Sandwich structured chitosan-aerogel nonwoven filter with asymmetric wettability and pore size differences for high-efficient oil-mist filtration

The removal of oil mist is essential for industrial process and worker's occupational health, as the oil mist will not only damage the industrial production device, but also increase human inhalation exposure risk. Traditional filters focus on high-efficiency low-resistance structured design for air filtration, while there is little research on cyclically sustainable filters for oil-mist filtration. Here, we developed a chitosan aerogel based on sustainable sandwich structure filter (NW-CS-Nylon 6) with thickness-direction asymmetric wettability and pore size differences, including polypropylene nonwoven fabric, chitosan aerogel and Nylon 6 nanofibrous membrane. Spray-coating was used to endow the Nylon 6 nanofibrous membrane with oleophobicity, and provide the whole filter with directional oil-transport function. Results revealed that the initial filtration efficiency and pressure drop of the oil-mist was 99.4%, 0.5 kPa, respectively. Remarkably, the ultra-high filtration efficiency of 99% and 98% was still maintained when the filtration was carried out for 50 and 100 times. Compared with traditional filters, it had higher filtration efficiency and lower pressure drop when continuously recycled, which had important research significance for filter recycling and energy saving in the future.