Self-assembly Of Graphene-based Composite Materials And Their Adsorption Property For Organic Dye And Heavy Metal Ions

Three dimensional graphene self-assembled adsorbent has unique advantages in the field of wastewater treatment,including its large specific surface area,abundant pore structure,diverse functional groups and the overall network connectivity structure.In this paper,by using graphene oxide as precursor,terbium doped graphene adsorbent for organic dye（rhodamine B）and urea doped graphene composite for copper,lead ions were prepared,respectively.The physicochemical properties of the materials,the adsorption properties and the adsorption laws of the specific adsorbents were obtained by various characterization methods.The specific contents are as follows:（1）A new type of terbium doped reduced graphene oxide（Tb/rGO）adsorption material was prepared by microwave hydrothermal method.Microwave hydrothermal method owns the characteristics of high yield,low cost,uniform heating,mild reaction conditions and high energy utilization via microwave heating.Thus,it’s a unique way to prepare nanomaterials,especially for rapid preparation of graphene complexes.By scanning electron microscopy,we observed the microstructures of 3-5 nm uniformly dispersed in the graphene sheet and their photoluminescence behavior was similar to graphene quantum dots.This phenomenon is originated from the regulation of terbium on graphene.The energy transfer process of terbium and graphene was observed by photoluminescence spectrum.In the fluorescence quenching experiments,it’s ultrafast adsorption rate-rhodamine B was removed within 60 min by Tb/rGO-was studied.The optimum synthesis temperature is 170℃and the optimum concentration of terbium ion is 2mg/mL.The adsorption curve fitted with the first-order reaction model,indicating the adsorption rate is proportional to the concentration of pollutants.（2）The magnetic and fluorescence properties of terbium doped graphene were studied.It is found that the volume and post-treatment process of the preparation process have direct impacts on the construction of the three-dimensional network structure and pore structure,thereby affecting the intrinsic luminescence and magnetic properties of graphene.The terbium ion,as a dopant,has a certain paramagnetic and characteristic green fluorescence properties.Therefore,the photoluminescence behavior of the terbium modified graphene material and it’s hysteresis loop are determined by the integrative action of doped ions and graphene matrix.According to the theory of organic molecules of high spin state,we first introduced the coupling effect of quasi one-dimensional organic molecules into the magnetic interpretation of three-dimensional assembled materials.At the same time,we found the influence of slice spacing on intrinsic magnetic ordering through experimental results.In the fluorescence behavior of materials,using the intrinsic luminescence mechanism of graphene and the absorption spectrum of carbon oxygen bonds,we further establish the mechanism of energy transfer between carbon oxygen bonding and excitation electron of terbium ion.（3）By comparing the adsorption capacities of three dimensional graphene adsorbents modified by various dopants,the urea doped graphene self-assembled adsorbent with high adsorption capacity for copper and lead ions was selected.The experimental results show that the optimum mass of additive is 90 mg and the best resultant temperature is 180℃.When pH is 5,the adsorption capacity of adsorbent is up to 624 mg/g in 100 mg/L Cu²⁺solution.The adsorption process is in accordance with the quasi first order kinetic model and the Langmuir model.Through characterizations,we found the reasons of high adsorption capacity of urea doped graphene adsorbent:（a）in the hydrothermal process,urea release ammonia,carbon dioxide and other gases,increasing the distance of graphene sheets in self-assembly process;（b）the adsorbents provide more adsorption sites with the help of ammonia in the adsorption process.Finally,the adsorbent loaded with copper ions was applied for catalyzing 4-nitrophenol to 4-aminophenol,and 90%of the pollutants was degraded in 60 min.