Study On The Preparation And Catalytic Performance Of Graphene-based Aerogel

Organics which are difficult to be degraded in printing and dyeing wastewater are represented by azo dyes.The characteristics of this wastewater are large water volume,high concentration of inorganic salts,poor biochemical performance,and high toxicity.At present,it is generally treated by adsorption,coagulation and other methods.There are poor results and secondary pollution problems.Advanced oxidation technology is not selective to organic matter and can completely degrade organic matter.Its development direction is mainly as follows:on the one hand,the development of more efficient heterogeneous catalysts can improve the efficiency of catalytic oxidation while facilitating recycling and reducing secondary pollution;on the other hand,developing coupling technology which can play a synergistic effect and improve degradation efficiency.In this paper,two graphene aerogels which are named by MnFe₂O₄-r GO aerogel and MnFe₂O₄-TiO₂-r GO aerogel are prepared.Explore the catalytic oxidation performance in persulfate(PMS)system and ultraviolet(visible)light/PMS coupling system.1.Graphene aerogel improves the dispersibility of MnFe₂O₄ and TiO₂ nano-catalysts,and increases the specific surface area of the composite material.Among them,the specific surface area of MnFe₂O₄-r GO aerogel is 271.6 m²·g^-1,the specific surface area of TiO₂-r GO aerogel is 292.8 m²·g^-1,and the specific surface area of the MnFe₂O₄-TiO₂-r GO aerogel is 190.8 m²·g^-1.Graphene aerogel catalyst has the characteristics of easy recovery and stability.MnFe₂O₄-TiO₂-r GO aerogel still achieves 85.9%removal rate of Acid Red B dye after being recycled for five times.2.The introduction of graphene and manganese ferrite promotes the red shift of the absorption boundary of anatase,the energy gap bandwidth of TiO₂ is 3.13 e V,the energy gap bandwidth of TiO₂-r GO and MnFe₂O₄-TiO₂-r GO aerogels are 2.81 e V and respectively 2.44 e V,which is conducive to the use of light energy.Under visible light(>420 nm)irradiation,the photocatalytic oxidation efficiency of MnFe₂O₄-TiO₂-r GO aerogel on Acid Red B is increased by 9.8%compared with TiO₂-r GO aerogel.3.Research on condition optimization shows that the degradation effect of MnFe₂O₄-TiO₂-r GO aerogel on Acid Red B increases with the increase of the amount of catalyst and PMS.It has good effects under acidic and neutral conditions,and the p H range is wide;The chloride ions promote the reaction.At p H 7,the dosage of MnFe₂O₄-TiO₂-r GO aerogel is 0.4 g·L^-1,n(PMS):n(Acid Red B)=11:1.When UV light is applied for 105 minutes,the amount of MnFe₂O₄-TiO₂-r GO aerogel is Degradation rate reaches 99%4.The study of catalytic oxidation mechanism shows that the free radicals produced in the MnFe₂O₄-TiO₂-r GO/PMS/UV system are h⁺,SO₄^·-,·OH and O₂^·-,of which the main active substance is SO₄^·-;MnFe₂O₄-r GO/The free radicals produced in the PMS system are SO₄^·-and·OH,and the main active substance is SO₄^·-.X-ray photoelectron spectroscopy(XPS)analysis reveals that the valence states of iron and manganese change during the catalytic oxidation process,and various valence states of iron and manganese react with HSO₅^-to form SO₄^·-,·OH and SO₄^2-.The photo-generated electrons(e^-)generated in photocatalysis are used as electron donors to react with Fe³⁺,Mn³⁺and Mn⁴⁺to form Fe²⁺,Mn²⁺and Mn³⁺.Because the above reaction can effectively reduce the recombination of photoelectron-hole pairs,and holes(h⁺)can also react with SO₄^2-to form SO₄^·-.Therefore,there is a coupling of two systems in MnFe₂O₄-TiO₂-r GO/PMS/UV,which has a synergistic effect.In addition,in the MnFe₂O₄-r GO aerogel/PMS system,when n(PMS):n(acid red B)=20:1,the removal rate of acid red B can reach 91.5%;in MnFe₂O₄-TiO₂-r GO aerogel In the/PMS/UV coupling system,when n(PMS):n(Acid Red B)=7:1,that is,reducing the amount of PMS by about 2/3,the removal rate of Acid Red B can still reach 91.7%.The research results provide a new idea for the development of Fenton type catalytic oxidation technology,which is conducive to reducing the use of chemical reagents and secondary pollution,and has a good application prospect.