| A new type of microporous PTFE membrane is successfully made by Multi-layer spraying and high temperature plasticizing method, with a stainless steel substrate and a PPS-PTFE composite coating. The new membrane shows both hydrophobic and oleophilic properties, with contact angle of water more than 120°and that of oil close to 0°. Scanning electron microscope is used to observe the surface structure. It shows a three-dimensional multi-level network structure with high porosity on the surface.The new oil-water separation membrane has good hydrophobic and oleophilic properties. It is able to withstand high pressure without the risk of flooding. The maximum pressure that the membrane can endure increased significantly with the increase of membrane thickness. Membrane with thickness more than 0.30mm can withstand over 20Kpa. The mechanical performance of the new oil-water separation membrane is fine through adhesion and hardness test and it can be applied to a high load oil-water separator.The new membrane is installed on the six-stage oil-water separator to test the separation performances. Orthogonal test is carried out in order to investigate the effect degree of oil, water flow and pressure difference on separation. It shows water flow has maximum influence on the separation effect, followed by oil flow and pressure difference. A series of experiments are carried out to test the membrane effect on the separator. It shows with the number of the separation stage increased the oil content in water decreases gradually. At the same oil and water flow conditions, the higher pressure, the lower oil content in water. Contrasting the data of oil content in water of the separator outlet on different operating conditions, the results show that the smaller water and oil flow rate the lower oil content in water of the outlet, and the higher separation pressure difference the better. In the conditions of water flow 20L/h, oil flow 1.02L/h(40.76g/L) and outlet pressure difference 8.0KPa, oil content in water of the oil-water mixture separated by a six-stage separator can be reduced to 7.31mg/L. The analysis of the separator permeat shows that the water in oil significantly increased with the increase of separation pressure. Oil-water separation membrane will encounter membrane fouling, so the membrane flux will decline. but the rate of decline in membrane flux decreased significantly. The new oil-water separation membrane is considered as Micro-filtration membrane. Membrane pore size and emulsion oil droplets are at a similar size, so it can be used for the separation of emulsified oil. Emulsified oil separation experiment shows the removal rate increase with the increase of initial oil content. Emulsion of initial oil content higher than 20g/L can reach a removal rate of 90%after a membrane separation. At the same time membrane flux is measured, it shows membrane flux decrease with prolonged separation, but the rate is significantly decline.Membrane separation mechanism for both floating oil and emulsion oil is discussed here, the results show that the properties of hydrophobic-oleophilic of materials play a key role for oil-water separation. Surface energy characteristics of hydrophobic-oleophilic materials are analyzed and the the maximum pressure membrane can bear is estimated theoretically.
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