Flexible and robust polyimide membranes with adjustable surface structure and hierarchical pore distribution for oil/water emulsion and heavy oil separation

Highly porous membranes with super-wetting property have been widely researched for oil/water separation. However, most membranes can only be used for a single type of oil-water mixture or emulsion due to their fixed microstructure. Experimental fabrication of multifunctional membranes for efficient separation of various oily wastewater and heavy oil is still a challenge. Herein, flexible and super-hydrophobic polyimide membranes modified by MCNTs and fluorosilane (MCNTs/FPIMs) are innovatively fabricated with adjustable surface structure and hierarchical pore distribution by a versatile and simple phase inversion strategy. Surface corrosion is adapted to adjust the surface pore size by using triethylamine to dissolve the surface dense layer, which aims to construct rough surfaces and effectively increases the oil/water separation performance. The results demonstrate that the hierarchical pore distribution can achieve both high oil/water selectivity and high separation efficiency. The as-prepared FPIMs can realize the rapid gravity-driven separation of light oil (~ 69510 L h^-1·m^-2), oil/water emulsion (~ 895 L h^-1·m^-2), and heavy oil (~ 195 L h^-1·m^-2) by adjusting the surface structure and pore size distribution. The flexible and robust FPIMs with adjustable surface structure exhibit highly efficient oil/water separation performance and reusability, which makes them promising application in practical oil spills and wastewater purification.