Highly Efficient and Selective Transport of Au(III) through a Bulk Liquid Membrane using Potassium-dicyclohexyl-18-crown-6 as Carrier

Abstract

The facilitated transport of Au(III) through a chloroform bulk liquid membrane containing potassium-dicyclohexyl-18-crown-6 as a selective ion carrier was designed. Au(III) as [AuBr₄]^?, quantitatively transported across the liquid membrane. In the receiving phase, L-cysteine acts as a specific stripping agent. The amount of Au(III) transported through the liquid membrane after 120 minutes was (96.2±1.3)%. The type of halide and its concentration, pH of source and receiving phase and also the type of stripping agents were optimized. The selectivity and efficiency of gold(III) transport from aqueous solutions containing various metal ions were investigated. The presence of EDTA in the source phase diminished drastically the competitive effect of interfering metals ion.     

Highly efficient and selective membrane transport of silver(I) using hexathia-18-crown-6 as a specific ion carrier

Hexathia-18-crown-6 (HT18C6) was used as a specific ion carrier for the transport of silver ion through a chloroform bulk liquid membrane. In the presence of thiosulfate ion as a suitable stripping agent in the receiving phase, the amount of silver transported across the liquid membrane after 60 min is 99.5±1.0%. The selectivity of Ag⁺ transport from the aqueous solutions containing other Mⁿ⁺ cations such as Tl⁺, Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, and Cr³⁺ ions was investigated. Except with Hg²⁺ ion, non of the cations used interfere the silver transport, even at a Mⁿ⁺/Ag⁺ molar ratio of 500. The interfering effect of Hg²⁺ ion was successfully eliminated in the presence of EDTA at pH 5.     

Highly Selective and Efficient Membrane Transport of Copper as Cu(SCN)2− 4 Ion Using K+-Dicyclohexyl-18-crown-6 as Carrier

Abstract

Potassium-Dicyclohexyl-18-Crown-6 Complex Was Used As A Highly Efficient Carrier For The Uphill Transport Of Copper As Cu(SCN)^2? ₄ Complex Ion Through A Chloroform Bulk Liquid Membrane. By Using Histidine As A Metal Ion Acceptor In The Receiving Phase At The Optimum Ph Of 7.4, The Amount Of Copper Transported Across The Liquid Membrane After 2 Hours Was 90.2 ± 1.0%. The Selectivity And Efficiency Of Copper Transport From Aqueous Solutions Containing Equimolar Mixtures Of Ag⁺, Cd²⁺, Zn²⁺, Ni²⁺, Fe²⁺, Co²⁺, Pb²⁺, Mn²⁺, Fe³⁺, Bi³⁺, And Cr³⁺ Ions Were Investigated. In The Presence Of Pyrophosphate As A Suitable Masking Agent In The Source Phase, The Interfering Effects Of Co²⁺, Zn²⁺, Pb²⁺, And Cd²⁺ Ions Were Completely Eliminated.     

Separation of Barium from Alkali and Alkaline Earth Metal Ions Using Octadecyl Silica Membranes Modified by Dibenzo-18-crown-6

Abstract

A simple method for rapid and selective separation of Ba²⁺ ion from alkali and alkaline earth metal ions by using octadecyl silica membrane disks modified with dibenzo-18-crown-6 in the presence of 0.01 M picric acid is presented. The influence of picric acid concentration, nature of the macrocyclic ligands, flow rates, and nature of the stripping acid have been investigated. Maximum capacity of the membrane disks modified by 10 mg crown ether was found to be 900 μg of Ba²⁺ ions. The method was applied to the recovery of barium ion from three different water samples and a certified reference material.     

Liquid Membrane Transport of Hg(II) by an Azocalix[4]arene Derivative

Abstract

A kinetic study of Hg(II) transport from an aqueous donor solution into an aqueous acceptor solution through a liquid membrane containing 25,26,27–tribenzoyloxy‐28‐hydroxy‐5,11,17,23‐tetra‐(4‐n‐butylphenylazo)calix[4]arene 1 as a carrier was studied. The kinetic parameters (k ₁, k ₂, R _m ^max, t _max, J _d ^max, J _a ^max) for the transport were investigated in terms of the effect of temperature, the stirring rate, the carrier concentration, and the type of solvent. The kinetics of transport was analyzed in the formalism of two consecutive irreversible first‐order reactions. The membrane entrance rate, and exit rate constants were increased with increasing of temperature stirring rate, and carrier concentration. The membrane entrance rate and exit rate constants depended on the type of solvent and was found to be in order of CH₂Cl₂> CHCl₃> CCl₄. The activation energy values are calculated as 30.67±2.64 and 57.33±4.90 kj mol^?1 for extraction and reextraction, respectively. The values of calculated activation energy indicate that the process is diffusionally controlled by species.     

丙氧基—18—冠—6硅胶键合固定相的合成及色谱性能的研究

以多孔硅胶为基质,固相合成并制备了一种新型丙氧基-18-冠-6键合固定相(P18-C-6 SB),详细研究了其合成反应条件。P18-C-6 SB 是一种热稳定性好、耐溶剂,表面键合浓度高的色谱固定相。已应用于芳香族异构体及同系物的分离。     

Highly Efficient and Selective Transport of Cu(II) with a Cooperative Carrier Composed of Tetraaza-14-Crown-4 and Oleic Acid through a Bulk Liquid Membrane

Tetraaza-14-crown-4 and oleic acid was successfully applied for transport of Cu(II) in chloroform bulk liquid membrane. The uphill moving of Cu(II) during the liquid membrane transport process has occurred. The main effective variable such as the type of the metal ion acceptor in the receiving phase and its concentration, tetraaza-14-crown-4 and oleic acid concentration in the organic phase on the efficiency of the ion-transport system were examined. By using L-cysteine as a metal ion acceptor in the receiving phase, the maximum amount of copper (II) transported across the liquid membrane was achieved to 96 ± 1.5% after 140 minutes. The selectivity of copper ion transport from the aqueous solutions containing Pb²⁺, Tl⁺, Ag⁺, Co²⁺, Ni²⁺, Mg²⁺, Zn²⁺, Hg²⁺, Cd²⁺ and Ca²⁺ ions were investigated. In the presence of CH₃COONH₄ and Na₄P₂O₇ as suitable masking agents in the source phase, the interfering effects of Pb⁺² and Cd²⁺ were diminished drastically.     

水化在18-冠醚-6对K+和Na+选择过程中作用的理论研究

A combination of molecular dynamics (MD) and density functional theory (DFT) calculations were used to study the hydration structures of K+ and Na+ ions under the confinement of 18-crown-6 in order to identify the role of water in the selectivity of 18-crown-6 towards K+. The radial distribution functions, coordination numbers, orientation structures and interaction energies were analyzed to investigate the hydration of K+ and Na+ in 18-crown-6/cation complexes. All calculations of K+ and Na+ in bulk water were also conducted for comparison. The simulation results show that the orientation distributions of the water molecules in the first coordination shell of K+ are more sensitive to the confinement of 18-crown-6 than those of Na+. It is more favorable to confine a K+ in 18-crown-6 than a Na+ in terms of interaction energy. Good agreement is obtained between MD results and DFT results.     

基于二苯并-18-冠-6基体改性的K+选择性离子交换膜的制备及性能研究

基于18-冠-6醚环腔体可与K⁺形成1∶1型稳定的络合物,通过掺杂的方式将4,4'-二氨基-二苯并-18-冠-6（A18C6）引入离子交换膜基材料中并成膜,然后利用1,3,5-苯三甲酰氯（TMC）对A18C6分子进行交联固定,制得一系列改性阳离子交换膜。通过改变A18C6的含量和TMC的反应时间来调控阳离子交换膜的基体结构,系统考察了改性膜在K⁺/Mg²⁺、K⁺/Na⁺ 和K⁺/Li⁺的二元体系中对K⁺的电渗析选择性。研究结果表明,在电流密度为5.0 mA·cm^-2的条件下,最优膜M-A18C6-10%-T30在K⁺/Mg²⁺和K⁺/Li⁺体系中对K⁺的选择性（P_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+}}^{{\mathrm{K}}^{+}}=\mathrm{6.96},P_{\mathrm{L}{\mathrm{i}}^{+}}^{{\mathrm{K}}^{+}}=\mathrm{3.73}）高于商业的单价选择性阳离子交换膜CIMS（P_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+}}^{{\mathrm{K}}^{+}}=\mathrm{5.36}）。A18C6的掺杂引入不仅提高了膜基体的致密性（孔径筛分效应）,也为K⁺在膜基体中的传输提供了新的离子传输通道（离子-偶极作用）。     

Mass transfer study in a pulsed bed electrode - application to the electrodeposition of a poly(dibenzo-18-crown-6) film

The polymerization of dibenzo-18-crown-6 has been carried out in an electrochemical reactor containing a granular electrode percolated by a pulsed solution. The influence of different parameters (pulse frequency, permanent flow velocity of the electrolytic solution, particle diameter and bed height) on the mass transfer has been studied. A correlation between the reduced mass transfer coefficient and the Strouhal number has been established. The maximum mass transfer coefficient and the maximum Strouhal number have been determined as a function of the Galilee number. The correlation predicts well the mass transfer coefficient over a larger range of the variables than previously achieved.     

Hydrogels with Acid Groups for Removal of Copper(II) and Lead(II) Ions

Acrylamide-maleic acid (AAM-MA) hydrogels having high acid group content prepared with different maleic acid ratios were used for the removal of Cu(II) and Pb(II) ions from aqueous solutions in competitive and noncompetitive conditions. The effects of pH, time, and initial metal ion concentration on the metal ion adsorption capacity were investigated. The adsorption isotherm models were applied on experimental data and it is shown that the Freundlich equation was the best model for Cu(II) ion while the Langmuir isotherm model was the best one for Pb(II) ion. The stability constants of acrylamide-maleic acid hydrogel-Cu(II) and Pb(II) complexes were also determined by van den Berg/Ruzic transformation, and K values obtained were 1.60 × 10³ and 1.81 × 10³ for Cu(II) and Pb(II) ions, respectively. The experiments under competitive conditions showed that the hydrogels prefered Pb(II) ion and this preference increased with increasing of carboxylic acid group content (AGC) of polymers. It is stated that these hydrogels can be regenerated efficiently (>95%) and used repeatedly.     

Synthesis, Characterization and Thermogravimetric Analysis of Two Dicyclohexyl-18-crown-6 Pd, Pt Isomaleonitriledithiolate Complexes

Two organic–inorganic hybrid dicyclohexyl-18-crown-6 complexes, [K(DC18C6-B)]₂[Pd(i-mnt)₂] (1) and [K(DC18C6-A)]₂[Pt(i-mnt)₂] (2) (DC18C6-A=cis-syn-cis-dicyclohexyl-18-crown-6, A isomer; DC18C6-B = cis-anti-cis-dicyclohexyl-18-crown-6, B isomer; i-mnt=1,1-dicyanoethene-2,2-dithiolate, isomaleonitriledithiolate), were synthesized by the reaction of dicyclohexyl-18-crown-6 with K₂(i-mnt) and PdCl₂ or K₂PtCl₄ respectively. These were characterized by elemental analysis, FT–IR, UV–Vis spectroscopy and single crystal X-ray diffraction. In complex 1, two [K(DC18C6-B)]⁺ complex cations and one [Pd(i-mnt)₂]²⁻ complex anion formed a neutral molecule through two K–N coordination bonds. The resulting molecule adopted a 1D chain arrangement via K N weak interactions. Complex 2 showed a 1D chain-like structure that was assembled by two [K(DC18C6-A)]⁺ complex cations and one [Pt(i-mnt)₂]²⁻ complex anion through N–K–N interactions. An erratum to this article can be found at     

Separation of Ethyl Esters of Eicosapentaenoic Acid and Docosahexaenoic Acid by Circulating Liquid Membranes Using Silver Nitrate as a Carrier. Uphill Transport by Use of Temperature and Solvent Dependencies of Distribution Ratio

Abstract

Experiments on the separation of ethyl ester of eicosapentaenoic acid (EPA-Et) and that of docosahexaenoic acid (DHA-Et) contained in ethyl ester of bonito oil (bonito oil-Et) were performed using circulating liquid membranes (CIRLMs) containing sliver nitrate as a carrier. In this liquid membrane system an aqueous silver nitrate solution was circulated between a stirred vessel containing an organic solution of bonito oil-Et and another stirred vessel containing a receiving organic solvent. Using the CIRLM, two types of uphill facilitated transport of EPA-Et and DHA-Et in bonito oil-Et were demonstrated. The first type utilizes the distribution ratio of EPA-Et and DHA-Et, defined as the ratio of the concentration in the aqueous phase to that in the organic phase at equilibrium, which is remarkably dependent on the temperature, and the second uphill transport was based on the fact that the distribution ratio is considerably dependent on the solvent of the organic phase. A model of permeation through the circulating liquid membrane was proposed to explain the experimental results.     

The Transport of Copper(II) through Hollow Fiber Renewal Liquid Membrane and Hollow Fiber Supported Liquid Membrane

Abstract

In this paper, hollow fiber renewal liquid membrane (HFRLM) and hollow fiber supported liquid membrane (HFSLM) were used to simultaneously remove and recover copper(II) from aqueous solutions, and the transport performance of these two techniques were compared under the similar conditions for the system of CuSO₄ +D2EHPA in kerosene +HCl. The results showed that the HFRLM process was more stable than the HFSLM process. The HFRLM process had a higher overall mass transfer coefficient than that of HFSLM process in single-pass experiments. These were because the renewal effect of the liquid membrane layer could reduce the mass transfer resistance of the lumen side and replenish the loss of the membrane liquid in the HFRLM process. The transport results were better in the HFRLM process than that in the HFSLM process with recycling experiments. Therefore, HFRLM technique is a promising method for simultaneous removal and recovery of heavy metal from aqueous solutions.     

Facilitated Transport of Cd(II) Through a Supported Liquid Membrane with Aliquat 336 as a Carrier

Selective removal of cadmium from wastewaters is very important, because cadmium is toxic for the environment and for human health. This work is a comprehensive study on the selective removal of Cd(II) from aqueous solutions by using a co-current flow flat sheet supported liquid membrane system. 4.4 × 10^?4 M Cd(II) concentration was used as a feed solution in the experiments. Toluene containing Aliquat 336 was used as the membrane liquid in the membrane system. Parameters such as the properties of feed and stripping solutions, carrier concentration, and flow rate, which have roles in transport of Cd(II) ions, were optimized. The efficiency of the system is expressed in terms of permeability and flux values, and transport efficiency. The optimum process conditions for the Cd(II) transport are experimentally found as follows: The feed solution as 2 M HCl, the carrier concentration as 0.1 M Aliquat 336, the stripping solution as 0.06 M EDTA, and the flow rates for the feed and stripping solutions as 50 mL/min and 80 mL/min, respectively. Under these conditions, the Cd(II) transport efficiency is found to be 82%.     

Separation of Water and Nitric Acid with Porous Hydrophobic Membrane by Air Gap Membrane Distillation (AGMD)

Abstract

This study investigates the effect of operation parameters on the separation of nitric acid‐water mixture using air gap membrane distillation (AGMD). Porous hydrophobic PTFE membrane was used. The performance was evaluated based on the permeate flux and the nitric acid selectivity. Operating parameters such as feed solution temperature, feed concentration, flow rate, and air gap width were varied. Nitric acid selectivity was found to increase with the increase in feed solution temperature, feed concentration, flow rate, and air gap width. Permeate flux increased, when the feed temperature and the flow rate were increased. The effect of recirculation of the feed solution was also studied. With the recirculation mode, at different initial solution volumes, it was observed that the nitric acid concentration in the feed and the permeate, increased. The rate of flux decline was greater, when the initial feed solution volume was lower.     

Selective Transport of Copper(I,II), Cadmium(II), and Zinc(II) Ions through a Supported Liquid Membrane Containing Bathocuproine,Neocuproine, or Bathophenanthroline

Abstract

Some selective transport systems for heavy metallic ions through a supported liquid membrane (SLM) containing a 2,2′-dipyridyl derivative ligand, 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline (bathocuproine), 2,9-dimethyl-1,10-phenanthro-line (neocuproine), or 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline), were investigated. The transport of copper(I, II), cadmium(II), zinc(II), lead(II), and cobalt(II) ions was accomplished with a halogen ion such as chloride, bromide, or iodide ion as a pairing ion species for any SLM. The ranking of the permeability of the metallic ions was Cu^+,2+, Zn²⁺, Cd²⁺ ? Pb²⁺, Co²⁺. When the oxidation-reduction potential gradient was used as a driving force for metallic ions, the transport of Cu⁺ ion was higher than those of Cd²⁺ and Zn²⁺ ions for any SLM containing bathocuproine, neocuproine, or bathophenanthroline. On the other hand, in the transport system which used the concentration gradient of pairing ion species, the permeability of the Cu²⁺ ion decreased whereas that of the Cd²⁺ ion increased. Moreover, it was found that the different selectivity for the transport of metallic ions is produced by using various pairing ion species.     

Modeling of Facilitated Transport of Phenylalanine by Emulsion Liquid Membranes with Di(2-ethylhexyl)phosphoric Acid as a Carrier

ABSTRACT

A mathematical model is developed in this paper to simulate the facilitated transport of phenylalanine (Phe) in emulsion liquid membrane (ELM) systems with di(2-ethylhexyl)phosphoric acid as a carrier. The model takes into account the mass transfer in both the external aqueous phase and the organic membrane phase interfacial reaction as well as membrane breakage during agitation. The model is tested by comparing theoretical predications with experimental results using Phe extraction by ELM processes. It is found that the model is valid for simulating the facilitated transport of Phe with ELM under various experimental conditions.     

Synthesis,Characterization and Properties of One-dimensional Complexes of <Emphasis Type="Italic">cis-syn-cis</Emphasis>-Dicyclohexyl-18-crown-6 with K<Subscript>2</Subscript>[M(mnt)<Subscript>2</Subscript>] (M==Ni,Pd, Pt)

Three complexes [K(DC18C6-A)]₂[M(mnt)₂] (DC18C6-A=cis-syn-cis-dicyclohexyl-18-crown-6, isomer A; M=Ni, 1; Pd, 2; Pt, 3; mnt = 1,2-dicyanoethene-1,2-dithiolate, maleonitriledithiolate, [C₂S₂(CN)₂]²⁻) have been synthesized and characterized by elementary analysis, UV–vis, FT-IR spectroscopy and X-ray single crystal diffraction. They are isomorphous and all display infinite one-dimensional chain-like structure formed by [K(DC18C6-A)]⁺ complex cations and [M(mnt)₂]²⁻ (M=Ni, Pd, Pt) complex anions through K–N interactions. Thermal analysis indicates that three complexes are all thermal stable under 260 °C and experience the same decomposition process of dissociation and evaporation of crown ether molecules. Their electrochemical behaviors have been studied by cyclic voltammetry.     

Effect of mixed solvent on selective removal of lead (II) ions by dicyclohexano‐18‐crown‐6 from aqueous solutions containing heavy metals

The effect of the organic solvent on the transport of lead ions through a bulk liquid membrane containing dicyclohexano‐18‐crown‐6 (DC18C6) as carrier was studied. Chloroform, 1,2‐dichloroethane, chlorobenzene, nitrobenzene and their binary solutions were employed as solvents. SCN‐, NO₃‐, CI‐ and CH₃COO‐ were used as anions. The selectivity and the efficiency of lead transport from aqueous solutions containing other cations such as Ni²⁺, Cu²⁺, Co²⁺, and Zn²⁺ were also investigated.