Liquid Anion Exchanger Research Articles

Liquid–liquid anion exchange extraction studies of samarium(III) from salicylate media using high molecular weight amine

Liquid–liquid extraction and separation of samarium(III) were carried out by using 0.025moldm−3 2-octylaminopyridine(2-OAP) in xylene at 298K. The extraction behavior of samarium was studied as a function of pH, weak acid concentration, extractant concentration, diluent, and equilibration time. Samarium was quantitatively extracted at pH 7.5 to 10.0 from 0.01moldm−3 sodium salicylate solution with 0.025moldm−3 2-OAP. The possible composition of the extracted species in organic phase has been determined by using model of slope analysis method and extraction mechanism was found to proceed via an anion exchange mechanism. The stripping efficiency was found to be quantitative in HNO3, HCl and CH3COOH. The robustness of the procedure was demonstrated by the average recoveries obtained (>99.6%) for samarium(III) extraction in the presence of several cations and anions which are commonly associated with it. The proposed method facilitates the separation and determination of samarium(III) from binary and synthetic mixtures. The various thermodynamic functions like free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of extraction mechanism were discussed.

Influence of the nature of liquid anion exchanger on the selectivity of anion selective electrodes

Selectivity coefficients of ion-selective electrodes on the basis of liquid anion exchangers, a quaternary phosphonium salt, and 20 higher quaternary ammonium and other nitrogen-containing salts differing in the length of hydrocarbon radicals, the nature of the quaternary nitrogen atom, and the presence of polar groups near to the exchange center with respect to 17 mineral, organic, and metal complex anions are presented. The effect of the nature of the anion-exchanger on the anion selectivity is discussed.

Reversed phase partition chromatographic separation of divalent copper with N-n-octylaniline on silica gel

A novel separation method was developed for the extraction and chromatographic separation of copper(II). The quantative extraction of 25.0–125.0μg copper(II) has been observed from 0.05 to 0.25mol/L of ascorbic acid at pH 9.0–12.0 with 0.087mol/L N-n-octylaniline (liquid anion exchanger) coated on silica gel at a flow rate of 1.0ml/min. The extracted metal ion has been recovered by eluting with 25.0ml of 1.0mol/L hydrochloric acid and determined spectrophotometrically by rubeanic acid method. The various influencing parameters viz. acid concentrations, reagent concentration, eluates effect of pH, and effect of flow rate on extraction were studied. The method is free from large number of interferences from cations and anions. A scheme for mutual separation of copper(II), gold(III) and bismuth(III) has been developed. Copper(II) has been separated from ayurvedic (Herbal) medicine and synthetic mixtures corresponding to alloy. The log–log plot of N-n-octylaniline concentration versus the distribution coefficient indicates that the probable extracted species is [RR′NH2+)3·Cu(C6H7O6)53-]org.

Enhanced liquid–liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate–nitrate exchange selectivity

When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and β-decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1 receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.

Scintillating adsorptive membrane for preconcentration and determination of anionic radionuclides in aqueous samples

A composite polymer membrane containing liquid anion exchanger and scintillator molecules was developed for preconcentration and quantitative determination of anionic radionuclides like pertechnetate and iodide ions. The radiation emitted by the radionuclides sorbed in the membrane lead to scintillation signals. This scintillating adsorptive membrane was prepared by immobilizing trioctylmethyl ammonium chloride (liquid anion-exchanger) along with 2,5-diphenyl oxazole (primary scintillator), and 4-bis(methylstyryl)benzene (wavelength shifter) in the plasticized polystyrene matrix. The anion selectivity of the membrane follows Hofmeister series i.e. hydrophobic anions are preferentially sorbed in the membrane matrix. It was observed that TcO4− ions were transferred quantitatively to the membrane matrix from equilibrating aqueous solutions having pH 2–8 and multicomponent feed solution like seawater. The amount of TcO4− ions preconcentrated in the membrane was directly quantified by counting the scintillations produced by β-particles in the membrane matrix. The scintillating membrane developed in the present work was optimized in terms of its scintillation efficiency, β-scintillation pulse height, anion-exchange capacity and reusability.

Reversed phase extraction chromatographic separation of ruthenium(III)

A new an innovative separation method has been developed using N-n-octylaniline (liquid anion exchanger) coated on silica gel. Ruthenium(III) has been extracted quantitatively from 0.05M hydrochloric acid, striped with aqueous solution of various acids and then determined by spectrophotometric method. Mutual separation scheme for ruthenium(III), iridium(III) and osmium(VIII) has been developed. Ruthenium(III) has been separated from commonly associated elements. Different parameter are studied viz effect of acid concentration, reagent concentration, striping agent, flow rate, foreign ion and synthetic mixture corresponding to alloys. Validity of method has been verified by separation of ruthenium(III) from fissium alloy.

Production and separation of no-carrier-added 93,94,95Tc from 9Be activated yttrium target

Abstract Proton rich Tc radionuclides have been produced for the first time through 89Y(9Be, xn)93,94,95Tc reactions. In order to optimize the yield of a particular radionuclide of choice, batch yield of 93Tc, 94Tc and 95Tc have been measured at different incident energies using stacked-foil technique followed by off-line γ-spectrometry. No-carrier-added (nca) 93,94,95Tc radionuclides have been separated from bulk yttrium by liquid–liquid extraction (LLX) and solid–liquid extraction (SLX) techniques. Trioctylamine (TOA) diluted in cyclohexane was used as liquid anion exchanger in LLX in presence of HCl. SLX was carried out using cation and anion exchanger resin, DOWEX-50 and DOWEX-1, respectively, in HCl medium.

In situ formation of stable gold nanoparticles in polymer inclusion membranes

Gold nanoparticles (Au nps) were synthesized in the matrix of a plasticized anion-exchange membrane. The membrane was prepared by solvent casting of the solution containing a liquid anion exchanger trioctylmethylammonium chloride (Aliquat-336), a matrix-forming polymer cellulose triacetate (CTA), and a plasticizer dioctyl phthalate (DOP) dissolved in CH 2 Cl 2 . For in situ synthesis of Au nps, the membrane samples were equilibrated with a well-stirred solution containing 0.01 mol L - 1 HAuCl 4 . AuCl 4 - ions were transferred to membrane matrix as an ion pair with Aliquat-336 by an ion-exchange mechanism. In a second step, AuCl 4 - ion-loaded membrane samples were placed in a well-stirred 0.1 mol L - 1 aqueous solution of NaBH 4 for reduction. It was observed that 80% of the anion-exchange sites were readily available for the exchange process after formation of the Au nps. The content of Au nps in the membrane was increased either by increasing the concentration of the Aliquat-336 in membrane or by repeating sequential cycles of loading of AuCl 4 - ions followed by reduction with BH 4 - in the membrane matrix. TEM images of a cross section of the membrane showed that Au nps were dispersed throughout the matrix of the membrane but excluded from the surface. The size distribution of the nps was found to be dependent on Au content in the membrane. For example, 7- to 16-nm Au nps with average size 10 nm were observed in the membrane after the first cycle of synthesis. On increasing the Au content in the membrane by repeating the cycle of synthesis, the size dispersion of nps broadened from 5 to 20 nm without affecting the average size. The λ max (530 nm) and intensity of the surface plasmon band of Au nps embedded in the matrix of membrane were found to remain unaltered over a testing period of a month in the samples kept in water as well as in air under ambient conditions. This indicated that Au nps were quite stable in the membrane matrix. The experimental information obtained by the radiotracers and energy-dispersive X-ray fluorescence (EDXRF) analyses has been used to understand the process of Au nps formation in the membrane matrix.

Extraction chromatographic studies of copper(II) and bismuth(III) with Aliquat-336

A selective method has been developed for extraction chromatographic studies of Cu II and Bi III with Aliquat-336 (liquid anion exchanger) coated on silica gel as a stationary phase. Quantitative extraction of Cu II has been achieved at 4.0-6.0 M HCl and quantitative extraction of Bi III has been achieved at 0.1-4.0 M HCl, 0.1-6.0 M HNO 3 and 1.0-3.0 M H 2 SO 4 . The effects of different acids, stripping agents, flow rate on extraction and elution have been investigated. Cu II and Bi III have been separated from several metal ions. In order to assess the possible analytical application, both the metal ions have been separated from several multicomponent mixtures containing metal ions commonly associated with it. Attempts have been made to extract Cu II from standard alloy and ore samples. The proposed method is simple, rapid and selective.

Extraction chromatographic method of preconcentration and separation of fluoride with high molecular mass liquid anion exchanger, Aliquat-336

A selective method has been developed for the extraction chromatographic separation of fluoride with Aliquat-336 (liquid cation exchanger) coated on silanised silica gel. Its quantitative extraction has been achieved in HCl medium at 0.1-0.3 M range. The effects of acid with different concentrations, flow-rate, stripping agents on extraction and elution have been investigated. Exchange capacity and break-through capacity of the prepared exchanger at different temperatures with respect to fluoride have been determined. The extraction equilibrium constant (K ex ) and different standard thermodynamic parameters have also been calculated by temperature variation method. Effect of influent concentration and influent volume on preconcentration factor (PF) has been investigated. Fluoride has been separated from synthetic binary and multi-component mixtures containing various anions associated with it in environmental samples. The method effectively permits sequential separation of fluoride from synthetic mixture containing its congeners, chloride, bromide and iodide of analytical group. The method was found effective for removal and recovery of fluoride from industrial waste and environmental samples following its preconcentration on the column. A plausible mechanism for the extraction of fluoride has been suggested.

Enhanced Anion Exchange for Selective Sulfate Extraction: Overcoming the Hofmeister Bias

In this communication, a new approach to enhancing the efficacy of liquid-liquid anion exchange is demonstrated. It involves the concurrent use of appropriately chosen hydrogen-bond-donating (HBD) anion receptors in combination with a traditional quaternary ammonium extractant. The fluorinated calixpyrroles 1 and 2 and the tetraamide macrocycle 4 were found to be particularly effective receptors. Specifically, their use allowed the extraction of sulfate by tricaprylmethylammonium nitrate to be effected in the presence of excess nitrate. As such, the present work provides a rare demonstration of overcoming the Hofmeister bias in a competitive environment and the first to the authors' knowledge wherein this difficult-to-achieve objective is attained using a neutral HBD-based anion binding agent under conditions of solvent extraction.

Separation of carrier-free 111In, 116,117Te and 116,116m,117Sb from a 11B-induced silver target

Heavy-ion activation with ~55 MeV 11B beam on silver target leads to the production of carrier-free 111In, 116,117Te and 116,116m,117Sb radioisotopes in the target matrix. Liquid-liquid extraction, using Aliquat-336 and trioctylamine (TOA) as liquid anion exchangers in HNO3 and HCl medium, respectively, and di-(2-ethylhexyl)phosphoric acid (HDEHP) as liquid cation exchanger in ammoniacal medium was used to investigate the separation of the produced radioisotopes from the bulk target matrix.

Speciation of chromium in wastewater and sludge by extraction with liquid anion exchanger Amberlite LA-2 and electrothermal atomic absorption spectrometry

A simple, integrated method for the speciation of chromium in wastewater and sewage sludge was developed, utilising liquid anion exchange by Amberlite LA-2 (LAES) and final determination by electrothermal atomic absorption spectrometry (ETAAS). Samples were filtered through a 0.45 μm membrane filter and chromium species were determined in filtered water samples and in sludge on the filters. In the former case (filtrate), total Cr was determined directly by ETAAS, while for the determination of Cr(VI) the filtrate was buffered to pH 6.4, extracted with LAES and Cr(VI) was determined in the organic extract. Cr(III) was determined by the difference. In the latter case (filter), the filters were leached with an alkaline buffer solution (pH 12.7) and the supernatant was subjected to the same extraction procedure. For the determination of total leachable Cr, the filters were subjected to acid leaching with dilute HNO 3 (pH 1) and the supernatant was subjected to ETAAS, after appropriate dilution with water. Then, Cr(III) was determined by the difference. The limits of detection (LOD) were 0.39 and 0.45 μg l −1 for total Cr and Cr(VI), respectively, in the dissolved phase and 2.10 and 0.87 ng g −1 for total Cr and Cr(VI) in the suspended solids. The recoveries of total Cr and Cr(VI) in filtrated wastewater samples and filters were quantitative, ranged from 93 to 106%. The effect of time and temperature of sonication and suspended solids concentration on total Cr and Cr(VI) recovery was studied. No significant difference in recoveries was obtained for sonication temperatures between 30 and 70 °C. However, sonication time equal to or higher than 30 min and concentration of suspended solids equal to or less than 30 mg significantly improved Cr recovery. The ETAAS program for the determination of Cr(VI) in Amberlite/MIBK extract was carefully optimised in the absence of a chemical modifier to avoid memory effects. The developed analytical method was applied for the determination of chromium species in wastewater and suspended solids of a municipal and a lab-scale wastewater treatment plant.

Synthesis and fungicidal activity of the complexes of N-alkylphenothiazines with titanium(IV) and zirconium(IV)

A selective method has been developed for extraction chromatographic studies of with aliquat-336 (liquid anion exchanger) coated on silica gel as a stationary phase. Quantitative extraction of Co II has been achieved at 6.0-8.0 M HCI. The effects of different acids with varying concentrations, stripping agents, flow rate on extraction and elution have been investigated. has been separated from binary, ternary and quaternary mixture of various metal ions. Selective separation of has been achieved from most of the common transition metals. The proposed method is simple, rapid and selective.

Alternative radiochemical heavy ion activation methods for the production and separation of thallium radionuclides

Heavy ion activation of natural gold foil with a 7Li beam results in the formation of carrier-free 199–201Pb radionuclides along with their corresponding decay products, 199–201Tl, in the matrix. At 49 MeV projectile energy, the production of 199Tl through its precursor 199Pb is maximal, while that of other thallium radionuclides is minimal. Another way for the direct production of carrier-free thallium radionuclides is to irradiate natural platinum foil with a 7Li beam; on this case, production of 199Tl is maximal at 43 MeV projectile energy. The carrier-free thallium radionuclides have been separated from the bulk target matrix gold and platinum by liquid–liquid extraction using trioctylamine as a liquid anion exchanger.

New process for the preparation of pigment-coated phosphors on the base of electroacoustic characterization

A simple and easily reproducible method for binding pigment particles to phosphor ones was realised, using an heterocoagulation process. An electrokinetic technique was used to measure the ζ potential of phosphor and pigment particles suspensions at different pH in the presence or not of dispersing and binding agents. Starting from the results of these measurements it was possible to optimise the process. This process introduced as binding agent a liquid fatty amine, generally used as liquid anion exchanger and never used before at this purpose, whilst as dispersing agent it was used an ammonium salt of polyacrilic acid. The pigment powder was coagulated over the phosphor powder in a pH region where surfaces had opposite charge, resulting in a stable deposition of pigment on the phosphor particles.

Determination of mercury at a dithizone-modified glassy carbon electrode by anodic stripping voltammetry.

Mercury is one of the most abundant heavy metals in the environment, and its toxic effects have been recognized for a long time. Due to its dangerous and harmful properties for the health of human being, the determination of mercury is very important for environmental protection. The typical methods for determining mercury are atomic absorption spectrophotometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and mass spectrophotometry (MS). Although these methods have good sensitivity, they require expensive instruments, well-controlled experimental conditions, and profound sample-making. Because of its advantages of easy fabrication, excellent sensitivity, fast response, good selectivity and low cost, chemically modified electrodes (CMEs) have drawn much attention in every field of analytical chemistry. CMEs have been widely used in analytical chemistry, especially in electroanalytical chemistry, and have been successfully used to determine trace levels of heavy metal. 1-5 Until now, various CMEs for determining mercury have been reported. Gao and his coworkers 6 determined mercury using a ferrocenylpolythia crown ether-Nafion modifeid GCE. Navratilova et al. 7 reported a humic acid-modified carbon paste electrode (CPE) for the determination of mercury. Cai et al. 8,9 have determined mercury using a liquid anion exchanger (Amberlite LA2) modified CPE and 2-mercapto-4(3H)-quinazolinone modified CPE, respectively. To our knowledge, the determination of mercury using a dithizone-modified glassy carbon electrode has not been reported. Dithizone contains azo and hydrosulfide groups, which are good electron donors. Dithizone is widely used in extraction spectrophotometry because it can form stable complexes with many metal ions under proper conditions. From this perspective, we fabricate a dithizone-modified glassy carbon electrode to improve the sensitivity of determining mercury. As expected, 1 x 10 -7 mol/L Hg 2+ had no voltammetric response at a bare glassy carbon electrdoe (GCE) after being accumulated at -0.80 V for 5 min. However, the peak current of 1 x 10 -7 mol/L Hg 2+ at a dithizone-modified GCE was greatly enhanced under the same conditions. In this work, dithizone-modified GCE was investigated to determine trace levels of mercury. Dithizone-modified GCE has the following advantages: easy fabrication, low detection limit, fast response and good selectivity. Using this dithizone-modified GCE, trace levels of meycury in seawater samples were determined and the average recovery was 100.96%.

Equilibrium and kinetics of Zn(II) bromide extraction with Amberlite LA-2 and methyl isobutyl ketone

The rates of extraction of Zn(II) from hydrobromic acid solutions into benzene solutions of the liquid anion exchanger Amberlite LA-2 and those into methyl isobutyl ketone (MIBK) have been investigated. The distribution equilibria of this system have been also studied. Under the used experimental conditions the extracted species of Zn(II) have been proposed. The kinetic data indicated a first order reaction with respect to Zn(II) in both systems, nearly one with respect to HBr and from 0–0.38 for LA-2. In case of extraction of Zn(II) with methyl isobutyl ketone, MIBK, the reaction order with respect to MIBK was found to be 4 and with respect to HBr inverse first order. The rate constants of these extraction processes were determined and the rate determining steps were discussed in the light of the obtained results.

Separation of 48V and 48,49Cr in 7Li irradiated Sc 2O 3 target by liquid–liquid extraction

A radiochemical heavy ion activation procedure was carried out for the simultaneous production of carrier-free 48V and 48,49Cr in 7Li ion irradiated Sc 2O 3 target, followed by the separation of the individual radio-elements in pure form through liquid–liquid extraction using liquid cation exchanger, di-(2-ehtylhexyl) phosphoric acid. Liquid anion exchanger, trioctylamine, was used to obtain extractants from aqueous acid solutions under different experimental conditions.

Alternative methods for the production of carrier-free 66,67Ga

Heavy ion activation of natural cobalt foil with 52 MeV 11B 4+ and 73 MeV 12C 6+ results in the formation of carrier-free 66,67Ge and 66,67As radionuclides, respectively, along with their corresponding decay products, 66,67Ga in the matrix. The carrier free gallium radionuclides have been separated from the bulk target matrix cobalt by employing liquid–liquid extraction method using TOA as liquid anion exchanger.