Research On The Nature Of The Interaction Between Mercury And π And Its Quantum Chemistry Calculation Methods

With the increasing awareness of environmental protection,mercury as a extremely severe toxic substance to global surroundings pollutant has aroused great attention.How to reduce the generation and effectively adsorption of mercury pollutants to control its pollution in a smaller range has become one of focuses of scientific research.In the industry,activated carbon is commonly used to treat exhaust gas,wastewater and residues containing mercury.The basic microcrystal of activated carbon is a graphene sheets and graphite has a hexagonal plane reticulated crystallite carbon structure with large π bonds composed of numerous sp2 hybrid carbon atoms.Similarly,there are also large delocalized π bonds with sp2 as the main hybrid in new nanomaterial adsorbents,such as graphene(GE)or carbon nanotubes(CNTs).The most important electronic structure has the extensive presence of delocalized π bonds in these low-dimensional carbon nanomaterials.One of the key issues of the noncovalent interaction between low-dimensional carbon nanomaterials interact and different valence states mercury and its compounds is the intermolecular interaction of mercury and π.At present,there has been not published about systematic research work in this domain.This article exerts quantum chemical computational method to study the Hg…π interaction between mercury and its compounds and activated carbon graphite crystallites,graphene and carbon nanotubes materials characterized by large π bond systems.All research work can be mostly divided into two parts.The first is by establishing the CCSD(T)/CBS standard value of the small system,the density functional theory(DFT)method is tested and evaluated,so as to screen out optimal DFT method suitable for Hg…π interaction to be applied to the calculation of the large systems binding energy.The second decompose the interaction energy of mercury and its compounds with the π bond carbon nanomaterials using the symmetry-adapted perturbation theory method,and further discuss the nature of the mercury and π interaction.In order to find precise and effective DFT method to compute the binding energy of Hg…π interaction,we first choose the interaction systems of different valence states mercury with benzene and borazine basic unit as the methods screening of DFT.The MP2/aug-cc-p VTZ method is used to optimize the geometric structure,and then regard the high-precision CCSD(T)/CBS calculation results as the benchmark,choose a variety of widely used DFT method with def2-QZVP basis set to calculate the binding energy,comparison with the benchmark CCSD(T)/CBS.We discover that ωB97M-V is greatest DFT method sultable for studying Hg…π interaction among numerous density functional methods.Therefore,we calculate the binding energy of Hg0,Me2 Hg,Hg Cl2 and Hg O with carbon nanomaterials such as activated carbon graphite microcrystals,graphene and carbon nanotubes using ωB97M-V method and def2-QZVP basis set.The calculation results show that the interaction of Hg0,Me2 Hg,Hg Cl2,Hg O and carbon nanotubes is strongest in the low-dimensional carbon nanomaterials such as activated carbon graphite microcrystals,graphene,and carbon nanotubes.Which may be due to have closely relevant to the dispersion interaction between the inner wall of one-dimensional carbon nanotubes and different valences mercury and its compounds.However,the intermolecular attraction of these carbon nanomaterials with uniform π electron density distribution and various valence states mercury compounds interaction systems mainly depends on the dispersion interaction,while the contributions of electrostatic and induction energy fail to play main effect,making these adsorption materials less selective and adsorptive.This enlighten us to modify carbon nanomaterials by changing the uniformity of the material or introducing oxygen,nitrogen,sulfur and halogen heteroatoms to obtain a mercury adsorption material with good selectivity,strong adsorption capacity and high mercury removal efficiency.We revealed the nature of the noncovalent interaction between mercury and π from the level of electronic structure.In this thesis,through the theoretical exploration of quantum chemical calculation methods,we provide useful reference information to experimental workers,and it is great value for research and development in related fields.