De Silva, S.M.Rajapakse, C.S.K.2022-02-082022-02-0820159789550481088http://www.erepo.lib.uwu.ac.lk/bitstream/handle/123456789/8317/68-MRT-Use%20of%20computational%20method%20to%20identify%20metal%20binding%20sites%20of%20.pdf?sequence=1&isAllowed=yA bioadsorbent chitosan; a derivative of chitin polysaccharide composed of randomly distributed β-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine (Cahyaningrum et al., 2004) was reported by our group to be much effective as a drinking water purification agent as the percent removal of Cd(II), Pb(II) and Cr(VI) from drinking water by chitosan were 94%, 64% and 70% respectively under optimized conditions (De Silva et al., 2014). It is widely known that chitosan can make complexes with certain metal ions as chitosan has different possible binding sites for metals (figure 1). But little attempt has been made to understand the interaction mechanism of chitosan and heavy metals. Hence the aim of this study was to simulate the IR spectrum of chitosan by DFT calculations and to identify the vibrational bands associated with the possible metal binding sites which can be used as a tool to investigate the interaction mechanism of chitosan and heavy metals. Methodology All theoretical calculations reported in this study were carried out by use of the Gaussian 09 program package. Although chitosan is a polymer, a trimer shown in figure 01 was used to represent chitosan in all theoretical studies. First the structural parameters of the optimized structure of the chitosan have been obtained using electron density functional theory (DFT) with the Becke–Lee–Yang–Parr functional (B3LYP) and 6-31G (d) basis set employing in a gas phase model. Then the IR spectrum of the chitosan was simulated by using the computed frequencies of the optimized geometrical configuration of the trimer in gas phase. The experimental FTIR spectrum for chitosan was obtained from a Bruker Alpha-T spectrometer.enMineral SciencesMaterials SciencesMineralWater ChemistryWaste Water TreatmentWater qualityChemistryOther