Waves: The Oxide Surface as a Variable Charge Adsorbent

Waves in a Two-Component System: The Oxide Surface as a Variable Charge Adsorbent

Joachim Gruber

Address at the time this paper was finished:

Arbeitsbereich Umweltschutztechnik
TU Harburg
P.O.Box 901052
D 21071 Hamburg


Abstract

Concentration waves, the solutions of the Riemann problem, are calculated in the framework of multicomponent chromatography. Unlike ion exchange surfaces, oxides bind cations by predominantly chemical forces, except perhaps in pristine water (at low ionic strengths I below 10-4 mol/L and trace metal concentrations), where electrostatic constraints give adsorption the appearance of a metal-proton exchange process. In addition to the ionic strength threshold there is another threshold in concentration space, a line along which the metal ions cover half of the surface sites (equivalence line). On its low pH side analytical expressions for the waves in pristine water are good approximations for the I = 0.1 mol/L case, as constructed from eigenvectors and eigenvalues of the Jacobian of the multicomponent isotherms. At pH above the equivalence threshold competition for adsorption sites has a negligible effect on the waves in water at I = 0.1 mol/L.


This paper is similar in contents to J. Gruber, "Waves in a Two-Component System: The Oxide Surface as a Variable Charge Adsorbent", Industrial and Engineering Chemistry Research, 34 (8) 2769 - 2781, 1995.

Full version


Location (URL) of this page
Physics Home
Last Changed: January 6, 1997
Page compiled by Joachim Gruber