Preparation And Performance Of Mxene-based Composites For Adsorption Desalination Application

With the continuous increase of population and the continuous development of urbanization,the problem of water resources has become increasingly prominent.Using efficient and energy-saving technology to convert salt water into fresh water is an effective solution.As an environment-friendly and low-energy water treatment technology,capacitive deionization technology（CDI）meets people’s needs.Therefore,the development of electrode materials with high efficiency and rapid desalination has become an urgent demand.MXene is an idea electrode material with unique layered structure and abundant surface functional groups,such as high conductivity,hydrophilic properties,specific surface area and rapid ion intercalation/deintercalation ability.However,due to its tendency of self-agglomeration,its performance is greatly reduced.Gelation is a good way to solve this problem.In this paper,MXene/graphene oxide（GO）hydrogel（MG）,manganese oxide/MXene gel（MGM）and Ni-Co double-layer hydroxide/MXene gel composite（MGL）were studied,and their electro-adsorption desalting were systematically studied.The main results are as follows:1.The MXene/GO hydrogel（MG-n）with different mass ratios was prepared.Electrochemical tests showed that the best electrochemical performance was obtained when the mass ratio of MXene to GO was 8:2（MG-2）.Its specific capacitance is 149 F g^-1 under a scanning rate of 1m V s^-1.On this basis,the Mn O/MXene aerogel was prepared by doping four hydrated manganese chloride.When the ratio of four hydrated manganese chloride was 12%（MGM-3）,it had the best electrochemical performance with the specific capacitance of 356 F g^-1 under a scanning rate of 1.0 m V s^-1.In addition,5000 charge-discharge cycles experiments with current density of 10 A g^-1 were carried out.The results showed that the retention rate of specific capacitance was 87.28%.In the adsorption performance test,under the operating voltage conditions of 1.2 V,feed inlet flow rate of 20 m L min^-1 and initial Na Cl concentration of 800 mg L^-1,the maximum adsorption capacity of MGM-3 is 41.05 mg g^-1,which is about 23%higher than that of MG-2(33.32 mg g^-1).The adsorption capacity of MGM-3 at various initial concentrations was fitted,and its adsorption behavior was more consistent with multilayer adsorption.2.Ni Co-LDH/MXene hydrogel composite（MGL-n）based on MG-2 was successfully prepared by loading nickel-cobalt double hydroxide.When the mass of cobalt is equal to MG-2（MGL-3）,its electrochemical performance is the best.When the scan rate is 1.0 m V s^-1,MGL-3 has a specific capacitance of 669 F g^-1.When the scan rate is increased to 20m V s^-1,the specific capacitance is 498 F g^-1.In addition,5000 charge-discharge cycles experiments with current density of 5 A g^-1 were carried out.The results show that the retention rate of specific capacitance is85.37%.In the adsorption performance test,under the operating voltage conditions of 1.2 V,feed inlet flow rate of 20 m L min^-1 and initial Na Cl concentration of 800 mg L^-1,the maximum adsorption capacity of MGM-3 is 56.92 mg g^-1,which is about 71%higher than that of MG-2(33.32mg g^-1).The adsorption capacity of MGM-3 at various initial concentrations was fitted,and its adsorption behavior was more consistent with multilayer adsorption.