated. Under the optimal conditions, the permeability coefficients obtained for the four main alkaloids allocryptopine, protopine, sanguinarine, and chelerythrine were 1.66, 1.99, 2.98, and 3.06×10^?4 cm/s, and the transport efficiencies were as high as 68, 77, 83, and 85%, respectively.     

Extraction of molybdenum by a supported liquid membrane method

This is a report on the extraction of molybdenum(VI) ions using a supported liquid membrane, prepared by dissolving in kerosene, the extractant Alamine 336 (a long-chain tertiary amine) employed as mobile carrier. A flat hydrophobic microporous membrane was utilised as solid support. Appropriate conditions for Mo(VI) extraction through the liquid membrane were obtained from the results of liquid-liquid extraction and stripping partition experiments. The influence of feed solution acidity, the carrier extractant concentration in the organic liquid film and the content of strip agent on the metal flux through membrane were investigated. It was established that maximal extraction of metal is achieved at a pH 2.0 if sulphuric acid is used in the feed solution and at a pH value over 11.0 if Na₂CO₃ is used as strip agent. Moreover, the molybdenum extraction through membrane is enhanced when a 0.02 mol l⁻¹ content of the amine carrier in the organic phase is used. The present paper deals with an equilibrium investigation of the extraction of Mo(VI) by Alamine 336 and its permeation conditions through the liquid membrane, and examines a possible mechanism of extraction.     

Origin and significance of the deviations from a pseudo first order rate law in the coupled transport of metal species through supported liquid membran

A new equation describing the permeation rate of metal species in the coupled transport through supported liquid membranes (SLM) was derived. The equation assumes that the concentration profile within the membrane never goes to zero and contains the independently measurable distribution ratios of the permeating metal species between the organic liquid membrane and the aqueous feed and strip solutions. The equation was experimentally verified by measuring the distribution ratios and the permeation rates of Eu³⁺ through SLMs consisting of a 0.1 F solution of bis(2-ethylhexyl)phosphoric acid (carrier) in n-dodecane absorbed on a thin microporous polypropylene film. The conclusion was reached that the deviations from a pseudo first order rate law, often observed when measuring the coupled transport of metal species at low concentration through SLMs, originate in the non-negligible value of the distribution ratio at the SLM—strip solution interface. Nevertheless, these deviations can easily be taken into account in a quantitative way and, by an appropriate linearization of the permeation data, information can be obtained on two, newly defined, permeability coefficients of the SLM.     

反萃分散组合液膜分离提取氨基酸

建立了分离提取蛋氨酸、亮氨酸、苯丙氨酸和色氨酸的磷酸二（2-乙基己基）酯(D2EHPA) 煤油-HCl反萃分散组合液膜体系,考察了料液相pH值、载体D2EHPA浓度、液膜相与反萃相体积比、反萃相组成、料液相与反萃分散相流速、传输时间以及支撑膜重复使用次数对氨基酸渗透系数和传输效率的影响。 在优化的条件下,建立的反萃分散组合液膜体系对4种氨基酸均可以获得大于35%的传输效率,其中色氨酸和亮氨酸的传输效率超过了79%,且传输效率呈Et,Trp＞Et,Leu＞Et,Phe＞Et,Met的趋势。 支撑膜重复使用25次,对氨基酸的传输效率没有明显改变。建立的液膜体系对考察的氨基酸展示了较高传输效率和优越的传输选择性,是一种简单和环境友好的分离技术。     

Dialkylphosphoric acids as carriers in separation of lanthanides and thorium on supported liquid membranes

Permeation of seven lanthanides (Ln) and thorium through a supported liquid membrane containing di-(n- octyl)phosphoric (DOPA) or di-(n-pentyl)phosphoric (DPPA) acid as a carrier has been studied as a function of the chemical composition of the system. The results have been compared with a previous study in which di-(2-ethylhexyl)phosphoric acid was used. Metal cations were transported from feed solutions of pH 1.1-4.8 (HNO(3)) into strip solutions of 0.015-0.1 mol l(-1) nitric acid. The ionic strength was kept constant at 0.1 mol l(-1) (HNO(3), KNO(3)). The initial lanthanide concentration and carrier concentration in the liquid membrane were varied from 0.5 to 500 mumol l(-1) and from 0.01 to 0.5 mol l(-1) respectively. To describe the mass transfer of metal cations, permeability coefficients have been determined by inductively-coupled plasma atomic emission spectroscopy or by on-line flow-injection analysis of metal concentrations in strip or feed solution. Probably as the result of a higher solubility of the carrier in aqueous media, transport of Ln with DPPA was not observed. By using DOPA, La, Ce, Pr, and Nd permeated through the membrane while transport of heavier Ln was partly or totally suppressed. This enables these four Ln (separation factor alpha = 3.0 for Nd and Sm) to be separated from the others. Furthermore, at a very low acidity gradient, only La (III) is transported over the membrane (alpha >/= 3.4 for La, Ce and next Ln). The seven elements from La to Tb can be separated from Th(IV) because no evidence of its permeation through the membrane was found under the conditions of Ln transport. In contrast to previous studies on Ln transport with dialkylphosphoric acid carrier, the possibility of participation of species other than Ln(AHA)(3) in the transport has been discussed. The decrease of permeability observed at higher Ln concentrations and higher pH of the feed solution has been explained as the result of formation of species, e.g. polymeric ones, that are unable to permeate through the membrane.     

Supported liquid membranes modification with sulphonated poly(ether ether ketone): Permeability,selectivity and stability

The development of a new type of composite membrane consisting of a microfiltration support membrane, an immobilised liquid membrane phase and a hydrophilic, charged polymer layer and its function as a supported liquid membrane (SLM) for copper selective transport are described. The ion-exchange layers function as stabilisation layers to improve the membrane lifetime and consist of sulphonated poly(ether ether ketone) (SPEEK). This polymer shows a high permeability for copper ions due to the presence of fixed negative charges and to its swelling capacity in an aqueous phase.A method was developed to prepare composite membranes composed of the support membranes Celgard with one stabilisation layer on either the feed or strip side of the membrane or on both sides. Good adhesion of homogeneous, negatively charged, hydrophilic SPEEK layers to the hydrophobic macroporous support membranes could only be established when the support membranes were first hydrophilised with a concentrated sulphuric acid solution containing 5 wt% free SO₃.The lifetime of the SLMs is significantly improved when one stabilisation layer is applied at the strip side or two layers at both sides of the SLM. A second advantage of this composite SLM is the increase in copper flux caused by a decrease in thickness of liquid membrane phase. However, when SPEEK penetrates entirely through some pores of the support membrane, ions diffuse non-specifically through the SPEEK matrix resulting in an undesired selectivity loss. This phenomenon occurs only when thin Celgard membranes are used as support membranes.     

Transfer rate and separation of Cd(II) and Zn(II) chloride species by a trilaurylammonium chloride—triethylbenzene supported liquid membrane

The transfer rate of Cd(II) and Zn(II) from aqueous feed chloride solutions to ammonium acetate strip solutions through a supported liquid membrane consisting of a trilaurylammonium chloride (TLAHCl) solution in triethylbenzene (t-e-b), adsorbed on a polypropylene microporous film, was studied. The influence of the stirring speed, feed chloride concentration, and TLAHCI carrier concentration was investigated. The data were explained by a previously derived equation in terms of membrane diffusion, aqueous film diffusion, and aqueous complex formation chemistry. The best experimental conditions to perform a Cd(II)Zn(II) separation were identified. The separation of Zn(II) and Cd(II) was experimentally studied.     

Transport of99mTc across TBP-kerosene oil supported liquid membranes

Transport of^99mTc across tri-n-butylphosphate (TBP) kerosene oil supported liquid membranes (SLM) has been studied under various conditions. Presence of dichromate ions helps avoid activity scavenging effects. Concentration increase of TBP, the complexing carrier used in the present study has a positive effect on flux (J) and permeability (P) of these ions, as up to 2.87M there is an increase in J and P values. HCl concentration in the feed solution increases J and P with their maximum values at 2.5–3.0M HCl in the feed. Above this concentration there is a decrease in flux and permeability of^99mTc(VII) ions. The given ions are stripped with LiCl or NaCl solutions but more with NaOH. The optimum conditions of transport of the given ions are 2.5M HCl concentration in the feed, 2.87M TBP concentration in the membrane and 1M NaOH concentration in the strip solution. Equations have been developed to indicate the relation between flux, J, viscosity, of TBP in organic membrane phase, temperature, T, [H⁺], in the aqueous feed solutions and Tc ion concentration in the feed solution. Based on P, the values determined from liquid membrane experiments, the quantitative flux values of Tc(VII) ions were also determined as a function of TBP concentration in the membranes, and HCl and Tc concentration in the feed solution using the given equations. This experimental technique provides quantitative results from trace level activity transfer experiments.     

Carrier-mediated transport of yttrium(III) through a supported liquid membrane containing TOPO in n-dodecane

Transport of yttrium(III) from nitrate medium through liquid membrane containing tri-n-octyl-phosphine oxide (TOPO) in n-dodecane, supported on a nucleoporous filter, into a strip solution with ethylenediaminetetraacetic acid (EDTA) has been studied. The kinetic dependences of transport were obtained and compared with a model, resulting in calculation of permeability coeffients and initial fluxes of yttrium. The influence of salting-out agent, initial metal and nitric acid concentrations in the feed, and of concentration of carrier in membrane are discussed.     

Extraction and recovery of lignosulfonate from its aqueous solution using bulk liquid membrane

The paper presents an experimental study on the coupled transport of lignosulfonate (LS) through bulk liquid membrane (BLM) and thereby to identify the best set of solvent, operating conditions and mode of transport that would yield optimum performance of the BLM. Trioctylamine (TOA) is used as carrier. Among various solvents, tested for the above purpose, dichloroethane is found to be the best. The effects of operating condition, viz. pH, temperature, and carrier concentration, on the equilibrium distribution of LS are investigated. The effects of temperature, stirring of aqueous and organic phases, stirring speed, carrier concentration, initial feed and strip phase concentration on the separation of LS using BLM are also studied. It is observed that transport of LS can be enhanced by increasing the temperature and stirring speed of feed phase. Stirring of strip phase has no appreciable effects on the transport of LS. With increase in initial feed concentration the initial rate of the transport of LS is higher but continues for a longer time. Recovery of LS is much higher in co-transport mode in comparison to counter transport mode. Application of 1.25 M NaOH as stripping solution gives high recovery (70%) and high strip flux (70% of feed flux).     

离子液体内耦合液膜迁移苯酚的研究

本文以N-甲基咪唑为原料,采用微波合成法,制备了疏水性离子液体1-丁基-3-甲基咪唑六氟磷酸盐([BMIM]PF6),并将其作为液膜,对苯酚的内耦合液膜迁移进行了研究,考察了温度、搅拌速度、料液相酸度、初始浓度及解析相NaOH浓度等因素对苯酚迁移的影响,得出了最佳迁移条件:温度300 K,搅拌速度350 r/min,料液相pH为3.65,解析相NaOH浓度为0.8 mol/L.在最佳液膜条件下,对于10 mg/L苯酚溶液,迁移110 min,迁移率可以达到97.3%,膜相中有少量苯酚滞留.离子液体可循环使用.     

Simultaneous separation of mercury and lignosulfonate from aqueous solution using supported liquid membrane

This paper presents an experimental investigation on facilitated and simultaneous transport of mercury and lignosulfonate (LS) through a flat sheet supported liquid membrane (SLM) having Nylon 6,6 as support, trioctylamine (TOA) as carrier and dichloroethane as solvent. The experiments were performed at various operating conditions such as strip phase concentration, feed pH, carrier concentration and feed concentration to find the best set of parameters that would yield the maximum separation of pure mercury as well as its mixture with LS. The experiments were performed in co-transport mode using NaOH as the strip phase. It was observed that extraction of mercury as well as its mixture increases with increase in concentration of NaOH up to a certain limit 0.1 M NaOH in case of pure solution and 0.2 M NaOH in case of mixture). Feed phase pH significantly affects the mercury separation process. However, initial feed concentration does not affect the extraction process appreciably. Separation of mixture of mercury and LS behaves in a similar way as their pure solution; however the extraction is low in comparison to pure solution. The extraction of mercury from its pure solution is about 81% in 1 h. The extraction of mercury and LS from their mixture is about 52.6% and 50.2%, respectively at optimum condition and in a period of 2 h.     

Evaluation of a calix[4]-bis-crown-6 ionophore-based supported liquid membrane system for selective Cs transport from acidic solutions

Facilitated transport of Cs(I) from aqueous nitrate feed solutions to a receiver solution containing distilled water through a supported liquid membrane (SLM) containing calix[4]-bis-2,3-naphtho-crown-6 (CNC) in 0.45 μm PTFE (polytetrafluoroethylene) membranes was investigated. The carrier solution usually consisted of CNC dissolved in a mixture of 80% 2-nitrophenyl octyl ether and 20% n-dodecane. The transport rates were found to be influenced by the mobile carrier concentration, cesium concentration as well as the feed acidity. The extracted species conformed to a stoichiometry of 1:1 metal to ligand ratio suggesting the extraction of an organophilic mono-Cs-crown complex. Fission products obtained from an irradiated natural uranium target were found to be poorly transported while Cs-137 got significantly transported suggesting the possible application of the separation method for the removal of bulk Cs-137 from radioactive waste solutions. Durability/chemical stability of the membrane was remarkably good when tested over 20 days of continuous operation.     

Transport of ionic species through functionalized poly(vinylbenzyl chloride) membranes

Solid polymeric membranes of poly(vinylbenzyl chloride) (VBC), lightly crosslinked with divinyl benzene, were incompletely reacted such that a fraction of the benzyl chlorines in different membranes was replaced with either dimethyl phosphonate esters (MPE) or triethyl ammonium chloride groups (QA). This work was conducted in an effort to investigate ionic transport through charged and uncharged membranes and to develop fixed site carrier membranes to facilitate the transport of selected metal ions from an aqueous feed stream to a concentrated acid receiving stream. Bulk solution flow does not occur through these membranes. Instead, solute diffusion occurs through the membrane matrix. The effects of hydrogen ion gradient, metal ion identity and charge, reactive site type, acid type, and ionic strength on metal ion transport were investigated. Results are also presented on the effect of membrane orientation and pretreatment (swelling) on metal ion transport. Facilitated transport was investigated through the testing of membranes with varying MPE percent functionalization. The results presented compare the metal ion transport rate to the functionalization of the membranes.     

Selective facilitated transport of benzene across supported and flowing liquid membranes containing silver nitrate as a carrier

Separation of benzene from cyclohexane was performed using two types of liquid membranes, i.e., a supported liquid membrane and a flowing liquid membrane. Silver nitrate was used as the carrier of benzene. The permeation rate of benzene increased with increasing carrier concentration, and the separation factor, which is defined as the ratio of permeability of benzene to that of cyclohexane, was about 630 when the supported liquid membrane prepared by immobilizing 4 mol/L aqueous silver nitrate solution in cellulose filter paper was used. Compared with the supported liquid membrane, the flowing liquid membrane, where a liquid membrane solution was forced to flow in a thin compartment between two microporous membranes, showed one order of magnitude higher permeation rate at high flow rate of the membrane solution. The flowing liquid membrane was very stable and no noticeable decrease in both the flux and the selectivity was observed during 11 days operation. The mechanisms of the facilitated transport of benzene through both types of liquid membrane were proposed. The permeation rate and the selectivity were quantitatively simulated by the proposed model.     

Simulations of photomodulated solute transport in doubly illuminated liquid membranes containing photoactive carriers

A steady-state model describing photofacilitated transport in liquid membranes under double illumination is presented. The model allows for the exploration of the effects of a wide range of thermodynamic and kinetic carrier properties on the control of photoinduced transport rates of solutes, called photomodulation. Most previous experimental and theoretical studies have explored the illumination of only the feed or sweep side of the membrane, while this study examines the effects of illuminating both sides simultaneously. Under double illumination, solute transport rates can be as much as five times greater than those measured in the dark and 2.5 times greater than rates obtained under single illumination. Carriers that are predominantly in the weakly binding form in the dark generally provide slightly better performance at lower light intensities than do carriers that are predominantly in the strongly binding form in the dark. The greatest enhancement in solute transport under double illumination is seen for carriers with very slow interconversion rate constants between the strongly and weakly binding forms. These results provide guidelines to help those studying photofacilitated membranes select or design photoactive molecules that will act as optimal carriers in liquid membranes under double illumination.     

Integrated Microanalytical System Coupling Permeation Liquid Membrane and Voltammetry for Trace Metal Speciation. Technical Description and Optimization

A new minicell coupling the liquid‐liquid extraction technique called permeation liquid membrane (PLM) with an integrated Ir‐based Hg‐plated microelectrode array for voltammetric detection has been developed for the speciation of heavy metals in natural waters. Lead and cadmium have been used as model compounds. The PLM consists of a carrier (0.1 M 22DD+0.1 M lauric acid) dissolved in 1 : 1 mixture of toluene/phenylhexane held in the small pores (30 nm) of a hydrophobic polypropylene membrane (Celgard 2500). One side of this membrane is in contact with a flowing source solution, containing the metal ions of interest. An acceptor or strip solution (pyrophosphate) is placed on the other side of the PLM with the microelectrode array placed at 480 μm of the PLM. The analyte is transported by the carrier from the source solution to the strip solution. The originality of the new minicell is that accumulation in the strip solution is voltammetrically followed by the integrated microelectrode array in real time, and at low concentration level, using square‐wave anodic stripping voltammetry (SWASV). In order to protect the Hg microelectrodes from the adsorption of the hydrophobic carrier, the microelectrodes are embedded in a thin gel layer (280 μm) of 1.5% LGL agarose gel containing 10% of hydrophobic silica particles C18. The choice of optimum conditions is discussed in details in this article. Due to the very small effective strip volume of the new cell (less than 1 μL), high enrichment factor can be obtained (e.g., 330 for Pb) after 2 hours of accumulation. No deaeration of the solutions is required for SWASV measurements. Detection limits under these conditions are 2 pM and 75 pM for Pb and Cd, respectively, using a voltammetric deposition time of 5 min. In addition, no fouling effects were observed with natural water samples.     

Separation of Cd(II) and Ni(II) ions by supported liquid membrane using D2EHPA/M2EHPA as mobile carrier

The separation of Cd(II) and Ni(II) ions was studied in an aqueous sulphate medium using supported liquid membrane (SLM). D2EHPA/M2EHPA was used as a mobile carrier, microporous hydrophobic PTFE film was used as a solid support for the liquid membrane, and the strip phase was sulphuric acid. The effects of different parameters such as feed concentration, carrier concentration, feed phase pH, and strip phase pH on the separation factor and flux of Cd(II) and Ni(II) ions were studied. The optimum values obtained to achieve the maximum flux were 5.0 for feed pH, 40 vol. % for D2EHPA/M2EHPA concentration in the membrane phase, 0.5 for strip pH, and 0.012 mass % for feed concentration. Under these optimum conditions, the flux values of Cd(II) and Ni(II) were 15.7 × 10^?7 kg m^?2 s^?1 and 2.6 × 10^?7 kg m^?2 s^?1, respectively. The separation factors of Cd(II) over Ni(II) were studied under different experimental conditions. At a carrier concentration of 10 vol. % and feed concentration of 0.012 mass %, the maximum value of 185.1 was obtained for the separation factor of Cd(II) over Ni(II). After 24 h, the percentages of the extracted Cd(II) and Ni(II) were 83.3 % and 0.45 %, respectively.     

支撑液膜体系渗透系数和反萃液酸度的关系

A new permeability coefficient equation was theoretically derived. It contains both the acid concentration of feed solution and the carrier concentration as well as the acid concentration of stripping solution. The relationship of permeability coefficient and acid concentration of stripping solution was further confirmed by the experimental results of Co2+、Ni2+、 Er3+ ions transporting through the supported liquid membranes.     

Au(I) extraction by LIX-79/n-heptane using the pseudo-emulsion-based hollow-fiber strip dispersion (PEHFSD) technique

The extraction of Au(I) from alkaline cyanide solutions through PEHFSD was conducted in a microporous hydrophobic polypropylene hollow-fiber membrane contactor. The organic extractant LIX-79 (N,N-bis(2-ethyl hexyl)guanidine) in n-heptane was used. The alkaline cyanide feed solution containing Au(I) was passed through the tube side, and pseudo-emulsions of LIX-79/n-heptane and NaOH were passed through the shell side in counter-current mode, using a single microporous hydrophobic polypropylene hollow-fiber contactor for extraction and stripping. In PEHFSD the aqueous strip (0.2 M NaOH) solution is dispersed in the organic (12% LIX-79/n-heptane) membrane solution in a container with a mixing arrangement (impeller stirrer) designed to form a strip dispersion. The strip dispersion is circulated from the mixer to the membrane module to provide a constant supply of the LIX-79/n-heptane solution to the membrane pores. Various hydrodynamic and chemical parameters, such as variation in feed pH; gold cyanide concentration in feed; variation in concentrations of NaOH, LIX-79/n-heptane and Au(I); variation in feed, strip and LIX-79/n-heptane volume ratios and variation in feed and strippant flow rates, were investigated. Mass transfer modeling was performed and the validity of the model was evaluated with experimental data and found to tie in well with theoretical values. It was possible to concentrate Au(I) in product (NaOH) using the PEHFSD technique.