Self-cleaning superhydrophobic aerogels from waste hemp noil for ultrafast oil absorption and highly efficient PM removal

Environmental pollution and resource waste are two major concerns with the development of civilization. During hemp fiber separation short fiber noil is produced as a waste. This paper demonstrates the reuse of waste hemp noil by dissolution in a precooled NaOH/urea system to form porous aerogels. After hydrophobization, the hemp aerogels exhibited self-cleaning ability and could be used for oil adsorption and air purification. The superhydrophobic hemp aerogels exhibited elastic behavior with 75 % recoverable strain after 10 cycles of compression. The high porosity and compressibility endowed hemp aerogels with excellent oil absorption capacity and reusability. With a fiber concentration of 1.5 %, the hemp aerogel could achieve an oil removal of 29.4 times of its own weight, whilst 85.4 % of the initial absorption capacity remained after 10 absorption/desorption cycles. The ultrafast oil absorption was completed within 0.048 s. The oil contaminated hemp aerogel could be self-cleaned in an ethanol solution. The hemp aerogels also had high removal efficiencies of particulate materials (PM) such as PM2.5 and PM10 at both 94 %. The remodeled waste hemp noil showed great potential in environmental governance and recycling of natural resources.