Theoretical study of the adsorption capacity of potentially toxic Cd2+, Pb2+, and Hg2+ ions in hemicellulose matrices

Abstract

Hemicellulose is widely available in nature, is a sustainable resource and has a wide range of applications. Among them, adsorption stands out for the removal of potentially toxic ions. Thus, in the study, the adsorption of Cd²⁺, Pb²⁺ and Hg²⁺ ions in two hemicellulose matrices were elucidated through computational simulations using density functional theory. Molecular electrostatic potential and frontier molecular orbitals demonstrated whether the interactions could happen. Four interaction complexes were highlighted due to the interaction energy criteria, ΔE_Bind, ΔH and ΔG < 0.00 kcal mol^-1, that is: Hm1^… Pb (1); Hm2^… Pb (3); Hm2^…Cd (4) and Hm2^…Hg (4) and the results show that they occur through physisorption. In structural parameter studies, interaction distances smaller than 3000 Å were identified, which ranged from 2.253 Å to 2.972 Å. From the analysis of the topological parameters of QTAIM, it was possible to characterize the intensities of the interactions, as well as their nature, which were partially covalent or electrostatic in nature. Finally, based on the theoretical results, it can be affirmed that the hemicellulose can interact with Cd²⁺, Pb²⁺ and Hg²⁺ ions, evidencing that this study can support further experimental essays to remove contaminants from effluents.

Keywords: Biopolymers; DFT; Hemicellulose; Toxic ions.