Theoretical insight of ciprofloxacin removal from water using boron nitride (B12N12) nanocage

Abstract

In the present study we used B12N12 nanocage for the removal of ciprofloxacin (CIP) from water using DFT approach. Three positions of CIP are considered for the interaction with B12N12 nanocage i.e. complex-1 (CMP-1), complex-2 (CMP-2) and complex-3 (CMP-3) in aqueous and gas phase. The optimized bond distances show that CMP-1 and CMP-2 interacts strongly with the nanocage. The adsorption energies (Ead) reveal that the CMP-1 and CMP-2 are chemisorbed having -26.83 and -24.67 kcal/mol in gas phase and -24.34 and-22.88 kcal/mol in aqueous medium while complex-3 (CMP-3) physisorbed having -8.94 kcal/mol in gas phase and -8.40 kcal/mol in aqueous medium. The charge transfer analysis shows significant charge transfer between adsorbate and adsorbent. The atoms in molecule analysis (AIM) also confirm that OHN bond in CMP-1 is strong hydrogen bond while the O—B bond in CMP-1 and CMP-2 is a covalent bond. Non covalent interactions (NCI) and reduced density gradient (RDG) analyses also show the presence of strong interactions between adsorbate and adsorbent. Energy decomposition analysis (EDA) analysis suggests that electrostatic (ES) energy has a larger contribution to the total interaction energy compared to exchange (EX), dispersion (DISP) and induction (IND) energy in all complexes showing maximum overlap of orbitals demonstrating strong interactions. Variations in electronic band gap (Egap) show that B12N12 is a potential adsorbent for CIP. The negative values of ∆H and ∆G suggests the exothermic, chemisorption and spontaneous nature of adsorption process. The overall study shows that B12N12 may be a better adsorbent for the adsorption of CIP.