Theoretical insights into benzophenone pollutants removal from aqueous solutions using graphene oxide nanosheets

Abstract

In this study, we investigate the adsorption behavior of three benzophenone derivatives, namely 2,4-Dihydroxybenzophenone (benzophenone-1; BP-1), 2,2′,4,4′-tetrahydroxybenzophenone (benzophenone-2; BP-2), and 2-hydroxy-4-methoxybenzophenone (benzophenone-3; BP-3) on the surfaces of graphene oxide (GO) using density functional theory method. The geometric optimization of the unaltered structures of GO adsorbent, benzophenone derivatives, and their respective complexes was conducted via the M052X/6-311 + G* level of theory. The optimal temperature for the interaction between the GO adsorbent and BPs pollutants in the aqueous phase was found to be 298.15 K. The adsorption process was found to be spontaneous, exothermic, and irreversible based on the calculated values of adsorption energy, Gibbs free energy (ΔG_ad), and enthalpy (ΔH_ad). The negative values of the calculated chemical potential for all structures indicated that the studied structures were thermodynamically stable. The adsorption of BP-2 pollutant on the surface of GO results in a highest dipole moment (μ_d = 28.22 D) compared to the corresponding unadsorbed molecule (μ_d = 7.93 D). The adsorption efficiency of GO–BPs complexes follows an increasing trend of GO–BP-2 (−1009.75 kcal/mol) > GO–BP-3 (−1006.31 kcal/mol) > GO–BP-1(−1000.65 kcal/mol). Moreover, infrared (IR) frequency calculations confirmed the feasibility of the structures, showing true local minima. The recovery time values indicate that GO is a highly effective adsorbent in removing organic BP-2 pollutants (\(\tau =\) 3.158 ms) from aqueous media rather than BP-3 (\(\tau =\) 2.120 ms) and BP-1 (\(\tau =\) 1.831 ms) counterparts. Other key parameters engaged in the adsorption behavior of considered molecules, including charge capacity, electrophilicity, band gap, chemical potential, and chemical hardness, were also deliberated.