Ion exchange measurement

The capacity of an ion-exchanger measures the amount of material that can be exchanged by a given amount of the resin, and is normally expressed in milliequivalents per g of dry resin. 

Resins, Ion Exchange, Measurement of Complex Ion Stability, by Use of (Schuben). .. 3... 

L. V. C. Rees (Imperial College, London) In the kinetics of ion exchange measurements, can you tell me what length of time was required before the fractional attainment of equilibrium reached approximately 100% ... 

Octadentate anion DTPA forms stable complexes with Np in solution. In contrast to EDTA, the absorption band of [Np(DTPA)] with maximum at 983 nm is very broad and has low intensity. Based on the spectrophotometry stability constant logy5i=30.33 0.12 was calculated [47,74]. In the work [122], the similar value, logy5i=29.29 0.02, was obtained using the same technique. Ion exchange measurement yields the value logy5i=30.96 [53]. Potentiometry titration gives very similar value for Pu(lV), logy5i=29.49 0.10 [123]. 

The experimental data analysed in this review using the NONLINT-SIT program included solubility, solvent extraction and ion exchange measurements. Optimisation is carried out by minimising the penalty function, viz. the standard deviation, (o), of the set of N experimental data points defined by ... 

Samec, Z., Trojanek, A., Langmaier, ]., Samcova, E. 1997. Diffusion coefficients of alkali metal cations in Nation from ion-exchange measurements. Journal of the Electrochemical Society, 144,4236-4242. 

Roen, L. M., Paik, C. H. and Jarvi, T. D. (2004) Electrocatalytic corrosion of carbon support in PEMFC cathodes. Electrochem. Solid-State Lett. 7, A19-A22 Samec, Z., Trojdnek, A., Langmaier, J. and Samcova, E. (1997) Diffusion coefficients of alkeili metal cations in Nafion from ion-exchange measurements - An advanced kinetic model. J. Electrochem. Soc. 144, 4236-4242... 

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

The speciation scheme of Batley and Florence requires eight measurements on four samples. After removing insoluble particulates by filtration, the solution is analyzed for the concentration of anodic stripping voltammetry (ASV) labile metal and the total concentration of metal. A portion of the filtered solution is passed through an ion-exchange column, and the concentrations of ASV metal and total metal are determined. A second portion of the filtered solution is irradiated with UV light, and the concentrations of ASV metal... 

Ion-exchange columns can be substituted into the general HPLC instrument shown in Eigure 12.26. The most common detector measures the conductivity of the mobile phase as it elutes from the column. The high concentration of electrolyte in the mobile phase is a problem, however, because the mobile-phase ions dominate the conductivity, for example, if a dilute solution of HCl is used as the mobile phase, the presence of large concentrations of H3O+ and Ck produces a background conductivity that may prevent the detection of analytes eluting from the column. 

Capacity. Capacity is a measure of the quantity of ions, acid, or base removed (adsorbed) by an ion-exchange material. The quantity removed is direcdy correlated with the number of functional groups. Capacity is reported ia several different ways, but requites further definition because the word by itself does not cover ad situations. Total capacity is a measure of ad the functional groups on a resia and is recorded on a weight as wed as a volume basis. 

Hardness can also be calculated by summation of the individually deterrnined alkaline earths by means of atomic absorption analysis. Basic samples must be acidified, and lanthanum chloride must be added to minimise interferences from phosphate, sulfate, and aluminum. An ion-selective electrode that utilizes ahquid ion exchanger is also available for hardness measurement however, this electrode is susceptible to interferences from other dissolved metal ions. 

Many experimental approaches have been appHed to the deterrnination of stabihty constants. Techniques include pH titrations, ion exchange, spectrophotometry, measurement of redox potentials, polarimetry, conductometric titrations, solubiUty deterrninations, and biological assay. Details of these methods can be found in the Hterature (9,10). 

The working capacity of a sorbent depends on fluid concentrations and temperatures. Graphical depiction of soration equilibrium for single component adsorption or binary ion exchange (monovariance) is usually in the form of isotherms [n = /i,(cd or at constant T] or isosteres = pi(T) at constant /ij. Representative forms are shown in Fig. I6-I. An important dimensionless group dependent on adsorption equihbrium is the partition ratio (see Eq. 16-125), which is a measure of the relative affinities of the sorbea and fluid phases for solute. 

Truly porous, synthetic ion exchangers are also available. These materials retain their porosity even after removal of the solvent and have measurable surface areas and pore size. The term macroreticular is commonly used for resins prepared from a phase separation technique, where the polymer matrix is prepared with the addition of a hq-uid that is a good solvent for the monomers, but in which the polymer is insoluble. Matrices prepared in this way usually have the appearance of a conglomerate of gel-type microspheres held together to... 

R indicates the organic portion of the resin and SO3 is the immobile portion of the ion active group. Two resin sites are needed for nickel ions with a plus 2 valence (Ni ). Trivalent ferric ions would require three resin sites. As shown, the ion exchange reaction is reversible. The degree the reaction proceeds to the right will depend on the resins preference, or selectivity, for nickel ions compared with its preference for hydrogen ions. The selectivity of a resin for a given ion is measured by the selectivity coefficient. K. which in its simplest form for the reaction... 

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