Highly Compressible Wood Sponges with a Spring-like Lamellar Structure as Effective and Reusable Oil Absorbents

Abstract

Aerogels derived from nanocellulose have emerged as attractive absorbents for cleaning up oil spills and organic pollutants due to their lightweight, exceptional absorption capacity, and sustainability. However, the majority of the nanocellulose aerogels based on the bottom-up fabrication process still lack sufficient mechanical robustness because of their disordered architecture with randomly assembled cellulose nanofibrils, which is an obstacle to their practical application as oil absorbents. Herein, we report an effective strategy to create anisotropic cellulose-based wood sponges with a special spring-like lamellar structure directly from natural balsa wood. The selective removal of lignin and hemicelluloses via chemical treatment broke the thin cell walls of natural wood, leading to a lamellar structure with wave-like stacked layers upon freeze-drying. A subsequent silylation reaction allowed the growth of polysiloxane coatings on the skeleton surface. The resulting silylated wood sponge exhibited high mechanical compressibility (reversible compression of 60%) and elastic recovery (∼99% height retention after 100 cycles at 40% strain). The wood sponge showed excellent oil/water absorption selectivity with a high oil absorption capacity of 41 g g–1. Moreover, the absorbed oils can be recovered by simple mechanical squeezing, and the porous sponge maintained a high oil-absorption capacity upon multiple squeezing-absorption cycles, displaying excellent recyclability. Taking advantage of the unidirectional liquid transport of the porous sponge, an oil-collecting device was successfully designed to continuously separate contaminants from water. Such an easy, low-cost, and scalable top-down approach holds great potential for developing effective and reusable oil absorbents for oil/water separation.

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

“…Scale bar: 500 and 500 nm. b–d) Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…Oil–water separators are generally porous meshes, foams and sponges made from a wide range of materials, including metal, polymers, ceramics, fabrics, cellulose‐based derivatives, particles, and novel nanomaterials . Recently, Wang et al reported a highly compressible wood sponge with spring‐like lamellar structure (Figure b–d), which was fabricated by sequential chemical treatment, freeze drying and chemical vapor deposition of natural balsa wood. After silylation treatment, the original amphiphilic wood sponge became hydrophobic, which ensured the selective absorption of oil.…”

“…[201] Based on the principles mentioned above, novel materials were invented and fabricated as proof-of-concept. Oilwater separators are generally porous meshes, foams and sponges made from a wide range of materials, [202,203] including metal, [204][205][206] polymers, [207,208] ceramics, [209,210] fabrics, [211,212] cellulose-based derivatives, [213,214] particles, [215,216] and novel nanomaterials. [86,217,218] Recently, Wang et al [213] reported a highly compressible wood sponge with spring-like lamellar structure (Figure 13b-d), which was fabricated by sequential chemical treatment, freeze drying and chemical vapor deposition of natural balsa wood.…”

“…b-d) Reproduced with permission. [213] Copyright 2018, American Chemical Society. e) Schematic illustration of the fabrication and hierarchical structure of the superhydrophobic foam.…”

Biomass‐Derived Lignocellulosic Graphene Composite: Novel Approach for Removal of Oil and Organic Solvent

“…had introduced biomaterials like barley straw, flax straw, wheat and oat straws for adsorption of oil showing oil sorption capacity less than 7 g/g. [24] Also there were reports about the use of lignin-cellulosic sponge material for the absorption of oil and organic solvents from water, but the synthesis of such lignin based materials requires multistep procedures and by the use of harsh chemicals like NaClO 2 , [25] silane, [25] fluorinating [26] agents etc. Hence the feasibility and sustainability of the process are missing.…”