Research On The Preparation Of Porous Surface And The Air-liquid Interface Spreading Behavior Driven By Phase Separation

In recent years,the environmental pollution caused by frequent oil spills has become more and more serious,causing great damage to human beings and the entire ecosystem.To adsorb the spilled oil,it is necessary to create a high-performance adsorption material.In the domain of petroleum adsorption,porous materials with large specific surface areas and high porosity possess significant benefits.Therefore,the focus of research in this area has turned to the controlled fabrication of porous structural materials with high specific surface area and good adsorption ability.Porous adsorption materials still struggle with issues including ineffective preparation,excessive energy utilization,and poor oil absorption capability.The preparation of porous surface materials employing mass-transfer-induced phase separation technology is studied in this study in light of the above challenges,and a method for "Patchy structure"surface preparation is presented.The porous surface can be obtained by curing and drying the"Patchy structure".The formation mechanism of the "Patchy structure" surface was discussed,and the porous structure nanofiber membrane material was prepared by electrospinning technology.The main contents are as follows.First,in order to prepare a porous structure surface,a Patchy structure surface preparation method based on mass-transfer-induced phase separation technology was proposed.The phase separation system was composed of PEGDA 700,glycerol and ethanol.Monodisperse droplets were prepared by a single-phase driven microfluidic chip.When the droplets are contacted with liquid paraffin,due to the interfacial tension between the droplets and liquid paraffin,the droplets are suspended at the air-liquid paraffin interface and spontaneously formed the airdroplet interface.At the same time,ethanol volatilizes rapidly and forms a Patchy structure at the air-droplet interface.By adjusting the volume ratio of PEGDA 700 to glycerol,the concentration of the surfactant Span 80,and the concentration of anhydrous ethanol,a surface with different morphologies can be achieved.According to the experimental results,a Patchy structure will emerge on the surface when the ratio of monodisperse droplet QPEGDA:Qglycerol=1.The conditions for the formation of the air-droplet interface were analyzed by the interfacial tension balance method.Finally,the Patchy structure surface was crosslinked and polymerized by ultraviolet light to prepare a porous surface.By examining the surface microstructure,the morphology of the air-droplet interface phase separation process was confirmed.Then,to study the formation mechanism of the Patchy structure at the air-drop let interface,the spreading behavior of the air-liquid interface is revealed by integrating the spreading coefficient theory and the fluid mechanics theory.The spreading coefficient of each phase was calculated to verify the correlation between surface morphology and the spreading coefficient.The spreading coefficient theory based on the air interface was established:when the intermediate phase is air and the spreading coefficients of the three phases are all less than 0,the Patchy structure would be formed.In order to verify the hypothesis of the spreading coefficient at the air interface,the patchy structure droplets were produced in an air environment,and the microparticles with porous surfaces were created by UV crosslinking curing.Finally,the ethanol volatilization rate of the droplet at the air-droplet interface and the liquid paraffinliquid interface was calculated,and the evaporation-driven floating droplet model was established.The occurrence of capillary flow and Marangoni flow in the droplet was analyzed,and the conditions for the formation of the Patchy structure at the air-droplet interface were explored based on fluid mechanics.Finally,the phase separation system of PVDF/DMAc/deionized water was explored based on the modified spreading behavior theory.By using the mass transfer phase separation technique and electrospinning,the porous PVDF nanofiber membrane was constructed.Using PVDF as a solute,DMAc and deionized water as the solvent,the three-phase spreading coefficient of the air-liquid interface in the spinning process was calculated to verify the spreading behavior of the air-liquid interface.The effects of solution concentration and solvent composition on the morphology of nanofibers were investigated,and the optimum process parameters of porous fibers were determined:CPVDF=12wt%,CH2O=1wt%.The reason why porous PVDF nanofibers can be used in oil adsorption applications was analyzed by the theory of wettability and interfacial energy per unit area.The porosity and adsorption capacity of the surface porous fiber membrane were characterized.When 12 wt%PVDF and 1 wt%deionized water were added,the specific surface area,porosity,and adsorption capacity of the porous nanofiber membrane reached the maximum,were 50.81 m2/g,89.6347%and 8.4387 g/g,respectively.