Mn(Ⅱ)在伊利石(001)面和(010)面吸附的密度泛函研究

为探究Mn(Ⅱ)在伊利石表面的吸附机理，采用密度泛函理论(DFT)模拟Mn(Ⅱ)在伊利石(001)面和(010)面的吸附，研究了活性位、吸附构型、电荷和态密度。结果表明:在(001)面，Mn(Ⅱ)优先吸附于硅氧环空穴处，且与活性氧O_S1形成1个共价键，吸附能为-262.55 kJ/mol；在(010)面，Mn(Ⅱ)与羟基基团的氧原子形成1~3个共价键，随着共价键数量的增加，吸附能增大，吸附的最稳定构型为Mn(Ⅱ)吸附于3个≡Al—OH基团之间的空穴处，吸附能为-533.62 kJ/mol；Mn(Ⅱ)与(001)面和(010)面均存在共价键作用和静电作用，在(001)面的吸附能小于(010)面，且与(001)面以静电作用为主，与(010)面以共价键作用为主；Mn(Ⅱ)与伊利石表面共价键的形成主要是Mn(Ⅱ)的4s轨道与表面O_S的2p轨道间的相互作用。研究结果可为黏土吸附材料的开发和污染土壤的净化提供理论基础。

A DFT Study of Mn(Ⅱ) Adsorption on Illite Surfaces

In order to explore the adsorption mechanism of Mn(Ⅱ) on illite surfaces, the density functional theory (DFT) was used to simulate the adsorption of Mn(Ⅱ) on the (001) and (010) surfaces. The active site, adsorption configuration, charge and state density were studied, and the following conclusions were obtained. On the (001) surface, Mn(Ⅱ) was adsorbed preferentially on the hole of silicon oxygen ring and formed a covalent bond with the active oxygen O_S1, with an adsorption energy of -262.55 kJ/mol. On the (010) surface, Mn(Ⅱ) formed 1 to 3 covalent bonds with O_S from hydroxyl groups, and the adsorption energy increased with the increase of covalent bonds. The most stable adsorption configuration was Mn(Ⅱ) adsorbed on the holes between three ≡Al—OH groups, and the adsorption energy was -533.62 kJ/mol. There were covalent bond interactions and electrostatic interactions between Mn(Ⅱ) and the (001) and (010) surfaces. The adsorption energy of Mn(Ⅱ) on (001) surface was less than that on the (010) surface. The adsorption of Mn(Ⅱ) on the (001) surface was mainly electrostatic interaction and that on the (010) surface was mainly covalent interaction. The formation of the surface covalent bond between Mn(Ⅱ) and illite was mainly due to the interaction between the 4s orbital of Mn and the 2p orbital of O_S. The results can provide a theoretical basis for the development of clay adsorption materials or the purification of contaminated soil.