Desorption-adsorption kinetics metal oxide-solution

Adsorption-Desorption Kinetics at the Metal-Oxide-Solution Interface Studied by Relaxation Methods... 

Yasunaga, T., and Ikeda, T. (1986). Adsorption-desorption kinetics at the metal-oxide-solution interface studied by relaxation methods. ACS Symp. Ser. 323, 230-253. 

See especially Chaps. 2 and 3 in D. L. Sparks and D. L. Suarez, op. cit.10 A summary review of chemical relaxation methods is given by T. Yasunaga and T. Ikeda, Adsorption-desorption kinetics at the metal-oxide-solution interface studied by relaxation methods, Chap. 12 in J. A. Davis and K. F. Hays, op. cit.2... 

Yasunaga, T., and T. Ikeda. 1986. Adsorption-desorption kinetics of the metal-oxide-solution interface studied by relaxation methods, p. 230-253. In J.A. Davis and K.F. Hayes (ed.) Geochemical processes at mineral surfaces. Proc. Am. Chem. Soc. Symp. Ser. 323, Chicago, IL. 8-13 Sept. 1985. ACS, Washington, DC. 

Yasunaga, T. and T. Ikeda (1986), Adsorption-Desorption Kinetics at the Metal-oxide-Solution Interface studied by Relaxation Methods, in J. A. Davies and K. F. Hayes, Eds., Geochemical Processes at Mineral Surfaces, American Chemical Society, Washington, DC, pp. 230-253. 

For the investigation of adsorption/desorption kinetics, SECM is employed to locally perturb adsorption/desorption equilibria and measure the resulting flux of adsorbate from a surface. In this application, the technique is termed SECM-induced desorption (SECMID) [5], but this represents the first use of SECM in an equilibrium perturbation mode of operation. The principles of SECMID are illustrated schematically in Figure 13.1, with specific reference to proton adsorption/desorption at a metal oxide/aqueous interface. For this type of investigation, the tip UME is placed close to the surface of the substrate, such that the tip/substrate separation, d, is of the order of, or less than, the electrode radius, a. The substrate is immersed in a solution of the adsorbate of interest and the adsorption/desorption process is initially at equilibrium. 

Chemical relaxation methods can be used to determine mechanisms of reactions of ions at the mineral/water interface. In this paper, a review of chemical relaxation studies of adsorption/desorption kinetics of inorganic ions at the metal oxide/aqueous interface is presented. Plausible mechanisms based on the triple layer surface complexation model are discussed. Relaxation kinetic studies of the intercalation/ deintercalation of organic and inorganic ions in layered, cage-structured, and channel-structured minerals are also reviewed. In the intercalation studies, plausible mechanisms based on ion-exchange and adsorption/desorption reactions are presented steric and chemical properties of the solute and interlayered compounds are shown to influence the reaction rates. We also discuss the elementary reaction steps which are important in the stereoselective and reactive properties of interlayered compounds. 

A related method involves the use of the tip reaction to perturb a reaction at a surface an example of this approach is SECM-induced desorption (SECMID) (22). For example, the adsorption/desorption kinetics of protons on a hydrous metal oxide surface can be studied in an unbuffered solution by bringing the tip near the surface and reducing proton (to hydrogen) at the tip. This causes a local change in pH that results in proton desorption from the surface. The tip current can be used to study the kinetics of proton desorption and diffusion on the surface (Chapter 12). 

Proton adsorption/desorption kinetics may be studied by pressure-jump type techniques. Protonation is usually very fast deprotonation may be slower but time scales of a few tens of seconds are not exceeded For practical purposes, the oxide surface charge can be considered as being instantaneously established on contact with the metal-containing solution. 

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