摘要:

ABEC™-5000, an aqueous biphasic extraction chromatography resin consisting of monomethylated polyethylene glycol (PEG)-5000 covalently bound to a polystyrene support, was investigated for its ability to remove pertechnetate from simulated Hanford tank wastes. Retention of TcO4−on the resin in batch mode from 2 and 4 M NaOH and from the waste simulants NCAW, SY-101, and SST, indicated that pertechnetate can be selectively removed from these solutions. Column studies were conducted with 4 M NaOH and the NCAW simulant spiked with Na99mmTcO4or Na95mMmTcO4. The columns can be easily stripped using water, thus concentrating the pertechnetate.

ISSN:0736-6299    

DOI:10.1080/07366299708934493

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The extraction equilibria of Co(II) from 1.0 M KC1 medium by the commercial extractant Cyanex 301 dissolved in toluene has been studied. The effects of pH, extractant concentration and metal concentration on the extraction behaviour have been examined. Experimental data have been treated graphically and numerically and can be explained by assuming the extraction of the dominant species CoL2. HL being bis(2,4,4-trimethylpentyl) dithiophosphinic acid, the major component of Cyanex 301. The numerical treatment also indicated the extraction of a minor species of probable stoichiometry CoClL(HL), but whereas the former species has been clearly identified, the latter species, probably due to the fact that its contribution to the extraction process is very little, can only be considered as an approximation as its stoichiometry is not defined precisely by this numerical treatment. Conditional equilibrium constants of the extraction process are also given.

ISSN:0736-6299    

DOI:10.1080/07366299708934494

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The association equilibria of tetrakis(acetylacetonato)zirconium(IV) and hafnium(IV) (M(acac)4) with 3,5-dichlorophenol (Hdcp) in carbon tetrachloride has been studied through an investigation of the solvent extraction behavior of zirconium(IV) and hafnium(IV) ions with acetylacetone (Hacac) in the presence of Hdcp. The extractability of the metal(IV) ions with Hacac in carbon tetrachloride is much enhanced with increasing concentration of Hdcp. From analysis of the extraction data, the effect is quantitatively explained in terms of the formation of association complexes, M(acac)4nHdcp (n = 1, 2, 3), and their association constants are determined. The reliability of the association constants as well as the existence of hydrogen bonds between M(acac)4and Hdcp has been confirmed by IR spectrometry. The constants reveals that both Zr(acac)4and Hf(acac)4are much stronger as hydrogen-bond acceptors than tris- and bis-acetylacetonates previously investigated, and Hf(acac)4is a little stronger than Zr(acac)4.

ISSN:0736-6299    

DOI:10.1080/07366299708934495

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The extraction of copper with N,N,N'N'-tetrahexyl-3,5-pyridinedicarboxamide in the presence of the decanol and the co-association of the amide with alcohol were studied. Alcohol associates with the amide forming hydrogen bonds mainly with the oxygens of the carbonyl group without blocking the chemically active pyridine nitrogen. Hydration occurs in the same way. The effect of the alcohol on copper extraction is relatively small and weaker than the effect of chloride concentration.

ISSN:0736-6299    

DOI:10.1080/07366299708934496

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The extraction equilibrium of 2-chlorophenol from an aqueous solution by the sulfuric acid salts of trioctylamine (TOA sulfate salts, or TOA salts) in an organic solvent was investigated. Sulfuric acid first reacts with trioctylamine (TOA) to form the TOA salts; then 2-chlorophenol is extracted into the organic phase from the aqueous phase by the TOA salts. The modified Wilson model, which accounts for the equilibrium of the chemical reaction of trioctylamine and sulfuric acid to form the various TOA salts, was applicable to the reaction in any organic solvent at various temperatures to predict the extraction of 2-chlorophenol. The number of water molecules accompanying the various TOA salts, which reflects the extraction capability of 2-chlorophenol, was determined. The results obtained from the modified model of equilibrium of the chemical reaction of trioctylamine and sulfuric acid are fairly consistent with the experimental data. The effects of the initial concentration of 2-chlorophenol, inorganic acids and organic solvents on the distribution coefficient of 2-chlorophenol were investigated.

ISSN:0736-6299    

DOI:10.1080/07366299708934497

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Hater sorption isotherms of uranium and thorium forms of Dowex 50W exchangers of polystyrene sulphonate (PSS) type with varying degree of crosslinkage were obtained by isopiestic technique. The osmotic pressures and swelling free energies have been determined using the conventional approach. Primary hydration of the cations, total bound water of the cations and the free osmotic water have been calculated from crosslinking effects, differential free energy of swelling, BET and D'Arcy & Watt methods. The calculation of bound water using an alternate method is also discussed.

ISSN:0736-6299    

DOI:10.1080/07366299708934498

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Equilibrium isotherms at high total ionic concentration have been measured for exchange of light cations and hydrogen, as reference ion. with a sulphonic highly-crosslinked polystyrene-divinylbenzene resin. All but one of the isotherms show an inflexion point, even at low solution concentrations, and none of them can be fitted with the constant-selectivity model. This behaviour can be explained assuming that ion-exchange beads are heterogeneous. In fact, the copolymerization process of macroporous styrene-divinylbenzene resins leads to particles composed by highly crosslinked microparticles pasted together with less crosslinked material. Moreover, the sulphonic styrene may show a different selectivity to that of the sulphonic divinylbenzene. A mathematical model was developed based on the postulation of two areas inside the resin beads, having different selectivity coefficients. The volumetric fraction of these areas is supposed to be the degree of cross-linking. Therefore, the model has only two adjustable parameters: the selectivity coefficient of both areas. In spite of its simplicity, it was fitted quite successfully to the whole set of laboratory data and also predicted the data collected by other authors for resins covering the complete range of cross-linking.

ISSN:0736-6299    

DOI:10.1080/07366299708934499

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A comparison of four different ion exchange resins (two strong acid ones, with different crosslinking ratios, and two weak acid resins, one an iminodiacetic chelating resin and the other a carboxylic one) has been carried out in order to study the behavior of counter and co-ions. The systems under study were K+-Na+as counterions, and CI−-SO42− as co-ions in possible combinations as single electrolytes. All the solutions were highly concentrated, the behavior of co-ions may be important since Donnan exclusion does not take place completely and electrolyte penetration inside the resin is observed Ion exchange under such conditions may be very useful for application in industrial processes, thus offering a method of using ion exchange in conditions which are not habitual. Equilibrium and kinetics were studied in batch experiments; equilibrium was analyzed using the separation constant factor isotherm and kinetics was modeled by a pore diffusion model.

ISSN:0736-6299    

DOI:10.1080/07366299708934500

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Simulations are performed using models developed to predict ion exchange performance in fixed cylindrical resin beds. One model predicts performance in a conventional bed in which the flow is parallel to the bed's axial, while the other model predicts performance in a wedge-shaped radial bed. In this radial bed the injected solution flows radially from the inlet located at the annular bed's axis to the outlet located at the bed's periphery. The simulated breakthrough curves for the exhaustion and regeneration cycles for the Ca-H cation exchange system are compared to study the effects of operating conditions. It is found that because dispersion grows less in radial flow than in linear flow, radial ion exchange processes are more efficient than the conventional ion exchange column processes under identical operating conditions for the geometries simulated.

ISSN:0736-6299    

DOI:10.1080/07366299708934501

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Ion-exchange equilibrium of alkali metal ions and protons have been studied thermodynamically on α-type manganese dioxide. The ion-exchange material was synthesized by pyrolysis of manganese carbonate and potassium tert-butoxide with content of 4.8% on molar basis at 530°C. The plot of the corrected selectivity coefficient vs. fractional exchange X¯M(Kieiland's plot) was almost straight and, therefore, only one kind of exchange site was suggested. The order of the selectivity coefficient at the infinitesimal exchange is: Li < Na < Cs K, Rb. This order does not change in the temperature range of 30≿60°C. The thermodynamic functions represent me ion-exchange selectivities. The negative values of AG°idealfor K+/++ and Rb+H+exchanges. -22 kJ/mol for ΔG°ideal(K) and -23 kJ/mol for ΔG°ideal;(Rb), indicate me high preference for K+and Rb+by this ion exchanger. This high preference for K+and Rb+can be ascribed to the best fit of the exchange site to these ions. The large entropy changes for these exchanges, 271 J/K mol for ΔS°exch(K) and 262 J/K mol for ΔSexch(Rb), exhibited

ISSN:0736-6299    

DOI:10.1080/07366299708934502

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor