Structure and bonding nature of [PbCl]+ adsorption on the kaolinite(0Â 0Â 1) surface in aqueous system

Adsorption of [PbCl]+ on the basal hydroxylated (0 0 1) surface of kaolinite in aqueous system was investigated by the plane-wave pseudopotential density functional theory calculations. Structures of the adsorption complexes including the coordination geometry and effective coordination number on the two different types of surface sites were examined, with the PbO (or Cl) bonding mechanism explored. [PbCl]+ prefers to bind with the hydroxylated kaolinite(0 0 1) surface in monodentate way on the site of Ou in “upright” hydroxyl. Complexation of [PbCl]+ in bidentate way on OuOl (oxygen of “lying” hydroxyl) site of single Al center is also probable. All adsorption complexes feature coordination number of 3-5 within the hemidirected geometry. Charge transfer occurs with ligating atoms of oxygen denoting some electrons to Pb(II) and Cl. Upon the partial density of states (PDOS) projections and Mulliken bond populations, both bonding and antibonding state filling are involved in the PbO (or Cl) interaction. Pb 6p interacting with the antibonding combination of Pb 6s and O 2p states is the dominant orbital contribution of Pb(II) with surface oxygen, while the bonding Pb 6sCl 3p state filling is primarily responsible for the PbCl interaction.