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Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: II. Estimation of Intrinsic Acidity and Electrolyte Ion Site Binding Constants
Citation:
LOUX, N. T. Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: II. Estimation of Intrinsic Acidity and Electrolyte Ion Site Binding Constants. CHEMICAL SPECIATION AND BIOAVAILABILITY. Science and Technology Letters, 20(3):161-172, (2008).
Impact/Purpose:
It is the purpose of this work to report on recent findings concerning improvements in our ability to extract effective acidity constant values from published titrimetric data.
Description:
The two-pK metal oxide surface acidity constant model relies on generic mass action expressions of the form: Ka = [>SOHx-1x-2]aH+EXP(-ΔGexcess/RT)/[>SOHxX-l] where x equals 1 or 2. While all current two-pK surface complexation models require numerical estimates of "intrinsic" acidity constants (i.e., Ka values when ΔGexcess equals zero), there exists a large range in the metal oxide intrinsic acidity constant values reported in the literature. This paper describes improved procedures for obtaining intrinsic acidity constants from published metal oxide titrimetic datasets. Because of the observed ionic strength sensitivity of acidity constant estimates at zero charge conditions, these constants were interpreted within the context of a new procedure for estimating historical electrolyte ion site binding constants.
