Downhole oil–water separation (DOWS) is a new type of oil recovery technology to overcome water treatment constraints. However, the existing technologies have deficiencies in terms of cost, efficiency, and complexity. Superwettability membranes have excellent separation performance, whereas the conventional superwettability membranes are hydrophobic-lipophilic. When encountering high viscosity oil, the holes on the membrane are easily blocked, resulting in the failure of separation. Herein, we report superhydrophilic-superoleophobic nanoparticles based on poly (diallyldimethylammonium chloride), perfluorooctanoate acid, and fumed silica. Two kinds of oil-water separation membranes with the function of "oil blocking and water passing" were prepared by a simple spray coating on circular hole mesh and tapered hole mesh. The proof to the surface wettability, microstructure, separation mechanism was studied by contact angle measurement, scanning electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, etc. And the separation process of the superwettability membrane was investigated by an indoor simulation DOWS device. The results indicate that the surface formed by the nanoparticles exhibits superhydrophilic-superoleophobic in air. The contact angle of oil reaches 153°, and that of water is close to 0°. The surface is covered with nano-micron rough structures, which and the perfluorocarbon chain together promote the superhydrophilic-superoleophobic property.Both circular hole separation membrane and conical hole separation membrane can filter and separate oil/water mixture with high viscosity and high salinity at 50°C, and the separation efficiency exceeds 90%. Compared with the circular hole, the circular hole structure presents the performance of rapid separation. This filtration membrane based on superhydrophilic-superoleophobic nanoparticles might have potential application in downhole oil–water separation.

New filtration method based on superhydrophilic-superoleophobic nanoparticles for downhole oil-water separation

ACS Fall 2021

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