Preparation Of Wood-based Superhydrophobic Material And Its Application In Oil-water Separation

With the rapid development of industry,the discharge of oily waste has greatly increased,causing serious damages to ecological environment.In recent years,membrane separation materials have shown broad application prospects in the field of oil-water separation due to their low energy consumption and high efficiency.Because of the advantages of unique porous structure,large specific surface area,and light mass,the natural wood has been widely used to separate oil-water pollutants.However,most of membrane materials have disadvantages such as low separation efficiency,slow speed,and secondary pollution.What’s more,membrane materials are difficult to separate emulsion and crude oil wastewater,which greatly limits their application in practical production.In this paper,bio-based wood was used as the raw material.Through the delignification treatment to enlarge the aperture of wood,the separation speed of the wood-based oil-water separation materials was greatly improved.At the same time,the introduction of functional materials endowed the wood with special performances.The superhydrophobic woods with degradation ability,photothermal and Joule-heat effect,and demulsification ability were prepared,and successfully applied to separate a variety of oil-water pollutants.The main research contents and results of this paper include the following three aspects:（1）The PDMS@TiO₂wood with excellent photocatalytic and superhydrophobic properties was successfully prepared by delignifying wood,providing titanium dioxide（Ti O₂）,and using low-surface-energy polydimethylsiloxane（PDMS）for hydrophobic modification.The prepared wood has an anisotropic porous structure,vertically arranged smooth channels,and stable superhydrophobicity with a water contact angle of 160°.The PDMS@Ti O₂wood showed excellent oil-water separation capacity with separation efficiency over 90%,separation flux of 6111 L·m^-2·h^-1,and excellent separation stability in cyclic experiments.In addition,the weight of the PDMS@Ti O₂wood was reduced by 8.56wt%after UV degradation for 720 h,indicating the good photocatalytic degradability.（2）Superhydrophobic PDMS@GSH wood with excellent Joule heat and photothermal effects was prepared via chemical treatment,graphene oxide（GO）coating,thiourea reduction,and finalvinyl-terminated polydimethylsiloxane（V-PDMS）modification on the surface by thiol-ene click reaction.The prepared wood has excellent superhydrophobicity with a water contact angle of 156°.V-PDMS wascrosslinked with GSH on the wood by chemical bonds,making the material maintain stable superhydrophobicity and electrical conductivity after 50 cycles of heating experiment.The GSH layer provides a good Joule heat effect for the wood,and the surface temperature reaches 139℃in 120 s under 20 V voltage.Thus,the PDMS@GSH wood presents excellent crude oil-water separation ability under Joule heat effect with a separation rate of 1.78×10⁵kg·m^-3·h^-1.In addition,the PDMS@GSH wood has a good photothermal effect,and the surface temperature reaches83.2℃at 2.0 k W/m²light intensity within 240 s.The photothermal effect can assist the Joule heat effect to heat the wood to achieve rapid crude oil-water separation and reduce electricity consumption.（3）The wood was chemically treated to possess a spring-like structure,and then loaded the carboxyl-modified carbon nanotubes（c CNTs）.Next,the polyethylenimide（PEI）was coated through the reaction between the amino group with the carboxyl group of the c CNTs to form a firm crosslinking structure.Finally,the polydimethylsiloxane（PDMS）was used for modification to obtain the superhydrophobic PDMS@PEI-c CNTs wood with excellent Joule heat and demulsification ability.The prepared wood exhibited superhydrophobicity with a water contact angle of 156°and excellent compression property with a complete structure after 50 compression cycles at a strain of 40%.The PDMS@PEI-c CNTs wood presented a multilayer structure and strong absorption,and the water-in-oil emulsion could be demulsified quickly with a separation efficiency greater than 99.7%.Meanwhile,the wood showed a good Joule heat effect,and the surface temperature reached 160℃at 35 V of voltage in 120 s.The crude oil emulsion could be separated by the wood via Joule heat effect,with separation speed of 4.33×10⁴kg·m^-3·h^-1,and separation efficiency of 93.4%.