Preparation Of Graphene Composite Aerogel And Its Application In Water Pollution Treatment

Nowadays,water pollution is a worldwide problem becoming more and more serious,which threatens the ecological balance and human health.Because of its simple operation,low cost,and low tendency to produce secondary pollution,the adsorption method become one of the most common approaches of water pollution treatment.Graphene aerogel(GA)has shown good application prospects in water pollution treatment due to its high specific surface area,high porosity,and excellent chemical stability,and has become a hot research topic in recent years.However,the GA prepared by conventional self-assembly manners still has some problems,such as poor mechanical properties and easy structural collapse.The reduction strategy has been commonly used to improve the mechanical stability of GA,while often making it to be more hydrophobic,which would be not ideal for the adsorption of polar pollutants.These problems and shortcomings limit its application in water pollution treatment.To address the above problems,this thesis prepared graphene oxide(GO)based on graphite and prepared two types of composite aerogels.Firstly,copper oxalate nanoparticles were used to enhance cross-linking between GO sheets and prevent stacking,and bubble templates were introduced to optimize the pore structure of GA,and the hydrophilicity of the material was improved by adjusting pH,thereby graphene/copper oxalate composite aerogel GA-SC with oil-water amphiphilicity and good mechanical properties was prepared.Then natural latex NRL was used as a cross-linking agent,by combining with the introduction of bubble templates,a lightweight porous graphene/natural latex particle composite aerogel GA/NRL with excellent mechanical stability was prepared.The adsorption performance of the prepared two types of graphene composite aerogels on typical pollutants such as heavy metal ions and organic dyes in water and the absorption performance of leaked organic solvents were investigated to reveal their application prospects in water pollution treatment.The structural characterization of the samples was carried out by scanning electron microscopy(SEM),X-ray diffractometer(XRD),X-ray photoelectron spectroscopy(XPS),atomic absorption spectrophotometer(AAS),and ultraviolet absorption spectroscopy(UV-Vis),and the laws of the influence of different conditions on the mechanical and adsorption properties of the prepared GA-SC and GA/NRL were systematically investigated to explore the relevant mechanisms,and the knowledge obtained in this work is of certain guiding significance for exploring novel ways to improve the performance of GA and expand its applications.In the first part,graphene composite aerogel GA-SC with good mechanical stability,super amphiphilicity,and good water pollution treatment ability was prepared based on the strategies of bubble/nanoparticle dual templates with synergistic surfactants and pH modulation.Here,the surfactant plays a role in both dispersing GO and stabilizing the bubble template.The hydrophilicity of the prepared GA was improved through pH adjustment of the aqueous phase dispersion of GO.The introduced bubble template enables the GA to form pore-linked micron-level pores,while the copper oxalate nanoparticles act as cross-linked GO sheets on the one hand and prevent the accumulation of graphene sheets on the other.The prepared GA has good mechanical stability and has a high adsorption capacity for both heavy metals and organic pollutants.The maximum adsorption capacities of GA-SC for Pb2+,Cd2+,and MB in water can reach 192,107,and 472 mg/g,respectively,and the absorption capacities of organic solvents trichloromethane and dodecane can reach 307 and 130 times of their own weight,respectively.And the absorbed organic solvents can be recycled after being discharged by mechanical extrusion.The adsorption kinetic mechanism of the material for the adsorption of various pollutants was analyzed.In the second part,the composite graphene aerogel GA/NRL was prepared using natural rubber latex(NRL)as a cross-linking agent.NRL is dispersed in an aqueous solution to form emulsion droplets,which are dispersed between graphene sheet layers and form a sandwich-like sandwich structure with graphene sheets to promote the formation of structurally ordered three-dimensional pore structure of graphene in the hydrothermal reduction process.The pore structure of the aerogel was optimized by introducing a bubble template.The prepared GA/NRL exhibited excellent mechanical stability and fatigue resistance,and the structure remained stable after 60%strain and 50 cycles of compression.The material has excellent adsorption performance for cationic organic dyes in water,with a maximum adsorption capacity of 622 mg/g for MB in water.The absorptions of organic solvents trichloromethane and dodecane reach 276 and 130 times of their own weight,respectively,and has good recycling performance.