Preparation,Characterization Of Graphene-Based Nano-biomaterials And Application In Waste Water Treatment

Graphene and graphene nanocomposites are new type of functional materials with strong comprehensive performance,which widely used in various fields,especially in the field of environmental restoration.For the preparation of graphene,the traditional preparation methods have their own limitations.For example,the chemical reagents used in the widely used redox method are very harmful to the environment and human health.Therefore,this study used waste biomass bagasse（B）as a reducing agent to synthesize reduced graphene oxide（RGO）by green reduction method,and combined with microbial immobilization technology to prepare nano-biomaterials（NBMs）to study their removal performance of environmental pollutants.Firstly,RGO was prepared as a green reducing agent for graphene oxide（GO）through a resource-rich,low-cost,environmentally-friendly waste biomass bagasse.RGO was detected by ultraviolet-visible spectroscopy（UV）,and a maximum absorption peak appeared at 270.5 nm,indicating that the conjugated structure of RGO was restored,that is,RGO was successfully synthesized.Functionality,crystal structure,interplanar spacing,and electronic properties of GO and RGO by means of infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,Raman and X-ray photoelectron spectroscopy（XPS）The analysis of element content and bond energy showed that the absorption peak intensity of the oxygen-containing functional groups（-OH,C=O,-COOH）of RGO was significantly decreased,the C content was increased,the O content was decreased,and the conjugated structure in RGO was recovered.The apparent and internal structures of GO and RGO were characterized by field emission scanning electron microscopy and energy dispersive spectroscopy（FESEM-EDS）and high resolution transmission electron microscopy（HRTEM）.The results show that RGO was flatter and wrinkled than the surface of GO.The degree of improvement was significantly improved,the O content was less,and the layer spacing was smaller.This proves that GO was successfully restored.Through the electrochemical test of RGO and GO and the adsorption performance of RGO on the typical heavy metal ion Cd（II）in wastewater,the results show that the peak current of RGO/GCE was 1.78 times and 1.16 higher than that of GO/GCE and bare GCE,respectively.At the same time,the removal rate of Cd（II）by RGO can reach 58.0%.It shows that RGO has better electrochemical performance than GO and good adsorption performance for Cd（II）.Secondly,B-RGO was prepared by loading RGO with B to improve the adsorption and stability of the material.Bagasse can be used as a carrier for microorganisms and provide a nutrient source.B-RGO was then used to immobilize NBMs by Burkholderia cepacia,a commonly used dye in the biodegradable printing and dyeing industry,by microbial immobilization technology,by comparing NBMs（99.3%）.The removal of MG by B-RGO（73.0%）and free Burkholderia cepacia（93.6%）showed that the removal performance of NBMs was superior to the other two materials.The response surface analysis showed that the optimal removal conditions for MG removal were optima at temperature of 31.50°C,initial MG concentration of 114.5 mg·L^-1,initial pH of 5.85,and NBMs dosage of 0.11 g·L^-1.The MG removal rate reached 99.3%.By fitting the adsorption kinetics and degradation kinetics of the process of removing MG from NBMs,it was found that the removal process was more in line with the pseudo-secondary adsorption kinetics model and the first-order degradation kinetics model.According to the pseudo-secondary adsorption kinetics model（R²>0.99）,the removal rate of MG by NBMs is more dependent on the number of adsorption sites than the MG concentration.Through UV,FTIR,and GC-MS analysis,it was found that the degradation products of NBMs to MG were N,N-dimethylaniline and 4-（dimethylamino）benzophenone.In summary,the removal of MG by NBMs was proposed.The mechanism is first degradation after adsorption.Finally,the functional groups,crystal structures,electronic properties and thermal stability of NBMs were further characterized by UV,FTIR,Raman,specific surface area test（BET）and thermogravimetric analysis（TG）.The experimental results showed RGO and onion.Burkholderia cepacia was successfully fixed on bagasse.The BET test showed that NBMs have a larger specific surface area(35.43 m²·g^-1),and TG tests show that NBMs have better thermal stability.The apparent and biological activity of NBMs was characterized by FESEM and fluorescence microscopy（FM）.The results showed that both RGO and Burkholderia cepacia were successfully immobilized on bagasse and fixed on bagasse.It has better biological activity than the free Burkholderia cepacia.Simultaneous removal of heavy metal ions and dyes by NBMs revealed that the removal efficiency of Cd（II）by NBMs was 56.9%,and the removal efficiency of MG was 98.9%.And the study of its removal process shows that the removal of Cd（II）by NBMs is adsorption,while the removal of MG is first adsorption and degradation.In summary,the waste biomass bagasse can be used as a reducing agent for GO,and the RGO prepared by green synthesis is more excellent,and the NBMs prepared by the microbial immobilization technology are combined.This new type of material plays a role in promoting the reuse of waste biomass and the development of green chemistry,and has a good potential application in the field of practical industrial wastewater treatment.