The effect of parameter uncertainty on blind prediction of Np(V) sorption onto hematite using the Diffuse Double Layer Model

The aim of this work is to illustrate the effect of parameter uncertainty (protolysis constants) in surface complexation modeling. As example the blind prediction of Np(V) sorption onto hematite was selected, applying the Diffuse Double Layer Model (DDLM).
None of the pK parameter sets randomly generated within a space of two standard deviations did deliver unacceptable predictions for the distribution coefficients. Thus the formally large spreading of the pK values as extracted from literature (even after normalization and extrapolation to infinite dilution) is actually not critical. For well-defined mineral systems, provided a suitable database is accessible, the DDLM approach seems to be promising.