Molecular modeling of anionic and cationic dyes adsorption on sludge derived activated carbon

The work deals with the adsorption of two dyes, namely Food Red 17 (FR17) and Methyl Violet (MV), onto a sludge derived activated carbon (SDAC). An experimental analysis of adsorbent properties is preliminary carried out, in order to determine its chemical and textural properties. Subsequently, a molecular simulation analysis based on the reviewed TPSS density functional is performed for the calculation of the molecular structure and properties of both SDAC and the two dyes, as well as for the determinations of their interaction parameters and chemical reactivity descriptors. The nucleophilic and electrophilic attacks within active sites are related to the Fukui function indices and the dual descriptor f (r). A comparison between the descriptors calculated through vertical energy values and those arising from the Koopman's theorem approximation are performed in order to check for the validity of the procedure. The simulations results show that, although FR17 showed a better affinity with SDAC according to the interaction energy calculations, MV was adsorbed more efficiently than FR17 on SDAC, which was demonstrated by the HOMO-LUMO energies and by the retrieved optimized molecular conformation during adsorption of each dye on SDAC.