Font Size: a A A

Theoretical Study On Adsorption Of Water Molecules On Charged Kaolinite Surface

Posted on:2016-03-22Degree:MasterType:Thesis
Country:ChinaCandidate:M J ZhongFull Text:PDF
GTID:2271330461954168Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
As a kind of layered aluminosilicate, kaolinite shows a lot of physicochemical properties,so it has been used widely in many industrial productions, at the same time, the study on interaction between kaolinite and other molecules has become a new research field and has attracted much attention. The water, as one of the most common solvents in nature, is cheap and easy to get. It provides the necessary basis for interaction between kaolinite and other molecules, so the study on interaction between water and kaolinite is significant for the application of kaolinite.Although many researches about interaction between water and kaolinite have been reported, the acknowledgement about the adsorption of water molecules on kaolinite surface with a permanent negative charge is not completely. In this study, X2+(X= Ca, Mg, Mn, Fe,Co, Ni, Cu, Zn) doped kaolinite octahedral layer and Al3+doped kaolinite tetrahedral layer have been prepared and presented by the(Al5XO24H30)-(X=Ca, Mg, Mn, Fe, Co, Ni, Cu, Zn)and(Si5AlO18H12)-cluster models. Several gas phase properties of n(n=1-3) water molecules adsorbed on kaolinite charged surface have been investigated systematically at the level of MP2/6-31G(d,p)//B3LYP/6-31G(d,p) using Density Functional Theory(DFT), and compared with the adsorption of water molecules on kaolinite neutral surface(Al6O24H30 for octahedral surface and Si6O18H12 for tetrahedral surface). The gas phase properties include optimal structures, structural parameters, hydrogen bonds, adsorption energies, Natural Bond Orbital(NBO) charge distributions, vibration frequencies and electronic potentials.The results show that several hydrogen bonds formed during the adsorption process, and the number of hydrogen bond increases with the increase of water molecules, simultaneously,the formation of hydrogen bonds reduced the energy of complex system after adsorption, so the complex system becomes more stable; the adsorption energy when water molecules are adsorbed on kaolinite charged surface is lower compared to the adsorption on kaolinite neutral surface, so the adsorption on charged surface is more stable; comparing to the adsorption of water molecules on X2+(X=Ca, Mg of same group) doped kaolinite octahedral layer suggests the stability when water molecules are adsorbed on(Al5CaO24H30)-surface is stronger, and the comparison between the adsorption of n(n=1-3) water molecules on(Al5CaO24H30)-or(Si5AlO18H12)-surface shows that the interaction between water molecules and(Al5CaO24H30)-is stronger than(Si5AlO18H12)-when n(n=1-2) water molecules are adsorbed. However, the interaction of the former is weaker than the latter when three water molecules are adsorbed; when water molecules are adsorbed on X2+(X=Mn, Fe, Co, Ni, Cu,Zn of same period) doped kaolinite octahedral layer, the adsorption affinity order of surfaces for water molecules is K(Al-Mn) > K(Al-Fe) > K(Al-Ca) > K(Al-Zn) > K(Al-Ni) >K(Al-Mg) > K(Al-Cu) > K(Al-Co) when n(n=1,2) water molecules are adsorbed and K(Al-Mn) > K(Al-Ni) > K(Al-Fe) > K(Al-Ca) > K(Al-Zn) > K(Al-Cu) > K(Al-Mg) >K(Al-Co) when three water molecules are adsorbed; the adsorption of n(n=1-3) water molecules on Mn2+doped kaolinite octahedral layer is easiest, and the complex system after adsorption is more stable.
Keywords/Search Tags:Kaolinite, Water Molecule, Hydrogen Bond, Adsorption
PDF Full Text Request
Related items