Strong Acid Cation Exchange Research Articles

Study on separation of Eu(II) from trivalent rare earths via electro-reduction and ion exchange

Abstract Separation of Eu(II) from trivalent rare earths was carried out in 0.01 mol dm −3 hydrochloric acid medium. Eu(III) was selectively reduced to Eu(II) at glassy carbon cathode in flow type electrolyzer. For Eu(II) separation strong acid cation exchanger based on sulfonated polystyrene/DVB copolymer impregnated into porous silica beads was used. Breakthrough and chromatography curves were measured. Eu(II) exhibited lower affinity towards the sorbent than trivalent rare earths and therefore it was the first species to breakthrough the column. Excellent separation from middle rare earths was achieved while the separation from heavy rare earths was difficult. The back-oxidation of Eu(II) was a problem despite all the measures that were taken to prevent oxidation by dissolved oxygen and photo-oxidation.

Preparation and preliminary assessment of polymer-supported zirconium phosphate for selective lead removal from contaminated water

In the present study, polymer-supported zirconium phosphate (ZrP-CP) was prepared for selective removal of lead from the contaminated water. ZrP-CP was characterized using nitrogen adsorption technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lead sorption on ZrP-CP was found to be pH dependent due to the ion- exchange mechanism. Also, ZrP-CP was proved to be more selective than the polystyrene strong-acid cation exchanger D-001 to remove lead ion from water, where other competing cations such as Na +, Ca 2+, and Mg 2+ ions coexist at high concentrations. Generally, lead sorption isotherms on ZrP-CP can be divided into two distinct regions at different load levels, and isotherms at both regions can be well elucidated by Langmuir model. The distribution coefficients ( K d) and binding constants ( B L) obtained experimentally indicated that stronger sorption affinity of ZrP-CP towards the lead ion occurs at a relatively lower load level. Also, lead sorption onto ZrP-CP was found to be an endothermic and entropy-driven process. High selectivity of ZrP-CP towards the lead ion was possibly attributed to the crystal state of zirconium phosphate and a specific interaction between orthophosphate and lead ion. Fixed-bed column runs showed that lead sorption on ZrP-CP could result in a conspicuous decrease of this toxic metal from 0.5 mg/L to below 0.01 mg/L, which is recommended as the standard of drinking water by WHO (the treatment technique standard set by US EPA is 0.015 mg/L). Also, the spent sorbent can be readily regenerated for reuse by dilute HNO 3 or HCl solution.

Uptake of Benzene and Alkylbenzenes by Cation- and Anion-Exchange Resins from Aqueous Solutions

Uptakes of benzene and 12 alkylbenzenes (from toluene to n-pentylbenzene including xylene and trimethylbenzene isomers) by both strong acid cation (Dowex 50W-X4 and X8) and strong base anion (Dowex 1-X4 and X8) exchange resins have been studied in aqueous solutions at 25 degrees C; their distribution constants (K) have been determined. The relationship between the octanol-water partition coefficient (K(ow)) and the resin affinity for solutes has been analyzed. The K values of benzene and alkylbenzenes were larger than the K values of aliphatic hydrocarbons expected from the K(ow) values. While the K value was increased with the alkyl chain length, no further increase in the K value was observed for n-butylbenzene and n-pentylbenzene.

Radiotracer measurements of protein mass transfer: Kinetics in ion exchange media

We describe a method to measure protein mass transfer kinetics in ion exchange adsorbents for preparative chromatography based on the use of radioactively labeled protein. The method was developed and evaluated using lysozyme as a test protein with the three commercial strong-acid cation exchangers SP-Sepharose-FF, SP-Sepharose-XL, and S-HyperD. Iodination with 125I was used to label the protein, which was added in trace amounts (approximately 0.1%) to an unlabeled protein solution. The solution was recirculated through a shallow bed of the adsorbent particles and the radioactivity accumulated in the bed measured with a gamma-counter as a function of time. Radiotracer-based kinetics measurements were found to be in good agreement with results obtained with a conventional shallow-bed technique, provided that freshly labeled protein solutions were used. The method has advantages in terms of simplicity, ability to deal with adsorption from complex mixtures, and the potential for measurements under tracer diffusion conditions. Kinetics results obtained for the three different stationary phases were generally consistent with previous studies. Protein mass transfer can be described by a pore diffusion model with a nearly salt-independent pore diffusivity for SP-Sepharose-FF and by a homogeneous diffusion model with a saltindependent adsorbed phase diffusivity for S-HyperD. However, it appears that a more complex model, accounting for parallel pore and surface diffusion, is needed to describe protein mass transfer in SP-Sepharose-XL. The modeling results were found to be correlated with the apparent pore sizes determined by inverse SEC.

Influence of shaped and modified Hβ zeolite on etherification of FCC light gasoline

Oxygenated compounds such as ethers produced by the reaction of methanol and tert-olefins have good potential for use as performance and environmental enhancing additives for transportation fuels. Catalytic etherification of tert-olefins with methanol has been carried out over a series of solid-acid catalysts such as Hβ (Si/Al = 25), HM OR(Si/Al = 50), HZSM-5 (Si/Al = 50) and strong acidic cation exchange resin D005 using a flow fix-bed reactor. Hβ zeolite shows higher conversion and catalytic stability than other catalysts for the production of tert-amyl methyl ether (TAME). In the shaping process, the catalytic activity of extruding zeolite Hβ before impregnating two oxides on it is higher than the reverse order. The best extruding condition is that pore-enlarging agent is PEG-4000 (10%), the dosage of binder (α-AlOOH) is 20% and the dosage of peptizer (HNO 3) is 10%. The regeneration of Hβ zeolite is much better than other catalysts. At the optimal reaction condition 70 °C, 1 h −1, 0.8 MPa and a 1.05:1 molar ratio of methanol to tert-olefins, the highest conversion of tert-olefins could reach 62.93%, the yield of TAME is high too and the technology can be applied to commercial industry well.

Ferrous–Ferric Ion exchange dosemeter

In this work a three-dimensional ferrous-ferric ion exchange dosemeter is proposed and the dose response measured. The dosemeter consists of strong acid cation exchange resin beads in the H form in water. Amberlyst 15 Wet beads with a harmonic mean diameter of 0.600-0.850 mm were prepared by soaking them in an aqueous solution of ferrous ammonium sulphate to exchange ferrous ions for H(+) ions. The beads were rinsed with distilled water and packed in glass vials. Sets of samples with ferrous ion concentrations of 0.5 and 1.0 mM were dosed with 6 MV X rays from a Varian 2100C linac. The spin-lattice relaxation time constants (T1) for the samples were measured using an Apollo spectrometer (Tecmag, Houston, TX) interfaced to a 1.5 T magnet (Magnex, Abingdon, UK). Each sample had two T1 values; a long T1 at 1200 ms that did not significantly change with dose and a short T1 that ranged from 56 ms at 0 Gy to 36 ms at 100 Gy. The R1 vs. dose responses were linear with slopes of 0.066 and 0.079 s(-1) Gy(-1).

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.

Fractionation of calcium and magnesium in honeys, juices and tea infusions by ion exchange and flame atomic absorption spectrometry

An analytical procedure was proposed to study the operational fractionation of Ca and Mg in bee honeys, fruit juices and tea infusions. The protocol devised was based on the solid phase extraction of distinct metal fractions on different sorbents, namely strong acidic cation exchanger Dowex 50Wx4, weak acidic cation exchanger Diaion WT01S and strong basic anion exchange resin Dowex 1x4. For the evaluation of the amounts of the metal fractions distinguished, a flame atomic absorption spectrometry was used off-line prior to the determination of Ca and Mg concentrations in the effluents obtained. It was established that Ca and Mg are mostly present in the analysed samples in the form of cationic species (96–100%). The accuracy of the entire fractionation scheme and sample preparation procedures involved was verified by the performance of the recovery tests.

Radioactive wastewater treatment using a mixture of TANNIX sorbent and VARION mixed bed ion exchange resin

A wastewater treatment system has been developed by using a mixture of ammonium-insoluble tannin (TANNIX, this is the trademark of an adsorbent made by Mitsubishi Nuclear Fuel Co. Ltd) and mixed (strong acid cation exchanger and strong base anion exchanger) ion exchange resin (MIX) for the selective separation of transuranium isotopes, including Pu, Am, Cm, and U, as well as fission and radioactive corrosion products from boric acid solution (pH ∼ 4.1). The equilibrium and fixed bed sorption experiments resulted in Kd values of 104–105 ml/g, and decontamination factors of 1,000, with a breakthrough point between 1500 BV and 5000 BV of accumulated volume.

Uptake of Cycloalkanes and Bicyclic Aromatic Compounds by Ion-Exchange Resins from Aqueous Solutions

The uptakes of cycloalkanes (C5 - C8) and bicyclic aromatic compounds (naphthalene, biphenyl, and azulene) by both strong acid cation (Dowex 50W-X4 and X8) and strong base anion (Dowex 1-X4 and X8) exchange resins have been studied in aqueous solutions at 25 degrees C; their distribution constants (K) have been determined. The relationship between the octanol-water partition coefficient and the resin affinity for solutes has been analyzed. The K values of three aromatic compounds were found to be much higher than expected from the octanol-water partition coefficients. This is probably due to the pi interaction of aromatic rings with the resin matrix. Microscopic observations revealed that azulene molecules are uniformly distributed inside a resin particle.

Equilibrium studies of phenylalanine and tyrosine on ion-exchange resins

The ion exchange equilibria of amino acids (phenylalanine and tyrosine) on a strong-acid cation exchanger resin (PK220) and on a strong-base anion exchanger resin (PA316) has been investigated. Based on experimental fixed-bed saturations at constant pH, each of the resins was previously screened of a set of three commercial lots with different physical properties. Overall mass balances from the saturation curves enabled to evaluate the linear isotherm constants and its dependence with pH. An equilibrium model that takes into account energetic heterogeneities in ion exchangers was successfully used to correlate binary and multicomponent data.

SU-FF-T-236: Dose Response of Ion Exchange Resin Beads

Purpose: To investigate the x-ray dose versus 1H NMR spin lattice relaxation (T1) response of ion exchange resin beads, with and without ferrous ions. Method and Materials: Strong acid cation exchange resin beads (Rohm and Haas, Amberlyst 15 Wet) were rinsed in distilled water and packed in plastic vials. Similar beads were treated to produce a 1 mM ferrous ion concentration inside the beads, then rinsed with distilled water, and finally packed in plastic vials. Sample vials were placed in a water phantom and exposed to 6 MV x-rays from 0 to 100 Gy. The T1 for each sample was measured in a 1.5 Tesla MRI unit. Beads from two manufacturing lots, Lot 1 and 2, were tested. Density of the bead samples was 1.10 g/cm3. Results: Vials with beads containing ferrous ions exhibited a linear dose versus R1 (i.e., 1/T1) response with slopes of 0.102 and 0.093 sec −1 Gy−1 for respectively Lot 1 and Lot 2 beads. Vials of Lot 1 beads containing no ferrous ions exhibited a linear dose versus R1 response with a slope of 0.083 sec−1 Gy−1. Vials of Lot 2 beads containing no ferrous ions showed an exponential increase in R1 of 2.4 sec−1 from 0 to 50 Gy with minimal increase in R1 from 50 to 100 Gy. Conclusion: For both bead lots, the beads containing ferrous ions exhibited similar linear dose versus R1 responses. Beads containing no ferrous ions exhibited significant, but different dose versus R1 responses. When the ferrous ions are present in the beads, a ferrous oxidation reaction appears to dominate the dose response. The results support the concept of using strong acid cation exchange resin beads containing ferrous ions to create a three dimensional dosimeter which can be evaluated using MRI.

Lysine Adsorption on Cation Exchange Resin. III. Multicolumn Adsorption/Desorption Operation

A model previously developed to describe ion exchange equilibria, kinetics, and column dynamics of lysine adsorption on a strong acid cation exchanger is extended to simulate the cyclic adsorption/desorption of lysine in a multicolumn, simulated countercurrent system. The system simulated comprises an adsorption zone, a desorption zone, and two zones where unadsorbed feed components and excess desorbent are removed. Multiple columns are distributed among the four zones in different simulated countercurrent schemes, including a scheme that allows recycling of excess desorbent and another where the lysine recovery yield is enhanced at low flow rates by lowering the pH in the last column of the adsorption zone. Model predictions are validated by comparison with experimental results obtained in an eight‐column bench scale apparatus and a parametric study is conducted with the model to determine the effects of critical design variables. This research was supported by Ajinomoto Co., Inc.

Preparation of strong acid cation-exchange membrane using radiation-induced graft polymerisation

Polyethylene (PE) sheet modified with acrylic acid (AA) was grafted with p-vinyl benzene sulphonic acid sodium salt hydrate (SSS) using 60Co γ -rays in a direct grafting method in the presence of air at ambient temperature. It was observed that increasing dose results in increase of SSS grafting. Changes in surface area, thickness, ion-exchange capacity and water uptake with respect to dose were also evaluated. The grafting was confirmed by FTIR studies. The ion-exchange capacity of the grafted membrane under the conditions was 5.5–5.8 milli equivalent per gram (meq/g) which is better than most of the commercially available membranes.

Coagulation of natural waters with modified ion exchangers

A study has been carried out in order to establish the possibility for natural water coagulation via its treatment with strong acid cation exchangers modified with FeCl 3 or Al 2(SO 4) 3. Various trademarks of ion exchangers have been used, such as Wofatit KPS, Wofatit KS-10, Lewatit S-100, Varion KSM, Amberlite 200 C and Duolite C-26. It has been found that, while using modified ion exchangers the concentration of suspended solids, permanganate oxygen demand and humic acids in treated water are reduced respectively by approximately 95, 86 and 77% with FeCl 3 used as modifier, and 92, 80 and 73% with Al 2(SO 4) 3 as a modifier. The modified ion exchangers can be used for pretreatment of natural water needed for small water make up installations of a module principle. Different modules of these installations can be regenerated in a central station. A scheme has been proposed for natural water treatment combining the process of coagulation with modified ion exchangers and Na-Cl-ion exchange in a mixed bed filter. This can produce conditioned water suitable for thermal plants or for subsequent membrane desalting process.

Performance of a novel electrodeionization technique during citric acid recovery

This paper concerns with the behavior of an electrodeionization (EDI) system for concentration of citric acid from fermentation broth. Commercially cation-exchange membrane (MC-3470) and anion-exchange membrane (MA-3475) were used as ionic selective barriers of the EDI stack. The diluted compartments of the EDI stack were filled with mixed ion-exchange resins (purolite strong acid cation-exchange, C-100E and strong base type I anion resins, A-400). The experiment used feeds with citric acid concentration in the range of 500–10,000 ppm and feed flow rate in the range of 1–4 l h −1. The V– I characteristics indicated that there were essential differences in current transport and electrical resistance between the EDI and the electrodialysis (ED) processes. Moreover, the overall current efficiency was in the range of 40–96% and has been found to be a function of feed concentration and current density. The performance of the EDI system was also stable during 24 h operation.

Lysine Adsorption on Cation Exchange Resin. I. Ion Exchange Equilibrium and Kinetics

Ion exchange equilibria and kinetics are determined for lysine adsorption on the strong acid cation exchanger Dowex HCR‐W2. Average ion exchange selectivity coefficients of 5.0 g/cm3 and 0.75 are obtained for the ion exchange of divalent and monovalent cationic lysine with hydrogen ion, respectively, while values of 1.5 and 1.9 are obtained for the exchange of ammonium and potassium with hydrogen ion. A model based on these binary ion exchange measurements and accounting for the solution equilibria is then developed to predict lysine adsorption over a broad range of conditions. Similarly, resin phase diffusivities are determined by fitting batch binary ion‐exchange data with a mass transfer model based on the Nernst‐Planck equations. Diffusivities of divalent cationic lysine, monovalent cationic lysine, ammonium ion, and potassium ion are 0.05 × 10−6, 0.20 × 10−6, 1.6 × 10−6, and 1.9 × 10−6 cm2/s, respectively. Finally, a general rate model incorporating ion exchange and solution equilibria is developed to predict batch adsorption and desorption of lysine using these diffusivity values over a broad range of conditions.

Lysine Adsorption on Cation Exchange Resin. II. Column Adsorption/Desorption Behavior and Modeling

Column adsorption and desorption of lysine on the strong acid cation exchanger Dowex HCR‐W2 are studied experimentally and theoretically. The lysine breakthrough curves have a complex behavior that depends on the pH of the feed solution. At high pH, when lysine is predominately monovalent, an equilibrium binding capacity approaching the total resin ion exchange capacity is obtained but the breakthrough curve is gradual. Conversely, at low feed pH, when lysine is predominately divalent, a sharper breakthrough curve is obtained but the equilibrium binding capacity is only about one half of the total resin ion exchange capacity. Finally, at intermediate feed pH, when divalent and monovalent lysine forms coexist in the feed solution, a breakthrough curve comprising an initial gradual wave followed by a plateau and then by a sharper front is obtained. A local equilibrium model is developed to describe the wave shapes. The model is in agreement with the experimentally observed wave shapes although it only affords a qualitative prediction of the effluent concentration profiles. A rate model, taking into account the coupled diffusion of lysine cations, ammonium ion, potassium ion, and hydrogen ion in the resin as well as the reversible interconversion of divalent and monovalent lysine, is thus developed for a quantitative prediction. The rate model is in excellent agreement with experimental effluent concentration profiles and provides a means to rationally design and optimize lysine ion exchange processes.

Destruction of Cyanide in Water Using N-Chlorinated Secondary Sulfonamide-Substituted Macroporous Poly(styrene-co-divinylbenzene)

Cyanide ion in water is converted to cyanate ion by use of macroporous poly(styrene-co-divinylbenzene) bearing regenerable N-chlorinated N-alkylsulfonamide functional groups. Cyanide is converted first to cyanogen chloride that is then rapidly hydrolyzed to cyanate ion, which is stable at high pH. Cyanate ion can be further oxidized by active chlorine supplied by the resin to nitrogen and carbonates under weakly basic conditions or more rapidly hydrolyzed to ammonium ion and carbon dioxide by passage through a bed of a strong acid cation-exchange resin in the H+ form without use of additional active chlorine. Much of the active chlorine that escapes the reactor can be recaptured by unchlorinated polymer for subsequent use.

A new cation-exchange method for accurate field speciation of hexavalent chromium

A new method for field speciation of Cr(VI) has been developed to meet present stringent regulatory standards and to overcome the limitations of existing methods. The method consists of passing a water sample through strong acid cation-exchange resin at the field site, where Cr(III) is retained while Cr(VI) passes into the effluent and is preserved for later determination. The method is simple, rapid, portable, and accurate, and makes use of readily available, inexpensive materials. Cr(VI) concentrations are determined later in the laboratory using any elemental analysis instrument sufficiently sensitive to measure the Cr(VI) concentrations of interest. The new method allows measurement of Cr(VI) concentrations as low as 0.05 μg l −1, storage of samples for at least several weeks prior to analysis, and use of readily available analytical instrumentation. Cr(VI) can be separated from Cr(III) between pH 2 and 11 at Cr(III)/Cr(VI) concentration ratios as high as 1000. The new method has demonstrated excellent comparability with two commonly used methods, the Hach Company direct colorimetric method and USEPA method 218.6. The new method is superior to the Hach direct colorimetric method owing to its relative sensitivity and simplicity. The new method is superior to USEPA method 218.6 in the presence of Fe(II) concentrations up to 1 mg l −1 and Fe(III) concentrations up to 10 mg l −1. Time stability of preserved samples is a significant advantage over the 24-h time constraint specified for USEPA method 218.6.