To investigate the dispersion mechanism of sodium hexametaphosphate on kaolinite particles, we simulated the interaction between linear polyphosphate chains and kaolinite Al-OH terminated surface by molecular dynamics, as well as the interaction between the [HPO4](2-) anion and kaolinite Al-OH surface by density functional theory (DFT). The calculated results demonstrate that hexametaphosphate can be adsorbed by the kaolinite Al-OH surface. The oxygen atoms of hexametaphosphate anions may receive many electrons from the Al-OH surface and form hydrogen bonds with the hydrogen atoms of surface hydroxyl groups. Moreover, electrostatic force dominates the interactions between hexametaphosphate anions and kaolinite Al-OH surface. Therefore, after the adsorption of hexametaphosphate on kaolinite Al-OH surface, the kaolinite particles carry more negative charge and the electrostatic repulsion between particles increases. In addition, the adsorption of -[PO3](m)-species on the Al-OH surface should be more stable than the adsorption of -[HPO3](m)-species. (C) 2016 Elsevier B.V. All rights reserved.