Researches On Super-hydrophobic Membrane And Its Application In Oil/Water Separation

This paper aims to find a continuous, low-energy oil-water separation method. After emulsion breaking and separating with super-hydrophobic membrane, the oily water is separated into water and oil individually.Super-hydrophobic membrane is prepared with spraying and sintering method in this experiment. First, different composition of PPS-PTFE substances is sprayed on micro porous stainless steel plate in multi-way, then it is sintered in 330-350℃. The demulsification membrane is prepared with suction means to attach PPS-PTFE in porous stainless steel plate pores before spraying, and sintering.The water contact angle (CA) and sliding angle (SA) are 153.8° and 10° respectively, and the contact angle of diesel oil is nearly 0°.So the PPS-PTFE composite membrane has good super-hydrophobic and super-oleophilic properties.The membrane’s surfaces are analyzed by SEM. It shows many irregular, layered and micro-mastoids structure on surfaces. It is this structure that the membranes show super-hydrophobic properties. The membrane pore size is at micro level.Super-hydrophobic membrane is used for floating oil and water mixture separation. The results show that the separation effect not only related with the initial oil content in water, but also with the oil-water flow rate and the area of membrane. In three-stage separation device, the area of the separation is fixed, when the mixture flow rate is 10L/h, the initial oil content within a certain range, the oil content in water after the separation is less than 20mg/L; and when the initial oil content is 5g/L, within a certain velocity range, and the final oil content in water is also less than 20mg/L. Super-hydrophobic membrane is used for emulsion ("O/W", emulsifying agent-free) breaking. The results show that the more breaking membranes are, the less emulsified oil in remanent is.Finally, in order to simulate the industrial oily water separation, the mixture of water and oil ("O/W") is stirred, then is pumped to breaking and separating devices for separation. The study shows that with increasing pressure, the breaking flux increases, while the final oil content of water decreases and then increases. For 1000mg/L of a mixture of oil and water, at 70kPa, the final oil content in water samples is minimum with a value of 3 1mg/L, and the flux is 70L/(m2·h).