1pK and 2pK protonation models in the theoretical description of simple ion adsorption at the oxide/electrolyte interface: the analysis of temperature dependence of potentiometric titration curves.
Two models of oxide surface charging (1pK and 2pK) were used to describe the potentiometric titration curves measured by Blesa et al. (J. Colloid Interface Sci.101, 410 (1984)) at three temperatures and at three concentrations of electrolyte. Rudzinski et al. (Langmuir13, 483 (1997)) have applied the 2pK Triple Layer Model to analyze the above system earlier. Two calculation procedures based on the 1pK Basic Stern Model were developed to described Blesa's data. Since the experimental curves have the CIP (common intersection point) it was assumed that heat of electrolyte ion adsorption was equal to zero. We assumed two different values of the double layer innermost capacitance on both sides of PZC (point of zero charge), which was followed from asymmetry of surface charge curves relative to PZC. Moreover, it was necessary to take into consideration the dependence of capacitance on ionic strength and temperature. The quality of fit given by two models was comparable. Since the 1pK BSM is simpler than the 2pK TLM and includes not so many best-fit parameters it seems to be a better choice in this case. Discussion of the results obtained by other authors concerning the subject under consideration is also presented.
Piasecki
Wojciech
W
Laboratory for Theoretical Problems of Adsorption, Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Ul. Niezapominajek, Kraków, 30-239, Poland. piacho@hermes.umcs.lublin.pl