DFT calculations of different amine / ammonium cations adsorption on kaolinite (001) surface

To explore the adsorption mechanism of the cationic amine salts and quaternary ammonium salts on kaolinite surfaces,the authors built four configurations of amine / ammonium cations of CH6 N+(Amine cation),C2 H8 N+(Second- ary amine cation),C3 H10 N+(Tertiary amine cation) and C4 H12 N+ ( Quaternary ammonium cation). Also,the adsorp- tions of these four cations on kaolinite (001) surface were calculated using DFT (Density functional theory). The cal- culation results indicate that the four cations of CH6 N+ ,C2 H8 N+ ,C3 H10 N+ and C4 H12 N+ could be favorably adsorbed on kaolinite (001) surface, and the adsorption energies of the more stable configuration of these four cations are 125． 385,-126． 154,-128． 654 and -109. 711 kJ / mol,respectively. However,the mechanism of three amine cations and quaternary ammonium cation adsorption on kaolinite (001) surface are different,where the amine cations are ad- sorbed on kaolinite (001) surfaces through both electrostatic attraction and hydrogen bonds while the quaternary am- monium cation only through the electrostatic attraction. The electrostatic attraction plays the main role in different a- mine / ammonium cations adsorption on kaolinite (001) surface.