Fabrication and performance of a stable micro/nano composite electret filter for effective PM_2.5 capture

Airborne particulate matter (PM) pollution has raised serious concerns over both the global climate and public health. Therefore, there is an urgent need for air filters of high-efficiency and energy-saving. Pore structure optimization and electret enhancement are feasible means to improve their filtration performance. Herein, a novel sandwich-structured electret composite filter with a low pressure drop and robust filtration stability was successfully designed and fabricated. The composite filter was composed of fluffy PS microfibers with large electric resistivity and high porosity, and PAN nanofibers with high polarity and small pore size. Benefiting from the fluffy structure constructed by electrospinning at the right humidity, the tortuous pore channels created by the appropriate mixing of microfibers and nanofibers, and the abundant static charges generated by the hybrid of polar and nonpolar polymer materials, the PS/PAN/PS composite filter possessed a high filtration efficiency of 99.96% for particles of 0.30 μm, a low pressure drop of 54 Pa and a satisfactory quality factor value of 0.1449 Pa^-1 at an airflow velocity of 5.3 cm/s. In particular, the composite filter exhibited better electret stability and PM_2.5 loading performance than the commercial ones, which guarantees its long-term storage and usage.