Preparation Of Superhydrophilic Superoleophobic Membrane Material And Its Application In Oil-water Separation

With the development of industrial technology,the production and life of human beings are closely related to oil,however,a lot of oily wastewater generated from oil extraction,industrial production and daily life,it’s harmful to environment and human beings.Many methods were used for the treatment of oily wastewater,including physical,chemical,biological and membrane filtration.However,the treatment of membrane separation have been extensively applied to scientific research and industrial process due to its outstanding properties such as low energy consumption,high efficiency and low pollution.The membrane functional materials based on wettability can separate oil-water mixture in theory,therefore,it is necessary to be designed.The membrane functional materials based on wettability are divided into superhydrophobic superoleophilic and superhydrophilicsuperoleophobicmembrane.Althoughthesuperhydrophobic superoleophilic is easy to construct,it has disadvantages of serious membrane fouling,fast flux attenuation,short membrane life and uneasy cleaning.The superhydrophilic superoleophobic membrane has the advantages of easy cleaning,high life,high flux and high efficiency,however,the surface of superhydrophilic superoleophobic membrane is difficult to construct.In this study,firstly,an anatase TiO₂（101）molecular model was constructed through Material Studio and then doped with Si,The adsorption capacity for water of TiO₂molecules with different Si doping sites was investigated.Then superhydrophilic superoleophobic TiO₂/Si O₂ double-layer membrane materials and superhydrophilic superoleophobic TiO₂/SiO₂ composite membrane materials were successfully prepared through sol-gel method based on stainless steel wire mesh,and the surface structure were characterized microscopically.Finally,a device was designed for oil-water separation according to the separation performance of the material.The important conclusions are as follows:（1）An anatase TiO₂（101）molecular model was constructed through Material Studio and then doped with Si,The adsorption capacity for water of TiO₂ molecules with different Si doping sites was investigated.It is demonstrated that it can enhance the hydrophilicity of the system.Among them,the outermost layer of Si doping exhibited the optimum adsorption capacity of water.It provides theoretical support for later experimental studies.（2）An superhydrophilic superoleophobic TiO₂/SiO₂ double-layer film material was prepared through sol-gel method used Si O₂ and TiO₂ coated successively on stainless steel wire mesh,and after annealing at high temperature.The properties of TiO₂/SiO₂ bilayer membrane was characterized by SEM,XRD,XPS and water contact angle measuring instrument,the effects of different preparation conditions on surface morphology,contact angle and oil and water separation performance were studied.The results show that TiO₂/SiO₂ double-layer membrane material exhibited excellent hydrophilic behavior with a water contact angle 0°with different process conditions,and the water droplets in the air can spread quickly within the 0.1s on the membrane surface;the water oil contact angle can reach 157.5°±1.1°,it is shown excellent underwater superoleophobic performance at the optimum conditions.（3）SiO₂ colloid and TiO₂ colloid were prepared at optimum preparation conditions through sol-gel method,and then TiO₂/SiO₂ composite colloid obtained by mixing SiO₂colloid and TiO₂ colloid at a certain molar ratio at sol stage,after that coated on clean stainless steel wire mesh,after calcination and annealing,superhydrophilic and superoleophobic TiO₂/SiO₂ composite membrane material was obtained.The properties of TiO₂/SiO₂ composite membrane was characterized by SEM,XRD,XPS and water contact angle measuring instrument,the effects of different Si doping amount on surface morphology,contact angle and oil and water separation performance were studied.The results show that TiO₂/SiO₂ composite membrane material exhibited excellent hydrophilic behavior with a water contact angle 0°with different Si doping amount,and the water droplets in the air can spread quickly within the 0.1s on the membrane surface;the water oil contact angle can reach 150°±2.8°,it is shown excellent underwater superoleophobic performance at the optimum Si doping amount.（4）An device was designed for oil-water separation based on the assessment of oil-water separation efficiency of two systems by simulating the actual oil-water mixture and the analysis of the water quality of the actual oil-water mixture.The results show that the separation efficiency of two kinds of membrane materials could reach more than 90%,meanwhile,the membrane is easy cleaning,the filter can be made into a larger filter area;oil-water separation device not only can be efficient separation for oil-water,but also remove the colloidal substances and solid suspended substance at the same time.