| Graphene is a two-dimensional carbon allotrope with a honeycomb structure that is sp2-hybridized with a thickness of one atom.Its discovery has attracted enormous attention because of its outstanding physical,as well as chemical,properties,increased external surface area,and modification simplification,which are important for various applications.However,graphene nanosheets in aqueous solutions will commonly stack,which will reduce the exposure of the active sites.Moreover,after adsorption the active sites are difficult to reclaim but can be dispersed and transported by water;thus graphene nanosheets exhibit a potential ecological risk.So,three-dimensional graphene-based macrostructures(3D GBM)have been recognized as one of the most promising strategies for "bottom-up" nanotechnology and become one of the most active research fields during the last six years.In general,the basic structural features of 3D GBM,including its large surface area,which enhances the opportunity to contact pollutants,and its well-defined porous structure,which facilitates the diffusion of pollutant molecules into the 3D structure,enable 3D GBM to be an ideal material for pollutant management due to its excellent capabilities and easy recyclability.However,there were still many problems need to be explored.For example,the regulation of 3D GBM's raw materials that graphene nanosheets including their structures and surface properties,and the choose preference of the graphene nanosheets size to fabricate 3D GBM,and the modification method of 3D GBM to improve the pollutants removal performance.Focusing on the problems that the regulation of graphene nanosheets' structure and property,the size effect of graphene nanosheets,and the modification method of 3D GBM to improve the pollutant removal performance,this research firstly prepared reduced graphene,oxide graphene and sulfated graphene,and established the relationship between their conjugate ? region as well as the functional groups and the adsorption sites with different pollutants.Secondly,on the basis of graphene nanosheets' structure and property,the size effect of graphene nanosheets for construction of 3D GBM as adsorbent was clarified.And the relationships between the porous structure/surface properties and the adsorption rate/adsorption capacity were schematically demonstrated.Thirdly,two-dimensional graphene oxide(GO)nanosheets and one-dimensional carbon nanotubes(CNT)were mixed to construct three-dimensional macrostructures 3D GTs,whose adsorption capacity is high and can be attributed to the synergistic effects of GO and CNT.Fourthly,after the research about 3D GBM-based adsorbent,the research focusing on the 3D GBM as catalyst has also been carried out.The main original conclusion of this work are drawn as follow:(1)On the basis of graphene nanosheets' property and structure regulation,the double adsorption sites(conjugate?region and oxygen-containing functional groups) of graphene and their adsorption mechanisms to different pollutants were clarified. Reduced graphene(rGO)has a structure of conjugate?region with packed sp2-bonded carbon atoms and a few functional groups and attracted organic aromatic compounds.Graphene oxide's(GO)structure of sp2-bonded carbon atoms was destroyed,but it has the most oxygen-containing groups,and interacted well with the cationic dyes.Sulfonated graphene(GS)not only recovered the skeleton of the conjugate ? region with packed sp2-bonded carbon atoms but also exhibited oxygen- containing groups on the graphene.It possessed high adsorption performance for various environmental pollutants.The performance discrepancy of rGO,GO and GS were due to their difference in structure and surface groups.This study provided a basis for tunable synthesis and decoration of 3D GBM as adsorbent with high performance.(2)According to According to the analysis of 3D GBMs' structure characteristic, adsorption kinetics and adsorption capacity,the relationships between the graphene nanosheet size,3D GBM's porous structure/surface properties,diffusion rate/adsorption sites and the adsorption rate/adsorption capacity were firstly demonstrated.The 3D GBM that is constructed using larger graphene nanosheets exhibited a superior porous network and surface properties.The porous structure is in favor of the adsorption rate and the surface property is beneficial to adsorptionapacity of pollutant molecules in the 3D structure,thus improving the adsorption performance altogether.The size effect of GO nanosheets is to balance the consumed effective sites for assembly of stable 3D GBMs and the residual active sites for pollutant management.In addition to feasible manipulation and collection,the application of 3D GBM constructed by large graphene nanosheets should be widely applicable to the environmental fields.(3)Combining 1D CNTs and 2D GO to construct 3D GTs who had low density, abundant pores and exposed sites,and showed high adsorption performances to traditional and emerging pollutants.This should be attributed to the synergistic effects of GO and CNTs on the micro-environment,nano-substrate,and active sites.First,the GO nanosheets in the 3D GTs were highly separated and existed in monolayers,and the CNTs were randomly dispersed.The interspaces of the formed 3D GTs were majorized.Second,both the GO nanosheets and CNTs provided abundant oxygen-containing functional groups and conjugated?system as adsorption sites.Third,the adsorption sites of the 3D GTs can be purposely tuned to achieve selective adsorption of particular pollutants.The study provided theoretical direction to fabricate 3D GBMs with attractive characters such as high stability,low density,high adsorption capacity,easy separation and regeneration,which demonstrated high potential in water purification.(4)3D G-Ag NPs with high loaded and low agglomerated were synthesized rapidly in the normal pressure as well as temperature and ultrasonic environment.They possessed high catalytic transformation performance for nitrobenzene and dinitrobenzene,which had relationship with Ag NPs loaded amonts and Ag atoms agglomerated degree.The study provided a basis for fabricating 3D GBMs with metal catalyst loaded and catalytic transform pollutants. |
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