Construction And Water Treatment Performance Of MOF@nanofiber Composite Membrane

With the growing of the world’s population,the lack of fresh water resources is gradually threatening the survival of human beings.With its own advantages,membrane separation technology has now become the most widely used water treatment technology.Nanofiber membranes prepared by electrostatic spinning technology have high porosity and become the ideal base membrane material.However,single nanofiber membranes do not have excellent separation performance and still need to be modified to improve their separation capacity and broaden their application scope.Metal organic framework materials(MOFs)have been applied to the preparation of new membrane materials by relying on their high porosity and structural and functional diversity.In this paper,homogeneous nanofiber membranes were prepared by electrospinning technique and modified by introducing MOFs materials,and the water treatment performance of the resulting modified composite membranes was subsequently explored.The details are as follows:(1)Polyacrylonitrile nanofiber membranes were prepared by electrostatic spinning technique.The resulting fiber membranes were further pretreated and ZIF-8nanocrystals were grown on their surfaces.Based on the unique pore structure of ZIF-8crystals,the modified nanofiber membranes possessed good positive permeability performance.The separation experimental results show that the ZIF-8 fiber membrane has a low reverse salt flux and excellent Na Cl retention capacity,which meets the demand of forward osmosis process.(2)Continuous dense crystalline layer of MOFs was constructed on the surface of the nanofiber membrane using crystal seeding method,and then the crystals were modified with γ-polyglutamic acid to improve the water permeability of the composite membrane.Various characterization tests demonstrated that the MOFs crystal separation layer on the surface of the produced PGA@ZIF-8 nanofiber membrane had good morphology and high porosity.The contact angle test results showed that the composite membranes prepared by adding γ-polyglutamic acid during the incorporation growth process possessed good hydrophilicity and could be considered as a relatively successful modification strategy.The subsequent results of positive osmosis salt interception showed that the PGA@ZIF-8 crystal layer membrane had the ability to intercept all four different inorganic salts.(3)A self-assembly method was used to form a metal-polyphenol network coating on the surface of the nanofiber membranes to give the nanofiber-based membranes abundant reactive sites,and then the MOFs crystals are grown on the surface to obtain MOFs composite membranes with oil-water separation properties.The oil-water separation results showed that the retention rate of the composite membrane was above95% for all four different organic phases.Subsequent cycling tests also demonstrate that the membranes have good resistance to contamination.