Quaternary ammonium salts induced flocculation of graphene oxide for the fabrication of multifunctional aerogel

In this study, a novel method “spray-penetration-flocculation” was utilized to fabricate graphene oxide (GO)/quaternary ammonium salts (QAS) hybrid macroscopic aerogels to avoid the sudden precipitation of GO when it was combined with polycations and the collapse of three-dimensional monolith during the subsequent freeze-drying procedure. QAS could penetrate downward and induce the in situ flocculation of GO simultaneously, thus leading to the formation of GO-based hydrogel without any additional procedure requiring high-energy consumption. This unique method endowed an aerogel with hierarchically porous structure. The porous structure and low density made the aerogel a promising material for wastewater treatment with ultrahigh adsorption capacity toward soluble dyes, organic solvents and oils. Additionally, the QAS containing N-halamine groups loaded on GO functioned as an efficient biocidal component against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) and could inactivate the bacteria completely within 5 min of contact time. The as-constructed aerogel with these great attributes may serve as a promising candidate for water purification such as solvent recovery, oil/water separation and disinfection. Graphic abstract