Water-/Oil-Repellent Polyacrylonitrile Nanofiber Air Filter Modified with Silica Nanoparticles and Fluorine Compounds

Highly efficient particulate matter (PM) filter membranes with good resistance to wetting are highly desirable given the negative environmental impact of increasing PM pollution. In this study, a self-cleaning and PM-filtering fibrous membrane (F-SAPAN) was prepared by attaching silica nanoparticles (SiNPs) on the surface of modified polyacrylonitrile using a sol–gel approach and then adding a low surface energy 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FOTS) coating. The SiNPs were generated by the hydrolysis of tetraethyl orthosilicate and could be readily loaded on the surface of the fiber, thanks to hydrogen bonding. In this way, fibrous membranes with a uniform covering of SiNPs could be prepared in large quantities in a short time. The modification of SiNPs by FOTS endows the fibrous membrane with excellent water and oil resistance (a water contact angle of up to 156° and an oil contact angle of up to 144°), and the free-rolling of water droplets can be achieved on a slope of only 6°. The membrane is only 0.03 mm thick and displays excellent filtration efficiency (>99.9%) and pressure drop (366.4 Pa) for PM1. The membranes also display good flexibility, mechanical properties, corrosion resistance, and antiash properties and prove to be a reliable material for PM filtration in complex environments.