Enhancement of wastewater treatment by underwater superelastic fiber-penetrated lamellar monolith

During the removal of pollutants from wastewater, the underwater compressibility of three-dimensional biomass materials is the main factor determining their properties and service life. To construct a chitosan (CS)-based material with underwater superelasticity, a bidirectional freezing technique was used to introduce bamboo fibers (BFs) as bridges between CS lamellae to form a biomimetic CS/BFs monolith with an architecture similar to Thalia dealbata stems. BFs completely penetrated CS lamellae from the top down, which served as springs to dampen the elastic deformation during compressive cycles. After 10,000 underwater compressive cycles at 60% strain, the plastic deformation was negligible, and after 100 cycles at 90% strain, the monolith retained 93.8% of the maximum stress. Moreover, the CS/BFs monolith was loaded with CaCO3 nanoparticles via compression-release-compression to obtain a CS/BFs/CaCO3 monolith that exhibited excellent water purification capabilities. The CS/BFs/CaCO3 monolith removed water-soluble dyes, heavy-metal ions, and emulsified oils from water with a high separation efficiency by simple squeezing and pumping methods. The novel pumping technology using the CS/BFs/CaCO3 monolith provides a facile and rapid method to separate oil-in-water emulsions (maximum water flux of 11,776.9 L m−2 h−1). Therefore, the CS/BFs/CaCO3 monolith with underwater superelasticity has great potential applications for wastewater treatment.