Preparation Of Quaternized Graphene Hydrogel And Its Application In Water Filtration Sterilization

The graphene hydrogel is assembled from graphene oxide by hydrothermal method which has a three-dimensional porous structure,and the pores are uniformly inter-welld,and it is a kind of excellent filter material for water filtration from the structural point of view.However,graphene has inherently low antibacterial properties and takes a long time to achieve bacterial killing and cannot meet the requirements of filtration sterilization.Other antibacterial substances are usually mixed or grafted with graphene to improve their antibacterial properties,but these antibacterial substances often cause unnecessary release,so that the filtered water will be secondaryly contaminated.Therefore,this paper proposes a new method to improve the antibacterial ability of graphene hydrogel by pi-pi interaction.First,a newly designed pi-conjugated molecule was synthesized,which containing five aromatic rings and two side-linked quaternary ammonium?QA?groups,abbreviated as piQA,and the molecular structure and antibacterial properties of piQA were characterized;Secondly,a cylindrical reduced graphene oxide?rGO?hydrogel was obtained from aqueous graphene oxide by hydrothermal synthesis,and its physical properties and morphology were characterized;Finally,the quaternary ammonium salt groups were successfully immobilized on the graphene surface by pi-pi interaction between the graphene sheets in piQA and rGO hydrogels.The rGO hydrogel modified by piQA was named piQA-rGO.The large?structure of piQA forms a strong pi-pi interaction with rGO,resulting in a mass loading of approximately 31 wt%of piQA,further ensuring a high concentration of quaternary ammonium salt groups on the surface.Due to the porosity of rGO hydrogel and the synergistic antibacterial activity of rGO and piQA,the new filter based on piQA-rGO can remove more than 99.5%of Gram-negative Escherichia coli and 97.4%of Gram-positive staphylococcus aureus cells at a bacterial concentration of 10⁴,10⁵,10⁶ CFUmL^-1and at a bacterial concentration of 10⁵ CFU mL^-1,the water treatment capacity reached 10 L g^-1.This excellent performance could be attributed to a porous filtration structure with a large specific surface area provided by rGO hydrogel in the procress of bacterial filtration,while the positively charged quaternary ammonium group on the surface attract bacteria.The bacteria are killed by the synergistic action of the quaternary ammonium group and the rGO sheet.The release of piQA is also demonstrated practically negligible and the piQA-rGO show low toxicity towards two mammalian cell.