The impact of the competitive adsorption of ions at surface sites on surface free energies and surface forces

Abstract

The impact of the competitive adsorption of ions at surface sites on surface free energies and surface forces 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 OH + 2 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. C 2015 AIP Publishing LLC. [http://dx

Cation effects on haemoglobin aggregation: balance of chemisorption against physisorption of ions

“…rsfs.royalsocietypublishing.org Interface Focus 7: 20160137 G chem accounts for chemisorption, the charge transfer energy required to form the surface site charges s c and s a . Using the framework for describing competitive site binding [29], the chemisorption energy is G chem ¼ G c chem þ G a chem , with…”

Hydronium and hydroxide at the air–water interface with a continuum solvent model

“…A problem of crucial importance. [108] We can also apply the model to other anisotropic ions with unusual behaviors such as iodate, [63] perchlorate, [109] nitrate, and acetate; [110] to multivalent ions where water structure may be more important; to other surfaces where water's self ions may play an important role; [111] and to see if it can explain the negative adsorption entropy of ions to the air-water interface. [37] It is also obviously important to combine the model with a more sophisticated statistical mechanical description of ion-ion interactions.…”

Effect of electrolytes on proteins physisorption on ordered mesoporous silica materials

“…They found that about 1/5 of the silanols have a pK a ≤ 2 and the remaining 4/5 of the silanols have a pK a of about 8.2. Besides to be controlled by the dissociation of the silanol groups, the surface charge density of mesoporous silica is largely affected by the type and the concentration of supporting electrolytes [81]. As an example let us consider the effect of different chloride salts, at different ionic strength, on the surface charge density () of SBA-15.…”