First-principles calculation of cresol contaminants removal from wastewater environment

Abstract

In this study, the environment of different cresol (O-cresol, M-cresol, P-cresol) molecules in wastewater were simulated, so as to construct calculation models for the adsorption of single and multiple cresol molecules on Ag(111) surface. All the first-principles calculations are based on the density functional theory. The analysis of adsorption parameters shows that the aromatic ring plane remained horizontal orientation, but the methyl group and the hydroxyl group tilt upward. With the increasing number of cresol molecules, angles between the aromatic ring plane and the top atomic plane of Ag(111) surface increase, and this phenomenon is more obvious in 1O-1M_Ag(111) system. The angle between the aromatic ring plane of cresol molecule and the top atomic plane of Ag(111) surface does not change significantly when three types of cresol molecules are adsorbed, indicating that there is no strong effect between adsorbed cresol molecule and Ag(111) surface. The shortest atomic distance of 3O_Ag(111) system is 1.418 Å and its corresponding maximum adsorption energy is 13.190 eV. It indicates that the structure is the most stable and the adsorption process is the easiest to occur. Results of electron structure analysis show that the superposition peaks (-1.6eV) of O-p orbital and C-p orbital are closer to the Fermi level during the adsorption of single P-cresol molecule, indicating that the system is unstable. For two cresol molecules, 1O-1P_Ag(111) adsorption system shows more superimposed peaks in the range of (-15∼-2) eV. The number of overlapping peaks of adsorption of three types of cresols decreases due to the addition of the third type of cresol molecule. More charge transfers between Ag(111) surface and cresol molecules are observed in 3O_Ag(111) and 1O-1M_Ag(111) adsorption systems, which confirm the strong adsorption effect between them.