The impact of the competitive adsorption of ions at surface sites on surface free energies and surface forces
Parsons, D.F. and Salis, A. (2015) The impact of the competitive adsorption of ions at surface sites on surface free energies and surface forces. The Journal of Chemical Physics, 142 (13). Article 134707.
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The relationship between surface charge and surface potential at the solid-liquid interface is often determined by a charge regulation process, the chemisorption of a potential determining ion such as H+. A subtle ion-specific effect can be observed when other ions compete with the primary potential determining ion to bind to a surface site. Site competition may involve alternative ions competing for a first binding site, e.g., metals ions competing with H+ to bind to a negatively charged oxide or carboxyl site. Second-binding sites with site competition may also be found, including amphoteric OH2+ sites, or anion binding to amine groups. In this work, a general theoretical model is developed to describe the competitive adsorption of ions at surface sites. Applied to the calculation of forces, the theory predicts a 20% increase in repulsion between titania surfaces in 1 mM NaCl, and a 25% reduction in repulsion between silica surfaces in 0.1M NaCl compared to calculations neglecting ion site competition.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Engineering and Information Technology|
|Publisher:||American Institute of Physics|
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