Co-transport Behaviors And Mechanisms Of Graphene-based Nanohybrids With Typical Sulfonamides

The superior performance of nanohybrids in pollution remediation,electrochemical energy storage,environmental sensing and antibacterial applications has attracted more and more public attention,and their release and exposure in the environment will be inevitable.Up to now,researches on the occurrence,behavior and potential risks of nanohybrids in the environment are still lacking,and the multi-media interface processes and the influence mechanisms of nanohybrids under complex environmental conditions are absent in systematic and in-depth research.In this paper,the graphene-based nanohybrids-GO-Fe₂O₃ were synthesized by hydrothermal method,and their derivative was obtained by the light treatment,and the physicochemical properties of the nanohybrids and their derivative were explored by a variety of characterization methods.The results showed that the loading of Fe₂O₃ led to the decrease in the surface electron-negativity of the GO-Fe₂O₃ nanohybrids,the increase in hydrodynamic diameter and hydrophobicity,and the rougher morphology than the monomer materials.After light treatment,the GO-Fe₂O₃ nanohybrids were reduced,their oxygen-containing functional groups on the surface was decreased,and the graphite sheet structure was partially stacked,which resulting in the more distinct morphological heterogeneity compared to the pristine materials.In order to clarify the influence of the surface properties of nanohybrids and their derivative on their transport ability,this paper explored the transport and retention behavior characteristics of GO-Fe₂O₃ nanohybrids with different iron contents and their photo-reduced products in saturated quartz sand media under various environmental conditions（such as cation type,ionic strength and pH value）through classical column transport experiments and retention profile experiments.Based on the XDLVO theory,with the increase of Fe₂O₃ contents,the surface electro-negativity of the nanohybrids decreased,the aggregation as well as the hydrophobicity increased,and the transport in saturated porous media was inhibited.The photo-reduced product had poorer mobility relative to the pristine materials,and this inhibited transport was dominated by its increased surface roughness after light treatment and morphological heterogeneity instead of the XDLVO theory.It is worth noting that the inhibited transport of the nanohybrids with high Fe₂O₃ contents and their derivative was moderated to a certain extent in the CaCl₂ saturated media.This was because the surface oxygen-containing functional groups of two nanohybrids had the small proportion,and the cation bridging with Ca²⁺was weak.The effect of pH on the transport of nanohybrids further confirmed the influence mechanism of cation bridging on the transport and retention of nanohybrids in quartz sand media.In this paper,the typical sulfonamides-sulfamethazine（SMT）was used as a model antibiotic to discuss the multi-media interface processes in the antibiotic-nanohybrids-quartz sand composite system.The adsorption kinetic experiments showed that the adsorption of GO-Fe₂O₃ nanohybrids to SMT conformed to the Lagrange pseudo-second-order kinetic model.The nanohybrid reduced by light had a stronger adsorption capacity for SMT,but the adsorption rate was lower than that of the pristine materials.SMT showed strong transport ability under the tested water chemical conditions,and its mobility was not affected by the coexisting nanohybrids.SMT with higher mobility can promote the transport of nanohybrids through the"vehicle effect".In particular,the GO-Fe₂O₃ nanohybrids reduced by light had a stronger adsorption affinity with SMT due to the increased hydrophobicity and surface roughness,the decreased electro-negativity,and the increasedπstructure ratio as well as the adsorption sites caused by aggregation,and thus the stronger"vehicle effect".The bridging effect of Ca²⁺led to the irreversible retention of the graphene-based nanohybrids in the quartz sand media,which weakened the"vehicle effect"of SMT to a certain extent.The results of this study showed that the heterogeneity of the graphene-based nanohybrids makes their environmental transport behavior more complicated than that of monomer nanomaterials.This kind of nanohybrids could undergo photoreduction in the environment,and the surface functional groups,electrochemical properties,and morphology of their derivative have undergone significant changes,which in turn will cause indirect effects on their environmental behavior and fate as well as the interaction with coexisting organic pollutants.The research conclusions of this article laid a foundation for exploring the behavior and effects of new nanomaterials in real environments,and the prevention,control and treatment of organic compound pollution.