Theoretical insights into the possibility of removing CH3Hg+ using different adsorptive matrices: g-C3N4, cellulose xanthate, and vanillin-derived modified monomer

[Display omitted] •Identification of adsorptive sites of graphitic carbon nitride, cellulose xanthate and modified vanillin monomer.•The Schiff base is an excellent adsorption site for CH3Hg+.•Structural and electronic elucidation of the methylmercury (CH3Hg+).•Study based on DFT and QTAIM can elucidate the adsorption mechanisms. In this study, the adsorptive capacity of contaminant methylmercury (CH3Hg+) in the matrices of graphitic carbon nitride (g-C3N4), cellulose xanthate (XC), and modified vanillin monomer (VN) was theoretically determined using ωB97X-D/6-31 + G(d,p)/LANL2DZ level. The location of possible interaction sites between the structures was verified using an molecular eletrostatic potential, frontier molecular orbital, and atomic charges, which indicated that for the g-C3N4 matrix, the CH3Hg+ interacted preferentially at the center of the molecule. Conversely, for the XC and VN matrices, this interaction occurred in the -CS2- group and on the Schiff base, respectively. The reactivity indices indicated that the VN matrix demonstrates better interaction with CH3Hg+. Among the evaluated interaction sites, the Schiff base was the most effective for the interaction with methylmercury with a ΔEBind value of −4.80 kJ mol−1. Topological analyses showed that the XC-CH3Hg1 and XC-CH3Hg2 complexes and the interaction “b” for g-C3N4-CH3Hg2 interacted with a partially covalent character. The complexes g-C3N4-CH3Hg1, g-C3N4-CH3Hg3, VN-CH3Hg1, and the interaction “a” of the complex g-C3N4-CH3Hg2 exhibited electrostatic characteristics. Finally, based on the theoretical results, it can be affirmed that the Schiff base is the best adsorption site for CH3Hg+, evidencing that this study can support further experimental essays to remove contaminants from effluents.