Preparation Of Three-dimensional Reduced Graphene Oxide And Its Adsorptive Properties Of Organic Contaminants In Water

The pollution of organic pollutants in the water environment has been a long-standing problem.With the rapid development of industry,the random discharge of industrial waste water makes the organic pollution in the water environment more and more serious,which seriously affects people's health.China is a country with a shortage of water resources per capita in the world,and organic pollution makes the available water resources more scarce.Adsorption is a cost-effective and easy-to-control organic pollution treatment method.graphene has great application prospects in water treatment due to its excellent physical and chemical properties.Because graphene is easy to reunite in water and difficult to separate,it limits its application,and the emergence of three-dimensional graphene aerogels solves this problem.The natural drying method reduces the energy consumption of graphene aerogels,and provides the possibility for large-scale production and application.In this paper,the graphene aerogel material was prepared by natural drying method.Three typical organic dyes,methylene blue,rhodamine B,basic fuchsin,and a typical environmental endocrine disruptor bisphenol A were selected among organic contaminants.Using ethylenediamine as a reducing agent,the graphene hydrogel was prepared by a hydrothermal reduction-induced assembly method,and the preparation of graphene aerogel was achieved by natural drying and inert gas protection thermal reduction treatment.The prepared graphene aerogels was characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),specific surface area(BET)and contact angle.It is proved that during the preparation of graphene Oxide,the nanoscale layer has been well cross-linked,and the oxygen-containing groups are largely removed.The obtained graphene aerogels has a good three-dimensional network structure.Graphene aerogels was used to study adsorptive properties of orgnic dyes in water.The effects of p H,reaction time,initial concentration of pollutants and reaction temperature on the adsorption efficiency were investigated.The adsorption isotherm model,adsorption kinetics and thermodynamics were fitted,and the adsorption mechanism of the process was analyzed.The results show that the adsorption of dyestuffs by graphene aerogels is affected by p H,and the effect increases with the increase of p H.The adsorption equilibrium time is 480-540 min and the adsorption amount increases with the reaction time.It first increases rapidly,and then gradually increases slowly until it reaches equilibrium.In the first 120 minutes,the adsorption reaches 90% of the equilibrium adsorption capacity.The adsorption of dyes by graphene aerogels is affected by ions in water,and the presence of other cations has an inhibitory effect on the adsorption reaction.The adsorption of organic dyes by graphene aerogels conforms to the Langmuir isotherm adsorption model,and the kinetics is consistent with the pseudo-second-order kinetic model.Thermodynamic models indicate that the reaction is an endothermic spontaneous reaction.The adsorption abilities of graphene aerogels on methylene blue,rhodamine B,and basic fuchsine were compared,and the graphene aerogel material was found to have the effect of removing all three dyes.The amount of sorption is methylene blue > rhodamine B> basic fuchsin,but the difference between the latter is smaller.Due to the cross-linking of graphene oxide layer,the specific surface area of graphene aerogels is smaller than that of graphene oxide,and the natural drying shrinkage makes the specific surface area of graphene aerogels lower than that of partial freeze drying,which affects the adsorption efficiency,but according to the study its adsorption capacity is still stronger than the traditional adsorbent.The adsorption efficiency of graphene aerogel on bisphenol A,an endocrine disruptor,was investigated.It was found that the adsorption of bisphenol A by graphene aerogels was also in accordance with the Langmuir isothermal adsorption model and the quasi two class adsorption kinetic model,and the adsorption amount increased with the increase of reaction time and the initial concentration of bisphenol A.graphene aerogel has good adsorption effect on bisphenol A,the reaction equilibrium time is 400 min,and the removal rate of bisphenol A can reach99.9%.The results show that graphene aerogel is a good adsorbent material and has potential for large-scale application in water treatment.