Study On Functionalized Graphene And Its Composites In Water Purification

As the discharge of domestic and industrial wastewater increases,the problem of drinkable water shortage is becoming more and more serious.Toxic and harmful substances in wastewater pose a great threat to the stability of ecosystems and human health.Therefore,exploring efficient adsorbents to remove the toxic and harmful substances has become a hot topic of research in order to improve the quality of the water.As a high specific surface area two-dimensional material,graphene has an excellent theoretical adsorption performance,but it still needs to solve the problems of agglomeration stacking and difficult recycling.Based on this consideration,graphene-based composite materials and three-dimensional graphene have been widely studied.Because of its excellent adsorption capacity,easy separation and reusability,it has a very broad application prospect in practical applications.In this paper,the ascorbic acid?AA?was used as a reducing agent,proanthocyanidin?PC?as a dispersing agent to synergize the graphene oxide?GO?,and the reduction and non-covalent bond modification processes were completed in one step to prepare non-covalent bond modified graphene?PC-rGO?.Compared with AA-rGO?without adding dispersant PC?,PC-rGO has superior dispersibility,higher degree of reduction and lower defect density.SA/PC-rGO hydrogel was prepared by combining PC-rGO with sodium alginate?SA?for the adsorption of Cu²⁺,and SA/GO hydrogel complexed with GO and SA was used as a control group.The morphology and groups of the two hydrogels were compared and analyzed by various characterization methods.The results show that the SA/PC-rGO hydrogel has a smaller pore size,because the PC molecules on the surface of the SA/PC-rGO enter the substrate so that the hydrogen bonding increases between the SA molecules,thereby forming a denser porous structure.The adsorption of Cu²⁺by two hydrogels was analyzed by kinetics,isotherms and thermodynamic models.The results show that SA/PC-rGO hydrogel exhibits better adsorption performance,and its maximum adsorption capacity was 193.05 mg g^-1.The SA/PC-rGO hydrogel retained93.70%of initial adsorption after repeated use,indicating that the SA/PC-rGO hydrogel has a good recyclability.A three-dimensional graphene?IGR?hydrogel was prepared by covalently crosslinking GO with isophorone diisocyanate?IPDI?.Then the optimal addition amount of IPDI was investigated,and the aqueous solution containing methylene blue?MB?was purified.During the crosslinking process,the isocyanate groups of IPDI form amide bonds and urethane bonds with the groups on the GO.Excessive IPDI was found to reduce cross-linking between the sheets resulting in a fluffy and brittle hydrogel,while too low a loading could not completely graft the oxygen-containing functional sites.The whole adsorption process was fitted and analyzed by kinetics,isotherm and thermodynamic model.The results showed that the maximum adsorption amount was 972.99 mg g^-1.And after five adsorption-desorption cycles,the IGR hydrogel still has an initial adsorption capacity of 97.04%,indicating that the IGR hydrogel has a good reproducibility.