RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics
Conversion to zero ionic strength
Log K values of surface complexation reactions are usually determined at a constant ionic strength of a certain background electrolyte. To use the collected SCM data in speciation codes that support Surface Complexation Modelling (e.g. PHREEQC or Geochemist's Workbench), a conversion procedure has been integrated into RES³T, to calculate the LogK value at zero ionic strength using the Davies equation (1,2) (Davies 1962). This equation is valid up to an ionic strength of I = 0.5 mol L−1.
The parameters A and b (A = f(T,p), b = free parameter) are set to:
The LogK conversion to zero ionic strength and the LogK normalisation to a SSD = 2.31 nm−1 are seperate and not cummulative.