| Graphene and graphene oxide(GO)own excellent and unique properties,and GO emerges as a potential precursor for simple,cost-effective and large scale synthesis of graphene-based composite materials at the present stage.Graphene-based composite materials have many potential applications,including supercapacitors,photothermal therapy,molecular sensing,catalysis,adsorption energy conversion and storage.Chitosan,a natural polysaccharide,is synthesized by the incomplete alkaline N-deacetylation of chitin which is the second most abundant naturally occurring biopolymers,with many advantages,such as antibacterial properties,biocompatibility and biodegradability.Chitosan has considerable number of hydroxyl and amine groups in polymer chains,which have strong complexation ability to heavy metal ions.Therefore,we can use it to adsorb these heavy metal ions from contamination.Chitosan shows positive electricity when it is dissolved in acidic aqueous solution,so it can adsorb negatively charged dyes.Magnetic materials can be remote control and non-invasive monitoring,and are widely used in biomedicine,magnetic fluid,magnetic resonance imaging,environmental protection or other fields.So,in this paper,we designed and prepared the graphene-chitosan complex by utilizing the advantages of chitosan and graphene-based materials,and introducing the magnetic nanoparticles,hoping to achieve a certain value in environmental protection.In the thesis,we have developed a new method for the preparation of chitosan-GO composite membrane,and we studied the properties,formation mechanism and application of the membrane.Fe3O4 nanoparticles were introduced into the chitosan-GO composites,and the composites were used as water treatment adsorbent,and it was desirable to simplify the adsorption process and reduce the energy consumption.The contents of this master's thesis are divided into three chapters.Chapter 1 is the introduction of the research background and significance.The structure and properties of graphene and GO,the classification,development and application prospect of graphene-based materials were introduced.And then,the structure and properties of chitosan,the applications of chitosan composite were introduced.The purpose and significance of this master thesis were pointed out at the end of this part.In chapter 2,we have developed a method of using dialysis method for preparing O-(carboxymethyl)-chitosan(O-CMC)membranes by changing the pH of dialysate,and the dialysis bag was the template.GO was synthesized by modified Hummers method from natural graphite powder.The green-friendly reducing agent,sodium ascorbate,was used to reduce GO.Moreover,we obtain the composite membranes functionalized by GO and reduced GO(rGO)using the same method.The membrane structures and properties are investigated with different techniques,including SEM and Raman spectroscopy.Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)spectra and TGA-DTA indicate that the composition(O-CMC)of these membranes is protonated.The prepared membranes were used for the adsorption experiment of Cu2+ and the amido black 10B.It was found that the adsorption performance of the reduced graphene oxide functionalized carboxymethyl chitosan membrane was best.In chapter 3,we have prepared the magnetic GO by solvothermal method.Then it was composited with chitosan and used for adsorption dyes.The synthesized magnetic GO and its composites were characterized by SEM,Raman spectroscopy,infrared spectroscopy,XRD and magnetic test.Finally,the prepared magnetic composites were used for the adsorption of dyes(methyl violet,methylene blue,rhodamine B,congo red,etc.)We found that the composites had good adsorption effect on these dyes.The introduction of magnetic properties in the composites can also simplify the recovery process and reduce the energy consumption for recovery adsorbents.The Fe3O4 nanoparticles were adhered to GO,and then were coated with chitosan,which can prevent the leakage of magnetic nanoparticles during the process of adsorption. |
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