Study On Construction And Properties Of Underwater Superoleophobic/Underoil Superhydrophobic Materials

The increasingly serious problem of oil-water pollution has aggravated the global water shortage.The treatment of oily wastewater in a facile,fast and efficient manner has received a great deal of attention from government departments and the community.In recent years,materials with special wettability have been reported for oil-water separation,but most of them have the problem of single wettability,thus only one type of oil-water emulsion（oil-in-water or water-in-oil emulsion）can be separated.In addition,the smart-responsive wettability conversion materials are defective due to the cumbersome preparation process and harsh conversion conditions limiting the large-scale applications.In this paper,a series of materials with both underwater superoleophobicity/underoil superhydrophobicity were prepared,such as pine powders（PPs）coated polyvinylidene fluoride（PVDF）filter membrane,Janus fiber membrane,and hydrophilic-hydrophobic sprayed attapulgite（APT）separation mesh,of which performances were systematically investigated.The main research works are as follows.（1）By deposition of screened pine powders（PPs）on a polyvinylidene fluoride（PVDF）membrane,the separation membrane that maintained underwater superoleophobicity and underoil superhydrophobicity in harsh corrosive environments（acid,alkali and salt）was prepared.The separation membrane could achieve the separation of 12 surfactant-stabilized oil-water emulsions.After 500 bending tests,the membrane material had no cracks,showing excellent mechanical stability.In addition,the separation membrane could also adsorb anion and cationic dyes（methyl blue,Congo red and crystal violet）.Even after several cycles,the adsorption efficiency remains relatively constant.（2）The superhydrophilic candle soot（CS）and hydrophobic ZIF-8 were dispersed into N,N-dimethylformamide（DMF）,respectively,followed by the addition of polymer polyacrylonitrile（PAN）with different qualities to prepare the precursors CS-PAN/DMF and ZIF-8-PAN/DMF.Asymmetrically wetted Janus fibre membrane was successfully prepared by electrostatic spinning of both precursors.The fiber membrane exhibited underwater superoleophobicity on one side and underoil superhydrophobicity on the other side,which achieved efficient separation of surfactant-stabilized oil-water emulsions under gravity alone.Even after several cyclability tests,the separation flux and efficiency of the fiber membrane showed no significant decay and exhibited favorable cycling stability.（3）Superhydrophilic attapulgite（APT）,TiO₂ and loess were selected as the base materials and modified with octadecyltrichlorosilane（OTS）to form superhydrophobic OTS-APT,OTS-TiO₂ and OTS-Loess.Subsequently the three materials and their respective superhydrophobic counterparts with different contents were mixed and sprayed to prepare different mixed coatings.The mass ratios of OTS-APT,OTS-TiO₂and OTS-Loess in the mixed coatings were determined to be 0.3,0.4 and 0.2 when the three materials exhibited underwater superhydrophobicity/underoil superhydrophobicity.Most importantly,the as-prepared mixed APT mesh membrane was applied to separate various surfactant-stabilized oil-water emulsions.The proposed universal strategy will show great application value in solving the scientific challenges in the field of interfacial chemistry.