Application Of Asymmetric Wettability Janus Membrane In Oil-water Separation

Aiming at the problems of serious oil-water emulsification and low oil-water separation efficiency in offshore oil spills and oil spill accidents,this paper proposes to construct a Janus membrane with asymmetric wettability to achieve efficient oil-water separation and oil recovery.The method of combining experimental research and mechanism analysis analyzes the influence of the basic properties of the prepared Janus membrane on the oil-water separation effect.Through the mechanical analysis of droplets at different stages of the Janus membrane surface,the mechanism of Janus membrane capable of efficient oil-water separation is revealed,which provides a new method for efficient recovery of offshore oil spills and rapid repair of the marine environment.Firstly,the Janus membrane with asymmetric wettability was prepared by unilateral spraying method using polyvinylidene fluoride(PVDF)membrane as substrate,and the basic properties of Janus membrane were investigated.Secondly,the prepared Janus membrane was used to simulate the separation experiments of oil slick and oil-in-water emulsion.The membrane flux,oil-water retention rate and recycling of the prepared Janus membrane in oil-water separation were studied by the conditions of membrane thickness,pore size and oil properties.Finally,the preferred Janus membrane was prepared into a barrel shape,and the performance and practicability of the’one-way oil gathering water resistance’and’one-way drainage water storage’of the barrel Janus membrane in oil-water separation were explored.Through the analysis of the mechanical model of droplets at different stages on the membrane surface,the internal mechanism of Janus membrane capable of efficiently treating oil-water mixtures was revealed.The results show that:(1)The surface wettability of the prepared Janus membrane is asymmetric,one side is hydrophilic and underwater oleophobic,and the other side is lipophilic and hydrophobic.(2)The oil-water separation flux and oil-water retention rate of Janus membrane increased first and then decreased with the increase of spraying density.The Janus membrane with a pore size of 0.45μm and a spray density of 0.08 ml/cm~2showed excellent oil-water separation performance for both floating oil and oil-in-water emulsions.The membrane flux for separating floating oil reached 2292.99±69.3 L/m~2·h,and the oil-water rejection rates were 98.91±0.087%and 99.86±0.068%,respectively.(3)The prepared bucket Janus membrane has considerable separation effect,oil storage effect and practicability for oil-water mixture.The oil collection efficiency is 97%and the oil discharge efficiency is 98%.(4)Based on the influence of the asymmetric wettability of the membrane,the change of the force of the droplets in the pores of the Janus membrane will lead to membrane penetration,membrane obstruction and demulsification.The liquid phase after oil-water separation will aggregate to form a’liquid film’covering the membrane surface and form a’gate’control channel,so that the barrel-shaped Janus membrane has the advantages of efficient oil-water separation and oil recovery.