The aim of this work was to develop a simple linear model (LPH) that could be used to fit the huge amount of data available in the literature concerning the effect of pH on the adsorption of metal ions. A total of 52 datasets of available published data dealing with two different adsorbents, activated carbon and kaolinite, were analyzed. The equilibrium constants (log K) and coordination numbers (n) of the complexes of metal ions with the surface ( S-) were determined from linear plots of log K-d (partition coefficient) versus log[ S-]. The values of log K and n increased with the decrease of initial metal ions concentration. When compared with the state-of-the-art surface complexation model, the model developed in this study (LPH) was found to be simpler and have more predictive abilities.