| With the increasingly serious global water pollution problem,many powdered cobalt-based nanomaterials have been widely reported for their variety and high catalytic efficiency.However,the disadvantages of powdery nanocatalysts,such as their agglomeration and difficulty in separating from water,limit their applications.Compared with the conventional stirred catalytic device,the operation of the flow device is more convenient,and wastewater can be continuously processed.Therefore,constructing a three-dimensional(3D)macroscopic nano-catalyst suitable for a flow dynamic device is an important method to solve the above disadvantages.Graphene materials with three-dimensional structures are more suitable as supports for nanocatalysts because of their larger specific surface area and higher porosity.In this paper,on the one hand,the advantages of the flow dynamic system are demonstrated by an isotropic cobalt ferrite/graphene aerogel;on the other hand,an anisotropic graphene aerogel with uniform arrangement is obtained by directional freeze-drying.After improving the original system,a better catalytic effect was achieved.The specific research contents are as follows:(1)Aiming at the problem that powdery nanocatalysts are easy to agglomerate,a new type of cobalt ferrite/graphene hydrogel was synthesized by a one-step hydrothermal method,and then isotropic aerogel was obtained by freeze drying.CoFe2O4 nanoparticles will be uniformly supported on the graphene sheet after adding sodium dodecyl sulfate(SDS),which greatly improves the catalytic effect.The experiment found that the aerogel flux can reach 1600 L m-2 h-1 at 5 minutes,which is stable to 300 L m-2 h-1.The results show that the three-dimensional composite aerogel has significant advantages in degrading water pollutants under dynamic conditions.In addition,at a constant flow rate of 60 mL h-1,the aerogel can degrade 100%of the 25 ppm IC solution within 5 hours,with the flow rate increasing to 90 mL h-1 and 120 mL h-1,the degradation efficiency of the IC solution showed a downward trend.The above data shows that the isotropic cobalt ferrite/graphene composite aerogel is more suitable for degrading low concentrations of pollutants in a short time.Therefore,appropriately improving the internal structure of the aerogel will facilitate the long-term of the catalytic process.(2)In order to solve the problem of low flux of isotropic cobalt ferrite/graphene composite aerogels,a directional freezing process was used to make the graphene sheets vertically aligned in the hydrogel to obtain an anisotropic porous structure.The obtained long-distance aligned pores can not only reduce the erosion of CoFe2O4 by the pollutant solution,but also ensure that the aerogel still maintains a flux of 1100 L m-2 h-1 after 90 minutes of using,making the material resistant to a variety of dyes(indigo carmine,methyl orange,orange III and malachite green)and organics(phenol and norfloxacin)all show excellent degradation efficiency.In addition,the improved material can also continuously treat wastewater,and can achieve 100%removal efficiency of indigo carmine solution within 30 hours.In addition,stacked aerogels can degrade high concentrations of dyes at high flow rates.This anisotropic cobalt ferrite/graphene composite aerogel with better stability and higher catalytic activity could become an ideal material for wastewater treatment. |
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