IP6 sorbs to kaolinite over a wide pH range, decreasing somewhat above pH 8 Modeling indicates that IP6 is sorbed by both inner and outer-sphere complexes. IP6 significantly increases the sorption of Cd(II) to kaolinite from pH 4 to 8. Modeling indicates that two ternary surface complexes are formed. IP6 sorption on kaolinite involves similar surface species to gibbsite.