Efficient Absorption and Sensing of Haloacetonitriles on Fullerene C20 Surface at DFT Level.

Haloacetonitriles (HANs) are hazardous water disinfection by-products due to their adverse health effects. In this study, the interaction and adsorption of the key HAN pollutants on the fullerene C₂₀ surface were investigated by density functional theory (DFT). Thus, the pristine structures of fullerene, four HANs, and their complexes were geometrically optimized at the B3LYP/6-31G^* level of theory with the help of ORCA software package. Natural bond orbital (NBO) results indicate that interaction between the surface of the C₂₀ adsorbent and adsorbate could be chemical in nature. Infrared (IR) frequency computations exhibited that the studied structures are experimentally feasible showing no imaginary frequency. The HANs adsorbed on the surface of C₂₀ confer a greater dipole moment than corresponding unabsorbed compounds. The adsorption energy, Gibbs free energy (ΔG_ad), and enthalpy (ΔH_ad) values revealed that the adsorption of HANs on the fullerene C₂₀ surface is exothermic, spontaneous, and irreversible. The calculated chemical potential values are negative for all structures affirming that the scrutinized structures are thermodynamically stable. The increasing trend of adsorption efficiency for fullerene-HANs complexes is C₂HBr₂N―C₂₀ > C₂HBrClN―C₂₀ > C₂HCl₂N―C₂₀ > CCl₃CN―C₂₀. The results demonstrate that fullerene C₂₀ is a proficient adsorbent in removing of HAN contaminants from aqueous media. Besides, C₂₀ provides a proper sensing capability during adsorption due to its increased specific heat capacity and decreased bandgap. To verify the adsorption behavior of considered fullerene, other significant properties such as band gap, chemical hardness, electrophilicity, chemical potential, and charge capacity were also discussed in detail. The molecular electrostatic potential surface (ESP) of haloacetonitriles (HANs), by-products of water disinfection, fullerene C₂₀ adsorbent, and HANs―C₂₀ complexes in aqueous phase using DFT approach [ABSTRACT FROM AUTHOR]