Amberlite LA-2 Research Articles

Method Development for the Speciation of Chromium in River and Industrial Wastewater Using GFAAS

A simple, sensitive and inexpensive method for the speciation of Cr(VI) and Cr(III) in river and industrial wastewater was developed, optimized and validated. Samples were collected, filtered and then chromium species were determined in the filtrate. In the filtrate, total Cr was determined directly by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). A portion of the filtered sample was buffered to pH 6.4, extracted with Amberlite LA-2/MIBK and finally Cr(VI) was determined in the organic extract and Cr(III) in the aqueous phase using GFAAS. The method was evaluated by analysis of the certified reference material, CRM 544, and good accuracy was obtained. The limit of detection for Cr(VI) and Cr(tot)/Cr(III) was found to be 0.30 and 0.08 µg L−1, respectively, and a precision expressed as relative standard deviation of better than 11% was achieved for nine replicates. A number of water samples from the Tinishu Akaki River, Ethiopia, and wastewater samples from a chemical plant in Germany, were analysed. In addition to the GFAAS method, Cr(tot) was also determined using ICP-MS (in CRM 544, lyophilized water, and Tinishu Akaki River water samples) and Cr(tot) and Cr(VI) using UV-VIS spectrophotometry (in CRM 544 and industrial wastewater samples). Good agreement between the different methods was found.

Liquid-liquid extraction of Au(I) by Amberlite LA2 and its application to a polymer-immobilized liquid membrane system

The liquid-liquid extraction of Au(I) by Amberlite LA2 (secondary amine) in kerosene from cyanide media has been investigated. The analysis of metal distribution data suggested the formation of R2NH2 +Au(CN)2-species in the organic phase with formation constant log Kext=6.5 ± 0.03, whereas the use of mixtures of the amine with a solvation extractant (e.g. a phosphine oxide) shifted the gold-pH1/2 extraction towards more alkaline values. The results obtained on Au(I) distribution have been implemented in a polymerimmobilized liquid membrane system, using NaOH solutions (e.g. 0.01 mol/L) to strip the metal from the organic phase.

The influence of pH and solvent polarity on the mechanism and efficiency of folic acid extraction with Amberlite LA-2

Studies on the reactive extraction of folic acid with Amberlite LA-2 in three solvents of different polarity (n-heptane, chloroform, dichloromethane), at various extractant concentrations and pH-values of the aqueous solutions, indicated that the pH-value controls the extraction mechanism through the dissociation of carboxylic groups of folic acid. Thus, the solute and the extractant participate at the interfacial reaction at a molar ratio of 1:2 for pH below pK1, and 1:1 for pK1 < pH < pK2. The solvent polarity and pH-value exhibit a significant effect both on the extraction degree of folic acid (for an Amberlite LA-2 concentration of 80 g/l the extraction degree in dichloromethane was about 2-2.7 times greater than that corresponding to extraction in n-heptane, this difference increased with increasing pH of the aqueous solution) and on the extraction constant (by increasing the pH-value from 3 to 5.2, the extraction constants obtained for dichloromethane increased about 2.7 to 27.1 times compared with those obtained for extraction in n-heptane).

Synergistic extraction of uranium( VI) in presence of 2,2' -dipyridyl and neutral donors by absorption spectrophotometric method

The extraction behaviour of uranyl ion from dilute nitric acid medium employing 2,2'-dipyridyl and their mixture with several neutral donor, viz. trioctyl phosphine oxide (TOPO), tributyl phosphine oxide (TBPO), triphenylphosphine oxide (TPPO), tributyl phosphate (TBP), trioctyl amine (TOA) and Amberlite LA-2 was investigated. The extraction constant (log k e x ) for the binary species [UO 2 (dipy)(NO 3 ) 2 (H 2 O) 2 ] was determined to be 14.06. The overall extraction constant (log K) for the ternary species for various donors are : 15.55 (TOPO), 15.49 (TBPO), 15.44 (TPPO), 15.35 (TBP), 17.14 (TOA) and 17.11 (Amberlite LA-2).

CYANEX® 301 binary extractant systems in cobalt/nickel recovery from acidic chloride solutions

The extraction and stripping characteristics of CYANEX 301 binary extractant systems were investigated for the recovery of cobalt and nickel from chloride solutions. The selectivity of these systems against calcium, manganese and magnesium was also studied. These binary extractant systems consisted of mixtures of CYANEX 301 with basic extractants (Primene® JMT, Amberlite® LA-2, Alamine® 336 and Aliquat® 336). Based on criteria such as extraction and stripping characteristics (efficiency and rates) and selectivity against calcium, manganese and magnesium, screening experiments were performed to select the most appropriate binary extractant systems. From this screening work, the CYANEX 301–amine systems all demonstrated that cobalt and nickel could be selectively extracted from calcium, manganese and magnesium. A large synergistic effect on the stripping kinetics and efficiencies of cobalt and nickel was also observed when either amine was added to CYANEX 301. Depending on the amine concentration, near complete stripping of cobalt could be achieved with all systems, while the stripping of nickel still remained very low with the amines Primene JMT, Amberlite LA-2 and Alamine 336. Among the amine extractant systems, CYANEX 301–Aliquat 336 was shown to be the most promising binary extractant system. McCabe–Thiele extraction and stripping isotherms with this system were then constructed to determine the number of stages required. Complete extraction of cobalt and nickel could be achieved in 2–3 stages while still maintaining a high selectivity against calcium, manganese and magnesium. A decrease in cobalt stripping was observed when the hydrochloric acid concentration was increased from 2 to 4 M. The hydrochloric acid concentration had a reverse effect on nickel where nickel stripping was shown to increase with increase in acid concentration from 2 to 4 M.

Modeling of the selective pertraction of carboxylic acids obtained by citric fermentation

Facilitated pertraction was applied for the selective separation of citric, maleic and succinic acids from a mixture obtained by citric fermentation. The pertraction equipment included a U-shaped cell containing 1,2-dichloro-ethane as the liquid membrane and Amberlite LA-2 as the carrier. The experimental data indicated that maleic and succinic acids can be initially selectively separated from citric acid, followed by the selectively separation of maleic acid from succinic acid. Using statistical analysis and a second order factorial experiment, two mathematical correlations describing the influence of the main process variables on pertraction selectivity were established. For both extraction systems, the considered variables controlled the extraction process to an extent of 92.9-99.9%, the carrier concentration inside the liquid membrane exhibiting the most important influence.

Synergistic effect of neutral donors on the extraction of zirconium(IV) by salicylaldoxime in dichloromethane

Liquid–liquid extraction of zirconium(IV) was investigated from dilute hydrochloric acid medium by salicyaldoxime (HA) in dichloromethane. The metal was spiked with 95 Zr and analyzed by its radioactivity. The effects of different donors, like trioctyl phosphine oxide (TOPO), triphenyl phosphine oxide (TPPO), tributyl phosphine oxide (TBPO), tributyl phosphate (TBP), trioctyl amine (TOA) and Amberlite LA-2 were studied. The adduct formation constants for both binary species (metal–ligand) and ternary species (metal–ligand–donor) were also calculated form the distribution data.

Vanadium Extraction from Fly Ash—Preliminary Study of Leaching, Solvent Extraction, and Sorption on Chitosan

Fly ashes resulting from the combustion of fuel containing high concentrations of vanadium that can be slightly removed by water and more efficiently by alkaline or acid solutions. This uncontrolled release can contaminate water sources and requires appropriate storage of fly ashes. This study investigated the possibility of cleaning the ashes by leaching the material and recovering vanadium by solvent extraction (for metal concentration solutions higher than 200 mg V L−1) using several amine extractants (Primene JM-T, Amberlite LA-2, Alamine 336, and Alamine 304), a quaternary ammonium salt (Aliquat 336), and by a sorption process (for low-metal concentration solutions) using chitosan. Extraction and stripping were investigated with liquid extractants and showed that Aliquat 336 was the best of these extractants. However, since Aliquat 336 exhibits a greater difficulty at stripping, secondary or tertiary amine extractants appear more suited for the extraction process. Vanadium sorption occurs on chitosan through anion exchange with a maximum sorption capacity of 400 to 450 mg V g−1 at pH 3. The treatment of acid leachates with chitosan does not appear possible, since it requires a pH control to pH 3, which precipitates ferric ions and coprecipitates vanadium. Alternative routes could be the alkaline leaching of fly ashes and a further pH control.

Facilitated transport of Au(CN)<sub>2</sub> and other metal-cyanide complexes using amines

The use of different amines, Hostarex A327 (tertiary), Amberlite LA2 (secondary) and Primene JMT (primary), as carriers in the facilitated supported liquid membrane transport of metal-cyanide complexes, with special attention to gold, along with the addition of neutral organophosphorous derivatives (Lewis bases) to the amine organic phase as synergistic agents for the transport of Au(CN) 2 , at alkaline pH values and selectively against other metal-cyano complexes, is investigated.

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.

Recovery of phenol from aqueous streams in hollow fiber modules.

A setup with two parallel hollow-fiber modules was used to study the recovery of phenol from aqueous solutions. Cyanex 923, Amberlite LA-2, and trioctylamine (TOA) in aliphatic kerosene were used as carriers. A solution of 0.2 M NaOH was used for stripping. It was found that each of the studied carriers permitted the effective removal of phenol. Cyanex 923 showed the best performance, removing phenol in the shortest time and giving the highest fluxes and the highest mass-transfer coefficients. The maximum fluxes of phenol entering the receiving phase changed in the following ratio: Cyanex 923/Amberlite LA-2/TOA = 3.5/1.5/1. The mass-transfer coefficient in the extraction step changed in the same order: 34/5.2/1. The mass-transfer coefficients of the stripping step were 2-4 orders lower than in the extraction step and were comparable for each carrier: Cyanex 923/Amberlite LA-2/TOA = 1.1/0.7/1. Using Cyanex 923, only 5 min were needed to recover 99% of the pollutant from the aqueous stream, containing 0.5-2 g L(-1) phenol.

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%.

Thermodynamics of the solvent extraction of Zr(IV) by Amberlite LA-2, TBP and HDEHP from different aqueous media

Solvent extraction on Zr(IV) were carried out at 5, 25 and 40 °C using Amberlite LA-2, TBP and HDEHP in toluene or kerosene from solutions of HCl, HBr or KI. The equilibrium constant Kex as well as the thermodynamic functions DG°, DH° and DS° of the nine extraction systems were deduced. The overall extraction equilibria were postulated from the obtained data.

Fractionation of the mixture obtained by the enzymatic hydrolysis of penicillin G

Using the experimental data on the individual physical and reactive extraction of 6APA with 1,2-dichlororethane, D2EHPA and Amberlite LA-2 together with data on the influence of the pH value of the aqueous phase and the Amberlite LA-2 concentration on the selective separation of 6APA, PG and PAA from a mixture, a process flow sheet for the fractionation of the solution obtained by the enzymatic hydrolysis of PG has been elaborated and applied. Thus, at pH=10, 6APA was selectively separated by four extraction stages, the overall extraction degree being 98.8%. PG was selectively extracted from the raffinate at pH=6 by three extraction stages, adjusting the molar concentration of Amberlite LA-2 to the value of the PG molar concentration for each extraction stage. The antibiotic extraction degree was 99.6%.

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.

Reaction equilibrium of penicillin G with amberlite LA-2 in a nonpolar organic solvent.

Studies have been made of the reactive extraction of penicillin G by Amberlite LA-2, a secondary amine, dissolved in kerosene. On the basis of the previous works about extraction equilibria of monocarboxylic acids by some secondary amines in low polar organic solvents, four equilibrium models were suggested to describe the reaction equilibrium of penicillin G in the liquid-liquid extraction system. The calculated results from the models were compared with the experimental data of 96 runs, and only two equilibrium models seemed to be probable. Ultimately, the most reasonable extraction equilibrium model was chosen through spectroscopic studies on organic solutions obtained by five specific extraction equilibrium experiments.

Extraction of AuCl4- from HCl solutions by the chloride salt of the secondary amine Amberlite LA2 and estimation of the interaction coefficient between AuCl4- and H+

The equilibrium distribution of AuCl4- between hydrochloric acid and the chloride salt of the secondary amine Amberlite LA2 in xylene was investigated. The extraction reaction is exothermic (ΔH° = −20.8 kJ/mol). The stoi-chiometry of the complex formed in the organic phase can be represented by R'R″NHH+AuCl4- and the extraction equilibrium constant depends on the ionic strength. From this dependency it was found that log K° = 3.9 and the interaction coefficient between AuCl4- and H+ is 0.24.

Fractionation of low-molecular-mass heparin by centrifugal partition chromatography in the ion-exchange displacement mode

Centrifugal partition chromatography in the ion-exchange displacement mode allowed a preparative and efficient fractionation of low-molecular-mass heparins from enoxaparin sodium. Amberlite LA2 — a lipophilic liquid secondary amine — was chosen as a weak anion exchanger. The biphasic system methyl isobutyl ketone–water was selected. Protonated LA2 (10%, v/v) was added to the organic stationary phase. Hydroxide (Na +, OH −) was chosen as a displacer in the aqueous mobile phase. The observed pH and concentration profiles are typical of displacement chromatography, as supported by numerical simulation. The Dubois test for the analysis of sugar content and an analysis of sulfur content (and consequently sulfatation rate) were carried out to monitor the effectiveness of the procedure. Moreover, the fractions were analyzed by high-performance size-exclusion chromatography and the 1H NMR spectra confirmed the fractionation of the sample of enoxaparin sodium.

NON-DISPERSIVE LIQUID EXTRACTION OF Cr(VI) BY TBP/ALIQUAT 336 USING CHITOSAN-MADE HOLLOW FIBER

ABSTRACT TBP and alkylammonium extractants were investigated for chromate removal from dilute solutions using chitosan-made hollow fibers. Chromate is adsorbed by the chitosan fiber and simultaneously desorbed by the extractant. The influence of chromate concentration, extractant concentration, extractant volume on relative concentration deccrease were investigated as a function of time. These experimental parameters barely influenced the decrease in the relative concentration. Fiber length is more significant in the control of the extraction kinetics. In recirculation flow mode, the relative concentration can be well described as an exponential function of time. The kinetic constant varies as a linear function of fiber length. Amine extractants (Aliquat 336, Alamine 336, Amberlite LA-2) are better extractants than TBP both from the kinetics and equilibrium standpoints. With Aliquat 336 the final Cr(VI) concentration tends to zero, while with TBP, the equilibrium is controlled by the volume of the extractant.

Determination of Roxarsone Using Carbon Paste and Amberlite LA2 Modified Carbon Paste Electrodes

The methods for determination of the growth promoter 4-hydroxy-3-nitrobenzenearsonic acid (Roxarsone) in veterinary product and in poultry drinks have been developed using differential pulse voltammetry with carbon paste and Amberlite LA2 chemically modified carbon paste electrodes. Optimal conditions have been found for Roxarsone determination with nonmodified carbon paste electrodes with limit of determination being 3 µmol L–1. The sensitivity of the determination was further improved through Amberlite LA2 modification of the carbon paste with limit of determination being 0.1 µmol L–1. Modification also enabled preliminary accumulation of Roxarsone with the exchange of the supporting electrolyte.