Kinetics of ion exchange

M. Nativ, S. Goldstein, and G. Schmuckler, Kinetics of ion-exchange processes accompanied by chemical reactions, J. Inorganic Nuclear Chem., 37 (1975), p. 1951. 

Bunzl and co-workers have investigated the kinetics of ion exchange of several metals, including Ca2+, Cd2+, Cu2+, Pb2+, and Zn2+, on humic acid and peat (Bunzl, 1974a,b Bunzl et al, 1976). In each of these studies, the rate-limiting step for ion exchange of a metal ion for H30+ was FD. 

Helfferich, F. (1983). Ion exchange kinetics—Evolution of a theory. In Mass Transfer and Kinetics of Ion Exchange (L. Liberti and F. Helfferich, eds.), pp. 157-179. Matinus Nijhoff Publishers, Dordrecht, The Netherlands. 

BunzI, K. (1974a). Kinetics of ion exchange in organic matter. II. Ion exchange during continuous addition of Pb2+ -ions to humic acid and peat. J. Soil Sci. 25, 343-356. 

Ogwada, R. A., and Sparks, D. L. (1986c), Kinetics of ion exchange on clay minerals and soil. II. Elucidation of rate-limiting steps. Soil Sci. Soc. Am. J. 50, 1162-1164. 

Kinetic aspects are significant in ionic exchange in zeolites. The kinetics of ion exchange is represented with a plot of U(t) versus, time t (Figure 7.3), in which... 

In Section 7.3, it was stated that the kinetics of ion exchange is normally represented by the help of the plot of U(t) versus time t (see Figure 7.3). It was also acknowledged that the ion-exchange process in zeolites is described in three steps (see Figure 7.3). Here, we study separately these processes [23-25,44-46],... 

It is possible that the rate-determining process in the kinetics of ion exchange is the film diffusion. Consider a spherical particle encircled by an aqueous solution sphere (see Figure 7.8), in which the zeolite is homoionic at t = 0, the electrolytic solution has a very high volume (i.e., C2A == constant), and the diffusion is stationary and one-dimensional in a direction perpendicular to the zeolite surface [44], Then, under the conditions discussed above, it is possible to calculate the exchange flux of cation B, that is,. 7 , as follows [23] ... 

The limiting step in the kinetics of ion exchange in the zeolite is the interdiffusion of the electrolyte ions A zi and ions of the species B [24], In the case where the solid ion-exchanger particle is spherical (see Figure 7.9) and the particle diffusion control is the rate-determining process, then Fick s second law equation in spherical coordinates is [47]... 

Here, we report kinetic data measured during the ion-exchange process in the NH4 -Ni2+ system in the sample CMT-C [5,37], CMTC-C was obtained from deposits located in Tasajeras, Cuba (see Table 4.1) [5], The parameters characterizing the kinetics of ion exchange of NH4 and Ni2+ in the sample CMT-C [5,37], that is, R, De and the TEC, are reported in Table 7.3. 

K. Bunzl, Competitive ion exchange in mixed cation exchanger systems Kinetics and equilibria, J. Inorg. Nucl. Chem. 39 1049 (1977). See also K. Bunzl, Kinetics of ion exchange in polydisperse systems, Anal. Chem. 50 258 (1978) for an application to a set of exchangers with different specific surface areas. 

Sparks, D. L., and D. L. Suarez, Rates of Soil Chemical Processes, Soil Science Society of America, Madison, WI, 1991. Chapters 4 and 5 of this conference proceedings volume describe methodologies in the kinetics of ion exchange. 

The theoretically based interpretation of the kinetics of ion exchange that has been developed has been confirmed by experiments that have shown the interdiffusion rates in the exchanger phase to depend, as predicted, on diffusivity and selectivity factors as well as on bulk solution concentrations. For unfavorable ion-exchange isotherms these dependencies are formally similar to those observed in film diffusion [49]. 

L. Liberti and F. Helfferich, Eds., Mass Transfer and Kinetics of Ion Exchange, Martinus Nijhoff, Hague, 1983. 

A detailed kno edge of the kinetics of ion exchange is important not only for economic employment of ion exchange materials in the laboratory and in industry but also for a better understanding of these processes in natural systems, as e.g., in the soil or in biological membranes. For this reason numerous theoretical and experimental investigations on this subject are available. For excellent review articles see e.g., [1-10]. 

In this presentation we, therefore, investigate the kinetics of ion exchange in such mixtures for the case vdiere diffusion of the ions across a hydrostatic boundary layer (Nemst film) surrounding the particles is the rate controlling step (film diffusion). In well-stirred systems, liquid-phase mass transfer will usually be fevored by a low concentration of the external solution, a high ion-exchange capacity, and a small particle size [I]-... 

A. I. Kalinitchev, in Chapter 4, deals with the kinetics of ion exchange in selective systems. In particular he uses the kinetic model developed in his research to show that phenomenological regularities and criteria describing intraparticle diffusion kinetics for conventional ion exchange are not applicable to selective ion-exchange systems. 

In Chapter 6, K. Bunzl examines the kinetics of ion exchanger in heterogeneous systems in order to provide a better understanding of the behavior of natural ion exchangers in the soil (clay minerals, humic substances, sesquioxides). With film diffusion as the rate-controlling factor in these mixtures, several important characteristics become predictable. 

Although the kinetics of ion exchange on type A zeolites has been discussed previously in several papers 4, 10, 12, 15, 19), no systematic... 

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% ... 

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