Selective uphill Zn2+ transport via a bulk liquid membrane using an azacrown ether carrier (original) (raw)
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Selective transport of zinc and copper ions by synthetic ionophores using liquid membrane technology
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2012
This work highlights the role of synthetic carrier (ionophore) in the separation of heavy metal ions. A new series of ionophores; 4,4 0-nitrophenyl-azo-O,O 0-phenyl-3,6, 9-trioxaundecane-1,10-dioate (R 1), bis[4,4 0 nitro-phenylazonaphthyl-(2,2-dioxydiethylether)] (R 2) 1,8-bis-(2-naphthyloxy)-3,6-dioxaoctane (R 3), 1,11-bis-(2-naphthyloxy)-3,6,9trioxaunde-cane (R 4), 1,5-bis-(2-naphthyloxy)-3-oxa-pentane (R 5) have been synthesized and used as extractant as well as carrier for the transport of various metal ions (Na ? , K ? , Mg 2? , Ni 2? , Cu 2? and Zn 2?) through liquid membranes. Effect of various parameters such as metal ion concentration, ionophore concentration, liquid-liquid extraction, back extraction, comparison of transport efficiency of BLM and SLM and different membrane support (hen's egg shell and PTFE) have been studied. In BLM ionophores (R 2-R 5) transport Zn ? at greater extent and the observed trend for the transport of Zn 2? is R 2 [ R 4 [ R 3 [ R 5 respectively. Further transport efficiency is increased in SLM. In egg shell membrane ionophores (R 2-R 5) transport Zn ? due to their non-cyclic structure and pseudo cavity formation while ionophore R 1 transports Cu 2? ions at greater extent due to its cyclic structure and cavity size. Among the membrane support used egg shell membrane is found best for the transport of zinc ions because of its hydrophobic nature and exhibits electrostatic interactions between positively charged zinc ions and-COOH group of egg shell membrane. Thus structure of ionophores, hydrophobicity and porosity of the membrane support plays important role in separation of metal ions.
Modelling of zinc (II) transport through a PC-88A supported liquid membrane
Desalination, 2008
Zinc has been permeated through a flat-sheet supported liquid membrane, using 2-ethylhexylphosphoric acid mono-2-ethylhexyl ester (PC-88A) in kerosene. Liquid-liquid experiments were conducted as a function of aqueous pH (1-6) to establish optimum conditions for both extraction and stripping of the metal. A mass-transfer model was developed to predict the extent of Zn(II) permeation through the supported liquid membrane (SLM) under different experimental conditions. The effect of stirring rate, carrier concentration and temperature upon metal transport has been evaluated. The metal flux has been derived taking into account stagnant layer aqueous diffusion and liquid membrane diffusion as controlling factors. The overall transport evaluated from the proposed resistances model was in reasonable agreement with those obtained from experimental data. Under the studied experimental conditions the resistance of the intrinsic organic phase is masked by the aqueous stagnant layer resistance; therefore the Zn (II) transport through the liquid membrane is mainly controlled by the hydrodynamic of the system.
Journal of Chemistry, 2017
The facilitated passage of Zn (II) across flat sheet supported liquid membrane saturated with TDDA (tri-n-dodecylamine) in xylene membrane phase has been investigated. The effect of acid and metal ion concentration in the feed solution, the carrier concentration in membrane phase, stripping agent concentration in stripping phase, and coions on the extraction of Zn (II) was investigated. The stoichiometry of the extracted species, that is, complex, was investigated on slope analysis method and it was found that the complex (LH)2·Zn(Cl2) is responsible for transport of Zn (II). A mathematical model was developed for transport of Zn (II), and the predicted results strongly agree with experimental ones. The mechanism of transport was determined by coupled coion transport mechanism with H+and Cl−coupled ions. The optimized SLM was effectively used for elimination of Zn (II) from waste discharge liquor of galvanizing plant of Zn (II).
Transport of zinc complexes through an anion exchange membrane
Desalination, 2008
The transport of zinc complexes ions through an anion exchange membrane was evaluated by the treatment of solutions with and without cyanide. The ionic transport was analyzed as a function of the applied current density and of the cyanide and hydroxyl concentration. Experimental results showed that the ionic transfer in electrodialysis was mainly affected by concentration. There is an ideal molar relationship among the concentration of the cyanide ions, hydroxyl and zinc ions, in solution, in which the zinc transport is maximized. For values above or below this, the transport decreases. Zinc extraction from solution containing CN ! was more effective when the current density of 29 mA.cm !2 was applied. The current-voltage curves (CVC) of the anion exchange membrane show that the electrical resistance of the AMV membrane increases with the presence of the zinc-cyanide complex in the solution.
This paper presents experimental results obtained at the transport of metal cations, such as Cr (III), Mn (II) and Zn (II), through a kerosene liquid membrane in the presence of D2EHPA and Cyanex 301. The influence of the metal cation concentration in the feed phase and the molar ratio Cyanex 301: D2EHPA on the system efficiency was studied. The transport process assay was done by calculating the efficiency (E%) and recovery factor (RF%) of mentioned cations. Thus it has been revealed the possibility of separation and recovery of Zn (II) cations in the presence of Mn (II) with efficiency of 96% when used as a carrier a mixture of Cyanex 301 and D2EHPA at a molar ratio 0.01 : 0.09. The recovery factor had a high value even in conditions of a low yield as a result of metal cations accumulation in the membrane phase.
Journal of Colloid and Interface Science, 2010
In this work the effect of zinc concentration, pH, and boric acid concentration on the zinc transport properties through an IONICS 67-HMR-412 cation-exchange membrane was evaluated. The limiting current density and the transport numbers were determined by means of chronopotentiometry. A model between the limiting current density and the bulk zinc concentration was established, assuming a potential relationship between the zinc transport number through the membrane and the bulk zinc concentration together with the Levich equation for the DBL thickness. A decrease in the initial pH value of the solutions causes considerable modifications both in the plateau region and in the overlimiting current density region of the current–membrane potential curves. The results show that the presence of boric acid produces the precipitation of zinc metaborate on the anodic layer of the cation-exchange membrane.Effect of the concentration of ZnSO4on the transport numbers of Zn2+ through the cation-exchange membrane.
Desalination, 2007
Cellulose triacetate membranes doped with imidazole azocrown derivatives as fixed carriers have been prepared and applied for investigation of facilitated transport of Zn(II), Cd(II), and Pb(II) ions from aqueous nitrate source phase (c Me = 0.001 M, pH = 5.0). The transport selectivity of the Polymer Inclusion Membranes (PIMs) with 1-5 were: Pb(II) > Zn(II) > Cd(II). The influence of HCl concentration in receiving phase on metal ions transport across PIM doped with azocrown was studied. The initial fluxes of Zn(II), Cd(II), and Pb(II) ions increase with HCl concentration in receiving phase whereas the selectivity coefficients Pb(II)/Zn(II) and Pb(II)/Cd(II) are the best for pure water. The influence of azocrown ether concentration on metal ions transport across PIM was studied. The initial fluxes of transported metal ions depend on the hydrophile-lipophile balance (HLB) and molecular volumes (V x ) of azocrown ethers. The initial fluxes of Zn(II), Cd(II), and Pb(II) ions decrease with increase of hydrophile-lipophile balance value for azocrown, i.e. 3 > 4 > 5 > 1 > 2. The best selectivity Pb(II)/Cd(II) coefficient (46.0) was found for compound 3, whereas the best selectivity Pb(II)/Zn(II) coefficient (17.4) for compound 4. The influence of the plasticizer, i.e. o-nitrophenyl pentyl ether (o-NPPE), o-nitrophenyl octyl ether (o-NPOE), or bis(2-ethylhexyl)adipate (DOA) on the metal ions transport through PIM with azocrown ethers was also presented. The initial fluxes of Pb(II), Zn(II), and Cd(II) ions slightly increase with decrease of plasticizers viscosity, in the following order: DOA < o-NPOE < o-NPPE. The highest initial Pb(II) ions flux (1.7859 µmol/m 2 ·s) was found for o-NPPE, while the lowest value was observed for DOA (1.5369 µmol/m 2 ·s). Moreover, the influence of Cu(II), Co(II), and Ni(II) ions on the initial fluxes and on percentage removal of Zn(II), Cd(II), and Pb(II) ions in PIMs was studied.
2013
Transfer of Zn(II) ions from a mixed sulphate and thiocyanate solution through a supported liquid membrane (SLM) containing CYANEX 925 in kerosene as carrier has been studied as a function of stirring rate, [H], [CYANEX 925], [SCN], [H2SO4] and ammonia solution concentrations. The experimental results show that the transfer of Zn(II) ions increases with the increase in stirring rate, thiocyanate concentration in the feed and concentration of NH4OH used as the stripping solution. The transfer experiments of Zn(II) from its admixture with Co(II) indicated that Zn(II) could be extracted more than Co(II) by CYANEX 925; the transfer rate increased with time. The investigated SLM system could be used for removal of Zn(II) from an aqueous mixed thiocyanate/sulphate medium of [H] = 0.01. In addition, the present system is selective for Zn-Co separation from aqueous mixed thiocyanate/sulphate medium. This selectivity was found to decrease with time and a maximum value of 25 is reached after ...
Transportation of Zinc(II) in Bulk Liquid Membranes Containing Phosphonium Ionic Liquid
Investigations on trihexyl(tetradecyl)phosphonium chloride as selective carrier to remove zinc(II) from HCl solution in bulk liquid membrane system were carried out. The use of trihexyl(tetradecyl)phosphonium chloride as a selective carrier of zinc(II) in the membrane process is disadvantageous. Zinc(II) and the carrier form strong bounded ionic pair that makes zinc stripping very difficult. And the obtained zinc(II) concentration in the stripping phase is small, what disqualifies the use of the system on a larger scale.
Desalination, 2009
Supported liquid membranes (SLMs) have demonstrated all along the years very high selectivity in facilitated transport of metal ions, however, they have some well known limitations, such as the gradual loss of the organic phase to the aqueous solutions. This paper describes two different types of novel membranes developed for the general purpose of separating and concentrating metal ions of interest in order to improve SLM physical and chemical characteristics. Both hybrid (organic Áinorganic) membranes and activated composite membranes have been tested for the selective transport of Zn/Cd and Pt/Pd mixtures. For this purpose, different carriers have been used: 2-ethylhexyldithiophosphoric acid and 2-ethylhexylphosphoric acid for the separation of Zn and Cd whereas Aliquat 336 for Pt/Pd mixtures. The choice of these metal couples is related to environmental detoxification and catalyst recovery, respectively.