| The clay minerals on the surface of the earth are prone to ion exchange in nature due to their special layered structure.Because of the limitations of the experiment and the complexity of the clay mineral microstructure,it is difficult to study the interaction between clay minerals and microscopic particles.Therefore,on the basis of first-principle calculations,this paper conducts a series of analysis studies on clay minerals from a microscopic perspective.conclusion as below:1.Montmorillonite is a common and widely used clay mineral.Because of its ability to adsorb heteroatoms,studying montmorillonite has practical significance for engineering safety.In view of the difficulty of experimental studies to make a microscopic interpretation of the adsorption characteristics of montmorillonite,this paper uses density functional theory to calculate various properties of five types of heteroatom(Mg,Na,K,Ca and Cs)montmorillonite crystals,including geometric electrons Structure and energy changes caused by heteroatoms incorporated into the unit cell.The calculation results show that the hydrogen-oxygen bond in all models is 0.98?,and the aluminum-oxygen bond is longer than the silicon-oxygen bond.The density of state density is small but overlaps with the waveform of oxygen,indicating the presence of a covalent bond;analysis of the energy change caused by the heteroatom incorporation into the smectite unit cell shows that Mg montmorillonite,Na montmorillonite,K Montmorillonite crystals are relatively stable.These stable montmorillonite structures obtained through theoretical calculations provide molecular understanding of the development of new montmorillonite materials.2.The adsorption properties of montmorillonite supercell structure to metal atoms were studied.Through the analysis of interstitial adsorption,the substitution of internal positive atoms with metal atoms replaces the adsorption.The adsorption calculation of metal atoms by the three adsorption methods of surface adsorption shows that the surface has the best adsorption effect on metal atoms and the most stable adsorption effect on Cr.As,Pb and Ni are second,and Zn is the worst.3.In the study of the adsorption properties of montmorillonite supercell structure to water molecules,three adsorption sites of top,bridge and hollow were established on the cell surface(001).Calculation of the adsorption of water molecules shows that the hollow position has the best adsorption effect on water molecules,and the optimal adsorption is a distance of 1.8?.The adsorption energy of the top position and the bridge position is not much different,but the bridge position is the best adsorption The adsorption energy of the distance is relatively small,and the adsorption energy of the top position changes greatly with the increase of the adsorption distance.In the interlayer domain,montmorillonite crystals can stably adsorb multiple water molecules,and the adsorption energy decreases with the increase of the number of water molecules.At the same time,the volume of montmorillonite supercells increases with the amount of interlayer water molecules adsorbed.And get bigger.4.Among the adsorption of carbon dioxide gas on the surface of montmorillonite supercell,the adsorption energy of the hollow position is the smallest among the top,bridge and hollow adsorption sites,the distance of the adsorption energy of the top site is the largest,the distance of the adsorption energy of the hollow site is the smallest and the adsorption energy changes with the distance small.When carbon dioxide molecules are adsorbed between the layers of montmorillonite crystals,as the number of carbon dioxide molecules increases,the crystal volume becomes larger,and the adsorption energy decreases as the number of carbon dioxide increases. |
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