Anion Exchanger Dowex Research Articles

The Synthesis of Glycerol Carbonate from Glycerol and Dimethyl Carbonate in the Presence of Strongly Basic Anion-Exchange Styrene-Divinylbenzene Anionites Dowex

The synthesis of glycerol carbonate from glycerol and dimethyl carbonate in the presence of strongly basic styrene-divinylbenzene anionites Dowex 1×2, Dowex 1×4 and Dowex 1×8 in the –OH form with different cross-linking degree of polystyrene matrix (the divinylbenzene content of 2, 4 and 8 wt.%) at 90–105 °C and a dimethyl carbonate/glycerol molar ratio equal to 2 was studied. The yield of glycerol carbonate was shown to decrease with an increase in the cross-linking degree of the anion-exchange resin. The maximum conversion of glycerol (95 %) and selectivity to glycerol carbonate (45.5 %) were observed in the presence of Dowex 1×2 at 105 °C after 5 h of the reaction. Advantages of the studied systems were demonstrated in comparison with the anion-exchange and cationexchange resins proposed in the literature.

Distribution Coefficients of 60 Elements on Cation and Anion-Exchange Resin in Ammonium Chloride Solutions

ABSTRACTAmmonium chloride is a widely available non-corrosive and non-toxic chemical. When in contact with protein NH4Cl is non-destructive and allows softer conditions for labeling of organic substances. These properties make NH4Cl appropriate for use in multiple areas such as pharmaceutical production, low-background research, etc. For such purposes, a multitude of pure elements could be applied. In order to obtain pure elements their separation (purification) is necessary. One of the most successful methods of elements separation is ion exchange. In this work, we study the distribution coefficient of 60 elements on anion exchange (Dowex 1-x8) and cation exchange (Dowex 50w-x8) resins with NH4Cl solutions with varying concentrations via ICP-MS.

Investigations of chromium (VI) ion sorption and reduction on strongly basic anion exchanger

ABSTRACTRemoval of chromium(VI) ions and their reduction were studied on the anion exchanger Dowex PSR-2 in the pH range from 1.5 to 10. The parameters of Cr(VI) sorption process on the anion exchanger were calculated based on the most popular isotherm models such as: Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich (D-R). The Langmuir isotherm was the most appropriate to describe Cr(VI) sorption. The Cr(VI) uptake by Dowex PSR-2 was found to follow the pseudo-second-order rate kinetics. Reduction of chromium(VI) in the pH range 1.5–10 was observed using the HPLC-ICP-MS (high-performance liquid chromatography–inductively coupled plasma-mass spectrometry) method. Oxidation of tri-n-butyl quaternary ammonium groups during the chromate (VI) removal process was observed.

Adsorption of arsenic by hybrid anion–exchanger based on titanium oxyhydrate

The article has investigated the removal of anion–exchange forms of As(V) by organic anion–exchangers Dowex Marathon 11, Dowex SBR-P and organoinorganic anion–exchangers containing titanium oxyhydrate, from 0.2–2.0 mM solutions of NaH2AsO4 in the range of equilibrium values pH 3–10. It has been found that introduction of an inorganic component in the amount of 7 fractions of total mass, % results in non-additive (up to 50 fractions of total mass, %) increase of absorption of ions of As(V) in adsorption from weakly alkaline solutions. It was assumed that nonadditive change of the value of absorption may be caused by the influence of the negative charge of the surface of oxide component of organic anion–exchangers. It is shown that in acid media and also at an increase of the amount of the introduced titanium oxyhydrate the values of adsorption and distribution coefficient of As(V) ions approaches additive ones.

Sorption Behavior of Dowex PSR-2 and Dowex PSR-3 Resins of Different Structures for Metal(II) Removal

ABSTRACTThe sorption behavior of palladium(II) (Pd(II)) onto strongly basic anion exchange Dowex resins was studied depending on the concentration of hydrochloric acid (0.1–6.0 M HCl–100 mg Pd(II)/L), concentration of hydrochloric and nitric(V) acids (0.1–0.9 M HCl–0.9–0.1 M HNO3–100 mg Pd(II)/L), and the time of contact of the solution with the anion exchange resin in the batch mode. Similar research was carried out also for the base metal ions such as cobalt(II) (Co(II)), copper(II) (Cu(II)), nickel(II) (Ni(II)), and zinc(II) (Zn(II)). The sorption process was also examined depending on the initial Pd(II) concentration, agitation rate, bead size distribution, and temperature. Pd(II) sorption was also checked in the column mode. The equilibrium and kinetic characteristics of the sorption of Pd(II) with the Dowex PSR-2 and Dowex PSR-3 anion exchange resins were determined. The possibilities of Pd(II) elution and reuse using the batch method was exploited. Pd(II) and Zn(II) sorption on the Dowex resins is time and concentration of acids dependent. Evaluating the determination coefficients, the kinetic studies showed that the pseudo-second-order equation and the Langmuir model described the data more appropriately than others. The maximum sorption capacity was 165.15 mg Pd(II)/g for Dowex PSR-2 and 184.39 mg Pd(II)/g for Dowex PSR-3. Dowex resins give quantitative Pd(II) removal from diluted acidic solutions.

Effect of Incorporation of Hydrated Oxides of Sn (IV), Zr (IV) and Fe (III) in a Matrix of the Anion Exchanger Dowex SBR-P on the Sorption Capacity towards the Arsenic (V) Anions

Effect of Incorporation of Hydrated Oxides of Sn (IV), Zr (IV) and Fe (III) in a Matrix of the Anion Exchanger Dowex SBR-P on the Sorption Capacity towards the Arsenic (V) Anions

Ion Exchange of the Organometallic Aqua‐Ion fac‐[99mTc(CO)3(H2O)3]+ from Aqueous Solutions

Dynamic (column) studies on the ion exchange of triaquatricarbonyltechnetium(I) cation, fac‐[99mTc(CO)3(H2O)3]+ (1), in the system: amphoteric ion exchange resin (Purolite S‐950) ‐ aqueous HNO3 solutions (0.05–2 M) corroborate the +1 charge of 1. Stability constants of fac‐[99mTc(CO)3(H2O)3−nCln]1−n complexes, determined from the distribution coefficients in the system anion exchanger (Dowex 1X4) ‐ aqueous HCl solutions (0.1–12 M) differ from the literature values determined at a constant ionic strength. This difference, resulting from the decrease in the activity of water with increasing HCl concentration, may be a measure of the effect of non‐constant ionic strength on ion‐exchange equilibria. Weak acidic properties of 1 in aqueous solution at n.c.a. (no carrier added) level (pKa ⩽9) have been demonstrated by paper electrophoresis.

Effect of adsorption of Pb(II) and Cd(II) ions in the presence of EDTA on the characteristics of electrical double layers at the ion exchanger/NaCl electrolyte solution interface

The main propose of this work was to describe the basic parameters of electrical double layer structures of the ion exchanger/NaCl before and after the sorption process of Pb(II) and Cd(II) ions from aqueous solutions in the presence of the complexing agent EDTA (ethylenediaminetetraacetic acid). In the studies the following ion exchangers were used: cation exchangers Micro-ionex (in the H + and NH + 4 forms), Dowex 50W×4 (in the H + form), and Dowex 50W×12 (in the H + form); anion exchangers Dowex 1×4 (in the Cl − form) and Dowex 1×8 (in the Cl − form). Study of the physicochemical properties of the sample surface was carried out. The influence of ionic strength, pH, and solution interface was investigated. Electrophoretic mobility, surface charge density, and parameters for different concentrations of the electrolytes under question were presented. pH was changed from 3 to 10. The studies were carried out for the M(II)–EDTA = 1:1 system. The effects of the concentration of the solution containing the above-noted complexes and of the ion exchange/solution phase contact time on sorption capacities of the ion exchangers under consideration were studied. Kinetic parameters of the sorption process were also determined.

A novel technique for the effective concentration of 99mTc from a large alumina column loaded with low specific-activity (n, γ)-produced 99Mo

Molybdenum-99 of low-to-medium specific activity, 7.4–14.8 GBq/g, obtained by the 98Mo(n, γ) 99Mo reaction in research reactors requires a large alumina column to adsorb the molybdenum since the capacity of alumina to adsorb Mo is limited (20 mg Mo/g of alumina). The large size of alumina column, in turn, requires large eluant volumes to elute the 99mTc, and the radioactive concentration (RAC) of the pertechnetate becomes unacceptably low for radiopharmaceutical applications. This study describes a method for obtaining high RAC pertechnetate solutions from a column generator loaded with 99Mo of low specific activity. Molybdenum-99 of specific activity, 7.4 GBq/g, was absorbed on an alumina column [60 g, 70 mm, ( H)×35 mm (diam.)]. The 99mTcO 4 −, eluted with 60 ml normal saline (0.15 N NaCl), was applied to a 12 mm (H)×1 mm (diam.) column containing 15 mg of the strong anion exchanger Dowex 1×8. The retained pertechnetate was eluted with 5 ml of 0.5 mM tetrabutylammonium bromide (TBAB) solution in methylene chloride. The organic solvent was subsequently removed under vacuum and the dry residue was reconstituted with the desired volume of normal saline. All the operations were carried out in a closed cycle with sterile connecting tubes and multi-way stop-cocks. The concentrated pertechnetate obtained contained about 90% of the total saline eluate and had a pH of 6–7, a radiochemical purity (RCP) consistently >99%, the 99Mo breakthrough was around 10 −4%. Colorimetric spot tests (limit tests) for Al and Mo showed <10 ppm in the final 99mTcO 4 − solution. The RCP of the labelled compounds prepared using the pertechnetate obtained and five different radiopharmaceutical kits were >95%. The procedure may be equally applicable for the effective concentration of 188ReO 4 − from 188W– 188Re generators.

Development and prevalidation of a method for phenol determination by solid-phase spectrophotometry

A simple, sensitive and rapid solid-phase spectrophotometric procedure was developed for the determination of traces of phenol with 4-aminoantipyrine as a reagent (AAP-SPS), and the optimal experimental conditions were established. This method was performed by sorption and direct absorbance measurements of the product phenol-AAP sorbed on the anion-exchanger Dowex 1-X4 (0.2 g) at 495 nm (absorption maximum) and 700 nm (non-absorption wavelength). The sensitivity offered by the AAP-SPS procedure was higher by a factor of 40 compared with the respective conventional spectrophotometric method. Metrological characteristics were established using a prevalidation strategy. The AAP-SPS procedure is characterized by a linear calibration function in the working range of 0.05–0.50 µmol, low standard deviation of procedure (±0.012), low limit of determination (0.021 µmol), and favorable random (±0.85 to ±11.27%) and systematic deviations (−4.55 to +11.50%). Moreover, the accuracy of the system investigated by the recovery test is acceptable (99–102%). Favorable working and performance characteristics make the new SPS method ideal for phenol monitoring in pharmaceutical preparations as well as other matrices.

Determination of Ca, Mg, Fe and Zn partitioning in UHT cow milks by two-column ion exchange and flame atomic absorption spectrometry detection

An operationally defined fractionation protocol was developed to study the partitioning of Ca, Mg, Fe and Zn in UHT cow milks. The method was based on sorption of distinct metal species by two ion exchange columns, namely strong cation exchanger Dowex 50Wx4 and strong anion exchanger Dowex 1x4, connected in a series. The evaluation of the donation of metal species classes distinguished, that is cationic and anionic fractions, was made after splitting the columns and elution of metal groupings with a 2.0 mol l −1 HCl solution, followed by the determination of metal concentrations in the resulting eluates. The amount of third, inert fraction was assessed by measuring metal contents in the effluents obtained after passage of the samples through the columns. The results achieved utilizing two-column ion exchange based procedure were compared with those obtained for the approach in which the columns were considered separately. The fractionation pattern for each metal studied was thoroughly discussed in light of available knowledge relating to the composition of milk.

Simple and versatile operational fractionation of Fe and Zn in dietary products by solid phase extraction on ion exchange resins

A simple and versatile protocol, based on use of solid phase extraction on strong ion exchangers and off-line detection by flame atomic absorption spectrometry, was devised to fractionate iron and zinc in common dietary food and beverages products, i.e., bee honeys, fruit juices and tea infusions. In the procedure proposed, cation exchanger Dowex 50Wx4 and anion exchanger Dowex 1x4 were used separately for distinguishing broadly meant the cationic metal fraction and the fraction of stable anionic metal complexes, respectively, after retention of metal species and their exhaustive elution by means of a 4.0 mol l −1 HCl solution. The third fraction, referred to the residual metal species, was retrieved by difference between total soluble metal contents and sum of metal quantities in separated cationic and anionic fractions. The fractionation pattern observed for both metals was described and discussed.

Deionization of water for small factories or laboratories by a four-stage ion-exchange device

Deionization of water by a small singe-body device with four-stage ion-exchange processes for production of deionized water for laboratory analyses (according to BDS ISO 3696 and BS 3978) or small factories was studied. Four ion-exchange processes were performed in a single filter body: cation exchange by weak acid cation exchanger Lewatit CNP 80; cation exchange by strong acid cation exchanger Lewatit S 100; anion exchange by weak base anion exchanger Lewatit MB 64; anion exchange by strong base anion exchanger Dowex SBR. Conventional water treatment ion exchange plants use the same four processes but in more than one filtration body (minimum two). Besides, they need at least 12 valves for water and regeneration flows redistribution and quite a large space for technological localization and service. The small water treatment ion exchange device developed is compact compared to the conventional ones and has only 4 valves.

Regeneration of Mixed Solvent by Ion Exchange Resin: Selective Removal of Chloride and Sulfate

The selective extraction of sulfate and chloride ions from mixed solvent solutions was investigated. The mixed solvents consisted of water and 50 to 100%‐w (salt‐free solvent) ethylene glycol. The extraction was measured for mixed solvent solutions containing only sulfate and chloride, and mixed solvent solutions saturated with trona (sodium sesquicarbonate, Na2CO3 · NaHCO3 · 2H2O(s). Three anion exchange resins, Dowex 1X8‐50, Dowex 21K‐Cl, and Dowex MSA‐1, were investigated for their chemical and physical resistance to the mixed solvent carbonate/bicarbonate solutions, for their swelling behavior in the different mixed solvents, and for their extraction efficiency for chloride and sulfate. The loading of the ion exchangers was fitted to a Langmuir‐type sorption model. While the extraction from trona‐free mixed solvents was well reproduced, the loading of the ion exchangers with chloride and sulfate from trona‐saturated mixed solvent solutions did not fit the sorption model. It appears, rather, that under these conditions chloride and sulfate are “salted out” of the bulk solution and driven into the ion exchangers.

Copper, zinc and manganese determination in saline samples employing faas after separation and preconcentration on Amberlite XAD-7 and Dowex 1x-8 loaded with Alizarin Red S

Two procedures have been proposed and compared for separation and preconcentration of trace amounts of manganese, copper, and zinc in saline samples. The procedures are based in the use of Amberlite XAD-7 and an anion-exchanger Dowex 1X8-50 loaded with Alizarin Red S (ARS). In order to obtain quantitative recoveries of metal ions, various experimental parameters such as pH, shaking time, sample volume, amounts of solid phase, effects of concomitants, capacity and cations desorptions from solid phases were optimized. For Amberlite XAD-7 impregnated with ARS (XAD 7-ARS), Mn, Cu, and Zn were quantitatively retained, in the pH range 8.5-10.0, by using 0.50 g of solid phase, stirring time of 5 min and a total mass up to 200 µg of each cation. The sorbed elements were subsequently eluted with 5 mL of 3 mol L-1 HNO3, with recovering over 95%, and a fifty-fold preconcentration factor for Zn and a ten-fold preconcentration factor for Mn and Cu were obtained. For Dowex 1X8-50 impregnated with ARS (Dowex-ARS), Cu and Mn were quantitatively retained in the pH range 8.1 to 9.0, and Zn pH 8.1, by using 0.75 g of solid phase, 90 min of stirring time and a total mass up to 50 µg of each cation. The sorbed elements were subsequently eluted with 20 mL of 2 mol L-1 HNO3, and a five-fold preconcentration factor to Cu and Zn was obtained. The precision of the procedure was determined by running 10 replicate samples, each one containing 250 µg L-1 of each element and the relative standard deviations were 0.2% (Cu), 0.4% (Mn), and 0.4% (Zn), to XAD 7-ARS and 0.3% (Cu), 0.5% (Mn), and 0.3% (Zn), to Dowex-ARS. The procedures were used for determining of Mn, Cu, and Zn in physiological solutions and seawater samples, from Salvador-Bahia. The analyte addition technique was used and the recoveries obtained (³ 95%) revealed that the proposed procedure shows good accuracy and precision.

Kinetics of 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene-3,6-disulphonic acid immobilization on anion exchangers

Abstract The sorption of 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene-3,6-disulphonic acid (PACA) onto the anion exchange resins, Dowex 1-X8 and Dowex 2-X8, from aqueous solutions with pH between 1 and 10 was studied spectrophotometrically. Conditions for obtaining modified sorbents with a given capacity for the azo compound were determined. The absorption and reflectance spectra of the sorbed dye were recorded. The immobilized reagent retained similar chromic characteristics as in the solution. The sorption mechanism was investigated under static conditions in the temperature range from 0 to 25 °C, by determining the amount of sorbed dye as a function of contact time. The sorption was a first order process in all cases. The pore diffusion was found to be a rate-limiting step in the sorption process. The diffusion coefficient values from 6.0 to 7.4×10−7 cm2 s−1 were calculated from the experimental results. The activation energy of PACA sorption is −8.56 and −8.05 kJ mol−1 for Dowex 1-X8 and Dowex 2-X8, respectively.

Solid-phase spectrophotometric determination of trace amounts of vanadium using 2,3-dichloro-6(3-carboxy-2- hydroxynaphthylazo)quinoxaline

Solid-phase spectrophotometry (SPS) has been applied to analysis for trace amounts of vanadium in several environmental water (potable and polluted), biological samples (human blood and urine), and soil samples. Vanadium was sorbed in a styrene-divinylbenzene-type anion-exchanger Dowex 1-X8 as a vanadium—2,3-dichloro-6(3-carboxy -2-hydroxynaphthylazo)quinoxaline. Resin phase absorbances at 606 and 800 nm were measured directly which allowed the determination of vanadium in the range 0.03–2.2 ng ml −1 with a relative standard deviation (R.S.D.) of 1.4%. The comparison of the SPS method and the gallic acid persulphate method shows that the linearity, analytical sensitivity, and precision were better for the SPS method, and that the latter method has lower detection and quantification limits compared with the gallic acid persulphate method.

Studies of the Effect of Crosslinking in the Strongly Basic Anion Exchanger Dowex 1 and the HNO3 Concentration Employed on the Separation of the SmIII–NdIII Pair in the Polar Organic Solvent–H2O–HNO3 System

Because of their specific structure, rare earth elements are used for the modification or structural stabilization of many metallic or ceramic materials employed in modern technology and also in the metallic form, i.e. in alloys and compounds with unique properties. Industrial demand for rare earth metals has increased lately due to their new application possibilities, e.g. in supermagnets of the Nd–Fe–B type or in ceramic high-temperature superconductors. Equally, the application of rare earth elements in metallurgy, catalysis, ceramics, etc. remains of significant importance. The separation and purification of rare earth elements(III) which occur in groups with similar physicochemical properties involve extremely difficult and complex processes. Ion exchange is one method which enables such separation. This paper presents the results of studies of the influence of the extent of crosslinking in the anion exchanger Dowex 1 and the concentration of nitric acid on the separation of the SmIII–NdIII pair by frontal analysis in 90% v/v CH3COCH3– or the CH3OH–10% v/v × M HNO3 systems. The most effective results were obtained in the 90% v/v CH3OH–10% v/v 7 M HNO3 system employing the anion exchanger Dowex 1 × 4 allowing 0.11 kg samarium(III) to be purified on 1 dm3 ion exchanger in the nitrate form and leading to a decrease in the micro-component content to a value below 10−3%.

Raman Spectroscopic Study of the Aging and Nitration of Actinide Processing Anion-Exchange Resins in Concentrated Nitric Acid

Degradation of two types of anion exchange resins, Dowex 11 and Reillex HPQ, from the action of concentrated nitric acid (4 to 12 M) and radiolysis [from depleted uranium as UO22+ nitrate species and 239Pu as Pu(IV) nitrate species] was followed as a function of time with Raman vibrational spectroscopy. Elevated temperatures (∼ 50 °C) were used in the absence of actinide metal loading to simulate longer exposures of the resin to a HNO3 process stream and waste storage conditions. In the absence of actinide loading, only minor changes in the Dowex resin at acid concentrations ⩽10 M were observed, while at 12 M acid concentration, the emergence of a Raman peak at 1345 cm−1 indicates the addition of nitro functional groups to the resin. Similar studies with the Reillex resin show it to be more resistant to nitric acid attack at all acid concentrations. Incorporation of weakly radioactive depleted uranium as the UO22+ nitrate species to the ion-exchange sites of Dowex 11 under differing nitric acid concentrations (6 to 12 M) at room temperature showed no Raman evidence of resin degradation or nitration, even after several hundred days of contact. In contrast, Raman spectra for Dowex 11 in the presence of 239Pu as Pu(IV) nitrate species reveal numerous changes indicating resin alterations, including a new mode at 1345 cm−1 consistent with a Pu(IV)-nitrate catalyzed addition of nitro groups to the resin backbone.

Separation of Y(III) complexes from Dy(III), Ho(III) and Er(III) complexes with iminodiacetic acid on the anion-exchangers type 1 and type 2

The affinity series of rare earth elements complexes with iminodiacetic acid (IMDA) [Ln(III):IMDA=1:2] and with N-hydroxyethylenediaminetriacetic acid (HEDTA) [Ln(III):HEDTA=1:1] for the anion-exchanger Dowex 1 were determined. These series are atypical. Taking into account the position of Y(III), Dy(III), Ho(III) and Er(III) in the determined affinity series the purification of Y(III) from Dy(III) complexes with IMDA as well as Y(III) from Ho(III) and Y(III) from Er(III) in the macro–micro system on the anion-exchangers Dowex 1 (type 1) of cross-linking 2, 4 and 8% DVB and Dowex 2×8 (type 2) was studied by frontal analysis. The best results were obtained using Dowex 1×8 and Dowex 2×8 in the acetate form. In this way the purification of Y(III) from Dy(III) complexes with HEDTA also was studied on the anion-exchangers Dowex 1×2 and Dowex 1×4 in the HEDTA form.