Preparation Of Surface With Special Wettability And Its Application Research In Oil-water Separation

Owing to the frequent occurrence of water pollution caused by chemical leakage and oil spill,oil/water separation has attracted widespread attention.Oils and organic pollutants would lead to reduction of dissolved oxygen in water,which would significantly affect the normal growth of aquatic organisms and then destroy the water resources.The carcinogenic hydrocarbons in oily wastewater would be enriched by fishes and shellfishes,which would endanger human health through the food chain.On the contrary,water in oil would have a great impact on the physicochemical properties of the oil,resulting in decline in its quality.Furthermore,the existence of water in oil could easily form stubborn emulsions,which would accelerate oxidation and reduce lubricity of the oil.On the whole,polluted water by oil would cause serious damages to environment and ecology,and oil products contaminated by water would cause great losses of oil quality.Therefore,oil/water separation technology is of great significance in industrial and agricultural production and daily life.Compared to other separation methods,the application of superwetting materials for oil/water separation has attracted much attention due to its high selectivity,high separation efficiency and high recyclability.Therefore,it is necessary to develop simple methods for preparation of excellent oil/water separation materials to overcome the aforementioned issues.In this dissertation,functional materials with superwetting interface were fabricated to solve the above disadvantages for oil/water separation.The obtained superwetting materials exhibiting high efficiency,stability and recyclability in the process of oily wastewater treatment.The research results of this study have an important practical value for the development of a new type of oil/water separation material.In order to achieve above goals,this study focus on the following aspects:First,the durable and low-cost GW was converted to superhydrophobic simply by polymerization of dopamine followed by chemical vapor deposition of polydimethylsiloxane?PDMS?.The polymerization of dopamine generated a lot of polydopamine?PDA?nanoparticles on the surface of GW microfibers,forming hierachical micro-/nanostructures.The combination of the hierarchical micro-/nanostructure and the PDMS layer successfully made the GW superhydrophobic with a water contact angle of 156oand water drops could easily roll off.In addition,the superhydrophobic GW showed high chemical stability in corrosive solutions and oils and high thermal stability.Moreover,the superhydrophobic GW showed high efficiency in selective oil absorption and oil/water separation as well as high recyclability.Second,the FG@PDA membranes were prepared by virtue of dopamine self-polymerization under mild conditions.The morphology,structure,composition,thermal stability and water contact angle of the as-prepared membranes were analyzed by scanning electron microscopy?SEM?,X-ray photoelectron spectra?XPS?,thermogravimetric analysis?TGA?andcontactanglesystem,respectively.Toluene-in-water,1,2-dichlorobenzene-in-water and diphenyl oxide-in-water are used as simulated emulsions,meanwhile,methylene blue,methyl violet and xylenol orange in aqueous solution are used as simulated pollutants,then the separation of oil-in-water emulsion and adsorption of soluble dyes by FG@PDA membranes were studied.The results show that the as-prepared membranes showed underwater superoleophobicity after being modified by polydopamine.In water,the trichloromethane droplets are spherical in shape(CA_TCM^water=162o)on the FG@PDA membrane.At the same time,the as-prepared membranes show excellent separation efficiency for insoluble oils and high adsorption properties for water-soluble dyes.The kinetic study shows that the quasi-second-order kinetic equation is more suitable to describe the adsorption process of FG@PDA membrane to MB.The mechanism of emulsion separation shows that the different wetting properties of FG@PDA membrane to water and oil are the main reasons for its effective separation of water-oil emulsion.Finally,the superhydrophobic membranes were fabricated by chemical vapor deposition of PDMS on FG@PDA,which from the optimal results of the previous section.In order to study the structure-performance relationship,the membranes were characterized using field emission scanning electron microscope,X-ray photoelectron spectroscopy,and Fourier transform infrared spectroscopy,etc.The membranes are superhydrophobic with a water contact angle of 152oand meanwhile superoleophilic with an oil contact angle of 0°.Also,the membranes demonstrate excellent acid,alkali and fire resistance.Moreover,the membranes can remove more than 98%of water from the surfactant-stabilized water-in-oil emulsions.Similarly,the kinetic study shows that the quasi-second-order kinetic equation is more suitable to describe the adsorption process of FG@PDA@PDMS membrane to oil red O,The mechanism of emulsion separation shows that the different wetting properties of FG@PDA@PDMS membrane and coalescence separation are the main reasons for high separation efficiency of water-in-oil emulsions.The adsorption of dyes is attributed to the superhydrophilicity of the FG@PDA@PDMS membrane with abundant N and O-containing groups.It is expected that the superhydrophobic FG membranes can be used for effective separation of diverse water-in-oil emulsions.