Preparation Of Cardanol-based Benzoxazine Superhydrophobic Materials And Their Applications In Oil-water Separation

The rapid development of the global economy has prompted a substantial increase in the demand for petroleum energy.In such a context,oil spill accidents often occur in frequent maritime oil transport.An efficient and easy way to achieve oil-water separation performance is to develop materials with special wettability to selectively filter or absorb oil-water mixtures.However,most of the current research on superhydrophobic oil-water separation materials uses non-renewable petroleum-based resources,causing problems such as high production cost,difficulties in degradation,and secondary pollution after disposal in contrast to the concept of green chemistry and sustainable development of socialist economy in China.Therefore,it is of great significance to China’s comprehensive ecological improvement and water resources purification that we develop superhydrophobic oil-water separation materials with degradable biomass resources as raw materials.Cardanol is a natural phenolic compound derived from cashew nut shells,a type of agricultural and forestry residues.It is a commonly used biomass resource.In this paper,cardanol-based benzoxazines with low surface energy were synthesized using the unique molecular structure of cardanol,and then applied onto cotton fabrics to form a superhydrophobic coating.The obtained superhydrophobic cotton fabrics not only achieved efficient separation of oil-water mixtures and oil-water emulsions but also showed excellent mechanical and environmental stability.The main research contents are as follows:（1）Cardanol-based benzoxazine（C-aps）monomers were synthesized through Mannich reaction with cardanol,paraformaldehyde,andγ-aminopropyltriethoxysilane（APTES）as the raw materials.Superhydrophobic cotton fabrics（PC-aps/TEOS/CF）were then prepared by using a“one-pot”ultrasound-assisted in-situ growth technique.The effect of the mass ratio of tetraethyl-orthosilicate（TEOS）to C-aps on the surface hydrophobicity of PC-aps/TEOS/CF was studied.The mechanical stability of PC-aps/TEOS/CF was evaluated through a sandpaper friction test and ultrasonic cleaning test.The environmental stability of PC-aps/TEOS/CF was investigated by immersion in acid-base solution and high-temperature treatments.At the TEOS-C-aps mass ratio of 0.6,the water contact angle（WCA）on PC-aps/TEOS/CF surface was the highest,up to 158.5°,showing excellent superhydrophobicity.The superhydrophobicity of PC-aps/TEOS/CF decreased slightly after 270 times of sandpaper rubbing,but WCA was still larger than 150°.PC-aps/TEOS/CF also showed high stability to strong acids and bases as well as droplet impact.According to the oil-water separation experiments,PC-aps/TEOS/CF can efficiently and quickly separate a series of heavy oil or light oil-water mixtures,showing good flux and separation efficiency,as well as reusability.（2）The superhydrophobic cotton fabrics（PC-aps/ECF）modified by C-aps were constructed through successive enzyme etching,dip coating and heat curing processes.The effects of C-aps content and cellulase etching time on the surface morphology were investigated by scanning electron microscopy（SEM）.The hydrophobicity of the cotton fabric coatings were studied by contact angle measurements.When the C-aps concentration was 5%and the cellulase etching time was 40 min,the decent hydrophobicity of PC-aps/ECF was obtained with a WCA of 154.6°.The results of sandpaper friction,ultrasonic cleaning and washing tests showed that PC-aps/ECF had excellent mechanical stability.The WCA of PC-aps/ECF remained above 149°after soaking in acid/alkali solution for 24 hours,which proved that it had good chemical stability.PC-aps/ECF also exhibited outstanding separation performance for various oil-water mixtures.In addition,the designed composite membranes could be used for efficient separation of water-in-oil emulsions with fluxes higher than 19,800 L·m^–2·h^–1·bar^–1.（3）Cardanol-POSS based benzoxazine（C-a POSS）monomers were synthesized through Mannich reaction with cardanol,paraformaldehyde,and aminopropyl isobutyl POSS（NH₂-POSS）as raw materials.The superhydrophobic cotton fabrics（PC-a POSS/CF）were prepared by in situ polymerization method.The best hydrophobicity of PC-a POSS/CF was obtained when the C-a POSS concentration was 2 wt.%and immersion time was 40 min with a WCA of 155.0°and good anti-fouling properties for common liquids.As shown by the sandpaper friction test and ultrasonic cleaning test,PC-a POSS/CF possessed excellent chemical and mechanical stability.PC-a POSS/CF also exhibited high stability against strong acids and bases as well as high temperature environments.We investigated the performance of PC-a POSS/CF as a filter membrane in separating oil-water mixtures and water-in-oil emulsions.According to the results,PC-a POSS/CF can not only well separate oil-water mixtures with the separation efficiency higher than 99.86%and the flux higher than 3600 L·m^–2·h^–1,but also achieve high filtrate purity（oil purity greater than99.99%）and good reusability under external pressure.