水合Pb(OH)^+在高岭石(001)晶面的吸附机理(英文)

Adsorption Mechanism of Hydrated Pb(OH)^+ on the Kaolinite(001) Surface

采用密度泛函理论广义梯度近似平面波赝势法,结合周期平板模型,探讨了水体环境中Pb(OH)+在高岭石铝氧八面体(001)晶面的吸附行为和机理,确定了吸附配合物的结构、配位数、优势吸附位和吸附类型.结果表明,Pb(II)与高岭石铝氧(001)面的氧原子形成单齿或双齿配合物,其配位数为3-5,均为半方位构型.高岭石表面存在含"平伏"氢原子的表面氧(Ol)位和含"直立"氢原子的氧(Ou)位,后者更易与Pb(OH)+单齿配位,该吸附配合物具有较高的结合能(-182.60 kJ·mol-1),为优势吸附物种;高岭石表面位于同一个Al原子上的"OuOl"位可形成双齿配合物.表面Ol与水分子配体形成氢键,对配合物的稳定性起到关键作用.Mulliken布居和态密度分析表明,高岭石单齿配合物中Pb―O成键机理主要为Pb 6p轨道与Pb 6s―O 2p反键轨道进行耦合,电子转移到反键轨道.双齿配合物"Pb―Ol―H"共配位结构中,受配位氢原子影响,Pb―Ol成键过程成键态电子填充占主导地位.

The adsorption behavior of Pb（OH）＋ on the basal octahedral （001） surface of kaolinite has been investigated using the Perdew-Burke-Ernzerhof generalized gradient approximation （GGA-PBE） of density functional theory with periodic slab models, where the water environment was considered. The coordination geometry, coordination number, preferred adsorption position, and adsorption type were examined, with binding energy estimated. All the monodentate and bidentate complexes exhibited hemi-directed geometry with coordination numbers of 3-5. Site of ＂Ou＂ with ＂up＂ hydrogen was more favorable for monodentate complex than site of ＂O1＂ with ＂lying＂ hydrogen. Monodentate complexation of ＂Ou＂ site with a high binding energy of -182.60 k J·mo1-1 should be the most preferred adsorption mode, while bidentate complexation on ＂OuOt,＂ site of single AI center was also probable. The stability of adsorption complex was found closely related to the hydrogen bonding interactions between surface O, and H in aqua ligands of Pb（ll）. Mulliken population and density of states analyses showed that coupling of Pb 6p with the antibonding Pb 6s--O 2p states was the primary orbital interaction between Pb（ll） and the surface oxygen. Hydrogen complexation occupied a much large proportion in the joint coordination structure of bidentate complex, where bonding state filling predominatedfor the Pb--O1 interaction.