Molecular dynamic simulations and computational DFT of adsorption performances of malachite green on the metal fluorides in aqueous medium

This work focused on the elucidation of the adsorption mechanism of malachite green (MG) on different metal fluorides MF2 surface (where M=Mg, Mn, Zn or Ni) using DFT and molecular dynamics (MD) simulation. Global and local electronic parameters, dynamic descriptors and radial distribution function (or pair correlation function) g(r) were evaluated and discussed. Results proved that the investigated molecule has a high electron accepting ability which allow it to be adsorbed strongly on the MF2 surfaces. MD simulations suggest adsorption energies of -340.26, -313.62, -309.08 and -302.82 kcal/mol, respectively, for MgF2, ZnF2, MnF2 and NiF2. These energies are negative, which indicates that the adsorption process is spontaneous in nature. Moreover, it was found that the studied dye is oriented with the ring parallel to the MgF2, ZnF2 and MnF2 and vertical to the NiF2 surface. Also, the MD simulations demonstrate that the interactions that occurred during MG adsorption being assigned to a chemical and physical adsorption. This result is confirmed by the radial distribution function (RDF) analysis. Intramolecular interaction is found to be equal to zero for all systems.