Study On The Preparation And Properties Of Janus Membranes With Unidirectional Transport Characteristics

Oily sewage has become an urgent problem to be solved in our daily life because of its huge discharge and potential harmfulness.Due to its unique liquid transport characteristics,Janus membrane has attracted more and more attention in the fields of oil/water separation and intelligent control.However,most of the current methods for preparing Janus membrane involve complex operations and have low efficiency,which hinders the wide application of Janus membrane.In this paper,two simple methods are proposed to prepare Janus membrane with asymmetric wettability on both sides.Using hydrophilic cotton cloth as the base material and adopting the strategy of liquid/liquid interface limited surface engineering,Janus membrane was constructed with the aid of mussel-inspired chemistry.The polydopamine-coated cotton cloth placed at the oil-water interface reacts with octadecylamine molecules in the oil phase at the oil-water interface to achieve the unilateral hydrophobic modification of cotton cloth.The results show that the prepared fabrics have asymmetric chemical properties,wettability and surface morphology.The phenomenon of droplet transport at the oil/water interface verifies the unidirectional water transport characteristics of Janus membrane.In addition,the collector made of our Janus membrane successfully demonstrated the remarkable ability to collect water from the oil/water mixture.Under optimized conditions,Janus membrane realized the separation of oil-in-water emulsion.The permeation flux reached ca.20.8 L m^-2 h^-1 with an oil rejection of 99.6%during the gravity-driven emulsion separation.In addition,both heavy oil/water interface and light oil/water interface can realize the preparati on of Janus membrane with water unidirectional transport characteristics.The electrospinning polyvinylidene fluoride?PVDF?layer was used as a hydrophobic layer on the oxidized super hydrophilic copper mesh substrate by means of electrospinning technology to prepare Janus membrane with water unidirectional characteristics.On the hydrophobic stainless steel net,the electrospinning hydrophilic layer-polyacrylonitrile?PAN?on the front and the electrospinning hydrophobic layer-polyvinylidene fluoride?PVDF?on the back achieved the preparation of oil unidirectional Janus membranne.The results showed that the concentration of spinning solution had a great influence on the morphology and wettability of Janus membrane.The prepared water unidirectional Janus membrane can be used for collecting water droplets from oil;The prepared oil unidirectional Janus membrane can be used for surface oil collection.In addition,this method has universality.Electrospinning PVDF on hydrophilic substrate and electrospinning PAN on hydrophobic substrate can prepare Janus membrane with wettability difference on both sides.