Preparation And Performance Of Superhydrophilic/Underwater Superoleophobic Cu-Based Membranes For Oil/Water Separation

The massive discharge of oily wastewater will not only cause huge waste of resources and serious ecologically environmental damage,but also endanger human health.Therefore,oily wastewater must be effectively treated and recycled before it can be discharged according to related regulations.Recently,membrane filtration has been deemed to be the most promising method to separate oil from oily sewage because of its low energy consumption,excellent selectivity,strong adaptability and eco-friendly separation process.Separation performances of membranes with selective permeability often determine the cost and efficiency of oily wastewater treatment.Membranes often suffer from serious fouling problems,leading to severe decline of separation performance.Therefore,it is extremely important to design filtration membranes with excellent high separation performance,anti-oil-fouling property and strong adaptability to efficiently separate oily wastewater.Membranes can be divided into metal mesh membranes,ceramic membranes and polymer membranes.Among them,separating membranes based on metallic meshes have been extensively studied to separate oily wastewater because of their simple fabrication process,outstanding mechanical property,strong mechanical strength,low cost and adjustable pores.In this thesis,the Cu meshes with excellent mechanical property,corrosion resistance and low price were selected as the substrate of the membranes,and the membranes were modified with special wettability by adjusting the chemical compositions and microstructures of the Cu meshes surfaces to prepare superhydrophilic/underwater superoleophobic and low-oil-adhesive membranes for solving the problem of membrane fouling in oil/water separation.The main content of this thesis is as follows:（1）A mushroom-like Cu-CAT-1 hierarchical structures with micro/nanoscale roughness was grown onto Cu mesh by in situ growth and transformation,referred to as Cu/Cu-CAT-1（CCMOF）.Plenty of Cu（OH）₂ nanowires were grown on the pristine Cu mesh by low-temperature solvothermal method.And microphone-like Cu-CAT-1nanorods arrays were grown onto the Cu mesh by sacrificing Cu（OH）₂ nanowires as templates by the local concentration effect.The CCMOF possessed excellent superhydrophilicity/underwater superoleophobicity and low-oil-adhesive property due to its ingenious mushroom-like structures and its high affinity for water.Therefore,it could separate various types of oil/water mixtures with a considerably high flux of over 25,000 L m^-2 h^-1 and an extremely low oil content in filtrate of below 10 ppm.（2）An anti-oil-fouling hierarchical structured membrane decorated with urchin-likeα-Fe OOH particles and superhydrophilic Fe（OH）₃ nanotubes arrays was successfully obtained via the layer-by-layer（LBL）self-assembly method,referred to as CFFM.The Cu（OH）₂ nanowires arrays were fabricated at the first step,then were converted to Fe（OH）₃ nanotubes arrays by the immersion precipitation phase transformation method.The microscale urchin-likeα-Fe OOH particles with nanoscale thorns were self-assembled onto the obtained Fe（OH）₃ nanotubes arrays,yielding hierarchical structures（CFFM）with high porosity and a large number of micro-nano pores.The as-obtained biomimetic hierarchical structured membrane exhibited superior superhydrophilicity/underwater superoleophobicity,high water-retention ability,and preferable anti-oil-fouling property.Furthermore,the biomimetic membrane with controllable pore sizes could not only separate common layered oil/water mixtures(water flux up～74479.1 L m^-2 h^-1,separation efficiency～99.9%)but also effectively separate immiscible surfactant-stabilized high-viscosity crude oil-in-water emulsions with an ultrahigh water flux up to 2598.4 L m^-2 h^-1 and an outstanding separation efficiency above 98%,which might have a bright application prospect for immiscible oil/water mixtures and oil-in-water emulsions separation.The superhydrophilic/underwater superoleophobic Cu-based membranes prepared in this thesis provide theoretical guidance for the design and development of low oil-adhesive membranes for efficient oil/water separation,showing broad application prospects in the field of oily wastewater treatment.