Preparation Of Functional Magnetic Graphene Sponge And Its Application In Wastewater Treatment

Water pollution,air pollution,soil pollution and global climate change are the most concerned environmental issues in 21 st century.Each of them is closely related to people's life.In recent years,the increasingly serious water pollution during the urbanization has become the focus of public and scientists' attention.Water pollution remediation has become an urgent problem for people's livelihood.Graphene has become a hotspot in recent years owe to its large specific surface area,rich pore structure,abundant surface functional groups and excellent adsorption properties.Graphene has excellent adsorption ability for many contaminants in sewage.Based on graphene oxide?GO?,we prepared Fe₃O₄ nanoparticles by co-precipitation,mixed them with GO,and obtained magnetic graphene sponge by lyophilization.We measured the adsorption behaviors of dye and antibiotics on magnetic graphene sponge,and also investigated the influence of reduction degree on the adsorption performance of graphene sponge.We improved the adsorption performance of graphene adsorbents,solved the problems of graphene adsorption technology?such as difficulty in separation after the adsorption?,revealed the influence of reduction degree on the adsorption performance of graphene sponge,and provided important data and concepts for designing better graphene adsorbents of high-performance and low operating cost.In this study,the GO dispersion was prepared by the improved Hummers method.Then,the dispersed Fe₃O₄ nanoparticles and the GO dispersion were stirred,the Fe₃O₄ nanoparticles were precipitated on the GO layer and dried to form sponge Fe₃O₄-GOS.Fe₃O₄-GOS was systematically characterized and the adsorption capacity/behaviors of methylene blue?MB?and tetracycline?TC?on Fe₃O₄-GOS were studied.Finally,in order to investigate the effect of the surface structure of graphene on the adsorption behaviors of pollutants,we prepared three GS samples of different reduction degrees,characterized them,and compared their adsorption properties for differently charged dyes.According to the aforementioned experiments,the main results were presented as below.?1?Fe₃O₄-GS was prepared and the adsorption of MB on it was evaluated.The adsorption capacity of Fe₃O₄-GS was 526 mg/g,much higher than those of the magnetic carbon nanoadsorbents in the literature.The adsorption kinetics of MB on Fe₃O₄ was very fast,which could be analyzed by the pseudo-second-order model and intrapaticle diffusion model.The thermodynamics study revealed that the adsorption was driven by the increased randomness on the interface.The p H and ionic strength had moderate influences on the adsorption capacity of Fe₃O₄-GS.The incorporation of Fe₃O₄ enabled the magnetic separation and of Fe₃O₄-GS after the adsorption of MB.The facile regeneration of Fe₃O₄-GS would definitely reduce its operating cost.?2?The adsorption behaviors of tetracycline on Fe₃O₄-GS were evaluated.The adsorption capacity of Fe₃O₄-GS for tetracycline was 473 mg/g,showing 50% increase of that of GO.The adsorption process was moderately fast and could be described by pseudo-second-order model.The thermodynamics investigation indicated that the adsorption of tetracycline on Fe₃O₄-GS was endothermic and the driving force was entropy increase.The pH had mild influence on the adsorption,while ionic strength nearly had no impact.?3?The influence of reduction degree on the adsorption of dyes on graphene sponge?GS?was investigated.We prepared three GS samples of different reduction degrees by vapor reduction method and compared their adsorption properties for different dyes.Our results indicated that the adsorption of MB on GS was inhibited at high reduction degree by reducing the electrostatic interaction between oxygen containing groups and MB molecules.The adsorption kinetics slowed down at higher reduction degree,too.pH showed more significant influence for highly reduced GS,while ionic strength had ignorable effect on the adsorption.Beyond that,the dye properties also regulated the adsorption.