Preparation Of Highly Resilient Wood Sponge For Oil-Water Separation

The frequent occurrence of oil-spill and the leakage of organic pollutants have caused severe environmental and ecological crisis.Therefore,the oil/water separation has become an emerging and fast rising issue in both the research community and industry.Recently,special wettable 3D porous materials used for the cleanup of oil and organic liquids have received significant research attention.Cellulose aerogels have emerged as cost-effective and environmentally friendly oil sorbents due to their low density,high porosity and sustainability.However,the complicated fabrication procedures and the lack of sufficient mechanical robustness hamper practical application of cellulose aerogel fabricated by bottom-up approaches.This research fabricated highly compressible wood sponges with a spring-like lamellar structure directly from natural balsa via chemical treatment and freeze-drying.（top-down approach）.The as-prepared wood sponge was a potential absorbing material for effective oil/water separation by a subsequent silylation reaction.The main results are as follows:（1）Highly compressible and mechanically resilient wood sponges was prepared directly from natural balsa wood by selectively removing lignin and hemicelluloses via chemical treatment.The extraction of the lignin and hemicellulose resulted in highly porous wood sponges comprised of a cellulose skeleton,with a low density of 30 mg cm^-3 and a high porosity of 98%.The original honeycomb-like structure evolved into a spring-like lamellar structure after chemical treatment.（2）The wood sponge can bear a compressive strain as high as 60%and can completely recover its original shape after stress release,displaying excellent elasticity.A cyclic compression test at 40%strain revealed small plastic deformations with height retention of-93%,highlighting the structural robustness of the wood sponges.The good mechanical compressibility and fatigue resistance of the wood sponge was attributed to its spring-like lamellar structure with numerous large pores between the curved layers,which allow large deformation without localized structural collapse.The wood sponge exhibited obviously anisotropic mechanical properties.The wood sponge was easily crushed when the stress was applied parallel to the stacked layers.（3）A silylation reaction by CVD allowed the growth of polysiloxane coatings on the skeleton surface,which made the wood sponges quite hydrophobic,with a water contact angle of 150°.The wood sponge showed a high oil absorption capacity of 16-41 g/g.More over,the absorbed oils can be recovered by simple mechanical squeezing,and the wood sponge maintained a high oil-absorption capacity upon multiple squeezing-absorption cycles,displaying excellent recyclability.Taking advantage of the unidirectional liquid transport of the wood sponge,an oil-collecting device was successfully designed to continuously separate contaminants from water.