Preparation And Properties Of PEK-c And PVDF Nanomaterials Composite Ultrafiltration Membranes

Nano-materials have recently attracted wide attention and been found various applications in the field of membrane technology.The prepared separation membrane has the advantages of large specific surface area,high porosity,large flux and good selectivity,leading to good application prospect in sewage treatment,biochemical industry and so on.In this paper,a method for preparing polymer nanomaterials and their composite membranes is proposed.The polymer nanomaterial dispersion is prepared by freeze-extraction technique,and then the composite ultrafiltration membrane is prepared on the microporous base film.Cardo polyether ketone（PEK-c）and polyvinylidene fluoride（PVDF）were used to study the formation principle and preparation conditions of polymer nanomaterials.The structure and structure of the nanomaterials and the corresponding composite films were characterized,and their-separation performances studied.The main contents and results are as follows:（1）Preparation and properties of PEK-c nanomaterials and its composite membranes.The effects of solution concentration and temperature on the formation of nanomaterials were investigated.Likewise,the morphology of the nanomaterials and the corresponding separation properties of the prepared composite ultrafiltration membranes were studied in detail.The prepared PEK-c nanomaterials,which were dispersed in ethanol,were found to mainly consist of nanofibers and nanoparticles.Meanwhile,the thickness of the PEK-c composite ultrafiltration membranes is thin to 65 nm,with pore sizes in the range of 5～10 nm and displays pure water flux of up to 4.7×10³ L m^-2h^-1bar^-1.（2）Preparation and properties of PVDF nanomaterials and its composite membranes.Based on the preparation of PEK-c nanomaterials,PVDF nanomaterials and their composite ultrafiltration membranes were prepared.The preparation conditions of nanomaterials and composite membranes were investigated.The composite membranes were applied to the separation of oil-water nanoemulsion.It is found that PVDF nanomaterials have a bead-like structure,and a uniform separation layer can be formed on the microfiltration membrane to form a composite ultrafiltration membrane with small filtration resistance.The membrane with the pure water flux of 2.24 ×10³ L m^-2h^-1bar^-1 can efficiently reject ferritin.In addition,the membranes display high organic solvent flux with cyclohexane flux is as high as 1.32 ×10⁴ L m²h^-1bar^-1.Moreover,the water-in-oil nanoemulsion separation can reach 100%.The technology of fabricating the PEK-c and PVDF nanomaterials developed in this paper has the advantages of simple process,low cost and good versatility.The as-prepared composite ultrafiltration membrane with pore size of 5～12 nm has the advantages of low filtration resistance,adjustable thickness,large flux.All these advantages predict the potential application prospects in wastewater treatment,separation of nanoparticles,and separation of oil contaminated waters.