Thermodynamics and kinetics of cationic/anionic dyes adsorption on cross-linked chitosan

Cationic (Malachite Green) and anionic dyes (Indigo carmine) removal by cross-linked chitosan (CSglu) beads has been investigated using experimental and computational approaches. The experimental investigations of the adsorption isotherm, kinetics, and thermodynamics information correlated well with computational studies in term of structures and binding energies (Delta E-B). Cross-linked chitosan adsorb Malachite Green better than Indigo carmine using Langmuir adsorption isotherm. The CSglu beads in frozen dried form showed highly adsorption capacity (71429 mg.g(-1)) for malachite green (MG) but they are not favorable for indigo carmine (IND). In order to probe the atomistic-level detail between these two dyes and CSglu, molecular dynamics simulations (MDs) have been applied to determine detailed analysis of binding site of the complexes. MG is more preferable to bind with CSglu, than IND due to its complementary of the molecular electrostatic potential (MEP) to the CSglu, surface. The quantum calculations using density functional theory (DFT) with different levels and basis set super position error (BSSE) were used to calculate Delta E-B and to effectively predict the adsorption capabilities of cationic and anionic dyes by cross-linked chitosan. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Experimental and computational approaches were used to investigate the removal of cationic and anionic dyes by cross-linked chitosan beads. It was found that cationic dyes, specifically Malachite Green, were more effectively adsorbed compared to anionic dyes like Indigo carmine.