BOMD study on the reaction among one amaranth dye molecule and one chitosan repetitive unit

Abstract

The interaction between the reactants formed by a repeating unit of chitosan (adsorbent) and an amaranth dye molecule (adsorbate) is calculated using Born Oppenheimer Molecular Dynamics (BOMD) to determine possible adsorption. The attack of the adsorbent to the adsorbate is oriented between NH2 and OH of the functional group of C14H24N2O9 chitosan repetitive unit and the functional group of SO3Na sodium sulfonate dye. The electronic effects in the calculation of the dynamics are useful to determine the way these molecules interact. In the first model, it is observed the breakage of a sodium-oxygen bond and another of sulfur-oxygen, belonging to the dye molecule with a reorganization of hydrogens in the chitosan repetitive unit functional group. This shows that there are changes in the site where dye adsorption is predicted on chitosan assuming that the molecules are at neutral pH. For the second model it is observed that the collision of the dye molecule shows repulsive effects by the chitosan repetitive unit forming a deviation angle less than 90°. For this study, DFT was used with exchange and correlation using DZVP basis set function.