Experimental Research On Oil-water Separation With Super-Hydrophobic Membrane

With the development of modern industry and ecological civilization construction,the efficient treatment of oily wastewater has attracted attention and it is urgent to seek an efficient energy-saving oil-water separation method.With stainless steel mesh and porous plate as substrate respectively,polytetrafluoroethylene and polyphenylene sulfite as main coating materials,the super-hydrophobic separation membranes were prepared by spraying-plasticizing method successfully.Firstly,the surface morphology and properties were investigated.It is shown that,innumerable polytetrafluoroethylene microscale spherical particles and nanoscale sticks on these particles evenly distribute on the membrane surface and constitute the rough surface with micro-nano hierarchical structure.As a result,the separation membrane shows wonderful super-hydrophobic and super-oleophilic property and the static contact angle for water on this membrane is up 156.5°,the angle for diesel is about 0°.Besides,the super-hydrophobic membrane has uniform thickness,strong adhesive force and wonderful corrosion resistance.Secondly,the super-hydrophobic plate membrane and mesh membrane were installed respectively into the oil-water separator to test its oil-water separation capacity and investigate the effects of different operating conditions on separation efficiency.The results show that,for both types of membranes,the oil permeation flux raises with the increase of separation pressure.As the operating time goes on,the separation effects reach a steady state gradually.The oil-water mixtures with the initial oil content of 20 g/L were separated by 400 and 500 mesh membrane,the residual oil content in output water as low as 9 mg/L and 14 mg/L respectively;separated by average pore size 15 μm and 45 μm plate membrane,as low as 15 mg/L and 20 mg/L.With the increase of initial oil content,the separation efficiency declines slightly,but on the whole,it is less significant and the separation efficiency always remains above 99%.The oil-water mixture flowrate has less significa nt effect on the separation efficiency of super-hydrophobic mesh membrane,but efficiency of plate membrane declines with the increase of oil-water mixture flowrate.For both types of separation membranes,the effect always improves with the increase of separation pressure and stage.Comparing the separation capacity of mesh membrane with plate membrane,it is found that they have own advantages and disadvantages.We should select the proper separation component depending on specific conditions in a practical application.Finally,the mechanism of oil-water separation based on super-hydrophobic membrane was briefly analyzed.Based on the wettability difference of oil and water on the super-hydrophobic surface,both of oil and water have different permeation pressure.Once the proper operating pressure is provided,the oil droplet can penetrate through the separation membrane while the water can’t,so as to realize the separation of oil and water.This study could build up experimental experience for the technical innovation of oil-water separation.