Application Of Graphene Based Membrane In Water Treatment Mechanism

With the growth of population and the rapid development of industry,freshwater resources are increasingly exhausted,and it is increasingly important to develop sustainable freshwater resources.Membrane separation technology has been widely used in the development of freshwater resources.Due to the intrinsic structure and chemical properties of the membrane,the membrane usually has good water permeability and excellent retention.Graphene oxide has the advantages of easy film formation and functionalization,which is an excellent material for preparing separation membrane.However,when graphene oxide is used to prepare separation membrane,due to the large amount of functional groups in the oxidized graphene material,when water treatment is carried out,the oxygen-containing functional groups are prone to hydration and electrostatic interaction with water molecules,which seriously affects the screening quality of separation membrane and the life of separation membrane.Chemical method is the most commonly used method to enhance the service life of separation membrane.Reduction method is one of the methods to enhance the graphene oxide separation membrane.Many reduction methods,such as annealing,high-temperature thermal reduction,have the risk of increasing the impermeability of separation membrane,while hydrothermal reduction has the advantages of reduction and risk reduction.Therefore,hydrothermal reduction method is used in this paper Reducing agent is H₂O₂.The excellent two-dimensional nano flake structure of graphene material has good adsorption performance in water treatment because of its large specific surface area.In view of the above problems,HGO was prepared by hydrothermal reduction and the performance of HGO film was studied.In addition,the adsorption performance of modified graphene oxide PGO was also studied.The specific research contents are as follows:?1?Graphene oxide?GO?was prepared by improved Hummers method,and the prepared GO was characterized by physicochemical method to verify the successful preparation of GO.After obtaining GO,GO was hydrothermally reduced to prepare HGO material,and HGO membrane was prepared by vacuum filtration.The microstructure and chemical properties of HGO membrane were characterized,and the water flux and retention property of HGO membrane were studied.The results show that HGO materials still have a good two-dimensional sheet structure,and the nano materials between the layers of HGO films are compact.The water contact angle of HGO film is 65.6°and that of GO film is 55.3°.FT-IR data also confirmed that the number of oxygen-containing functional groups in HGO film decreased.In addition,HGO membrane still showed a high water flux of 24.83l/m2·h·bar under the condition of thick membrane loading?0.796g/m2?;the retention rate of Rhodamine B?RB?was about 100%under the condition of free diffusion,and the membrane remained good stability under the condition of long-time test?50h?.?2?In order to improve the problem which is difficult to separate graphene oxide?GO?from aqueous solution after adsorption of pollutants,PEI-GO composite was prepared by modifying GO with PEI,and the structure and morphology of the composite was characterized by FT-IR,Raman,SEM and EDS.The effects of different adsorption time and adsorbent dosage on the adsorption performance of MB were analyzed,and the kinetic and temperature line models were used to fit them.The separation time of MB adsorbed by GO and PEI-GO was recorded respectively.The results show that PEI-GO composite still has a good two-dimensional nanostructure and the O=C-NH covalent bond which is formed by the reaction of the oxygen-containing functional group in the nano film and the amino group in PEI.The composite PEI-GO has good adsorption property for MB.When the initial concentration of MB is 25mg/L and the input amount of PEI-GO is 30mg,the adsorption capacity of PEI-GO can reach204.87mg/g.The adsorption behavior was fitted to a quasi second-order kinetic model and Freundlich isothermal model.After adsorption,compared with GO adsorption,the separation rate is 4?5 times faster.