The Removal of Zn(II) Through Calix[4]Recorcinarene Derivative Based Polymer Inclusion Membrane From Aqueous Solution

In the present work, the transport of Zn(II) metal ion from an aqueous nitrate solution of different metal ions through a polymer inclusion membrane (PIM) containing calix[4]resorcinarene derivative used as a carrier were investigated. Zn(II)metal ion showing high permeability were transported through PIMs prepared from cellulose triacetate (CTA) as a polymeric support material and 2-NPOE as a plasticizer. Total Zn(II) concentration was determined with an Atomic Absorption Spectrometer (AAS) in the acceptor phase. The prepared PIM and supported liquid membrane (SLM) were characterized by using Scanning Electron Microscopy(SEM) and Atomic Force Microscopy (AFM) techniques. The effects of membrane composition, effects of type of plasticizer in the membrane, effects of carrier concentration, and the thickness of the membranes were examined in the facilitated transport experiments of Zn(II) ion through PIM. We compared the performance of SLM experiments under the optimum conditions identified by the PIM studies. Higher permeability coefficient values for Zn(II) was found for SLM, while lower values were ascertained for PIM. The kinetic parameters which have been calculated as the constant rate (k), permeability coefficient (P), flux (J) and diffusion coefficient (D).     

Elaboration and characterisation of a plasticized cellulose triacetate membrane containing trioctylphosphine oxyde (TOPO): Application to the transport of uranium and molybdenum ions

A cellulose triacetate (CTA) membrane containing trioctylphosphine oxyde (TOPO) as carrier and 2-nitrophenyloctyl ether (NPOE) as a plasticizer was prepared. The membrane CTA + NPOE + TOPO was characterised using chemical techniques as well as Fourier Transform InfraRed (FTIR) spectroscopy, X-ray diffraction and Scanning Electron Microscopy (SEM). The CTA membrane is characterised by well-defined pores; these pores are completely filled with the NPOE and carrier. Surfaces of membranes with TOPO are smooth. The systems constituted by the mixture of CTA + NPOE, CTA + NPOE + TOPO do not give any diffraction. This can be due to the absence of crystallization within the membrane. On the other hand, this result should be attributable to the amorphous state of the structure, which permits us to eliminate the mechanism of transfer of the ions by electron jump. A comparative study of transport across a polymer inclusion membrane (PIM) and a supported liquid membrane (SLM) containing the same carrier in chloroform has shown that uranium or molybdenum transport efficiency was increased using PIM instead of SLM. PIM showed higher stability than SLM, the flux of transport remain constant in the former case after 2 weeks.     

Zn(II), Cd(II) and Cu(II) separation through organic–inorganic Hybrid Membranes containing di-(2-ethylhexyl) phosphoric acid or di-(2-ethylhexyl) dithiophosphoric acid as a carrier

A membrane process for metal recovery from aqueous solutions was studied. Metal ions diffused from the feed solution to the stripping phase through an Hybrid Membrane containing di-(2-ethylhexyl) phosphoric acid (D2EHPA) and/or di-(2-ethylhexyl) dithiophosphoric acid (D2EHDTPA) as a carrier. Such membranes were prepared by a sol–gel route including cellulose triacetate and polysiloxanes. Transport behaviour was evaluated for both carriers under similar experimental conditions. The transport experiments reported here concerned transport at different cycles and selectivity towards different metal ions. Using D2EHPA the membrane provided a selective transport of zinc to the stripping compartment of the membrane cell, while copper and cadmium remained in the feed compartment. Whereas, using D2EHDTPA as carrier the transport rate increased and the selectivity profiles were inverted in relation with those of D2EHPA. With a mixture of both extracting agents it was observed an intermediate behaviour in selective transport, being possible to modulate it.     

Transport of U(VI) from sulphuric acid medium across supported liquid membrane (SLM) containing di-(2-ethylhexyl) phosphoric acid (D2EHPA)/n-dodecane as a carrier

This paper reports on the supported liquid membrane (SLM) based transport studies of U(VI) from sulphate medium using di-(2-ethylhexyl) phosphoric acid/n-dodecane as carrier. Polytetrafluoroethylene membrane was used as solid support and H₂SO₄ as receiver phase. The effects of various parameters such as receiver phase concentration, feed acidity, carrier concentration, U(VI) concentration, membrane thickness and membrane pore size on U(VI) transport had been investigated. With increase in H₂SO₄ concentrations and pH of feed solution there is an increase in U(VI) transport across the SLM. Similarly with increase in membrane thickness the U(VI) transport decrease whereas in case of pore size variation reverse results are obtained. The membrane thickness variation results showed that the U(VI) transport across the SLM is entirely diffusion controlled and the diffusion coefficient the D _(o) was calculated as 1.36 × 10^?7 cm² s^?1. Based on optimized condition, a scheme had been tested for selective recovery of U(VI) from ore leach solution containing a large number of other metal ions.     

Polymer inclusion membranes: The concept of fixed sites membrane revised

The mechanism of facilitated transport of metal ions across polymer inclusion membranes (PIMs) is revised on the basis of transport flux measurements and of new data brought by techniques sensitive to local inter-molecular interactions and molecular diffusion. Cellulose triacetate (CTA) membranes built with two types of inclusion carriers: a liquid one Aliquat 336 and a crystalline one Lasalocid A, both able to carry metal ions across PIMs and supported liquid membranes (SLMs) made of the same components, have been compared. Both PIM systems show similar effects for what concern the need of a carrier threshold concentration for the occurrence of a transport flux across PIM as revealed by flux and fluorescence correlation spectroscopy (FCS) measurements, and the dependence of the chemical nature of plasticizers on the metal ion flux. These systems also present similar Raman and far IR signatures of structural evolution of PIMs with the increase of the carrier concentration within the CTA matrix.

All the presented data are interpreted as concern PIMs, according to an evolution of chemical interactions between components of the polymeric membrane able to lead to a phase transition. This phase transition type of the carrier-plasticized polymer system is induced by the increase of carrier concentration in the polymer chains. The PIM progressively organizes itself like a liquid SLM because of the enhancement of preferential solvent interactions between the carrier and the plasticizer.

The main conclusion of this study is that the classically adopted “hopping” transport mechanism between fixed carrier sites in a PIM does not apply to such carrier chemically unbound to polymer membrane systems.     

Quantitative analysis of transport process of cerium(III) ion through polymer inclusion membrane containing N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as carrier

The facilitated transport mechanism of cerium(III) ions through polymer inclusion membrane (PIM) consisting of cellulose triacetate (CTA) as a polymer matrix, 2-nitrophenyl n-octyl ether (NPOE) as a solvent and N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as a carrier was studied. In order to evaluate the mass transport phenomena in the PIM, a mathematical model was derived from the Fick's first law and the equations for the extraction and the material balance. Methods to determine the values of the transport parameters such as the diffusion coefficient are described, and the dependency of the flux on the experimental condition was calculated. The model is very useful as a design tool to analyze and optimize the concentration process of low level radioactive wastewater using the PIM.     

Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier.

A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.     

Preparation of CTA-based polymer inclusion membrane using calix[4]arene derivative as a carrier for Cr(VI) transport

In this work, the transport of Cr(VI) ions from an aqueous donor phase solution to an acceptor phase that contained an acetic acid/ammonium acetate buffer at pH 5 through a polymer inclusion membrane (PIM) containing p-tert-butylcalix[4]arene amine derivative as carrier was studied. The Cr(VI) passed through a PIM comprised of cellulose triacetate as a support and 2-NPOE as a plasticizer. The transport efficiency of Cr(VI) was studied under various experimental conditions, such as effect of carrier concentration, acceptor phase pH, type of plasticizer in the membrane, stirring rate and membrane thickness. The kinetic parameters were calculated as rate constant (k), permeability coefficient (P), and flux (J). The transport efficiency of Cr(VI) was observed to be 95.07 % after 10 h under optimized conditions. The prepared PIM was characterized with Fourier transform infrared spectroscopy and the atomic force microscopy techniques as well as with contact angle measurements. This is an effective method for the removal of Cr(VI) which is toxic for human body and environment from the waste water.     

Studies of Anion Transport Through Supported Liquid Membrane

Abstract

Transport studies of anions were investigated through cellulose triacetate supported liquid membrane. The experimental variables explored were concentration of anions, sodium hydroxide, and stirring speed. The two-channel membrane system has been explored for the transport of carbonate ions from source to receiving phases. Carbonate ions are selectively transported through the cellulose triacetate supported liquid membrane in comparison with that of nitrate and sulfate. Sulfate and nitrate anions are strongly held in the cellulose triacetate membrane, and then stripped out later. Carbonate ions are loosely bound to the cellulose triacetate membrane and stripped out earlier.     

Mechanism of facilitated saccharide transport through plasticized cellulose triacetate membranes

Mechanistic insight is gained for saccharide transport through plasticized cellulose triacetate (CTA) membranes containing lipophilic ion-pair transport carriers. The molecular structures of the different membrane components are systematically varied and diagnostic transport characteristics such as saccharide–carrier diffusion constant and saccharide extraction constant are determined. The observed percolation thresholds support a jumping mechanism, however, the diffusion constants are found to decrease as the size of the saccharide, carrier cation, and carrier anion increase, indicating that the rate-limiting step in the transport process involves diffusion of a complex comprised of all three components. The data is reconciled in terms of mobile-site jumping mechanism where the saccharide is relayed along a sequence of ion-pair carriers that are locally mobile. In an attempt to improve saccharide selectivity, calix-[4]-arene dicarboxylates were evaluated as potential ditopic transport carriers. This produced no major change in saccharide extraction constants.     

Facilitated transport of copper(II) across supported liquid membrane and polymeric plasticized membrane containing 3-phenyl-4-benzoylisoxazol-5-one as carrier

The potential of 3-phenyl-4-benzoylisoxazol-5-one (HPBI) as metal extractant has been evaluated for the first time for Cu(II) transport from aqueous nitrate solutions by supported liquid membrane (SLM) in the solvents chloroform, 2-nitro phenyl octyl ether (NPOE) and dodecyl nitro phenyl ether (DNPE). The efficiency of the membrane transport was optimized as a function of pH, temperature, aqueous phases and membrane composition. It follows the sequence CHCl₃ > DNPE > NPOE. The results suggested that the transport mechanism was mainly controlled by the diffusion of the Cu(PBI)₂ complex in the membrane core. A comparative investigation of Cu(II) transport ions has been made between SLM and polymeric plasticized membrane (PPM), containing HPBI with NPOE and DNPE as organic solvents or plasticizers in order to evaluate the feasibility of PPM with HPBI.     

Uphill transport of uranium across a liquid membrane

A liquid membrane was prepared by entrapping tributyl phosphate (TBP) in a cellulose triacetate (TAC) membrane matrix. The membrane was used to separate two aqueous solutions, one acidic and the other alkaline, which were saturated with TBP to prevent its loss from the membrane. Uphill transport of uranium was achieved with the TBP liquid membrane. Both solutions containing TBP were stirred magnetically. When the initial concentration of uranium in the two solutions was 3.5 mM, more than 50% of the uranium contained in the acidic solution was transported to the alkaline solution across the liquid membrane within 5 h. A transport mechanism is described in which the membrane-bound TBP acts as a mobile carrier for uranium.     

钴离子在P507为载体的支撑液膜中的传输

本文用国内的膜材料设计了以2-乙基已基膦酸单(2-乙基已基)酯(HEH(EHF),P_(507))为载体的支撑液膜迁移钴的实验,获得的数据为深入实验提供了依据.基本原理支撑液膜(SLM)是依靠微孔塑料薄膜(支撑体)微孔的毛细管作用将含萃取剂(载体)的有机溶液吸附在支撑体上.P_(507)萃取钴表示为:     

Stability of supported liquid membranes containing Acorga P-50 as carrier

The coupled transport of copper(II) ions through supported liquid membranes (SLM) was examined in zeroth order steadystate kinetic regime using Acorga P-50 as carrier. SLM life-times were estimated using a new method based on kinetic analysis. The influence of different experimental conditions on the transport rate allowed to establish various factors determining membrane stability. SLM life-time seems to depend in a clearcut way on both the type of polymeric support and the nature of liquid membranes suggesting that solute-solvent (and polymer solvent) interactions play a dominant role in membrane stability. It was shown that water transport, if any, occurs only through empty pores of the polymeric support. No clear effect of osmotic pressure gradient on liquid membrane stability was found.     

Studies on ion transport of some rare earth elements through solvating extractants immobilised on supported liquid membrane

The studies on ion transport of terbium and dysprosium through a porous supported liquid membrane (SLM) containing TOPO (trioctyl phosphine oxide) and TBP (tributyl phosphate) as immobilised carriers have been carried out. The effect of stirring of bulk solutions on permeability coefficient has been investigated. The permeability coefficient increases with increase in pH of source phase from 0–6, and hydrogen ion concentration from 0.01 to 0.1 M of receiving solution. The dependency of permeability coefficient on the carrier concentration has been explored. The effect of ammonium thiocyanate concentration on permeability coefficient has been studied. In order to develop a method for enrichment of rare earth elements, further investigations were carried out by using a hollow fibre membrane extractor. The mechanism of ion transport of terbium and dysprosium in SLM systems has been explained.     

Performance and stability of supported liquid membranes using LIX 984N for copper transport

The transport of copper through supported liquid membranes (SLM) using Celgard and Accurel membranes as supports and a novel commercial extractant LIX 984N as a carrier was investigated. LIX 984N provides good overall transport performance for copper from the acidic and dilute solution to the concentrated copper sulfuric acid. The instability of the supported liquid membranes using Celgard 2500 as the membrane support has been studied. It has been demonstrated that initially the surface shear forces due to stirring are a main cause for membrane liquid loss leading to SLM instability. However, during long term permeation no single instability mechanism dominants. The instability of long term operation involves a complex interaction of a number of factors, including surface shear forces, Marangoni effects, changes to membrane morphology, Bernard instabilities and membrane preparation protocal.     

Selective removal of Cu versus Ni, Zn and Mn by using a new carrier in a supported liquid membrane

A study on transport, kinetic selectivity and stability in SLM operations using a new carrier, the molecule 2-hydroxy-5-dodecylbenzaldehyde (2H5DBA) in kerosene, is described. A simple transport model is derived to evaluate the mass transfer coefficient in the membrane. Finally a comparison with the di-(2-ethylhexyl) phosphoric acid (D2EHPA) carrier in kerosene is made. The SLM system was employed and tested in the removal of Cu²⁺ from wastewater by using the operating conditions obtained from L–L extraction tests. Studies on the kinetics of copper extraction by using the 2H5DBA showed that complexation reaction is very fast. Transport tests were performed at different carrier concentrations (10%, 30%, 50% (v/v)) showing the improvement of SLM performance with increasing its concentration. Operating the SLM at optimum conditions (50% (v/v) 2H5DBA concentration in kerosene, feed pH 5, strip pH 2.2) final copper concentrations in the feed and strip phases were, respectively, 2.0 and 47.0 mg L⁻¹, starting from 50 mg L⁻¹ in the feed, meaning a significant up-hill transport. The fluxes (J) were calculated by fitting the experimental data of copper concentration in the feed by an exponential equation. They were used to calculate the transport (kinetic) selectivities of Cu²⁺ SLM separation over Ni²⁺, Zn²⁺ and Mn²⁺, given by the ratio J₀(Cu)/J₀(M), where M = Ni, Zn and Mn. The values were 37.4, 48.2 and 42.1, respectively. Transport and stability tests at the optimal carrier concentration by using the 2H5DBA and the D2EHPA in kerosene were carried out to compare them in terms of flux, lifetime and mass transfer coefficients. Experimental data evidenced for 2H5DBA a lower copper flux (8.67 mmol h⁻¹ m⁻² versus 36.71 mmol h⁻¹ m⁻²), a lower lifetime (20 h versus 57 h) and lower mass transfer coefficient in the membrane (3.00 × 10⁻⁷ m s⁻¹ versus 2.00 × 10⁻⁶ m s⁻¹) but the selectivity of the separation process can overcome the disadvantages.     

Selective transport of cesium ion in polymeric CTA membrane containing calixcrown ethers

A series of calixcrown ethers for which the cavity size of the crown ring is varied from crown-6 to crown-7 to crown-8 were examined for the transport abilities toward alkali metal ions. These ligands were incorporated into supported liquid membranes (SLMs) and into polymer inclusion membranes (PIMs) composed of cellulose triacetate (CTA) as a support and 2-nitrophenyl octyl ether (NPOE) and tris(2-butoxyethyl) phosphate (TBEP) as a plasticizer. In both membrane systems, calixcrown-6 showed the best selectivity toward a cesium ion over other alkali metal ions. The polymeric CTA membrane showed more rapid transport rate as well as higher durability than did the SLMs.     

Extraction of glyphosate by a supported liquid membrane technique

The possible application of the supported liquid membrane (SLM) technique for the extraction of glyphosate is presented. For the extraction of this compound the SLM system has been applied with utilisation of Aliquat 336 as a cationic carrier incorporated into the membrane phase. The extraction efficiency of glyphosate [N-(phosphonomethyl)glycine] is dependent on the donor phase pH, carrier concentration in the organic phase and NaCl concentration in the acceptor phase. The optimal extraction conditions are: donor phase pH>11, acceptor phase of 2 M NaCl solution and the organic phase composed of 20% (w/w) Aliquot 336 solution in di-hexyl ether. Counter-coupled transport of chloride anions from the acceptor phase to the donor phase is a driving force of the mass transfer in this system.     

Carrier-mediated extraction of bipyridilium herbicides across the hydrophobic liquid membrane

Supported liquid membrane (SLM) method for preconcentration and enrichment of the two bipyridilium herbicides, namely diquat and paraquat, from environmental water samples has been developed. The permanently charged cationic herbicides were extracted from a flowing aqueous solution to a stagnant acidic acceptor solution across a liquid membrane containing 40% (v/v) di-(2-ethylhexyl) phosphoric acid dissolved in di-n-hexyl ether. The mass transfer of analytes is driven by the counter-coupled transport of hydrogen ions from the acceptor to the donor phase. The efficiency of the extraction process depends on the donor solution pH, the amount of the mobile carrier added to the liquid membrane and the concentration of the counter ion in the acceptor solution. The applicability of the method for extraction of these quaternary ammonium herbicides from environmental waters was also investigated by spiking analyte sample solutions in river water. With 24 h sample enrichment concentrations of diquat and paraquat down to ca. 10 ng/L could be detected in environmental waters.