Preparation Of Graphene-based Composite Aerogel And Its Adsorption Properties

In recent years,with the gradual expansion of industrial development,the ensuing problems of organic dyes and heavy metal ions pollution have posed a major threat to water resources.Adsorption is one of the common water treatment methods because of its simplicity and low cost.Graphene oxide（GO）has been widely used for the adsorption and removal of pollutants in water due to its chemical stability and strong adsorption capacity.However,GO is limited in adsorption due to its small particle size and high hydrophilicity,making it difficult to recover and prone to secondary contamination during the adsorption process.In this thesis,high adsorption performance graphene aerogel（Diethylene triamine reduced graphene oxide aerogel,DRA）was prepared by the reduction of Diethylene triamine,while solving the aforementioned problem of difficult GO recovery.Furthermore,this thesis presents an innovative approach to the preparation of hydrate manganese oxide（HMO）nanomaterials from the waste liquid of the modified Hummers method.The SA/HMO and SA/GO/HMO composite aerogel spheres were prepared by compounding HMO and GO with sodium alginate（SA）,which further improved the adsorption capacity and reduced the separation and recycling costs in the adsorption process.The main research contents and conclusions are as follows:（1）The preparation of DRA was optimized.At a reduction temperature of 95°C and a concentration of 16μL/m L of reducing agent,the aerogel was highly intact with a low density of 11.15 mg/cm³.During the gelation process,DETA partially reduced GO and modified GO with amino groups,increasing its defects and zeta potential.（2）DRA showed the high adsorption of MO and MB at p H 4 and 10,while the optimal adsorption of Pb（II）and Cd（II）was obtained at p H 5.5.The adsorption processes conformed to the Pseudo-second-order kinetic model and the adsorption rates were controlled by both external and internal diffusion on the surface as a spontaneous absorption reaction.The maximum adsorption of DRA at 298 K was 227.24 mg/g and266.82 mg/g for MO and MB,relying on electrostatic andπ-πinteractions,while the maximum adsorption of Pb（II）and Cd（II）was 106.87 mg/g and 62.95 mg/g,relying on electrostatic,ion exchange and amino chelation.After five adsorption recycles,DRA can maintain 87.63%,91.78%,84.26%and 82.18%of the initial adsorption capacities for MO,MB,Pb（II）and Cd（II）,respectively.（3）The formation mechanism of HMO was investigated based on the residual amount of H₂O₂in the waste liquid of the modified Hummers method.By optimizing the preparation process,δ-Mn O₂-type HMO with a stable crystalline shape and high adsorption performance was obtained.Meanwhile,with SA combined with HMO and GO,high stability composite aerogel spheres were obtained.The introduction of GO into SA/GO/HMO inhibited the shrinkage of the aerogel spheres and increased the pore interval compared to SA/HMO.（4）The adsorption capacities of Pb（II）and Cd（II）by SA/HMO and SA/GO/HMO were maximum at p H 5.5.The adsorption process conforms to the Pseudo-second-order kinetic model and belongs to monolayer adsorption.The maximum adsorption capacities of Pb（II）and Cd（II）at 298 K were 262.71 mg/g,148.22 mg/g and 297.59 mg/g,161.93 mg/g for SA/HMO and SA/GO/HMO.The adsorption mainly relied on ion exchange as well as electrostatic interaction.After five adsorption recycles,the adsorption capacities of SA/HMO and SA/GO/HMO for Pb（II）and Cd（II）remained above 74%of the initial adsorption capacity.