Preparation Of Graphene-based Composite Aerogels And Photocatalytic Degradation Of Organic Pollutants

Organic pollutants are one of the largest contaminants released from textile wastewater and other industrial processes into water bodies.Therefore,the removal and degradation of organic dyes have attracted attentions from scientific researchers all over the world.In general,the use of adsorbent materials is the primary method of treating organic contaminants in water bodies.Among diverse form of adsorption materials,reduced graphene oxide aerogel（GA）reveals much better adsorption activity and adsorption rate toward the organic pollutants owing to its delightful advantages,including low cost,easy of operation,high surface area,and large open pores.However,due to the general application limitations of adsorbent materials,the toxic organic pollutants are only gathered together,rather than be completely decomposed into non-toxic small molecules by GA.Besides,the GA adsorbent materials are difficult to regenerate and require treatment to release contaminants when reached their saturation,which undoubtedly increases the processing difficulty and cost.Therefore,in order to improve the insufficiency of GA,this paper mainly studies the preparation of graphene-based composite aerogels.The semiconductor/graphene aerogel composites were prepared,and the performance of GA was improved by the combination of different semiconductor photocatalysts.A series of characterization and analysis of graphene-based composite aerogels were also carried out.In addition,methylene blue etc were selected as target pollutants for photocatalytic degradation experiments under simulated sunlight to determine the photocatalytic activity of the as-prepared photocatalyst.The specific topics are studied as follows:1.Preparation of W⁶⁺doped TiO₂/reduced graphene oxide aerogel and its photocatalytic activity for degradation of Methylene Blue.Firstly,using graphene oxide（GO）as raw material,titanium sulfate（Ti（SO₄）₂）as titanium source,and hydrated ammonium tungstate(H₄₀N₁₀O₄₁W₁₂·XH₂O)as tungsten source,W⁶⁺doped TiO₂/reduction oxidation was synthesized by a simple one-step hydrothermal method.During the reaction,W⁶⁺was doped into TiO₂ and formed W-TiO₂ nanoparticles,which were uniformly and densely loaded in the three-dimensional porous graphene aerogel.After that,the prepared samples were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,Raman spectroscopy,UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）and X-ray photoelectron spectroscopy（XPS）.Finally,methylene blue was degraded under simulated sunlight to determine the photocatalytic performance of the as-prepared photocatalyst.The results confirmed that the degradation rate of methylene blue by the W-TiO₂/GA composite with the best W doping ratio and the GA composite ratio was 7.05 times and 2.38 times than that of the pure TiO₂ and GA,respectively.2.Controllable synthesis of Bi₂MoO₆/reduced graphene oxide aerogel composite and photocatalytic degradation performance for methylene blue.Bi₂MoO₆/reduced graphene oxide aerogel composite（BMO/GA）was obtained by using a simple one-step hydrothermal method and freeze-drying treatment,in which graphene oxide（GO）used as raw material,tetrabutyl titanate and ammonium molybdate tetrahydrate(（NH₄）₆Mo₇O₂₄·4H₂O)and bismuth（III）nitrate pentahydrate（Bi（NO₃）₃·5H₂O）used as raw materials for preparing bismuth molybdate（Bi₂MoO₆）.In this process,Bi₂MoO₆ was grown into nanosheets by adjusting the reaction pH,which could be exactly embedded in the pores of GA,and the composite exhibited a three-dimensional aerogel structure.The prepared samples were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,Raman spectroscopy,UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）,X-ray photoelectron spectroscopy（XPS）,photoluminescence（PL）spectroscopy,inductively coupled plasma atomic emission spectrometer（ICP-AES）and total organic carbon analyzer（TOC）.MB was selected as a target pollutant,and the removal rate of BMO/GA-10 composite（containing 10%GO mass ratio）has the highest degradation rate towards MB,which reached up 98.3%in 100 min and was about 2.1 times higher than that of the BMO.In addition,the photocatalytic mechanism of BMO/GA composite was verified by experiments and discussed in detail.3.Photocatalytic activity of BMO/GA-10 composite towards different organic dyes.In this chapter,a series of photocatalytic degradation experiments were carried out under simulated sunlight using methylene blue,methyl blue,methyl orange and rhodamine B as target pollutants.First,the effect of different initial concentrations on the photocatalytic activity of BMO/GA-10 was investigated by changing the initial concentration of the target contaminant.The results showed that the degradation rate of organic dyes by BMO/GA-10increased first and then decreased with the increase of the initial concentration of target pollutants.Besides,the effects of different organic dyes on the photocatalytic activity of BMO/GA-10 were explored under the same conditions.The results showed that BMO/GA-10has certain differences in photocatalytic degradation activity towards different dyes,and it has a tendency to decrease as the complexity of dye molecules increases.