A Theoretical Study Of Adsorption Of Water Molecule And Zinc Ion On Goethite (010) Surface And Relationship Between Structure Of Imidazoline Derivatives And Inhibition Performance

Goethite is a widespread and reactive mineral in the environment. The transport of contaminants are significantly affected by adsorption and reduction reactions involving goethite. An understanding of the goethite-water interface is critical for determining the molecular-scale mechanisms of adsorption and reduction reactions. In the present paper, periodic boundary conditions and density functional theory were used to investigate the character of bulk and Pnma (010) surface of goethite, a surface that few studies have been engaged, especially the adsorption of water molecule on it with various degrees of coverage. In order to know the mechanism of interaction between goethite-water interface, a detailed study on the adsorption and dissociation of water on goethite (010) surface was performed, and a possible path for water dissociation was found. In summary, periodic boundary conditions and density functional theory were used to investigate the mechanism of interaction between goethite-water interface, with various coverage degrees of both associative and dissociative adsorption. Low coverage and Medium coverage share a similar process that both are endothermic reactions with higher activation energy. On the contrary, high coverage is exothermic reaction with lower activation energy. So, water will dissociate spontaneously under high coverage and water reactivity was enhanced due to the formation of the adsorbed water layer.The adsorption of Zn(OH)42- ion has been studied on the basis of semidissociative adorption of water molecules on goethite (010) crystal surface. The variation rule of bond length change before and after adsorption was obtained that the average Zn-bridgeO bond lengths tended to extend, compared to the case of isolated Zn(OH)42- in vacuum, while the average Zn-O bond lengths tended to contract, with few exceptions. The stabilization order of all adsorption configuration of Zn(OH)42- ion were also obtained: DC2> SE1> DC1> SC1>SC2. And DC2 was the most stable adsorption configuration.The inhibition performance of two imidazoline derivatives, 3-ethylamino-2- undecyl imidazoline(EUI) and chloride-3-ethylamino-3-(2,3-two hydroxyl) propyl- 2-undecyl imidazoline sodium phosphate(CEPIP), for Q235 steel in CO2 saturated solution at 298 K have been tested by weight loss experiment and electrochemical techniques. The adsorption behavior of the two inhibitors on Fe surface have been studied using molecular dynamics method and density functional theory. The results indicated that the two imidazoline derivatives could both adsorb on the Fe surface firmly through the imidazoline ring and heteroatoms, the two inhibitors both have excellent corrosion inhibition performance. The molecular dynamics simulation results show that both the two imidazoline derivatives can adsorb on the Fe surface through the imidazoline ring and heteroatoms with the alkyl chain approximately perpendicular to the surface. Quantum chemistry calculation results show that the imidazoline ring and heteroatoms are the active sites of the two inhibitors. They can adsorb on Fe surface firmly by donating electrons to Fe atoms and accepting electrons from 3d orbitals of Fe atoms.