Preparation Of Graphene Based Aerogels By Pickering Emulsion Method And Their Performance Evaluation

As a new three-dimensional carbon material,graphene-based aerogel has ultra-low density,ultra-high specific surface area and huge porosity,which makes it a highly efficient adsorbent.Due to its unique properties,Pickering emulsion has a wide range of applications in the preparation of porous materials.In this paper,the Pickering emulsion was used as a soft template to prepare graphene-based aerogels,and the internal pore structure,elasticity,surface functional group properties,elemental composition and other properties of the prepared aerogels were characterized.Finally,the adsorption performances of the aerogels were comprehensively evaluated using pure organic matter,simulated floating oil,simulated emulsified diesel oil and methylene blue as adsorbates.Polyvinyl alcohol-graphene composite aerogel（PGA）was prepared by Pickering emulsion as a soft template,which was stabilized by graphene oxide（GO）and a polyvinyl alcohol（PVA）.The effects of GO concentration,homogenization speed,oil/water ratio,ethylenediamine（EDA）and PVA dosage on emulsion stability,droplet size distribution and aerogel molding were investigated.It was found that the droplet size of the emulsion and further the density and porosity of the prepared aerogels can be controlled through changing the emulsion formula.PGA-1,the polyvinyl alcohol-graphene composite aerogel prepared under optimal preparation conditions,and PGA-1-C obtained by burning PGA-1 were characterized by Raman,XRD,SEM,FT-IR and XPS.It can be seen that GO is reduced and assembled by hydrothermal reaction and a three-dimensional network aerogel structure was formed,and its pore diameter is basically consistent with the droplet size of the emulsion.Extrusion experiments on PGA-1 and PGA-1-C showed that they have both axial and radial biaxial extrusion resilience,and they still have good elasticity after repeated extrusion for more than200 times.PGA has good adsorption capacity for organic substances such as n-heptane,and its adsorption capacity can reach up to 292 g·g^-1,and it can be recycled by extrusion desorption and thermal desorption.The adsorption of organic matter by PGA is directly related to its porosity,and its adsorption capacity for organic matter can be increased by reducing its density.PGA-1 can quickly absorb simulated floating oil and has certain recycling performance.The single equilibrium adsorption capacities of PGA-1 and PGA-1-C for emulsified diesel in water can reach 2130 and 4273 mg·g^-1,respectively.The adsorption process conforms to the Freundlich isotherm model and the pseudo-second-order kinetics model.Based on the optimal ratio of Pickering emulsion,acrylamide（AM）was added to prepare a polyacrylamide-graphene composite aerogel（AGA）.It can be seen from the above characterization means that GO in AGA is reduced and assembled by hydrothermal reaction to form a three-dimensional network aerogel structure,and the pore diameter is substantially consistent with the particle size of the emulsion.The adsorption capacity of AGA on pure organic matter is up to 229 g·g^-1,and the adsorption mechanism is the same as PGA.The adsorption of emulsified diesel in water by AGA is also in accordance with the Freundlich isotherm model and the pseudo-second-orderkinetics model.The highest adsorption capacity can reach 3567 mg·g^-1.The adsorption of methylene blue（MB）by AGA accords with the pseudo-second-order kinetics model and the Langmuir adsorption isotherm model.The highest adsorption capacity is 113.8 mg·g^-1.