Computational study of the interaction of heavy metal ions, Cd(II), Hg(II), and Pb(II) on lignin matrices

Author(s)

Santos, Thifany Justo ^[1] ; Paggiaro, Juliana ^[1] ; Cabral Silva Pimentel, Helhe Daiany ^[1] ; dos Santos Pereira, Anna Karla ^[2] ; Cavallini, Grasiele Soares ^[1] ; Pereira, Douglas Henrique ^[1]

Affiliation

^[1] Fed Univ Tocantins, Chem Collegiate, Campus Gurupi Badejos, POB 66, BR-77402970 Gurupi, Tocantins - Brazil

^[2] Univ Estadual Campinas, Inst Chem, UNICAMP, POB 6154, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF MOLECULAR GRAPHICS & MODELLING; v. 111, MAR 2022.
• Web of Science Citations: 0

Abstract

Contamination by heavy metal ions, particularly in water resources, is a severe environmental problem. In this study, the interaction of metal ions, namely, Cadmium Cd(II), Mercury Hg(II), and Lead Pb(II), on lignin matrices was investigated based on theoretical calculations. Binding energy (Delta EBind) values proved that the Pb(II) interacted better with lignin matrices than Cd(II) or Hg(II), having energy values between -8.4 kcal mol-1 to -20.2 kcal mol-1. The Gibbs energy (Delta G) and enthalpy (Delta H) values for Pb(II) were <0, indicating that the process was spontaneous and released heat. However, the lignin matrices studied in this work did not interact efficiently with Cd(II) and Hg(II) ions because almost all Delta EBind, Delta G, and Delta H values were positive. The bond length of the interaction proved that the Pb ions yielded the smallest values, ratifying the values for the interaction energy. Analyses based on the quantum theory of atoms in molecules showed that the interactions between Pb(II) and the matrices were partially covalent, whereas the interactions of Cd(II) and Hg(II) were predominantly electrostatic, justifying the positive values of Delta EBind, Delta G, and Delta H. The natural bond orbital results showed that the ligand orbitals of the matrix interacted with the lone pair antibonding orbital (LP{*}) of the metal ions. The theoretical results of the study show the possibility of applying lignin to remove heavy metal ions, especially Pb, and providing information for research related to wastewater treatment. (AU)

• FAPESP's process: 17/11485-6 - Computational and theoretical developments based on ab initio methods and the Density Functional Theory
• Grantee: Rogério Custodio
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/08293-7 - CCES - Center for Computational Engineering and Sciences
• Grantee: Munir Salomao Skaf
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC