Synthesis and filtration properties of polyimide nanofiber membrane/carbon woven fabric sandwiched hot gas filters for removal of PM 2.5 particles

• Polyimide nanofiber membrane/carbon woven fabric composite hot gas filters were developed.
• The maximum filtration efficiency of this novel filter could reach 99.995% for PM 2.5.
• The filters could maintain reasonable filtration performance after 7 filtration cycles with repeated back air flushes.
• After heat treatment at 260 and 300 °C, this composite filter shows a relatively high filtration efficiency.

In this work, hot gas filters composed of polyimide nanofiber membrane sandwiched between carbon woven fabrics are fabricated to capture fine particles of PM 2.5 level. Polyimide (PI) nanofibers with an average diameter of 190 nm are electrospun on supporting carbon fabrics as filtration layers. The filtration performance tests show that the maximum filtration efficiency reaches 99.99% for PM 2.5, while the maximum pressure drop is only 251.86 Pa after continuously testing for 25 min under a constant flow rate of 20 L/min. As the areal density of the PI nanofiber membrane increases, the filtration efficiency increases first and then levels off when the areal density reaches 11.64 g/m2. In regeneration performance test with back air flush at a pressure of 500 KPa, the composite filter maintains a filtration efficiency of 99.99% and a pressure drop of about 410 Pa. After heat treatment at 260 and 300 °C, the composite filter shows a relatively high filtration efficiency while the tensile strength of the carbon fabric does not change significantly.

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