Study On Separation Of Oil-water Emulsion By Melt Differential Electrospun Nanofiber Membrane

In order to improve recovery efficiency,oilfields entering the late stage of development usually adopt techniques such as enhanced water injection to maintain reservoir pressure and greater driving force,which makes crude oil water emulsified and water is difficult to separate.As a method of preparing continuous polymer nanofibers,electrospinning technology provides a new opportunity for the preparation of polymer films.The porous structure,high permeability and special surface properties of electrospinning nanofiber membranes have great application potential in water-in-oil emulsion separation.A single fiber membrane layer cannot effectively separate complex emulsions,so the preparation of membrane layers with corresponding functions according to the emulsion separation mechanism is the current research focus.To this end,this paper designed a composite multi-stage nanofiber membrane,including a coalescence layer and a lipophilic and hydrophobic separation layer.And according to the needs of different layers,choose different additives,adjust their addition ratio and process conditions,and successfully prepare a green and efficient separation membrane.The specific research contents are as follows:(1)The oil-water emulsion is separated by melt differential electrospun polylactic acid(PLA)nanofiber membrane.When the spinning voltage is 40kV,the spinning distance is 70mm,the spinning temperature is 240?,and the receiving time is 3min,the oil flux under the gravity drive reaches 1054 L/m2·h,and the separation efficiency reaches 90.4%.At the same time,the prepared PLA nanofiber membrane was hydrophilically modified on the dopamine coated surface,and its water contact angle decreased from 128° to 26°,which was super hydrophilic.The hydrophilic PLA fiber membrane can effectively carry out demulsification coalescence,and the average size of water droplets in the water-in-oil emulsion increases from 2.7?m to 25.2 ?m.It can be used as the outermost nanofiber coalescence layer of the differentiated multi-stage composite nanofiber membrane.(2)Adding hydrophobically modified nano-silica particles into degradable PLA for melt blending to prepare nanofiber membrane by electrospinning can improve the tensile strength of PLA fiber membrane and the hydrophobic performance of the fiber membrane.When the spinning voltage is 40kV,the spinning distance is 70mm,the spinning temperature is 260?,and the silica mass fraction is 6%,the water contact angle of the prepared fiber membrane is 138°,and the oil contact angle reaches 30°.At the same time,the tensile strength of the fiber is increased to 48.9MPa compared with the pure PLA fiber.It can be used as the intermediate supporting separation layer of the differentiated composite multi-level structure nanofiber membrane.(3)In order to further improve the separation efficiency,adding silicone oil to the PLA fiber for blending modification can effectively reduce the viscosity of the PLA material.Studies have shown that the average diameter of fibers prepared at a spinning distance of 70 mm,a spinning voltage of 40 kV,a spinning temperature of 240?,and a silicone oil mass fraction of 4%is 480 nm,a water contact angle of 142°,good hydrophobic properties,and fiber membrane pore The concentrated distribution of 5?7?m can effectively intercept the smaller water droplets in the water-in-oil emulsion,and the rejection rate of the water droplets in the water-in-oil emulsion reaches over 95%.It can be used as the ultrafine separation layer in the inner layer of the differential composite multi-level structure nanofiber membrane.In summary,the above-mentioned three kinds of fiber membranes can satisfy the surface coalescence and demulsification,the inner layer is efficiently separated,and has a higher strength composite multi-stage fiber membrane.