Highly selective and efficient membrane transport of silver as AgBr2- ion using K+-decyl-18-crown-6 as carrier.

Potassium-decyl-18-crown-6 was used as a highly selective and efficient carrier for uphill transport of silver as AgBr2-complex ion through a chloroform bulk liquid membrane. When thiosulfate anion was used as a metal ion acceptor in the receiving phase the amounts of silver transported across the liquid membrane after 120 and 180 min were 87.0 +/- 1.8% and 96.0 +/- 1.9%, respectively. The selectivity and efficiency of silver transport from aqueous solution containing Cu2+, Zn2+, Ni2+, Cd2+, Pb2+ and Fe3+ ions were investigated. In the presence of EDTA at pH = 4 as suitable masking agent in the source phase, the interfering effects of Pb2+ and Fe3+ ions were diminished drastically.     

Highly selective transport of silver ion through a supported liquid membrane using calix[4]pyrroles as suitable ion carriers

Facilitated transport of silver ion across a supported liquid membrane (SLM) by calix[4]pyrroles, as selective ion carriers, dissolved in kerosene has been investigated. The influences of fundamental parameters affecting the transport of silver ion including ion carrier concentration in the membrane phase, thiosulfate concentration in strip phase, picric acid concentration in the feed phase, stirring speed of aqueous phases, type of membrane solvent and time of transport have been studied. In the presence of thiosulfate as a suitable metal ion acceptor in the strip phase and picrate ion as ion pairing agent in the source phase, transport of silver occurs almost quantitatively after 75 min. The selectivity and efficiency of silver transport from aqueous solution containing Cu²⁺, Mg²⁺, Ni²⁺, Ca²⁺, Zn²⁺, Pb²⁺, Co²⁺, Al³⁺, Hg²⁺, Cd²⁺, Fe³⁺, Fe²⁺ and Cr³⁺ were investigated.     

Separation and Preconcentration of Strontium from Calcium in Aqueous Samples by Supported Liquid Membrane Containing Crown Ether

Supported liquid membrane containing crown ether (DC18C6) and dinonylnaphthalenesulfonic acid (DNNS) is proposed for separation and preconcentration of strontium in an aqueous environmental sample. The effects of carriers in membrane on permeability and selectivity of Sr²⁺ were characterized. Crown ether has a key role in the selective transport of strontium ion while DNNS facilitates the transport of both Sr²⁺ and Ca²⁺. A strontium ion can be selectively transported to an acidic strip solution against its concentration gradient across the membrane. This SLM can be used as an efficient method for separation and preconcentration of strontium in a neutral aqueous sample.     

Study of Bulk Membrane Transport of Some Heavy Metal Cations Using Three Macrocyclic Ligands Containing Oxygen and Nitrogen Heteroatoms

The transport experiments of Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺ and Pb²⁺ metal cations were carried out by dibenzo-18-crown-6 (DB18C6), dibenzyl-diaza-18-crown-6 (Dibenzyl-diaza-18C6) and di-tert-butyl-dibenzo-18-crown-6 (Di-tert-butyl-DB18C6) using chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE) and nitrobenzene (NB) organic solvents as liquid membranes. The source phase contained equimolar concentration of these metal cations and the source and receiving phases being buffered at pH=5 and pH=3, respectively. The obtained results show that the selectivity and the efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membranes in these experiments. A good selectivity was observed for silver (I) ion by dibenzyl-diaza-18C6 in all membrane systems. Dibenzo-18C6 and di-tert-butyl-DB18C6 showed the highest transport efficiency for cobalt (II) ion. The effect of stearic acid on transport efficiency was also investigated and the results show that the efficiency of transport of the heavy metal cations increases in the presence of this organic acid.     

Recovery of silver nitrate by transport across a liquid membrane containing dicyclohexano 18 crown 6 as a carrier

The solvent extraction and transport through a bulk liquid membrane of silver nitrate from a copper nitrate medium by dicyclohexano 18 crown 6 (DC18C6) in dichloromethane takes place via the formation of the complex ion pair Ag(DC18C6)NO₃ in the organic phase. The selectivity of the transfer process characterises the semi-permeability of the liquid membrane, which is able to concentrate silver cations. Results show that the transport is well described by the two-film theory.     

杂元素冠醚研究(Ⅻ)──氧、硫、硒和碲杂冠醚的液膜迁移性能比较

报道了碲杂冠醚(TeB15C5)对Na⁺、K⁺、Ag⁺和Pb²⁺的液膜迁移能力,并与相应的全氧冠醚(B15C5)、硫杂冠醚(SB15C5)和硒杂冠醚(SeB15C5)作了比较;同时以SeB15C5对K⁺的迁移为例考察了冠醚浓度和盐浓度对迁移速率的影响,结果表明,TeB15C5对Na⁺、K⁺和Pb²⁺的迁移能力比SB15C5和SeB15C5强,但对Ag⁺的迁移速率比后两者慢;SeB15C5对Ag⁺的迁移速度比SB15C5快,两者对Ag⁺的选择性都相当高,可以用来分离和回收银等贵重金属。     

Transport of silver ion through bulk liquid membrane using macrocyclic and acyclic ligands as carriers in organic solvents

The bulk liquid membrane transport of silver (I) ion was studied by dibenzopyridino-18-crown-6(DBPY18C6), 4-nitrobenzo-15-crown-5(NB15C5), 2-aminothiaphenol and a new synthesized ligand, 1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as carriers in nitrobenzene (NB). The effects of pH on the source phase and receiving phase, the nature and concentration of stripping agents in the receiving phase and the picrate concentration as counter ion in source phase were investigated. The results show that the efficiency of transport of the Ag⁺ ion through membranes, changes with the nature of the ligand. The efficiency transport increases for the ligands with donating nitrogen and sulfur atoms with respect to oxygen donor atoms. Maximum transport efficiency was observed for silver (I) ion in the presence of thiosulfate ion ( ) as a suitable stripping agent. The results show that the sequence of transport efficiency for Ag⁺ ion using DBPY18C6, NB15C5, 2-aminothiaphenol and 1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as carriers in organic solvents is: nitrobenzene > dichloromethane > 1,2- dichloroethane > chloroform.     

杯芳烃衍生物液－液萃取和液膜传输银的对比研究及机理探讨

以4类含硫、硒、氮等杂原子基团二取代的杯[4]芳烃五衍生物（1－14）为中 性载体，在H2O-CHCl3-苦味酸体系萃取银和H2O-CHCl3-H2O液膜体系中传输银进行 了对比研究。萃取和传输结果具有一致性，除了苯并噻唑取代的杯[4]芳烃衍生物 （3－6）外，其它10个含硫、硒、氮的杯[4]芳烃衍生物1－14均对软重金属银和汞 有很高的选择性，而吡啶取代的杯[4]芳烃衍生物7－10对铅有一定的萃取选择性， 其中羟基硫醚取代的杯[4]芳烃衍生物11－14对银的萃取率和传输速率最大。并且 就杯[4]芳烃衍生物对银的传输机理进行了探讨，发现传输速率随源相中金属离子 浓度和有机相中载体浓度的增加而增大，因此推论这是由金属离子浓度梯度推动下 的传输。     

Artificial ion channel formed by cucurbit[n]uril derivatives with a carbonyl group fringed portal reminiscent of the selectivity filter of K+ channels

Novel artificial ion channels (1 and 2) based on CB[n] (n = 6 and 5, respectively) synthetic receptors with carbonyl-fringed portals (diameter 3.9 and 2.4 A, respectively) can transport proton and alkali metal ions across a lipid membrane with ion selectivity. Fluorometric experiments using large unilamellar vesicles showed that 1 mediates proton transport across the membranes, which can be blocked by a neurotransmitter, acetylcholine, reminiscent of the blocking of the K+ channels by polyamines. The alkali metal ion transport activity of 1 follows the order of Li+ > Cs+ approximately Rb+ > K+ > Na+, which is opposite to the binding affinity of CB[6] toward alkali metal ions. On the other hand, the transport activity of 2 follows the order of Li+ > Na+, which is also opposite to the binding affinity of 2 toward these metal ions, but virtually no transport was observed for K+, Rb+, and Cs+. It is presumably because the carbonyl-fringed portal size of 2 (diameter 2.4 A) is smaller than the diameters of these alkali metal ions. To determine the transport mechanism, voltage-clamp experiments on planar bilayer lipid membranes were carried out. The experiments showed that a single-channel current of 1 for Cs+ transport is approximately 5 pA, which corresponds to an ion flux of approximately 3 x 107 ions/s. These results are consistent with an ion channel mechanism. Not only the structural resemblance to the selectivity filter of K+ channels but also the remarkable ion selectivity makes this model system unique.     

冠醚配合物的研究XIII:三种大环配体液膜传输碱金属离子的动力学

本文报道以2,3-苯并-11-甲基-18-冠-6,2,3-苯并-8,15-二甲基-18-冠-6和2,3-苯并-8-11,15-三甲基-18-冠-6为液膜载体,研究其对碱金属离子的传输,发现当水相金属盐浓度和膜相配体相近时,金属离子的传输为串联一级反应,求得了串级速率常数,并讨论了传输速率和配位作用的关系及载体结构的影响.     

自组装杂化离子通道膜的构筑及阳离子传输机制

以3-异氰酸丙基三乙氧基硅烷和对甲氧基苯胺为原料合成了一种可以自组装形成有机-无机杂化材料的化合物--3-(脲基-4-甲氧基苯基)丙基三乙氧基硅烷. 采用FT-IR, ¹H NMR, DSC 和XRD 分析方法对该化合物的结构以及结晶性进行了表征. 将该化合物与聚乙烯醇(PVA)共混, 利用化合物的自组装性质构筑结构均一且致密无孔的离子通道杂化膜, 通过自制的膜运输实验装置测定膜对阳离子的传输性能并提出了相应的传输机制. SEM 照片显示, 自组装杂化膜致密无缺陷, 膜厚度为8 μm. 选择5 种阳离子进行运输实验测试, 结果表明, 自组装杂化离子通道膜对一价的碱金属离子Li⁺, Na⁺和K⁺有很好的传输功能, 这要归功于杂化材料中甲氧基苯基与碱金属阳离子形成的阳离子-π相互作用力. 碱金属阳离子在膜中的扩散过程可由溶解-扩散机制来解释, 结果显示, Li⁺, Na⁺和K⁺在杂化膜中传输的渗透率大小为: P_Na⁺ > P_K⁺ > P_Li⁺ , 说明本研究中的的自组装杂化离子通道膜对Na⁺有优先选择性. 杂化离子通道膜对二价的Ca²⁺和Mg²⁺没有传输作用, 此结果给一二价阳离子的分离带来很好的研究思路.     

Synthesis of Monoazacryptands and their Excellent Transport Ability Toward Alkali Metal Cations in Comparison with Monoazacrown Ethers

The effects of transport conditions and the structure of monoazacrownethers on their transport ability for alkali metal cations through a bulkliquid membrane are summarized and discussed based on transport dataobtained in our laboratories. To improve the transport ability,monoazacryptands have been prepared. A lipophilic derivative consisting oftwo 18-crown-6 rings and one 20-crown-6 ring can selectively transport K+from a mixture of Na+, K+, Mg2+, and Ca2+ under pH control.     

冠醚配合物的研究 XI: 若干苯并-18-冠-6甲基衍生物液膜传输碱金属离子

本文研究了2,3-苯并-11-甲基-18-冠-6,2,3-苯并-8,15-二甲基-18-冠-6和2,3-苯并-8, 11, 15-三甲基-18-冠-6的氯仿液膜对Na^+, K^+, Rb^+的传输速率。结果指出,传输速率随膜相冠醚浓度增是加而增加, 两者成线性关系; 当冠醚的醚环上甲基数增加则传输速率减小; 对同一冠醚, 不同金属离子的传输速率与相应配合物稳定常数的大小顺序有一致关系; 冠醚传输金属离子时, 阴离子一起迁移, 阴离子水合能力越强则传输能力越小; 传输速率与搅拌速度成线性关系。     

Synthesis and rare earth metal ion-sensing properties of aza-crown derivative incorporating with diaryl-1,3,4-oxadiazole

A new fluorescent chemosensor (A18C6-Ox) in which a monoaza-18-crown-6 is linked to a diaryl-1,3,4-oxadiazole fluorophore by a methylene spacer has been synthesized to evaluate binding interaction with the rare earth ions by means of absorption and emission spectrophotometry. Absorption spectra of A18C6-Ox showed a broad band at 289nm and there was no significant change in the presence of Sc3+, La3+, Pr3+, Sm3+, Gd3+, Tb3+, Yb3+ and Lu3+ except for Ce3+ and Eu3+. From the emission spectral change of A18C6-Ox, interaction of the rare earth ions with A18C6-Ox is very strong. The formation of A18C6-Ox complexing with Sc3+, La3+, Pr3+, Sm3+, Gd3+, Tb3+, Yb3+ and Lu3+ leads to an increase in fluorescence intensity of A18C6-Ox, while Ce3+ and Eu3+ ions interact strongly causing fluorescence quenching of A18C6-Ox. In addition, the optimal complexation stoichiometry of the rare earth ions with A18C6-Ox was investigated by the fluorescent titration.     

Double-armed crown ethers: synergic pi-coordination effect on potentiometric sensing for Ag(I)

Three diaza-18-crown-6 derivatives having methyl (L1), methoxy (L2) and phenyl (L3) end-groups in para-substituted phenolic side-arms have been investigated as potentiometric sensing materials for silver(I)-selective poly(vinyl chloride) membrane electrodes. The aim of the present work is to establish whether a combination of macrocyclic coordination to Ag+ ion and Ag-pi interaction might produce synergic effect in Ag+ ion sensing. The electrode based on the aromatic end-groups, L3 was found to give remarkably better electrochemical performance than their aliphatic counterparts (L1 and L2). The sensing ability for Ag+ ion with the proposed electrode was enhanced noticeably due to the pi-coordination of Ag+ ion, which was elucidated by NMR. The present findings may serve as an alternative approach for designing advanced sensing materials.     

Separation study of cadmium as CdI4(2-) through a bulk liquid membrane containing ketoconazole and oleic acid.

A chloroform membrane system containing a given mixture of ketoconazole and oleic acid was applied for the uphill transport of Cd2+ ions as CdI42-. In an HCl medium the ligand could form a stable ion-pair with CdI4(2-), which was readily extractable in the membrane phase. A weak basic solution (pH 8) was used as a suitable stripping medium for the quantitative transport of cadmium across the liquid membrane after 120 min. The selectivity and efficiency of Cd2+ transport from an aqueous solution containing other cations, such as Co2+, Cr3+, Ni2+, Fe2+, Mn2+, Pd2+ and Zn2+ ions, were investigated. It was found that none of these cations interfered with Cd2+ transport.     

Liquid crystals of silver complexes derived from simple 1-alkylimidazoles

A homologous series of silver complexes of 1-alkylimidazoles (R-im, R = CnH(2n+1), where n= 10, 12, 14, 16 and 18) was synthesized. All the CnH(2n+1)-im ligands are non-mesomorphic. Upon complexation, all the [Ag(CnH(2n+1)-im)2]-[NO3], except for n = 10, exhibit liquid crystalline properties. The crystal structure of [Ag(C12H25-im)2][NO3] shows that the silver center is two-coordinate and adopts a U-shaped conformation with bilayer packing. The non-mesomorphic [Ag(C16H33-bim)2][NO3](bim = benzimidazole) has a three-coordinate silver ion and has a chair conformation with monolayer stacking. Non-mesomorphic [Ag(C16H33-bim)2][BF4] has a linear geometry around the silver ion and also has a chair conformation. The mesophase for the Ag-(CnH(2n+1)-im) complexes has been identified as the smectic A (SmA) phase. [Ag(C16H33-im)2]+ with four different anions, NO3-, BF4-, PF6- and CF3SO3- were compared. Of the four Ag-im complexes, only that with the CF3SO3- anion does not show liquid-crystal behavior.     

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.     

Use of mobile phase 18-crown-6 to improve peak resolution between mono- and divalent metal and amine cations in ion chromatography

It is difficult to quantify NH4+ by ion chromatography in the presence of high concentrations of Na+ due to peak overlap. The Dionex IonPac CS15 column, which contains phosphonate, carboxylate, and 18-crown-6 functional groups, was originally developed to overcome this problem. We have found that the addition of 18-crown-6 to the eluent promotes improved peak resolution between Na+ and NH4+ even at concentrations as high as 60,000 to 1 using this column. Its use also improves the separation of alkali and alkaline earth metal and amine cations. Mobile phase 18-crown-6 increased the retention times of CH3NH3+, NH4+, and K+, and decreased the retention time of Sr2+. The retention times of Li+, Na+, Mg2+, Ca2+, (CH3)2NH2+, and (CH3)3NH+ were not affected. This method makes possible the direct analysis of ammonia from nitrogenase, the enzyme responsible for biological nitrogen fixation. The resolution of the NH4+ peak from the Na+ and Mg2+ peaks improved from zero resolution to values of 6.19 and 5.65, respectively. This technique considerably reduces the analysis time of NH4+ in the presence of high concentrations of Mg2+ and Na+ over traditional indophenol measurements.     

超分子化合物构筑的碱金属离子传输膜的制备与性能

采用苯并15冠5、没食子酸甲酯以及1-溴十一烯等物质为原料,合成超分子化合物2-(1-甲基羟甲基)-[1,4,7,10,13-苯并15冠5]-3,4,5-三[4-(10-十一烯-1-羰基)苄氧基]苯甲酸酯.然后用紫外光接枝法将其接枝到聚丙烯腈(PAN)微孔膜表面,构筑具有离子传输功能的离子传输复合膜,接枝量为3.025 mg/cm2.通过ATR,XPS,SEM以及AFM等手段对离子传输膜的结构性能进行表征.结果表明,这种超分子化合物在PAN膜的表面自组装成柱状通道,并形成致密皮层.采用自行设计的膜运输装置对膜的离子识别和运输功能进行评测.通过与非功能材料(丙烯酸)接枝膜的对比,可以认为本文制备的离子识别膜可以选择性识别和运输碱金属阳离子,其运输能力顺序为Na+>K+>Li+.