Sandwich-structured fibrous membranes with low filtration resistance for effective PM2.5 capture via one-step needleless electrospinning

Abstract

The airborne particulate matter has received much attention over the past 20 years because it has become the ninth largest preventable cause of disease in the global population. Therefore, there is a requirement for cost-effective air filters with excellent performance. Electrospun nanofiber membranes are emerging as one of the most versatile air filters for their small pore size distribution. However, it has proven to be extremely challenging to achieve a balance between low filtration resistance and high removal efficiency. Usually, small fiber diameter increases filtration efficiency but this is coupled with high-pressure drop irrespective of the particle size, so negatively influencing quality factor (QF). Herein, a low filtration resistance sandwich structured polyacrylonitrile (PAN) fibrous filters were fabricated through a controlled accumulation of bimodal sized fibers (172 ± 21 nm and 772 ± 118 nm) by alternate needleless electrospinning. The composite membrane possessed a heterogeneity structure and decreased package density, maintaining the same pore size with narrow distribution compared with the membrane consisting of single sized nanofibers. Consequently, the resulting sandwich structured filter after electrostatic removal demonstrates a lower filtration resistance (151.9 Pa) and competitive filtration efficiency (99.89%) to 260 nm mass median diameter sodium chloride (NaCl) aerosol particles compared with the nanofibers structured filter (207.76 Pa, 99.92%) under an airflow velocity of 32 L min−1. Moreover, the composite exhibited the highest QF, as well as excellent mechanical properties and good transmission. Furthermore, the productivity of sandwiched-structure membranes about 20 g h−1, which was several hundred times than traditional electrospinning, offered prospects for industrial production and commercial application. The present investigation may provide a feasible strategy for further improving and optimizing the comprehensive performance of electrospun filters.