Preparation And Characterization Of Porousgraphene Aerogel Based Materials Utilized For Water Treatment

Graphene has attracted intense interestbecause of its distinctive physical and chemical properties,and wide applications in various disciplines.Recently,three dimensional(3D)graphene macrostructures like graphene aerogels have been widely developed,primarily due to the fact that they not only retain the large surface area of graphene nanosheets,but also have highly porous structures.As a result,they have been widely used in areas of adsorption and water treatment.In this work,based on the research and practical application in water remediation,graphene aerogel based materials were prepared and the adsorptions for water pollutants were investigated in detail.The main results of our work were summarized as follows:(1)We report a simple one-step solvothermal method using GO as a precursor and DMF as a sole solvent to fabricate simultaneously meso/macroporous graphene aerogels(GAs)and strong green photoluminescent graphene quantum dots(GQDs).The adsorption performance of GAs was investigated by the solvothermal temperature,reaction time and concentration of GO to DMF.The result shows that the optimal GA was prepared by heating 10 mg/mL GO/DMF dispersion at 180? for 16 h and it was used for the following materials characterization and adsorption experiment.(2)The optimal GA sample was characterized by XRD,Raman,XPS,SEM,TEM,BET and compressive strain-stress tests.The self-assembly of GAs was driven by the hydrophobic and p-p stacking interactions of the conjugated structures of graphene.The resulting GAs exhibited a BET surface area of 90.13 cm2/g,an average mesopore size of 3.98 nm and pore volume of 0.061 cm3/g.The as-prepared GA also had a Young modulus of 35.8 kpa and a yield strength of 2.58 kpa.The water contact angle test indicates that the GA had an excellent hydrophobic property.The adsorption ability of GAs were evaluated by several types of oils,organic solvents and dyes.The largest absorption was achieved by chloroform as high as 74 g/g.The GA could be reused for at least ten times without significant reduction in adsorption capacity and structural deformation,showing excellent reusability.(3)The GQDs prepared by this solvothermal method were characterized by AFM and TEM.The result shows that the heights of the as-prepared GQDs were mostly around 2-3 nm,which means that they were composed of 3-5 graphene layers.The average diameter of GQDs is about 4.92 nm adn this value is close to the average pore size distribution of GAs.We believe that the GQDs were“chipping”from the GA sheets during solvothermal reaction.The as-prepared GQDs exhibited both typical excitation-and solvent-dependent PL behaviours for most fluorescent carbon-based nanomaterials.In addition,the quantum yield of GQDs was found to be about 11.2%.(4)The graphene aerogel/silicate composites were prepared by a hydrothermal method with different silicate concentrations.GA/SiO2 prepared by different silicate concentrations were used for the removal of Pb2+ and Cd2+ in the water.The as-prepared samples were characterized by XRD,XPS,SEM and TEM.The result demonstrated that the optimal sample was prepare with 10%silicate concentration.The adsorption kinetics and adsorption isotherms were well studied.The result indicates that the removal of Pb2+ and Cd2+ on 10%GA/SiO2 was more suitable for pseudo-first-order and Langmuir models.The 10%GA/SiO2 could be reused for at least five times without dramatic reduction(14.5%and 18.2%for Pb2+ and Cd2+,respectively)in adsorption capacity,showing excellent reusability.