Removal of methylene blue by using sodium alginate-based hydrogel; validation of experimental findings via DFT calculations

Abdulrahman Allangawi; Mona A Aziz Aljar; Khurshid Ayub; Ahmed Abd El-Fattah; Tariq Mahmood

doi:10.1016/j.jmgm.2023.108468

Removal of methylene blue by using sodium alginate-based hydrogel; validation of experimental findings via DFT calculations

J Mol Graph Model. 2023 Jul:122:108468. doi: 10.1016/j.jmgm.2023.108468. Epub 2023 Apr 4.

Authors

Abdulrahman Allangawi¹, Mona A Aziz Aljar¹, Khurshid Ayub², Ahmed Abd El-Fattah³, Tariq Mahmood⁴

Affiliations

¹ Department of Chemistry, College of Science, University of Bahrain, Sakhir P.O. Box 32038, Bahrain.
² Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, 22060, Pakistan.
³ Department of Chemistry, College of Science, University of Bahrain, Sakhir P.O. Box 32038, Bahrain; Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Alexandria, 21526, Egypt. Electronic address: aahussein@uob.edu.bh.
⁴ Department of Chemistry, College of Science, University of Bahrain, Sakhir P.O. Box 32038, Bahrain; Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, 22060, Pakistan. Electronic address: tmahmood@uob.edu.bh.

PMID: 37031664
DOI: 10.1016/j.jmgm.2023.108468

Abstract

Removal of commonly used dyes from water bodies has recently gained great interest from the scientific community. Presence of the methylene blue (MB) dye in drinking water poses harmful effects on the human health. The large-scale removal of MB is achievable through highly efficient, inexpensive, renewable, and biodegradable adsorbents. Our research group has recently synthesized a sodium alginate-based hydrogel and explored its application towards the removal of MB. Previous results have shown that the synthesized hydrogel exhibits a high adsorption capacity of 51.34 mg/g under basic conditions. Herein, we employed the density functional theory (DFT) calculations to explore the mechanism of MB removal by using sodium alginate hydrogel at various pH levels. Results of this study have shown that under acidic/neutral conditions the removal of MB is endergonic (ΔG_int = 6.10 kcal/mol). Whereas under basic conditions it is highly exergonic (ΔG_int = -97.58 kcal/mol). Moreover, the QTAIM and NCI analyses have shown that the MB dye is chemisorbed to the absorbent via strong covalent-like interactions between the polymer's carboxylate groups and the hydrogens in MB. Furthermore, preferability of basic conditions have been confirmed by the large charge transfer (0.104 |e|), as compared to no charge being transferred in the acidic/neutral conditions.

Keywords: DFT; Hydrogel; Methylene blue; NCI; QTAIM.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adsorption
Alginates
Coloring Agents
Density Functional Theory
Humans
Hydrogels*
Kinetics
Methylene Blue
Water Pollutants, Chemical*

Substances

Hydrogels
Methylene Blue
Alginates
Water Pollutants, Chemical
Coloring Agents