Polymer Inclusion Membrane System Research Articles

Separation of acetochlor through polymeric membrane system

In this study, an acetochlor belonging to the herbicide group was transported using a synthesized polymer inclusion membrane (PIM). Tricapryl-methylammonium chloride (Aliquat 366) and cellulose triacetate (CTA) were used as carrier and support material, respectively, in the membrane structure. The acetochlor samples taken during the transport from the donor phase containing 0.1 M HCl to the acceptor phase containing pure water were determined by Liquid Chromatography Mass Spectrometry (LC-MS/MS). The permeability coefficient (P), rate constant (k), and material flow rate (J) values were calculated at the end of the transportation processes. The recovery factor (%) was determined to be 91.2 % at the end of 240 min of transportation time. The effects of relative amounts of the target analyte, carrier, and acid type on the donor phase were determined, as well as those of the acceptor phase pH and stirring effect. The results achieved in this study suggest that a stable and environmentally sustainable polymer inclusion membrane system might be used to effectively transport acetochlor.

Separation of Co from Ni and Li from chloride media using polymer inclusion membrane system with thiosalicylate based ionic liquid

Separation of Co from Ni and Li from chloride media using polymer inclusion membrane system with thiosalicylate based ionic liquid

Modelling and optimization of a new complexing retardant-enhanced polymer inclusion membrane system for highly selective separation of Zn2+ and Cu2+

Polymer inclusion membranes (PIMs) have much application potential for metal ion separation. However, its separation selectivity highly depends on the extractant, and new efficient extractants are difficult to develop. This work proposes another approach, i.e., adding a complexing retardant to enhance the selectivity. The impurity ion (e.g., Cu2+) was retarded in the feed solution by the complexing retardant (e.g., citric acid), while the target ion (e.g., Zn2+) was transported across PIM. To reveal the enhancement mechanism, a mass transfer mathematical model was established. Contrast experiments proved that the complexing retardant can significantly enhance the overall separation coefficient βoverall,exp. The βoverall,exp of a conventional PIM system was 61.80, while βoverall,exp increased to 853.45 after the retardant was added. The effects of retardant concentration, initial pH of feed solution, membrane thickness, extractant dosage, and plasticizer dosage on the retardant-enhanced PIM system were investigated. Model calculation results agreed well with the experimental data. The maximal βoverall,exp 17525.68 was obtained at the optimal separation conditions of [CA] f,0 = 0.02 M, pHf,0 = 4.5, [H2SO4]s,0 = 0.5 M, and the optimal composition of the PIM casting solution, i.e., PVC: P507: DBP: THF = 0.125 g: 0.188 mL: 0.032 mL: 10 mL. Further studies indicated that the retardant mechanism was reflected in the difference increase of interfacial partition coefficients PZn2+,f and PCu2+,f. Finally, the optimization strategies of the separation effects for the retardant-enhanced PIM system are discussed in depth based on the simulated calculation.

Optimization of Cr(III) transport in a polymer inclusion membrane system through experimental design strategies

Optimization of Cr(III) transport in a polymer inclusion membrane system through experimental design strategies

Some Critical Remarks about Mathematical Model Used for the Description of Transport Kinetics in Polymer Inclusion Membrane Systems.

Two kinetic models which are applied for the description of metal ion transport in polymer inclusion membrane (PIM) systems are presented and compared. The models were fitted to the real experimental data of Zn(II), Cd(II), Cu(II), and Pb(II) simultaneous transport through PIM with di-(2-ethylhexyl)phosphoric acid (D2EHPA) as a carrier, o-nitrophenyl octyl ether (NPOE) as a plasticizer, and cellulose triacetate (CTA) as a polymer matrix. The selected membrane was composed of 43 wt. % D2EHPA, 19 wt. % NPOE, and 38 wt. % CTA. The results indicated that the calculated initial fluxes (from 2 × 10−11 up to 9 × 10−10 mol/cm2s) are similar to the values observed by other authors in systems operating under similar conditions. It was found that one of the most frequently applied models based on an equation similar to the first-order chemical reaction equation leads to abnormal distribution of residuals. It was also found that application of this model causes some problems with curve fitting and leads to the underestimation of permeability coefficients and initial maximum fluxes. Therefore, a new model has been proposed to describe the transport kinetics in PIM systems. This new model, based on an equation similar to the first-order chemical reaction equation with equilibrium, was successfully applied. The fit of this model to the experimental data is much better and makes it possible to determine more precisely the initial maximum flux as the parameter describing the transport efficiency.

New insights into the interfacial behavior and swelling of polymer inclusion membrane (PIM) during Zn (II) extraction process

Polymer inclusion membrane (PIM) has been progressively utilised in various chemical engineering applications. Understanding the interfacial interactions between PIM surface and surrounding solutions is significantly important for the industrial application of PIM systems. In this work, interfacial behavior of the PIM was studied during Zn(II) extraction process. The real-time change of the PIM under various environmental conditions was monitored by Quartz crystal microbalance with dissipation monitoring. Water penetration into the PIM layer was demonstrated when the PIM was in contact with Milli-Q water. Atomic force microscopy imaging confirmed that the swollen PIM had a looser network and rougher surface, as compared to its original state. When switching the surrounding environment to ZnSO4 solution, higher Zn(II) concentration could induce microstructure change and more significant membrane swelling in the PIM layer. Our results provide valuable implications for the design of effective PIM systems towards practical applications in wastewater treatment and hydrometallurgy.

An Efficient Polymer Inclusion Membrane-Based Device for Cd Monitoring in Seawater.

A novel and simple device that includes a polymer inclusion membrane (PIM) has been prepared and tested for the first time to detect low concentration levels of cadmium in seawater. The ionic liquid trihexyl (tetradecyl) phosphonium chloride (THTDPCl) has been shown to be an effective extractant when incorporated in a PIM that uses cellulose triacetate (CTA) as a polymer. However, it has been reported that the use of a plasticizer is mandatory to ensure an effective transport, which uses both ultrapure water and a nitric acid solution as a stripping phase. A special device incorporating a PIM made of 50% CTA, 40% nitrophenyl octyl ether (as a plasticizer), and 10% THTDPCl, effectively allows the quantitative transport and preconcentration of 10 µg L−1 Cd from seawater samples to a stripping phase consisting of 0.5 M HNO3 solution. This study shows that the efficiency of the PIM system is not affected by high salinity nor the presence of large amounts of other ions, and can thus facilitate Cd monitoring in seawater samples.

Selective transport and simultaneous separation of Cu(II), Zn(II) and Mg(II) using a dual polymer inclusion membrane system

A dual polymer inclusion membrane (PIM) system is proposed for the simultaneous separation and enrichment of Cu(II), Zn(II) and Mg(II). PIMs containing 2-hydroxy-5-nonylacetophenone oxime (LIX 84I) and di(2-ethylhexyl) phosphoric acid (D2EHPA) as carriers were prepared in order to separate Cu(II) and Zn(II) from solutions containing multiple cations. The transport results indicate that the simultaneous separation of the three metal ions is highly dependent on the feed pH. At pH 2, Zn(II) and Cu(II) can be selectively transported into the respective stripping solutions, leaving Mg(II) in the raffinate. The dynamic transport model was established and confirms that the kinetic reaction rate is the controlling factor in the transport and separation of the metal ions. XPS and IR spectral analyses were carried out to elucidate the membrane extraction mechanism. As a novel application of the PIMs, the stability and uphill effect of the dual PIM system were also tested and has been compared with the performances of liquid membrane systems.

Polimerowa membrana inkluzyjna z trioctanu celulozy (CTA) plastyfikowanego eterem 2-nitrofenylooktylowym

The article describes a structure of the polymer inclusion membrane (PIM) with cellulose triacetate (CTA) matrix and its use for the separation of chromium(III) ions from aqueous solutions. Di(2-ethylhexyl) phosphoric acid (D2EHPA) was used as a ion carrier. The efficiency of Cr(III) ions transport in the test system was dependent on the carrier concentration in the membrane. In periodic processes the performance of PIM system was stable, which indicates the possibility of using it for the selective separation of Cr(III) from a mixture of Cr(III)/Cr(VI) ions.

Determination of the initial flux of polymer inclusion membranes

The calculation of the initial flux (J0) of a polymer inclusion membrane (PIM) is an important task in characterizing its transport performance. This article outlines the difficulties in reliably determining J0 of a model PIM system for the extraction of U(VI) from its sulfuric acid solutions. The membrane consists of poly(vinyl chloride) and di-(2-ethylhexyl)phosphoric acid (D2EHPA). Several approaches for determining J0 are compared and most reliable results are achieved when the transient U(VI) solution concentration is fitted with an exponential decay function (Ψ=a1+a2e-ast), the first derivative of which ((dΨ/dt)t=0) is used to calculate J0.The use of a quantity referred to as dimensionless initial flux which is independent of the solution volume, membrane surface area and initial concentration of the solute is proposed. It will allow a more meaningful comparison of PIM transport properties on the basis of extraction and transport data obtained under different experimental conditions.The conclusions derived in this study are applicable to other membrane separation systems such as those incorporating supported liquid membranes.

Facilitated Transport of Cr(VI) through Polymer Inclusion Membrane System Containing Calix[4]arene Derivative as Carrier Agent

Chromium(VI) is one of the major toxic elements present in environmental samples. The polymer inclusion membrane (PIM), has been developed to provide metal ion transport with high selectivity. This study was conducted to discover efficient methods for removing Cr(VI) from wastewater. A functionalized calix[4]arene carrier 1 in a PIM system was used to transport Cr(VI) from an acidic aqueous donor phase solution to an acceptor phase that contained an acetic acid/ammonium acetate solution at pH 6. The prepared PIM was characterized with Fourier Transform Infrared (FT-IR) spectroscopy and the Atomic Force Microscopy (AFM) techniques as well as with contact angle measurements. The efficiency of Cr(VI) transport through the PIM was investigated by studying the effects of carrier concentration on the membrane phase as well as by measuring the amount of plasticizer in the membrane, the pH in the acceptor phase and the membrane's stability and thickness. The kinetic parameters were calculated as rate constant (k), permeability coefficient (P), flux (J) and diffusion coefficient (Do). The transport efficiency of Cr(VI) was observed to be 98.61% after 10 h under optimized conditions. The experimental results show that Cr(VI) can transport from the donor phase to the acceptor phase with high efficiency through the PIM. The results also suggest that the transport efficiency of the PIM was reproducible and that a PIM is effective for long-term separation processes.

PNP-16-crown-6 derivatives as ion carriers for Zn(II), Cd(II) and Pb(II) transport across polymer inclusion membranes

Transport rate of metal cations can be explained by the size of substituents, namely larger substituents such as 7 and 8 prefer Pb(II) cations. The bis-PNP-lariat ethers remove Zn(II), Cd(II) and Pb(II) more efficiently than simple PNP-lariat ethers. The increase of linker length in the bis-PNP-lariat ether molecules lowers the metal cations’ transport rate. In addition, the synergetic effect for lead(II) transport across polymer inclusion membrane (PIM) with PNP-lariat ether 9 and DNNS was using PNP-lariat ethers—carriers 1 and 2 in a PIM system, Zn(II) and Cd(II) were transported with low selectivity from acidic aqueous source phase solutions. The ether 3 used to transport Zn(II) and Cd(II) cations from aqueous phase at pH 5.0 into hydrochloric aqueous solution shows high selectivity of Cd/Zn, but small efficiency of process. The competitive transport of equimolar mixtures of Zn(II), Cd(II), and Pb(II) ions from aqueous source phase ( c Me = 0.0001 M) across polymer inclusion membranes with mono- and bis-PNP-lariat ethers as ion carriers has been studied. In these experiments the influence of substituents attached to the simple PNP-lariat ether molecules on the selectivity and efficiency of Zn(II), Cd(II), and Pb(II) transport through PIMs containing cellulose triacetate as the support and o-nitrophenyl pentyl ether as the plasticizer was investigated. The PIM contained 0.3 M lariat ether and 4.0 ml ONPPE per 1.0 g CTA. The transport selectivity order for the PIM with 7 and 8 was: Pb(II) > Cd(II) > Zn(II), whereas for 1 and 4 the order: Zn(II) > Cd(II) ≥ Pb(II) was found. We also found out that the transport of metal cations across PIM with bis-lariat ether 9 occurs at the same level when sodium nitrate in source phase is in the range of 10 −3 to 0.10 M.

LIX ®-loaded polymer inclusion membrane for copper(II) transport : 1. Composition–performance relationships through membrane characterization and solubility diagrams

The effects of different components on the performance of a selected polymer inclusion membrane (PIM) system developed for copper transport were assessed by means of different analytical techniques. Copper(II) transport data, thermal analysis, transmission infrared mapping microspectroscopy (TIMM) and AFM were used to characterize chemical and physical behavior of PIMs with different compositions. The prepared membranes, made using cellulose triacetate (CTA) as support, tris(2- n-butoxyethyl) phosphate (TBEP) as plasticizer, together with an additive (ethanol), and LIX ® 84-I, LIX ® 984 or LIX ® 54-100 as carrier, showed increasing copper(II) permeabilities in the order LIX ® 54-100 < LIX ® 984 < LIX ® 84-I. Membrane permeabilities increased up to 2.6-fold in the strip solution side for LIX ® 84-I PIMs cast with ethanol, and Cu(II) accumulation within the membrane was observed to vary with the amount of additive. The modifications of the transport properties of the PIMs were satisfactorily correlated with the distribution profiles of the membrane components (obtained by TIMM), glass transition temperatures, casting method and topographic structure of the films with the aid of a Teas graph implemented for PIM applications. From this graph it was possible to interpret the interactions between the different membrane components in a phenomenological way, thus contributing to improve the understanding of the role played by each one in the development of a more efficient PIM system for copper transport when using LIX ® reagents as carriers.

Selective ω-thiocaprolactam-based recovery of Au(III) from chloride media in solvent extraction and polymer inclusion membrane systems

The selective transport of Au(III) over Cu(II) and Hg(II) using ω-thiocaprolactam as extractant and carrier in solvent extraction and polymer inclusion membrane transport experiments is discussed. Solvent extraction experiments were carried out using the extractant dissolved in chloroform to establish the chemical equilibria involved in the Au(III)-ω-thiocaprolactam separation system. Au(III) is extracted into the organic phase quantitatively ( E (%) > 99%) at low extractant concentrations from aqueous HCl solutions. Cu(II) extraction kinetics is slow compared to Au(III) extraction, allowing for the efficient separation of both metals. Polymer inclusion membranes (PIMs) are designed as alternatives to the use of high amounts of hazardous and expensive reagents. Several stripping phases were tested. Up to 70% of Au(III) can be recovered from 1 M HCl feed aqueous phase solutions. Interference from Cu(II) or Hg(II) is negligible at short times (160 min) in competitive ([M(II, III)] 0,feed = 0.1 mM) membrane transport experiments using a cellulose triacetate/NPOE/ω-thiocaprolactam PIM and a potassium iodide–hydrochloric acid aqueous stripping solution. Apparent diffusion coefficients in the membrane for Au(III) and Hg(II) in the system were estimated to be 2.2 × 10 −11 and 3.4 × 10 −15 m 2 s −1, respectively.

Metal ion recognition. The interaction of cobalt(ii), nickel(ii), copper(ii), zinc(ii), cadmium(ii), silver(i) and lead(ii) with N-benzylated macrocycles incorporating O2N2-, O3N2- and O2N3-donor sets

The interaction of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) with a series of mixed-donor, N-benzylated macrocyclic ligands incorporating O2N2-, O3N2- and O2N3-donor sets has been investigated. The log K values for the respective 1 ∶ 1 complexes in 95% methanol (I = 0.1 mol dm−3; Et4NClO4, 25 °C) have been determined potentiometrically and the results compared with the values obtained previously for the parent (non-benzylated) macrocyclic systems. Examples of N-benzylation of individual parent macrocycles leading to enhanced discrimination for silver(I) are presented. In the case of a dibenzylated O3N2-ring and a tribenzylated O2N3-ring, both 17-membered, high selectivity for this ion was observed relative to the other metal ions investigated. Competitive mixed-metal transport experiments across a bulk chloroform membrane have been performed using the benzylated derivatives as ionophores. For each experiment the source contained equimolar concentrations of the above metal ions and transport was performed against a pH gradient; the aqueous source and receiving phases were buffered at pH 4.9 and 3.0, respectively. In parallel to the log K results, transport selectivity for silver(I) was exhibited by the di- and tri-benzylated ligands mentioned above. The remaining ligands proved to be poor ionophores, showing no significant metal ion transport under the conditions employed. In a further study, high silver ion (transport) selectivity was maintained when the above tribenzylated ligand was incorporated as the ionophore in a polymer inclusion membrane system. Single metal and mixed (seven-metal) solvent extraction experiments employing similar aqueous source and chloroform phases to those used in the bulk membrane transport runs have also been performed for the tribenzylated ligand derivative; significant selectivity for silver was again maintained in these solvent extraction experiments. An X-ray study of [AgL]ClO4 (where L is the above-mentioned dibenzylated derivative) confirms that all donor atoms of the macrocycle coordinate to the silver ion; the latter is five-coordinate with the complex cation exhibiting a highly distorted trigonal bipyramidal geometry.

Properties of 4-(1′- n-tridecyl)pyridine N-oxide in the extraction and polymer inclusion membrane transport of Cr(VI)

The N-oxide of 4-(1′- n-tridecyl)pyridine (TDPNO) is a novel agent which could be used for the separation of Cr(VI) from aqueous solutions of sulphuric acid. The distribution constants ( K D) of TDPNO in the systems: toluene/0.5 M (Na, H) 2SO 4 and toluene- n-heptane (3:1) mixture/0.5 M (Na, H) 2SO 4, were found to be 2350±30 and 2180±20, respectively. The protonation constant of TDPNO ( K H=12.0±0.1) was also determined. The interfacial activity of TDPNO in the systems hydrocarbon/water was found to be strongly dependent upon the Lewis basicity of hydrocarbons. The chromium(VI) extraction and transport with TDPNO in the CTA-based polymer inclusion membrane system were found to be strongly dependent upon the concentration of sulphuric acid in the aqueous and/or source phase, respectively. The complex L·H 2CrO 4, where L stands for TDPNO, was found to occur in the organic phase and/or at the source phase/membrane phase boundary.

Properties of the transport of alkali metal salts through polymeric membranes containing benzo-18-crown-6 crown ether functional groups

Lightly crosslinked polymeric membranes were created by photopolymerization of di(ethylene glycol) ethyl ether acrylate, 4′-vinylbenzo-18-crown-6 and a small amount of hexamethylene diacrylate monomer. These membranes were utilized to gain an improved understanding of the behavior of fixed site carrier membranes (FCMs) under ion transport conditions. Crown ether groups were ideal reactive sites because of the extensive studies which have been completed on their complexation, and the one chosen for these studies provides selective complexation for potassium over other alkali metal ions. Several classes of parameters were investigated, with primary emphasis on the composition of the solution in contact with the membrane, and separately, the membrane composition. The effects of some of the material properties of the membrane polymers were also investigated, with the most notable being the macroscopic swelling. The results of this study illustrate that the flux of the salts through these solid membranes is larger than that achieved with comparable liquid membrane (LM) and polymer inclusion membrane (PIM) systems in experiments with comparable solute concentrations and carrier species. The increase in transport rate is presumably due to the extremely large concentration of reactive sites that are able to be incorporated into the membranes because of their production method. The normalized flux values (depending on the level of functionalization) ranged up to 58 000–72 000 mol(m 2 s) −1(mol/l) −2 when multiplied by 10 7. These normalized flux values are up to 3 orders of magnitude larger than those obtained under similar experimental conditions with LM and PIM systems. The large reactive site concentration and highly hydrated nature of these membranes does produce reduced values of selectivity than those with LM and PIM systems. The hydrated nature of the membrane interior provides radically different behavior from traditional LM and PIM systems with variation of the anion accompanying the cation during transport. In fact the trend of flux as a function of anion hydrophilicity is contrary to that obtained in LM systems.