Adsorption of trivalent and pentavalent arsenic ions from the aqueous stream using natural Bombax ceiba fibers: Insights from density functional theory calculations

Natural fibres have recently emerged as a pool of organic compounds that for different applications. Among several natural products, the fibres of Bombax ceiba contain several naphthalene-based compounds. Hence, Bombax ceiba may exhibit the potential of adsorbing a variety of pollutants. In this study, the adsorption of arsenite (As(III)) and arsenate (As(V)), from the aqueous stream was investigated using density functional theory (DFT) calculations. 1,4-Naphthaquinone, 1-Naphthyl ether, Hemigossypol, and Naphthol were chosen as adsorbent molecules for As(III) and As(V) ions as they form the major portion of the Bombax ceiba fibres. CAM-B3LYP/6-311G level of DFT theory was used to calculate electrostatic potential maps, HOMO-LUMO distributions, chemical potential, and hardness to gain quantitative information on the interactions. The adsorption energies and recovery time were calculated based on the thermodynamic feasibility of the interactions of As(III) and As(V) ions with Bombax ceiba fibres. The results showed that As(III) and As(V) ions adsorbed physically on the Bombax ceiba fibres. The results can be used to further modify naturally occurring Bombax ceiba fibres to develop sustainable solutions.