Colloidal In Behavior Of Graphene Oxide Nanoplatelets In The Simulated Natural Aquatic Environment

Since the 21st century,nanomaterials have received extensive attention in the scientific and industrial fields,and more and more engineering nanomaterials have been applied to various fields.Studies have shown that graphene and its derivatives are significantly toxic to plants and animals.Therefore,an accurate understanding of the behavior and fate of these new anthropogenic source pollutants is needed.However,the polymerization characteristics of these engineered nanomaterials after entering the environment,and their interaction between natural particles,are still unknownTherefore,this study investigated the polymerization behavior of engineered nanomaterials in environmental systems,with emphasis on their self-assembly and binary assembly with environmental particles.Graphene oxide was selected as the research object of engineering nanomaterials.The interactions between graphene oxide and natural organic matter in the simulation of aquatic natural environment and different environmental conditions,pH and ionic strength,on the surface electric double layer charge or structure assembly were investigated.The influence of force1.The force-distance curve obtained from in-situ atomic force microscopy can show the effect of solution conditions on DLVO forces.The electrostatic repulsion of the electric double layer of graphene oxide increases with increasing pH,which may be due to the enhanced ionization of surface functional groups.However,as the ionic strength increases,the repulsion of the electric double layer decreases,and the obtained data is consistent with the DLVO theory.In the range of 0 mmol·L-1?30 mmol·L-1 of ion concentration gradient,the electrostatic repulsion force of the electric double layer of binary assembly structure of graphene oxide and humic acid increases gradually with the increase of ionic strength,and the reverse double-layer phenomenon occurs.This is because as the ionic strength increases,the dielectric layer is compressed,and the free humic acid in the solution is gradually adsorbed on the surface of go,resulting in the enhanced electrostatic repulsion of the double layer on the surface of the assembly.At the ions concentration gradient of 30 mmol·1-1?50 mmol·l-1,the double-layer repulsion decreases with the increase of ionic strength,which consistent with DLVO theory,indicating that the free huminic acid within this ions concentration range is completely adsorbed on the surface of Graphene oxide.)2.The surface charge non-uniformity of the graphene oxide sheet and its binary assembly structure was determined by zeta potential and Kelvin Probe Force Microscopy.3.The morphology of the assembled structure of graphene oxide and humic acid was obtained by scanning probe force microscope and transmission electron microscope,and the structure of nano-ring and nano-onion was found.The basic composition of graphene oxide structure is 6 carbon rings,which may be due to the nano-ring structure formed by humic acid adsorbed on the surface of graphene oxide with graphene oxide nano-sheets as the substrate through van der Waals attraction hydrogen bond and other interactions.Graphene oxide can be stably suspended in a pure water environment due to its rich hydrophilic group on the surface.Its rich functional groups and ideal surface area can effectively adsorb water pollutants and increase the migration and uncertain fate of pollutants in the water environment.The results of this study will provide a theoretical basis for the prediction of graphene oxide behavior,and it is the only way to conduct risk assessment and management control.