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

• Waste hemp noil was reassembled into aerogels and used as absorbance. • The hemp aerogel achieved an oil removal of 29.4 times of its own weight. • The ultrafast oil absorption was completed within 0.048 s. • The oil contaminated hemp aerogel could be self-cleaned in ethanol solution. • The hemp aerogel achieved high removal efficiency at 94 % of particulate materials. 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 PM 2.5 and PM 10 at both 94 %. The remodeled waste hemp noil showed great potential in environmental governance and recycling of natural resources.