ELECTROKINETIC POTENTIAL OF WATER AND STRUCTURE OF AIR/WATER INTERFACE

Abstract

As a result of analysis of structural features in water and behavior of its dzeta-potential under various conditions the molecular model of the structure of air/water interface is offered. Basis of structure is a superficial net consisted of flat cyclic clusters of N4 and N5, connected between them silver by additional molecules of Н2О. Unconnected groups of these two clusters are forced directed equally upwards and downwards from the plane of the net, therefore the net itself is electro-neutral. On the surface of water the lower side of the net exothermally adsorbs the ions of H3O+ that results in reorientation of all molecules of H2O in clusters by groups of OH in the direction of liquid phase and appearance of negative structural charge on the surface of the net. This charge forms a double electric layer under itself in which the adsorbed ions of H3O+ act a role of inside part and the ions of OH– take place in a diffuse layer.

The maximal size of negative dzeta-potential of water is arrived at рН 10 because due to adsorption of ions of Н3О+ of рН of water in an interface diminishes to 7. At рН > a 10 potential diminishes due to neutralization of adsorbable ions of Н3О+ the ions of ОН-. At рН < 10 more slow reduction of superficial charge occurs due to displacement of ion-adsorption equilibrium that arises up in the system at the increase of concentration of ions of Н3О+. At рН 4 a superficial charge disappears in an interface, but the structure of superficial net of clusters continues to remain an orientation one-sided. In area of рН < 4 ions of Н3О+ are adsorbed already on superficial atoms Оδ– and superficial potential of water becomes positive. Thus, there is electrokinetic potential in area of рН < 4 and рН > 13 has ion, and in an intermediate range рН- structural nature.

Influence of cations of metals on the superficial charge of water in solutions follows after an ion-adsorption mechanism. Adsorbed on the downside of superficial net of clusters they always reduce negative structural potential of water.

Model of forming of molecular structure of interface of air/water takes into account both an orientation and adsorption of molecules and ions. A new model allows easily explaining the phenomena of bubbling chemical effects in solutions of salts and anomalously high surface-tension of water.