Surface speciation kinetics

Sjoberg, E.L. Rickard, D.T. 1984. Calcite dissolution kinetics surface speciation and the origin of the variable pH dependence, Chemical Geology, 42, 119-136. 

In analyzing the kinetics of surface reactions, it will be illustrated that many of these processes are rate-controlled at the surface (and not by transport). Thus, the surface structure (the surface speciation and its microtopography) determine the kinetics. Heterogeneous kinetics is often not more difficult than the kinetics in homogeneous systems as will be shown, rate laws should be written in terms of concentrations of surface species. 

Stumm, W., and E. Wieland (1990), "Dissolution of Oxide and Silicate Minerals Rates Depend on Surface Speciation", in W. Stumm, Ed., Aquatic Chemical Kinetics, John Wiley and Sons, New York, 367-400. 

This is not to say that no progress has been made in surface speciation kinetics related to soils (Sparks and Suarez, 1991). Adaptation of elementary reaction mechanisms established for aqueous complexes, for example, has proved to be an effective means of classifying kinetic surface species and establishing rate laws for... 

W. Stumm and E. Wieland, Dissolution of oxide and silicate minerals Rates depend on surface speciation, Chap. 13 in Aquatic Chemical Kinetics, ed. by W. Stumm, Wiley, New York, 1990. 

W. Stumm and R. Wollast. Coordination chemistry of weathering Kinetics of the surface-controlled dissolution of oxide minerals, Rev. Geophys. 28 53 (1990). See also A. E. Blum and A. C. Lasaga, The role of surface speciation in the dissolution of albite, Geochim. Cosmochim. Acta 55 2193 (1990). 

Schott J. (1990) Modelling of the dissolution of strained and unstrained multiple oxides the surface speciation approach. In Aquatic Chemical Kinetics (ed. W. Stumm). Wiley, New York, pp. 337-365. 

More recently, Wehrli and Stumm (1988) reported on the catalytic effect of coordinated surface hydroxyl groups of <5-Al203 and Ti02 on the rate of autoxidation of V02+ over the pH range of 4-9. They formulated their kinetic observations in terms of a simple rate law that took into account the surface speciation (reactive-site-specific) of the metal oxides ... 

Stumm W, Wieland E (1990) Dissolution of oxide and silicate minerals rates depend on surface speciation. In Stumm W (ed) Aquatic chemical kinetics. Wiley-Interscience, New York, pp 367-400... 

Dissolution rates vary in the same way as these modeled concentrations (Fig. 5). The slow dissolution kinetics is enhanced by rapid adsorption reactions, and the extent of adsorption varies with pH, just as in the case of the iron dimer. Similar trends are found for other silicates, and a strong case can be made for surface-speciation control on inorganic silicate dissolution kinetics (Schott and Petit 1988 Brady and Walther 1989 Stumm and Wieland 1990). 

Krznaric [799] studied the influence of surfactants (EDTA, NTA) on measurements of copper and cadmium in seawater by differential pulse ASV. Adsorption of surfactants onto the electrode surface were shown to change the kinetics of the overall electrode charge and mass transfer, resulting in altered detection limits. Possible implications for studies on metal speciation in polluted seawater with high surfactant contents are outlined. 

Measurement of the extent to which the adsorbent removes the adsorbate from a liquid or gaseous phase. The data is used to construct adsorption isotherms and is often fitted to a model to provide information about binding constants, adsorption maxima and other parameters, and also speciation of surface complexes. Kinetic data may also be obtained. 

Ko, I., Kim, J.-Y. and Kim, K.-W. (2004) Arsenic speciation and sorption kinetics in the as-hematite-humic acid system. Colloids and Surfaces A-Physicochemical and Engineering Aspects, 234(1-3), 43-50. 

Classical chemistry literature provides comprehensive lists of rate data that can also be applied for predicting abiotic reaction rates of environmental importance when the pathways are well identified. For some reactions, such as hydrolysis or OH radical reactions, enough data are available to determine siructure-reactivity correlations that enable one to interpolate within series of chemically related compounds of known reactivity [for review, see Brezonik (Chapter 4, this volume) and Lyman et al. (1982)]. The aquatic chemist is, however, more often confronted with the fact that many classical studies have been performed in organic solvents, but that the speciation of many dissolved chemicals in aquatic systems may vary with pH (caboxylic acids, phenols, etc.) and with ligand concentrations (e.g., all dissolved heavy metal species) or that the chemical species may be adsorbed on surfaces or absorbed by colloidal organic materials. In all these cases, reaction-rate constants must be determined for each individual aqueous species contributing to the overall kinetics. The equilibrium distribution of these species must also be accounted for. Reductions of the... 

An essential beginning in a comprehensive and quantitative assessment of the kinetics of colloid chemical processes is the speciation at a surface that results from the reactions of solutes with surface sites. In some cases this formulation has been accomplished by a description of surface charge, but the diversity of solids and solutes in aquatic systems necessitates a broader assessment. An example is the adsorption of selenite on t lie surface of goclhite (Hayes et al., 1987) in which a... 

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