A DFT-based Analysis of Metals Adsorption on Chitosan Monomer

Abstract

The generation of waste electrical and electronic equipment (WEEE or E-waste) has been noted as an increasing category of waste. In this work, the density functional theory (DFT) was used to investigate the adsorption process between chitosan (CS) and metals at the B3LYP level with 6-31G(d,p) and LANL2DZ basis sets. The effect of solvent was included using the polarizable continuum model (PCM) consisting of water. Ag+, As3+, Ba2+, Be2+, Cd2+, Co2+, Cr3+, Cu2+, Hg2+, Li+, Mn2+, Ni2+, Pb2+, Pd2+, Sb3+, Sn2+, Sr2+, Tl+, and Zn2+ have been selected to be studied because of high impact in E-waste. Different analyses were carried out: adsorption energy, HOMO-LUMO energy gaps, hardness, softness, frontier molecular orbitals, and molecular electrostatic potential (MEP), and all of which are necessary to predict the formation of complexes. The interaction between CS and metal species was shown in almost all cases as covalent partial. In addition, all metals were placed closeer to the nitrogen atom than the oxygen atom of CS because the charge density of the nitrogen is increased in the formation of the Schiff base. Finally, the monomer derived from CS has good stability in water and is, therefore, considered as a good material in the field of environmental pollution.