| The application of microwave energy in chemical separation has always been a research hotspot in the field of chemical process strengthening.Based on the previous research results of this group,although microwave radiation could effectively separate polar substances from polar-nonpolar mixture systems,the capacity and separation efficiency were low.The main reason is that energy transfer between different polar molecules cannot be inhibited under microwave radiation.Therefore,it is of great significance to develop a method to inhibit the energy transfer between different molecules in the microwave field to improve the efficiency of microwave energy selective separation process.In this paper,the graphene-based separation membrane materials are used owing to the advantages in separating mixtures.The experiments of conventional membrane distillation and microwave-radiation membrane distillation were carried out.The influence of temperature,feed state was studied in order to explore the strengthening effect of microwave field on the graphene oxide membranes and reduced graphene oxide membrane in the process of membrane distillation.The effects of microwave energy radiation on the flux and selectivity of mixtures with different polarity were also studied.In the experiment,the graphene oxide membranes were produced by scraper coating machine and the reduced graphene oxide membranes were industrially produced.The physical structure and functional group properties of the membranes were characterized by means of XRD,XPS,SEM,AFM and FTIR.The results showed that two kinds of membranes are two-dimensional layered structures.The interlayer distance of graphene oxide and reduced graphene oxide were 7.794 (?) and3.365 (?),respectively.The oxygen content of graphene oxide and reduced graphene oxide were 27.37% and 1.61%,respectively.There were hydroxyl groups and epoxy groups on the two kinds of membranes and carboxyl groups on the graphene oxide membranes.Then,the experimental study of microwave-induced membrane distillation of graphene oxide was carried out.The pure chemicals such as water,methanol,ethanol,n-propanol,n-butanol,and the mixed systems such as water-methanol,water-ethanol,water-1-propanol,methanol-ethanol,methanol-1-propanol,methanol-n-butanol,ethanol-cyclohexane were used to study for comparing the permeation flux and selectivity under conventional membrane distillation and microwave-radiation membrane distillation.It was found that the permeation flux of the above systems could be increased by microwave irradiation,and the greater the dielectric properties of the system,the higher the permeation flux.The permeate flux of pure chemicals was increased by more than 10 times.The permeate flux of alcohol-water systems was increased by more than 5 times and that of mixed alcohol systems was increased by up to 2 times.Microwave had little effect on the selectivity of polar-non-polar systems.The ethanol content in the permeate side of ethanol-cyclohexane exceeded98 wt% in both ways.However,the microwave had a great influence on the selectivity of polar-polar systems.Compare microwave radiation to conventional membrane distillation,the water content of water-methanol system on the permeate side was from 86.258 wt% to 72.511 wt% and the water content of water-ethanol system was from 90.716 wt% to 33.294 wt%.Finally,the experiment of microwave-induced membrane distillation of reduced graphene oxide was carried out with the same system.The results showed that microwave has little effect on the permeation flux and selectivity of each system under the membrane distillation of reduced graphene oxide membranes.Compared with the results of membrane distillation of graphene oxide membranes,the effect of microwave on membrane distillation was related to the number of oxygen-containing functional groups on the membranes.The more oxygen-containing functional groups on the membranes existed,the greater microwave affected the permeation flux and selectivity of membrane distillation process. |
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