Morphology manipulation with dual solvent constructing sandwich-structure in PA66 nanofiber membrane enables efficient air filtration and oil-water separation

With the rapid industrial development, massive untreated polluting gases are discharged, causing irreversible environmental damage. Membrane filtration technology efficiently removes airborne pollutants, and preparing high-performance filter materials via structural adjustment offers a simple solution. In this work, the Polyamide 66 (PA66)/ Formic acid (FA) spinning solution, characterized by high viscosity, electrical conductivity, and relatively low surface tension, facilitates the fabrication of nanofibers with a diameter of merely 166 nm, rendering it an efficient intermediate filter layer. Conversely, the PA66/ 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) spinning solution yields a thick filament layer with a diameter of 638 nm, which imparts mechanical properties to the sandwich-structured nanofiber membranes on both lateral sides. The resulting sandwich structure membrane exhibits exceptional filtration performance, achieving a PM 0.3 capture efficiency of 99.5 % with a low-pressure drop of 63 Pa. After multiple air-filtration cycle tests, the membrane maintains stable filtration performance, demonstrating great potential in air filtration applications. Additionally, the oil-water separation effect can reach 99.79 % with water flux of 6534 L·m⁻²·h⁻¹ , which could be maintained after multiple cycle tests. This study presents a simple and effective approach to control the microstructure of nanofiber membrane, achieving eminent filtration performance and oil-water separation.