Dowex MSC-1 Research Articles

Radon emanation from radium specific adsorbents

Pilot studies were undertaken to quantify the total activity of radon that is eluted following no-flow periods from several Ra-226 adsorbents loaded to near exhaustion. The adsorbents studied included two types of barium sulphate impregnated alumina (ABA-8000 and F-1) and Dowex MSC-1 resin treated by either barium hydroxide or barium chloride. In parallel, radium loaded plain activated aluminas and Dowex MSC-1 resin were similarly investigated. The results revealed that radon was quantitatively eluted during the first few bed volumes of column operation after no-flow periods. Although similar radon elution profiles were obtained, the position of the radon peak was found to vary and depended on the adsorbent type. Radon levels up to 24 and 14 kBq dm−3 were measured after a rest period of 72h from radium exhausted Dowex MSC-1 treated with barium chloride and F-1 impregnated alumina with barium sulphate, respectively. The eluted radon values measured experimentally were compared to those calculated theoretically from accumulated radium quantities for the different media. For plain adsorbents, an agreement better than 10% was obtained. For treated resin-types a consistency within 30% but for impregnated alumina-types high discrepancy between respective values were obtained.

Pure Metal Chelate Solutions by Ion Exchange

Aqueous solutions of the industrially important metal chelate ferric N-(2-hydroxyethyl)ethylenediamine-N,N‘,N‘-triacetate (FeHEDTA) have been made by adsorbing an iron salt (nitrate or sulfate) on Dowex MSC-1 cation-exchange resin (Na form), flushing out the sodium salt, and eluting with Na3HEDTA. The resulting eluate contained FeHEDTA with iron concentrations approaching 2% that were free from sodium salts. Achieving industrially useful iron concentrations (>4.5%) required countercurrent ion exchange using an ISEP system. Careful manipulation of pH was required to prevent plugging due to precipitated iron oxide/hydroxide.

Selective alkene epoxidation and alkane hydroxylation with sodium periodate catalyzed by cationic Mn(III)-salen supported on Dowex MSC1

Dicationic Mn(III)-salen, containing phosphonium groups at 5,5′-positions of salen ligand, is supported on an ion-exchange resin, Dowex MSC1, via electrostatic interaction. The catalyst, Mn(salen)-Dowex, has been characterized by FTIR, UV–vis spectroscopic techniques, scanning electron micrograph (SEM), thermal and elemental analysis. This heterogenized homogeneous manganese(III)-salen complex can be used as catalyst in the alkene epoxidation with sodium periodate. This catalytic system shows a good activity in the epoxidation of cyclic, aromatic and especially linear alkenes and exhibits a high selectivity in epoxidation of α-pinene and R-(+)-limonene. Alkyl aromatic and cycloalkanes were oxidized efficiently to their corresponding alcohols and ketones in the presence of this catalyst. The stability and reusability of this new heterogenized metallosalen complex was also investigated.

Purification of a diluted nickel solution containing nickel by a process combining ion exchange and electrodialysis

The removal of nickel ions from diluted solution using some ion-exchange resins (Dowex MSC-1, Purolite C 100E, KU 2–8 and Dowex HCR-S) was studied. The purification process involved the use of an electrodialysis-type cell in which the centre compartment was filled with a packed bed of ion-exchanger particles. The Dowex HCR-S resin was shown to be the most suitable material for use in electrodeionization processes. The current efficiency under constant rate of nickel transport to the catholyte reached 14%. The energy consumption, which is needed for removal of 0.35 mol Ni (II) from 1 m3 solution containing 1 mol NiSO4, was estimated as 208 Wh. The apparent diffusion coefficients of Ni(II) ions in the ion exchangers were determined with the electromigration method. These values increased with decrease of the effluent pH and reached 1.30–10−12(DowexMSC-l), 1.36·10−12(Purolite C 100E), 2.69·10−12(KU 2–8), and 4.07·10−12 (Dowex HCR-S) m2 s−1 at pH 2.3–2.5. The largest magnitude of the nickel diffusion coefficient was obtained for the Dowex HCR-S resin, which contains the maximum quantity of functional groups per volume unit. It was found that the mobility of sorbed ions determines the efficiency of the purification process.

Correlations and characterization of porous solids by fractal dimension and porosity

The fractal dimensions of zeolite A, zeolite X, Dowex MSC-1, Mordenite, zeolite Y, ZSM-5 and MSC-5A carbon sieve have been obtained by physical adsorption of different-sized adsorbates. The porosity of the solids is obtained from literature. Two simple equations with two integral variables can be employed to characterize a porous solid with finite fractal dimension and porosity. These two equations also illustrate the correlation between fractal dimension and porosity of the porous solid and are also helpful to construct the fractal structure of the porous solids. Two integral variables are the number of divisions (cuts) in each dimension, and the number of the d-dimensional objects ( d can be 1, 2 or 3) that must be taken for iteration. Seven examples of porous solids are employed to characterize and illustrate the applicability of the two equations.

Fractal structure of porous solids characterized by adsorption.

The fractal dimensions of porous solids, zeolites A, X, and Dowex MSC-1 were determined by physical adsorption and the values were 2.57, 2.37, and 2.92, respectively. In fact, it is counting the coverages of the adsorbate on the adsorbent. The solids can be visualized and simulated by a reducing similarity transformation. The resulting difference and significance of using the volume and area of the adsorbate to obtain the fractal dimensions are discussed.

Casein hydrolysate. I. Continuous production using enzyme bioreactors

Proteolytic enzymes were immobilized onto suitable carriers with the objective of standardizing stable immobilized-enzyme (IME) bioreactors to hydrolyze casein continuously. Papain, trypsin, chymotrypsin, pancreatin, Rhozyme-41, chymosin, plasmin and Pronase E were immobilized either on aminopropyl-glass beads (pore size, 500 Å, 200–400 mesh) or PEI-silica, Dowex MSC-1, Dowex MR-3C, Dowex SBR-P, crosslinked with glutaraldehyde (3%, v/v). Papain, trypsin, chymotrypsin and Rhozyme-41 immobilized onto aminopropyl- (AP-) glass beads were stable in batch or continuous stirred tank reactor. Peptides were different for the various enzymes; IM-papain, trypsin, and Rhozyme-41 extensively hydrolyzed casein within 30 min, whereas IM-chymotrypsin was slower and gave fewer peptides.

Model systems for cytochrome P450 dependent monooxygenases. Part 8. A study of the epoxidation of (Z)-cyclooctene by iodosylbenzene catalysed by cationic iron(III) tetra(N-methylpyridyl)porphyrins adsorbed on Dowex MSC1

Tetra(N-methyl-4-pyridyl)porphyrinatoiron(III) pentachloride and its N-methyl-2-pyridyl isomer have been adsorbed onto the highly crosslinked cation ion-exchange resin Dowex MSC1 and have been used to catalyse the reaction of Z-cyclooctene with iodosylbenzene in methanol. Two oxidation products have been detected, epoxycyclooctane and formaldehyde. The dependence of the initial rate of epoxidation and the yields of the oxidation products on the concentrations of oxidant, alkene and catalyst and on the solvent composition and catalyst loading have been investigated. The results are interpreted in terms of the following competitive reactions of the active oxidant; alkene epoxidation, solvent oxidation and oxidative degradation of catalyst and support. Adsorption of the metalloporphyrins on the polymeric resin surprisingly leads to a decrease in the catalyst efficiency when compared with the same metalloporphyrin in free solution. The cause of this effect is discussed and it is proposed that it arises through the aggregation of the metalloporphyrins on the resin favouring the intermolecular self-oxidation of the catalyst.

Asymmetrische katalysen L. Heterogene enantioselektive hydrierungen mit immobilisierten rhodium(I)-komplexen

The supports BaSO 4, cellulose, silica gel, aluminum oxide, AgCl, and charcoal are impregnated with the complexes [Rh(COD)(−)-Diop]PF 6, [Rh(COD)(−)-Norphos]PF 6 and [Rh(COD)(+)-Norphos]PF 6, so that they are insoluble under the reaction conditions. These catalysts hydrogenate the substrate ( Z)-α- N-acetamidocinnamic acid (AAZ), dissolved in aqueous NaOH, with up to 79% ee to N-acetylphenylalanine (AcPhe). On repeated use of the [Rh(COD)(−)-Diop]PF 6 systems optical induction decreases, whereas it increases with the [Rh(COD)(−)-Norphous]PF 6 and [Rh(COD)(+)-Norphos]PF 6 systems in the first re-uses. The hydrogenation activity of all the catalysts declines on repeated use. The cations of the complexes [Rh(COD)(−)-Diop]PF 6, [Rh(COD)(−)-Norphos]PF 6, and [Rh(COD)(+)-Norphos]PF 6 are bound to the strongly acidic ion exchangers v DOWEX HCR-S and DOWEX MSC-1 and to the weakly acidic ion exchangers SERDOLIT CW-18 and SERVACEL CM-32. These catalysts hydrogenate the substrate ( Z)-α- N-acetamidocinnamic acid in aqueous or alcoholic solutions in optical yields of up to 87% ee. The results regarding the repeated use of the catalysts fixed on the ion exchange resins are similar to those obtained with the catalysts fixed on the other supports. N-Acetamidoacrylic acid (AAA) and methyl ( Z)-α- N-acetamidocinnamate (AAZM) are also hydrogenated enantioselectively by the heterogeneous catalysts.

Enzymatic elimination of phytate in soybean milk.

The phytic acid content of commercial soybean milk in Japan was from 0.52 to 1.11mg/g. Phytate in soybean milk was hydrolyzed by wheat phytase. The enzyme was immobilized on Dowex MWA-1, MSC-1, Duolite ES-762 with glutaraldehyde. The activity yield was in the range of 4.5-21% depending upon the immobilization method. The optimum pH and Km values of the immobilized enzyme on Duolite ES-762 were similar to those of the free enzyme. On the other hand, the optimum pH of the immobilized enzyme on Dowex MSC-1 shifted by one pH unit toward the alkaline region, and its Km value was considerably increased. The optimum temperature did not change by immobilization. Immobilized enzymes on Duolite ES-762 and Dowex MSC-1 were used for the hydrolysis of phytate in soybean milk.

COMPARISON OF CATION EXCHANGE RESINS FOR RECOVERING AMERICIUM AND PLUTONIUM FROM CHLORIDE SALTS

ABSTRACT Macroreticular and microreticular cation exchange resins were compared for their capability of recovering americium and plutonium from solutions of calcium, magnesium, potassium, and sodium chlorides. Americium and plutonium breakthrough capacity and elution behavior of the resins were determined. Of the resins tested, Dowex MSC-1 was selected as the most efficient because of its favorable capacity and excellent elution behavior. Actinide eluting agents were also studied. More concentrated (9.0M) nitric acid was found to elute plutonium faster than 7.0MHNO3used previously while 7.0MHNO3-0.1MNaNO2eluted americium fastest.