Preparation Of Superhydrophilic Alumina Ceramic Membrane With Gradient Pore And Its Oil/Water Separation Performance Research

Membrane technology has been extensively concerned for its low energy consumption,high separation efficiency.However,the widespread membrane fouling in the separation process has limited its development and application,so how to effectively control and reduce membrane fouling has become the key to its further development.Inspired by the"self-cleaning"phenomenon in natural plants and animals,a series of special wettable materials have been prepared for oil/water separation by constructingsurfacemicro/nano-structure.Inparticular,the superhydrophilic/underwater superoleophobic membrane possesses underwater superoleophobicity,allowing it to avoid contamination by oil droplets during separation and enhancing the anti-fouling properties of the membrane.Therefore,this thesis prepared superhydrophilic/underwater superoleophobic ceramic membranes for oil/water separation by designing surface micro/nano-structure,and the main research contents and conclusions are as follows:（1）Al₂O₃ ceramics with directional gradient pores were prepared by freeze-casting,and the effects for particle size and solid content of Al₂O₃ particle on slurry stability and microscopic morphology and properties of porous ceramics were studied.Results demonstrated that large particle size was not conducive to obtaining the ideal gradient lamellar pore structure,so the Al₂O₃ powder of 0.3μm was chosen as the raw material in this thesis.With the increase of solid content from 20 vol%to 30 vol%,the open porosity,pore size and pure water flux of the ceramics gradually decreased,and the compressive strength increased.When the solid content was 25 vol%,the compressive strength and permeation flux of the ceramics were 11.96 MPa and 2526.91L/m²·h·bar,respectively,satisfying the subsequent filtration requirements.（2）WO₃ nanosheets/Al₂O₃ membranes were successfully fabricated by hydrothermal method using Al₂O₃ ceramics as the substrate.When the hydrothermal time was 24 h,the instantaneous water contact angle of the membrane was 9.3°and the underwater oil contact angle was more than 153°,achieving superhydrophilicity and underwater superoleophobicity.The separation efficiency of different oil/water mixtures was more than 96%.After 10 cycles of separation,the separation efficiency still remained at more than 95%,with good anti-fouling property.After immersion in acid,alkali,neutral and strong saline solutions for 24 h,the membranes still maintained superhydrophilicity/underwater superoleophobicity with good chemical stability.（3）WO₃ nanowires/Al₂O₃ membranes were successfully prepared by hydrothermal method using Al₂O₃ ceramics as the substrate.When the hydrothermal time was 12 h,uniform WO₃ nanowires were formed on the membrane surface,and a cobweb-like nanowire bridging structure was formed between the pore channels of the separation layer.The instantaneous water contact angle and underwater oil contact angle of the membrane were 8.5°and 157.8°respectively.With the introduction of WO₃ nanowires,the pore channels of the membrane were cut and subdivided.The separation efficiency of the membrane for emulsified rapeseed oil was increased from42%before modification to 90.38%,obtaining a high permeate flux of about 1600L/m²·h·bar.After 10 cycles of separation,the separation efficiency was maintained above 90%,the permeate flux was stable at about 1500 L/m²·h·bar.The underwater oil contact angle of the membrane was still greater than 150°after immersion in acid,alkali,neutral and strong saline solutions for 24 h,and the separation efficiency was maintained above 88%,showing good durability and chemical stability.