Encapsulating Amidoximated Nanofibrous Aerogels within Wood Cell Tracheids for Efficient Cascading Adsorption of Uranium Ions

Continuous filtering adsorption has drawn the growing interest to explore the uranium resource in seawater or depress the environmental risks of uraniferous wastewater from nuclear industries.For most of filtering adsorbents, repeated filtration, high membrane thickness and high pressure were normally essential to achieve both the high rejection ratio and filtration flux.Herein cellulose fibrils were preferentially exfoliated from the lignin-poor layer of secondary cell walls of balsa wood during an in-situ amidoximation process.With the maintaining honeycomb-like cellular microstructures and cellulose aerogel stuffing in their cell tracheids, the resultant woods showed superior mechanical properties (e.g., compressive strength ~1.3 MPa in transverse direction) with large surface area (~80 m 2 g -1 ).When aligning their cell tracheids perpendicular to the flow and sealing the edge with a thermoset polymer, they could serve as efficient and high-pressure filtration membranes to capture aquatic uranium ions.In analogue to a typical cascading filtration, the filtrate passed successively the layered-organized cell tracheids through abundant micropores on their cell walls, enabling a high rejection ratio of >99% and flux of ~920 L m -2 h -1 under the pressure up to 6 bar (membrane thickness of 2 mm).Thus, this study not only provides an in-situ approach to producing robust woods with functional nanocellulose encapsulated into their cell tracheids, but also offers a sustainable route for high-efficiency extraction of aqueous uranium.