Ion exchange capacity measurement

It was also revealed by means of ultraviolet, visible and infrared optical absorption and hydrogen ion-exchange capacity measurements that the radiation induced defects such as fluorocarbon and peroxy radicals, and C=0 including in carbonyl groups were related to the new proton conduction processes. The modification of the hydrogen absorption characteristics due to the radiation induced defects in the near sttrface regions induces the enhancement of the proton conductivity. 

Ion-exchange capacities Measurements of distribution coefficients of both cations combined with knowledge of the concentration in the equilibrium aqueous solution should be sufficient information for computation of ion-exchange capacities. Values obtained in this way are expected to be less precise than those obtained by the more conventional method of converting the clay to a given ionic form, displacing these ions by ions of another type, and analyzing the displaced ions ("displacement"). 

Table 2. Ion-Exchange Capacity Measurements on Montmorillonite (equivalents/kg dry clay)... 

Fig, 11. Comparison of Ca(II)-Na(I) equilibrium quotients for exchange between aqueous CaCl2 NaCl solutions, otal " and montmorillonite, measured by different isotope-dilution techniques. Comparison of ion-exchange capacities measured by isotope dilution and by displacement of ions. 

Here, Ca is the capacity of the ion-exchange resin measured in moles of A per unit volume. The integral in Equation (11.49) measures the amount of material supplied to the reactor since startup. Breakthrough occurs no later than zr = L, when all the active sites in the ion-exchange resin are occupied. Breakthrough will occur earlier in a real bed due to axial dispersion in the bed or due to mass transfer or reaction rate limitations. 

Swelling water uptake, electric conductivity, and transport number of the membranes are measured as a function of the ion-exchange capacity (lEC). lEC has been estimated in terms of... 

DRIFT spectroscopy was used to determine Av0h shifts, induced by adsorption of N2 and hexane for zeolite H-ZSM-5 (ZSM-a and ZSM-b, Si/Al=15.5 and 26), H-mordenite (Mor-a and Mor-b, Si/AI— 6.8 and 10) and H-Y (Y-a and Y-b, Si/Al=2.5 and 10.4) samples. Catalysts were activated in 02 flow at 773 K in situ in the DRIFTS cell and contacted than with N2 at pressures up to 9 bar at 298 K or with 6.1% hexane/He mixture at 553 K, i.e., under reaction conditions. Catalytic activities of the solids were measured in a flow-through microreactor and kapp was obtained as slope of -ln(l-X0) vs. W/F plots. The concentration of Bronsted acid sites was determined by measuring the NH4+ ion-exchange capacity of the zeolite. The site specific apparent rate constant, TOFBapp, was obtained as the ratio of kapp and the concentration of Bronsted acid sites. 

Figure 6.1 The acid group content of pulps expressed as an ion exchange capacity as a function of kappa number (measure of lignin content) for Kraft and sulfite pulps.

A further difficulty is the distinction between a concept and an operation, for example in the definition of ion exchange capacity. Operationally, "the ion exchange capacity of a soil (or of soil-minerals in waters or sediments) is the number of moles of adsorbed ion charge that can be desorbed from unit mass of soil, under given conditions of temperature, pressure, soil solution composition, and soil-solution mass ratio" (Sposito, 1989). The measurement of an ion exchange capacity usually involves the replacement of (native) readily exchangeable ions by a "standard" cation or anion. 

Standard cations used for measuring cation exchange capacity are Na+, NHJ, and Ba2+. NH is often used but it may form inner-sphere complexes with 2 1 layer clays and may substitute for cations in easily weathered primary soil minerals. In other words, one has to adhere to detailed operational laboratory procedures these need to be known to interpret the data and it is difficult to come up with an operationally determined "ion exchange capacity" that can readily be conceptualized unequivocally. 

Ion exchange capacity is a measure of the quantity of cahons adsorbed or removed by the zeolihc adsorbent. As described in Section 6.5.1.3, the total capacity of a zeolite is a function of its Si02/Al203 mole raho. Theorehcal ion exchanged capacities of some common zeolites are calculated and summarized in Table 6.4. 

Tamura, H. Tanaka, A. Mita, K.-Y. Furuichi, R. (1999) Surface hydroxyl site densities on metal oxides as a measure of the ion exchange capacity. J. Colloid Interface Sd. 209 225-231... 

The experimental procedures of BET, TGA, and XRD have been described in detail elsewhere [8]. The interlayer d-spacing from XRD pattern is determined by the angle of ((X)l) reflection. For the measurement of ion-exchange capacity, SO mg of sample was suspended with 10 cm of NaCl solution (0.1 N), and the pH values were measured with addition of NaOH solution (0.1 N) to obtain the potentiometric titration curve at rocnn temperature. 

Conductivity detector is the most common and useful detector in ion exchange chromatography. However UV and other detectors can also be useful [10]. Conductivity detection gives excellent sensitivity when the conductance of the eluted solute ion is measured in an eluent of low background conductance. Therefore when conductivity detection is used dilute eluents should be preferred and in order for such eluents, to act as effective competing ions, the ion exchange capacity of the column should be low [1]. 

Sr(II), and Ba(II), for the sodium form of montmorillonite. The Sr(II) results are from a different set of measurements than those in Figure 2, but are in good agreement with them. Effects of loading are small up to the several percent of ion-exchange capacity covered. Values of distribution coefficients for these three ions fall in a narrow range. 

The hydrous aluminosilicates and Zr, Th, and Ti phosphates have significant ion exchange capacity (6). Further interpretive study of charge development in such systems will require recognizing the ion exchange properties and measuring trivalent cation site distribution as well as adsorption and mobility. 

Halloysite has a chemical composition similar to kaolinite, but with a higher water content. The layers of halloysite are like those in kaolinite, but they are stacked with highly random displacements parallel to the layers, as opposed to the regular stacking found in kaolinite. The interlayer distance is greater in halloysite, allowing for the presence of a sheet of water molecules. A small ion-exchange capacity is measurable in kaolinite and halloysite minerals, which arises from a small amount of iso-morphous replacement of Si4+ or Al3+ in the framework 234). 

The stability of toxicant-carrier combinations used in pesticide wettable powder formulations cannot be easily predicted by evaluating various properties of the carrier. Several types of synthetic calcium silicates and their modifications were evaluated for malathion stability and other properties. The carriers were evaluated for pH (slurry), pK (surface acidity), moisture content, absorptive capacity, and/or ion exchange capacity. These properties were correlated with actual malathion stabilities as measured at 40° C. storage for 1, 2, 3, and 7 months. The carrier properties evaluated did not offer a simple means of predicting compatibility in the variety of carriers tested. 

Analysis. During our project, we evaluated 97 variations of carriers (Table I). We did not measure all carrier properties on all samples, and unfortunately, we measured only a few samples for ion exchange capacity. 

ETS-10 is a titanosilicate with a three-dimensional 12-ring pore system and a very high ion-exchange capacity. The integral heats of adsorption of monoalkyl-amines on ETS-10 have been measured by isothermal calorimetry as a funchon of the n-alkylamine concentrahon [118]. The heats vary in the order methyl < ethyl < propyl < butyl amine. 

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