Studv On Preparation And Application Of Janus Micro-nano Fiber Membrane

With the development of industry and the improvement of human living needs,a large amount of oily waste water is discharged into nature,which has caused great harm to human health and the ecological environment.Therefore,how to separate oil and water mixture effectively has attracted great attention.The traditional oil-water separation method has a low separation rate,high energy consumption,and complicated operation.In view of the shortcomings of the traditional oil-water separation method,it is urgent to find a green,low energy consumption and high separation rate method for oil-water separation.As a simple and energy-saving separation method,the membrane separation method has been widely used in various fields.As a derivative of the separation membrane,the Janus membrane has great prospects in fluid manipulation and separation purification.However,at present,the application of the Janus membrane is restricted by the complicated preparation process and high cost,which seriously affects the application and development of Janus membrane.This work focused on the preparation of micro/nano fiber membranes by electrostatic spinning and centrifugal spinning,Janus fiber membrane was prepared by compounding hydrophilic and hydrophobic fiber membrane or surface modification of fiber membrane,and explored its oil-water separation performance.Firstly,a superhydrophobic PVDF fiber membrane carrying nano-SiO2 was prepared by centrifugal spinning.The PVDF fiber membrane prepared by centrifugal spinning is used as the substrate to receive the electrospinning CA.The obtained composite membrane is used for oil-water separation after hot pressing.The effects of spinning parameters of electrospinning CA on fiber morphology were investigated experimentally,and the oil-water separation performance of the composite membrane was investigated.The oil-water separation experiments showed that the prepared superhydrophobic/hydrophilic Janus-PVDF/CA fiber membrane could achieve high-efficiency separation of both water-in-oil emulsion and up water and down oil layered mixture,the retention rate of the water phase is 99.02%±0.84%and 98.81%±0.97%.Secondly,the one side of the PVDF fiber membrane obtained via centrifugal spinning was modified by hydrophilic dopamine to prepare the directional fluid transport Janus-PVDF.Moreover,the superhydrophobic/hydrophilic Janus-PVDF was prepared by plasma grafting hydrophobic octamethylcyclotetrasiloxane(D4)into a single-sided of the PVDF fiber membrane and hydrophilic modification with dopamine on the other side.The effects of the experiment variate of plasma conditions and the dopamine coating amount on the surface morphology and wetting properties of fiber membranes were investigated were studied.The surface structure of PVDF fiber membranes before and after modification was characterized by infrared,X-ray photoelectron spectrometer(XPS)and energy dispersive X-ray spectrum(EDX).The results show that D4 and dopamine were successfully grafted on the surface of PVDF fibers.The oil-water separation experiments show that the superhydrophobic/hydrophilic Janus-PVDF fiber membrane could effectively retain the water phase both in emulsion and up water and down oil layered mixture,and their retention rates can reach 98.52%±1.12%and 98.53%±1.31%.The directional fluid transport Janus-PVDF fiber membrane can retain the water phase of up oil down water layered mixture.The oil retention rates of the directional fluid transport Janus-PVDF can reach 98.61%±1.23%.In addition,compared with the Janus-PVDF/CA,the membrane flux of the directional fluid transport Janus-PVDF remains almost unchanged.Finally,the CA fiber membrane spun by centrifugal spinning was grafted with D4 on one side by plasma technology to prepare superhydrophobic/hydrophilic Janus-CA and directional fluid transport Janus-CA fiber membranes.The influence of spinning parameters on the morphology of the CA fiber membrane and the influence of plasma treatment time and power on the surface morphology and wettability of the prepared Janus-CA fiber membrane were investigated.The surface chemical structure of the CA fiber membrane before and after modification was characterized by infrared,XPS,and EDX.The experimental results showed that D4 was successfully polymerized on the surface of the CA fiber membrane.The results of oil-water separation showed that the superhydrophobic/hydrophilic Janus-CA could effectively retain the water phase of emulsion and up water and down oil layered mixture,with the retention rates of 98.81%±0.97%and 98.76%±1.05%,respectively.The oil retention rates of the directional fluid transport Janus-CA reach 98.73%±1.09%when the mixture is up oil down water layered mixture.The flux of the constant guide wet Janus-CA membrane for separating the aqueous phase remains almost constant.Compared with the other two methods,the preparation of Janus-CA is simple and the membrane flux is high.When the directional fluid transport Janus-CA was used to retain the water phase,it's membrane flux remains almost unchanged.The experimental preparation of Janus micro-nano fiber membrane has great potential value in the fields of oil-water separation and constant wetting.