| Seawater desalination is the main way to solve the problem of shortage of fresh water resources in coastal areas,the reverse osmosis is widely used in the industry.Since the membrane materials used for the seawater desalination are usually polymer membranes that are relatively thick,it affects the efficiency of the permeation,thus it is urgent to find a new material for permeable filter.Graphene is a new two-dimensional material with only one atom thickness and has excellent mechanical properties,making it as an ideal candidate for a permeable filter material.Many scientists have found that graphene has great potential application prospects in the fields of gas selecting,ion selecting and DNA sequencing.However,the accurate perforation of the graphene and the stability of the graphene oxide film in the solution remain unsolved and restrains the application of graphene in engineering.In this work,the screening of particles by graphene-based materials were studied combing experiment,theory and molecular simulations.The conclusions of the thesis can be summarized as follows:(1)The permeability and selectivity of nine kinds of gases commonly used in uniaxial and biaxial stretching of nanoporous graphene were studied through the first-principal calculation.It was found that strain can be applied to the film to modulate the permeability and selectivity;(2)Considering the structure of pores in the process of graphene oxide formation,molecular dynamics simulation was used to calculate the permeability of two layers of penetrating membrane and no penetrating membrane.The permeate flux of the penetrating membrane is significantly higher than that of no penetrating membrane.Through the study of the gas model in different water molecules and the gas distribution during the simulation,it is found that the graphene oxide film has different adsorption properties for different gases;(3)The effects of graphene oxide composite films with different thicknesses and various ratios of zinc oxide on different ion permeability were studied by experiments.In order to enhance the stability of the film in water,the film was reinforced by dipping epoxy.The test results show that the stability is enhanced while the ion permeability is reduced;(4)Through numerical simulations and theoretical analysis,as well as molecular dynamics simulation,it is demonstrated that the selectivity of different particle size particles can be achieved by selecting the size of different graphene oxide sheets,especially for the selecting of macromolecules. |
