engleski

Influence of ions on surface properties of quartz and the nature of iodine/iodide adsorption

In contact of quartz (SiO2) surface with aqueous electrolyte solutions, the rearrangement of ions near the interfacial region occurs, which leads to the formation of the electrical interfacial layer, ElL. These processes can cause a potential gradient between the crystal surface (O-plane) and the bulk solution. The potential difference between the surface and the bulk solution can be measured by use of specially constructed Single Crystal Electrodes, SCrE, which are constructed in a way that only one crystallographically well defined plane is exposed to the solution. The same processes also occur on surfaces of SiO2 nanoparticles suspended in electrolyte solutions - however, in that case, the inner surface potential cannot be directly measured, it can only be calculated by using electrokinetic measurements combined with chosen surface reactions model. Surface potential depends on the nature of the surface (i.e. density and charge of active sites), and the composition of the solution. In the case of inner surface potential measurements, the difference in measured potentials is caused only by the composition of solution. The (100) quartz SCrE potential was measured as a function of pH, and ionic composition (H3O+, Na+, K+, OH-, Cl-, Br-, I3-), Additional spectroscopic and electrokinetic experiments with SiO2 particles in iodine/iodide solutions were made. Correlation with Hoffmeister series has been observed. Unexpected results have been obtained with iodide solutions, which implied a specific adsorption of iodide species, possibly even as neutrall molecules.

Quartz ; surface potential ; single crystal electrode ; cations ; anions ; Hofmeister series

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