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PubMed2002

Microscale continuous ion exchanger.

A microscale continuous ion exchanger based on two liquid streams flowing in parallel is presented. The ion exchange reaction occurs through diffusional transfer of molecules between the ion exchanger phase and the eluent phase and is applied for conductivity suppression. Two approaches are demonstrated. In the first approach, a liquid ion exchanger (i.e. a strongly basic compound, e.g., tetraoctylammonium hydroxide, or a secondary amine, e.g., Amberlite IA-2) is dissolved in an organic solvent immiscible with the aqueous eluent. The system allows for sensitive suppressed conductivity detection of various inorganic cations. When the weakly basic secondary amine is used, conductometric detection of heavy metals is possible. In the second approach, a suspension of finely ground ion-exchange resin is used as the ion exchanger phase. In this case, the suspension need not involve an organic solvent. Theoretical models and computations are presented along with experimental results. The potential of such a system as a chip-scale post-separation suppressor/reactor is evident.

Cations↗
PubMed1973

Passive electrical properties of microorganisms. V. Low-frequency dielectric dispersion of bacteria.

Very high dielectric constants have been observed for bacteria at low frequencies. High dielectric constants such as these can be explained by a theory which has been developed for the low-frequency dielectric dispersion of porous charged particles and which has been tested successfully through measurements with ion exchange resins. The bacterial cell wall is electrically similar to an ion exchange resin. Observations show that the theory provides a quantitative explanation for the low-frequency dielectric dispersion of bacteria.

Bacterial Physiological Phenomena↗
PubMed2002

In situ remediation of groundwater contaminated by heavy- and transition-metal ions by selective ion-exchange methods.

Laboratory studies were conducted to investigate the feasibility of using ion-exchange resins in permeable reactive barriers (PRBs) for the remediation of groundwater contaminated by heavy and transition metals. Ion-exchange resins represent an essentially neglected class of materials which may, in addition to iron, activated carbon, and zeolites, prove effective for use in PRBs. Four resins were considered: two commercially available resins, Duolite GT-73 (Rohm and Haas) and Amberlite IRC-748 (Rohm and Haas), and two solvent-impregnated resins (SIRs). The SIRs were prepared from Amberlite IRA-96 (Rohm and Haas) and two different thiophosphoric extractants. All four resins are able to reduce cadmium, lead, and copper concentrations from 1000 microg/L (typical for contaminated groundwaters) to below 5 microg/L. Significantly, all of the resins are effective for the capture of cadmium, copper, and lead, even in the presence of CaCl2 and clay. Because of their high hydraulic conductivity, the use of these resins in clusters of wells, as an alternative to continuous walls, is considered in the design of effective PRBs. Numerical solution of the groundwater flow equations shows that, depending on the well configuration, most (or all) of the contaminated groundwater can pass through the resins. These results demonstrate the possibility of using selective ion-exchange resins as an effective, active material in PRBs for in situ groundwater remediation.

Ion Exchange↗
PubMed2006

Fe3O4 and gamma-Fe2O3 nanoparticles for the adsorption of Co2+ from aqueous solution.

The adsorption of Co2+ ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe3O4) and maghemite (gamma-Fe2O3) has been studied. The adsorption of Co2+ ions on the surface of the particles was investigated under different conditions of oxide content, contact time, solution pH, and initial Co2+ ion concentration. It has been found that the equilibrium can be attained in less than 5 min. The maximum loading capacity of Fe3O4 and gamma-Fe2O3 nanoparticles is 5.8 x 10(-5) and 3.7 x 10(-5) mol m(-2), respectively, which are much higher than the previously studied, iron oxides and conventional ion exchange resins. Co2+ ions were also recovered by dilute nitric acid from the loaded gamma-Fe2O3 and Fe3O4 with an efficiency of 86 and 30%, respectively. That has been explained by the different mechanisms by including both the surface and structural loadings of Co2+ ions. The surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles has been found to have the same mechanism of ion exchange reaction between Co2+ in the solution and proton bonded on the particle surface. The conditional equilibrium constants of surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles have been determined to be log K=-3.3+/-0.3 and -3.1+/-0.2, respectively. The structural loading of Co2+ ions into Fe3O4 lattice has been found to be the ion exchange reaction between Co2+ and Fe2+ while that into gamma-Fe2O3 lattice to fill its vacancy. The effect of temperature on the adsorption of Co2+ was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1).

Journal Article↗
PubMed1975

[Separation of guanidino compounds by means of ion-exchange thin-layer chromatography (author's transl)].

Thirteen guanidino compounds including glycocyamine, glycocyamidine, creatine, creatinine, arginine and guanidinosuccinic acid were chromatographed on thin-layer plates pre-coated with ion-exchange resins. Maximum resolution was obtained on layers of the cation-exchange resin eluted with 0.12 M sodium citrate buffer of pH 5.2, permitting the separation of nine of the thirteen guanidino compounds. Relationships between structure and physiochemical properties and the elution patterns of some selected guanidines were graphically evaluated.

Buffers↗
PubMed1998

Structural characteristics of low-molecular-mass displacers for cation-exchange chromatography. II. Role of the stationary phase.

The relative efficacy of a variety of low-molecular-mass displacers was examined on three different stationary phase materials. Several homologous series of displacer molecules were evaluated on these ion-exchange resins using a displacer ranking plot based on the steric mass action model. The results demonstrate that while aromaticity and hydrophobicity can play a significant role in the affinity of displacer molecules on polymethacrylate based and hydrophilized polystyrene-divinylbenzene based materials, this effect is much less pronounced on an agarose based resin. The work presented in this paper demonstrates that different structural features of low-molecular-mass displacers can dominate their affinity on various stationary phase materials employed and provides rules of thumb for the design of high affinity, low-molecular-mass displacers for a variety of commercial cation-exchange materials.

Cation Exchange Resins↗
PubMed1981

Neutron activation analysis of nickel purified by floating zone-refining and anion exchange.

Nondestructive neutron activation analysis was performed on the nickel purified by floating zone-refining and anion exchange. It is found that floating zone-refining in vacuum is effective to remove Na, Sc, Cr, Zn, As, Ag, Sb and Hg through vaporization in addition to elimination of Se, Sb, Ta, Sm and Tb through segregation. Anion exchange method is also effective to separate Fe, Co, Zn, Mo, Hg, Th and U usually contained in the commercial nickel sources. It is concluded that combination of these two purification methods is required to obtain high purity nickel, since floating zone-refining is known ineffective to eliminate Fe and Co, main impurities in commercial nickel sources.

Activation Analysis↗
PubMed1959

IONS in tissue.

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Ion Exchange Resins↗