Performance improvement of graphene oxide modified with L-methionine amino acid for adsorption of emerging pollutants in water

چکیده مقاله

Abstract With industry progress, environmental problems have begun to threaten human health. Meanwhile, water pollution is closely related to human life and has attracted the attention of researchers. Therefore, strategies to deal with these pollutants have become a priority today. In this study, we investigated the performance of graphene oxide (GO) and GO functionalized with different numbers of L-methionine (Met) in the removal of 4-nitrophenol (PNP) pollutants using the molecular dynamics (MD) and well-tempered metadynamics simulations. Our findings showed that all systems have electrostatic interactions due to forming hydrogen bonds between –OH groups of pollutant molecules and oxygen from the GO substrate. In addition, the studied systems have π-π interaction between π-electrons of graphene oxide and aromatic rings pollutant molecules interact. The MD results reveal that the contribution of the Van der Waals interaction in studied pollutant/adsorbent systems is more than electrostatic interaction. Moreover, the simulation results demonstrated the lowest energy values for the GO system, while the GO_4Met system with − 417.399 kJ/mol has the most negative energy value. Therefore, adsorption of the PNPs has improved with the functionalization of the nanosheets with Met groups. The well-tempered metadynamics simulation is accomplished to find the free energy surface of the investigated systems. The free energy calculation for the GO_4Met system indicates a most stable point in which the distance of PNP from the GO_4Met surface is 0.35 nm with a global minimum of − 322.900 kJ/mol. According to the obtained results, graphene oxide functionalized with 4-Met has been introduced as the best nanostructure for removing phenol molecules from aqueous medium, having the highest adsorption energy. This work paves the way to develop the usage of graphene oxide structures in phenolic wastewater treatment.