Inorganic salt-infused transparent nanofiber filters: A new approach to high-efficiency particulate matter removal via electrospinning

Although electrospun filters show promise for capturing particulate matter (PM), their application in windows, which rely on pressure differentials between indoor and outdoor environments, is hindered by low efficiency for PM <2.5 μm and resulting pressure drops. Enhancing the attractive forces on electrospun fibers through material engineering is often complex and expensive, and transparency is crucial for window filters. This study aimed to develop a straightforward method by blending polyacrylonitrile (PAN) with potassium iodide (KI) salts that dissolve easily and possess a high dipole moment (10.2D). Distinctive characteristics of KI facilitate the production of high-performance PM filters with exceptional transparency. Increasing KI loading during electrospinning resulted in a filter with 0.5 M KI, demonstrating a PM removal efficiency of 88.20 % and 90 % transmittance, surpassing the efficiency of pure PAN filters (72.81 %) by 16 %. The pressure drop was low (2.8 Pa), within the typical range of indoor-outdoor differentials, and the quality factor was notably higher at 0.76 Pa⁻¹. KI also served as a plasticizer, enhancing fiber connectivity and preserving nanostructures under weathering stress. After a 100-hour test, the filter retained its high efficiency and transparency. Therefore, PAN/KI electrospun filters are excellent for window applications and easy to produce commercially.