Fe3O4-4,4 '-biphenyldicarboxaldehyde superparamagnetic-nanomaterial for the high-efficiency removal of 9-phenanthrol: experimental combined with DFT investigations

Owing to the more significant health and environmental risks of 9-phenanthrol (9-PROL) compared to phenanthrene, it is imminent to solve the 9-PROL pollution issue. Herein, Fe3O4-0.75-4,4 '-biphenyldicarboxaldehyde (Fe3O4-0.75BIPHENY) was synthesized via a silane coupling reaction and condensation reaction and employed as an efficient nanocomposite for the removal of 9-PROL. The magnetic core provided the possibility for its fast and convenient separation and the aromatic rings on the BIPHENY shell contributed to improving the capturing ability of 9-PROL molecules via the formation of pi-pi interactions. Multiple characterization techniques were employed to obtain a comprehensive understanding of the prepared magnetic adsorbents. Fe3O4-0.75BIPHENY not only exhibited an excellent adsorption performance towards 9-PROL, but also showed a relatively excellent regeneration performance. The homogeneous surface of Fe3O4-0.75BIPHENY provided adsorption sites for the adsorption of 9-PROL molecules, which adhered in monolayer molecular form. Importantly, density functional theory calculations provided novel deep insights into the most possible adsorption bonding mode and verified that pi-pi interactions existed in the offset stacking form. Furthermore, the visible electrostatic potential and energy orbital distribution plots demonstrated the validity of the adsorption reaction and stability of a specific configuration. This study provides guidance for the assembly of novel magnetic nanocomposites for alleviating traditional and secondary pollution caused by polycyclic aromatic hydrocarbons.