Amberlite LA-2 Research Articles

Voltammetric determination of trace amounts of mercury with a carbon paste electrode modified with an anion-exchanger

A carbon paste electrode modified with a liquid anion exchanger (Amberlite LA2) was used for the voltammetric determination of mercury(II). Mercury is preconcentrated, as tetrachloromercurate(II), onto the surface of the modified electrode only by the ion-exchange effect of the modifier without application of potential. After exchange of the medium the accumulated amount of mercury(II) is determined by differential pulse anodic stripping voltammetry in a blank electrolyte solution. The response depends on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 1 μg Hg(II)/l when a suitable time for preconcentration was chosen. Preconcentration for 5 min yields a linear calibration graph for concentrations up to 1000 μg Hg(II)/l. The effect of other ions on the determination of mercury and the applicability of the method to the analysis of phenylmercury compounds in pharmaceutical preparations were investigated.

Liquid anion-exchange separation of vanadium from malonate media

Vanadium(IV) and (V) can be quantitatively extracted with 0.2 mol/l Amberlite LA-2 in xylene at pH 3.0 from 0.02 mol/l malonic acid, stripped with 0.5 mol/l hydrochloric acid, and determined spectrophotometrically. Five other liquid anion exchangers (Amberlite LA-1, Primene JM-T, Aliquat 336S, TOA and TIOA) were examined as possible extractants. The extraction of vanadium(IV) was found to be quantitative only with Amberlite LA-2, while that of vanadium(V) was quantitative with Amberlite LA-1 and LA-2, Primene JM-T and Aliquat 336S. Eight common solvents were tested as diluents; of these hexane, cyclohexane, benzene, and xylene were found to be satisfactory. Vanadium was separated from elements that do not form anionic complexes with malonic acid by selective extraction, from those that form weak complexes by washing the organic extract with water, and from metals that form strong malonato complexes by selective stripping with hydrochloric, nitric, or sulphuric acid. The method has been applied to the determination of vanadium in steel, coal fly ash and fuel oil. The precision of measurement is within ±5% and the detection limit of the method for vanadium is 0.5 mg/kg.

Electrochemical behaviour of persulphate on carbon paste electrodes modified with Prussian blue and analogous compounds

Peroxodisulphate (“persulphate”) may be determined by direct current voltammetry (DCV) using carbon paste electrodes chemically modified with Prussian Blue, iron(III)-hexacyanoruthenate(II) or iron(III)-hexacyano-osmate(II). The determination is based on the exploitation of catalytic currents from the reduction of the modifiers. Best results are obtained for iron(III)-hexacyanoosmate(II) yielding a detection limit of 1 μg O22−/ml (as persulphate) when using HCl (10−2 mol/l) as supporting electrolyte and measuring in the DCV-mode. Electrodes doubly-modified with the osmium compound and a liquid anion-exchanger (Amberlite LA2) allow determinations of persulphate after preconcentration under open circuit conditions, in the presence of hydrogen peroxide and perborate, with a detection limit of 20 ng O22−/ml (as persulphate).

Determination of molybdenum in plant reference material by thermal-ionization isotope-dilution mass spectrometry

An analytical method is described for the determination of the concentration and the isotopic composition of molybdenum in plant samples using thermal ionization mass spectrometry. After microwave acid digestion and liquid-liquid extractive separation with Amberlite LA-2, the molybdenum isotopes are measured as MoO 3 − -ions in a quadrupole mass spectrometer. In all cases, the relative standard deviation of the measurements of both natural and spike molybdenum was better than 3% for all ratios measured. The concentration of molybdenum found in three different plant reference materials agreed well with the certified values.

Determination of Titanium in High Alloy Steels and Iron Sand by Atomic Absorption Spectrometry after Solvent Extraction with Benzene Solution of Amberlite LA-2

The Atomic Absorption Spectrometry (AAS) for the determination of titanium, based on ion exchange extractions of the associated ions in high alloy steels and iron sand using benzene solution of Amberlite LA-2, is described.Titanium is extracted quantitatively in to the benzene solution of Amberlite LA-2 from O.1 M hydrofluoric acid-O.1 M hydrochloric acid mixture solution. It is back-extracted into 0.5 M hydrofluoric acid-1.2 M hydrochloric acid mixture solution.The effect- of various other elements and acids on determ ination of titanium was examined by AAS using a dinitrogen monoxide-acetylene flame. Absorption of titanium was measured at 364.3 nm and the sensitivity of titanium was 0.75 μg per 0.01 absorptivity. Mo(VI), V(V) and Zr (VI) interfere with the determination of titanium. This method was applied to the determination of titanium in high alloy steels and iron sand with the satisfactory results.

Extraction and separation of uranium and lead with liquid anion-exchangers

A method is proposed for the extraction and separation of microgram amounts of uranium(VI) and lead(II) from sodium salicylate solution with high molecular-weight amines such as Aliquat 336, TOA, TIOA, Amberlite LA-1 or Amberlite LA-2 dissolved in xylene. From a critical study of pH, salicylate concentration, amine concentration, diluent and period of equilibration, the optimum conditions were identified. The method permits separation of uranium and lead from binary mixtures with metal ions commonly associated with them, the determination of uranium, and of lead in air samples.

Separation and recovery of heavy metals from hydrometallurgical effluents by solvent extraction

The possibility of separating and recovering heavy metals from hydrometallurgical effluents by successive solvent extractions has been investigated by two different procedures with liquid waste from the Espindesa Zinc process. The waste (pH value near to 1.5) includes significant amounts of Zn (≈1.35), Cu (≈0.12), Co (≈0.32) and Mn (≈0.6 g/l) in the presence of big concentrations of macro-constituents (sulphate, chloride, Na) and Fe [≈8.8 g/l, mostly as Fe(II) salts]. As extractants, Amberlite La-2 (a secondary ammine, as chlorohydrate) and DEHPA (di-2-ethylhexyl-phosphoric acid) at 25% volume in kerosene were selected. The first method includes two extraction stages with LA-2 for Zn and Cu separation (the last one with 60 g/l of chloride ions) and three stages with DEHPA at pH values near to 1.5, 2.0 and 3.5 for isolating Fe, Mn and Co. The second method separates firstly Fe (as ferric salts) with DEHPA. Afterwards, one stage with LA-2 isolates Zn and three stages with DEHPA at pH values near to 2.0, 3.0 and 3.5 lead to fractions rich in Mn, Cu and Co. Reextractions from organic layers with water or HCl at different concentrations lead to purer solutions of the isolated metals. With both methods, the liquid waste can be converted into a saline solution with lesser problems for disposal.

Application of supported liquid membranes for removal of nitrate, technetium (VII) and chromium (VI) from groundwater

The separation of nitrate, pertechnetate and chromate ions from synthetic Hanford site groundwater was studied by liquid-liquid extraction and by supported liquid membranes, SLMs. Three different commercially available long-chain aliphatic amines, Primene JM-T (primary), Amberlite LA-2 (secondary) and trilaurylamine (TLA, tertiary), were investigated as membrane carriers, n-Dodecane was used as diluent and polypropylene membranes were used as the support. Sodium hydroxide was used as the stripping agent. The basic strength of the three amines in dodecane was studied by biphasic potentiometric titrations using a glass electrode. Flat-sheet membrane experiments, where the removal of nitric acid from the feed solution was followed by using either a glass electrode or a nitrate electrode, showed that the secondary and primary amines are more effective than the tertiary one. A detailed study of the permeation of nitric acid through SLMs as function of the concentration of the three amines in the liquid membrane was performed. Information was obtained on the diffusion coefficients of nitric acid in the aqueous phase and of the nitrate-alkylammonium salt in the membrane phase. A similar investigation was performed with HTcO 4. In this case the secondary and tertiary amines proved to be better carriers. The secondary amine also performed better than the other two as a carrier for H 2CrO 4. The primary amine showed the unique feature of removing U (VI) as an anionic sulfato-complex, together with nitrate, pertechnetate and chromate ions, from the synthetic groundwater.

Determination of manganese(II) in botanical samples by AAS after its separation with Amberlite LA-2

Determination of manganese(II) in botanical samples by AAS after its separation with Amberlite LA-2

Stability of supported liquid membranes containing longchain aliphatic amines as carriers

The stability of liquid membranes containing as carriers three different commercially available long-chain aliphatic amines, Primene JM-T (primary), Amberlite LA-2 (secondary) and trilaurylamine (TLA, tertiary) has been investigated in experiments where the feed solution was synthetic Hanford site groundwater, the strip solution was 1 M NaOH and n-dodecane was the diluent. By using flat-sheet supports the following order of stability was measured: tertiary > secondary > primary. This is the reverse order of the interfacial tension lowering at a water-n-dodecane interface. The water solubility of the amines also seems to play an important role in determining the membrane stability. Experiments performed with much thicker hollowfiber supports have shown that a larger inventory of organic phase absorbed in the membrane pores ensures a remarkably higher membrane stability. The secondary amine provides the best overall performance and is the carrier of choice for a SLM process for groundwater decontamination from anionic species. Possible alternative uses of the primary and tertiary amines for the same decontamination process are also discussed.

The Solvent Extraction of Gold Cyanide by Lauroimidazoline

The solvent extraction of gold cyanide from alkaline cyanide leach liquors by lauroimidazoline - a weak-base extractant - was investigated. The highly basic lauroimidazoline group extracted gold cyanide at a higher pH value than did Amberlite LA2 - a commercial alkylamine extractant with a pH value of protonation lower than that of the imidazoline group. The relative pH values where gold loading started to tail off were about 8 and 5 for the lauroimidazoline and the Amberlite LA2 extractants respectively. The pH value of extraction was higher for a higher concentration of lauroimidazoline in the organic phase with xylene as the diluent. The addition of tributylphosphate (an organic modifier) to the organic phase enhanced the basicity of imidazoline and hence the pH value of the extraction of gold cyanide by about two pH units. The extraction of gold cyanide passed through a minimum and increased above a pH value of 13. A synergistic solvation extraction mechanism, involving the sodium aurocyanide ion pair, tributylphosphate, and lauroimidazoline, is proposed for the extraction of gold cyanide above a pH value of 13.

Separation of Macroamounts of Metal Pairs – Part 1. Separation of Cadmium and Cobalt

The separation factors of cadmium and cobalt were performed on varying cadmium, zinc and cobalt concentrations in the original aqueous solution. A long chain amine (Amberlite LA-2) and an organophosphorus solvent (TBP) have been investigated. In most cases the values of the separation factor increases with the increase of metal concentration in the aqueous phase. The various possibilities of chemical and radiochemical separations of the metal pair are reported.

Study of the KAu (CN) 2-amine amberlite LA-2 extraction equilibrium system

The extraction equilibrium between aqueous gold (I) cyanide solutions and secondary amine Amberlite LA-2 was studied. The results showed that the amine extracts gold(I) cyanide mainly from relatively acidic solutions. The extracted complex can be represented by the formula R 2NH 2 + Au(CN) 2 −, the extraction is dependent on change in the diluent and presence of a third component in the organic phase. On the basis of experimental data a sequence for the extraction of different metal-cyanide complexes is suggested.

Some observations on the extraction of triphenylmethane dyes by ion-pair formation with amines as counterions

Triphenylmethane dyes such as xylenol orange, glycine cresol red, and methylthymol blue by formation of ion pairs with diphenylguanidine, Amberlite LA-2, and tri n-octylamine have been extracted into several solvents. The influence of the amine/solvent system, the concentration of amine, and the presence of electrolytes and the distribution parameters are discussed. As an application, the extraction of glycine thymol blue with Amberlite LA-2 solved into 1-pentanol as the most suitable extracting system was carried out.

Extraction of Cu(II) from hydrochloric acid media by Amberlite LA-1 hydrochloride dissolved in 1,2-dichloroethane

The extraction of hydrogen chloride by a secondary amine (B), Amberlite LA-1, dissolved in 1,2-dichloroethane was studied by two-phase potentiometric titration. The results, treated by a general minimizing program, indicate dimerization: 2BHCl⇌⇌(BCHl) 2. The equilibrium constant of this reaction was calculated. The extraction of cu(II) from 6 M hydrochloric acid by Amberlite LA-1 hydrochloride (BCHl) dissolved in 1,2-dichloroethane, was also studied. The extraction of cu(II) can be explained as due to formation of two species, (BCHl) 2 CuCl 2 and (BCHl) 3 CuCl 2, in the organic phase. The formation constants of these species were calculated.

Reactive extraction of penicillin G from mycel‐containing broth in a countercurrent extraction decanter

Penicillin was recovered from mycel-containing fermentation broth by direct reactive extraction into a counter-current extraction decanter, Type CA 226-290 of the Westfalia Separator Co., at room temperature via steady state operation. Penicillin concentrations in the feed varied from 3 to 41 g L(-1), Amberlite LA-2 carrier concentrations from 7 to 20 g L(-1)and/or DITDA carrier concentrations from 7.2 to 84 g L(-1), the LA-2-to-penicillin mole concentration ratio from 4 to 6.4, and/or the DITDA-to-penicillin mole concentration ratio was maintained at 2. The throughputs of the fermentation broth (520 to 880 L h(-1)) of the solvent phase (200 to 860 L h(-1)) and the over all throughput (800 to 1750 L h(-1)) were high. Extraction degrees of 72 to 96% were achieved between pH 4.6 and 5.1. Without carriers in the same pH range, extraction degrees of only 17 to 19% were attained. By reducing the pH to 2.3 and in the absence of carriers, the degree of extraction was increased to 61%. However, during the extraction, 6.5% of the penicillin decomposed. At these high throughputs, the steady state was attained within 1 to 4 min. Through the mechanical stress, the length of the hyphae was reduced and the protein content of the broth was increased by 50 to 100%. However, this protein content had no appreciable influence on the phase separation.

Extraction rates of zinc with ammonium chloride salts of Amberlite LA-2 in a horizontal rectangular channel.

Extraction rates of zinc with ammonium chloride salts of Amberlite LA-2 in hexane were measured in a horizontal rectangular channel. The experimental results were analyzed by considering the processes of diffusion in both solutions, adsorption and desorption to/from the interface and reactions at the interface for the species related as following steps;(BHCl)2,org + σ = (BHCl)2,ad (1)(BHCl)2,ad + ZnCli,aq–(i–2) = (BH)2ZnCl4,ad + (i – 2)Claq– (2)(BH)2ZnCl4,ad = (BH)2ZnCl4,org + σ (3)(BH)2ZnCl4,org + (BHCI)2,org = (BH)4ZnCl6,org (4)2(BH)2ZnCl4,org = ((BH)2ZnCl4)2,org (5)The extraction rates of zinc was interpreted from the rate equation that the interfacial reaction between (BHCl)2 adsorbed at the interface and zinc chloride in the aqueous solution shown in step (2) is the rate-determining step. Some parameters of the rate equations were estimated.

Simulation of the continuous re-extraction of penicillin G from the solution of its ion-pair complex in three different types of bench-scale column

The re-extraction of penicillin G from the solution of its ion-pair complex with the secondary amine Amberlite LA-2 was mathematically simulated, and the mass transfer coefficients were identified by means of the experimental investigations published in Likidis and Schügerl (1988, Chem. Engng Sci. 43, 27–32) for a bench-scale Karr column, a pulsated perforated plate column and a Kühni column. The longitudinal concentration profiles of penicillin in the aqueous phase in the different types of columns can be described by the same mathematical model and the mass transfer coefficient of the complex/carrier. Only the mass transfer coefficient of the penicillin acid anion differs for the column types.

Recovery of penicillin by reactive extraction in centrifugal extractors

Penicillin V and/or G were extracted from fermentation broth by Amberlite LA-2 in n-butylacetate at pH 5 in a laboratory centrifugal extractor, Type SA 01 of Westfalia, up to an overall phase throughput rate of 30 L/h, in a bench-scale four-stage extraction system, consisting of Type TA 1 of Westfalia, up to an overall phase throughput rate of 110 L/h, and in a pilot-plant three-stage extraction unit, consisting of Type TA 7 extractors of Westfalia, up to a phase throughput rate of 990 L/h with very high degrees of extraction (up to 99%). The reextraction from the ion-pair complex, which contained organic solvent, was performed by phosphate, borate, or carbonate buffer at pH 7.5-8.5 in all three extractor systems with degrees of extraction up to 98%, but at considerably lower overall phase throughput rates than those of the extraction, since no satisfactory phase separation is possible at higher throughput rates.

Reactive extraction of penicillin G in a pilot plant Karr-column II. Fermentation broths

Penicillin G was extracted from mycelfree fermentation broths by means of the carrier (Amberlite LA-2) in n-butylacetate at pH 5 in a 7.6 m high pilot plant Karr-column with degrees of extraction E=98–99% and penicillin enrichments up to 3. The reextraction was carried out with phosphate buffer at pH-values above 7.5 with degree of extractions E=86–88% and penicillin enrichments up to 3. The penicillin and carrier losses were negligible. The influence of the process variables on the extraction degree was investigated. The penicillin extraction of the model medium and the fermentation broths were compared. Recommendations are given for the optimal penicillin recovery with reactive extraction.