Preparation Of Super-wetting Materials Based On Phytic Acid-metal Chelation And Its Research In Oil-water Separation

The increasing number of oil spill accidents have caused catastrophic impact on our ecological environment,especially water environment.In recent years,special super-wetting materials for oil-water separation have received extensive attention.Because these superwetting materials have opposite wettability for water and oil,i.e.,hydrophobic/oleophilic,hydrophilic/oleophobic or Janus wettability.Such materials can remove one phase from the oil-water mixtures,while repelling the other phase,thus achieving selective oil-water separation.In addition,by adjusting the surface chemistry and surface structure,the synergistic effect between the surface can further promote superwetting behavior,resulting in different separation effects and improving separation efficiency.In this paper,two different superwetting materials were prepared based on the chelation of phytic acid and metals for water-oil separation.The main work completed in this article is as follows:The one material is the superhydrophobic/superoleophilic metal mesh with phytic acid-siloxane coating.Using phytic acid and vinyl siloxane as modifiers,a superhydrophobic/superoleophilic coating was formed on the surface of the metal mesh by a one-step method,with WCA higher than 154°,WSA lower than 6.5°and adhesive force smaller than0.1405m N.The morphology of the coating morphology with scanning electron microscope(SEM)revealed that the size of the nanospheres in the PA/VTES coating is related to the wettability,which can be adjusted by controlling the ratio of phytic acid and vinylsiloxane.The superhydrophobic/superoleophilic PA/VTES coating can be used for the separation of water-oil mixtures.The separation efficiency and separation flux are up to 98.3%and 1.5×10⁴ L m^-2 h^-1,respectively.In addition,under the protection of phytic acid corrosion resistance and superhydrophobic coating,the modified metal mesh can withstand the 48-hour salt spray test,and confirmed by the electrochemical test and seawater immersion test.Moreover,the coating has good mechanical properties,which still maintaining super-hydrophobic properties after tape peeling and sandpaper wear test.The other material is Janus fabric with modified by phytic acid/metal ion/PDMS.Through the chelation between phytic acid and metal ions,the micro/nano rough structure was constructed on the original fabric,and then immersed in water to form a protective layer,after that the PDMS solution is sprayed on one side and cured.Finally,Janus fabric was prepared with the two sides of different wettability.Using the contact angle measuring instrument to study the wetting performance of Janus fabric,it was found that the wetting performance can be controlled by adjusting the spraying amount of PDMS.Among them,the prepared Janus fabric-2 is hydrophilic on one side and metastable hydrophobic on the other side.The initial contact angle of water droplets on the hydrophobic surface is145.8°±0.7°,and the water droplets will gradually penetrate into the fabric within 6.5s;The Janus fabric-5 is hydrophilic on one side and stable hydrophobic on the other.The contact angle of water droplets on the hydrophobic side is 154.4°±0.4°,and it can keep a spherical shape on the fabric for a long time without penetration.After research on Janus fabrics,it is found that Janus fabric-2 and Janus fabric-5 with different wetting effects have different applications.Janus fabric-5 with switchable permeation can separate the water/light oil and water/heavy oil mixture by simply reversing the fabric.The separation efficiency can reach 99.3%,and the separation flux is greater than 2.38×10⁴ L m^-2 h^-1.The hydrophobic and the hydrophilic layer of Janus fabric-2can work synergistically to realize the water unidirectional transport,which can be used in the following three applications:water collection under oil,demulsification and moisture-wicking fabric.In addition,the prepared Janus fabric has excellent mechanical strength.It can still maintain its original performance after tested by tape peeling,sandpaper wear,ultrasonic peeling and machine washing test.