Preparation Of ZnO Nanorod Modified Superhydrophobic Ceramic Membrane And Its Membrane Distillation Performance

In the process of vacuum membrane distillation separation,to achieve the separation effect,the pressure difference between the two sides of the membrane is used as the driving force to make the water vapor produced by the hot material liquid on the membrane surface pass through the membrane hole and be condensed after entering the vacuum side.Membrane distillation is widely used because of its high separation effect and low energy consumption.However,it also has the problems of easy fouling and wetting.To solve the problems of membrane material tolerance and membrane fouling,a micro/nano hierarchial structure with low surface energy was constructed on the ceramic hollow fiber membrane surface by using ZnO nanorod arrays and fluorosilane coatings,which make it superhydrophobic and self-cleaning.In this thesis,the hydrophobic modification process of the original ceramic membrane can be divided into the following steps:First,the ZnO seeds layer was planted on alumina ceramic hollow fiber membrane at 350℃ by the pyrolysis-adhesion method.On this basis,new ZnO nanorods modified ceramic hollow fiber membrane with micro/nanoscale hierarchical structured was fabricated by the hydrothermal method.Finally,a novel superhydrophobic membrane structure was created by coating1H,1H,2H,2H-perfluorodecyltriethoxysilane（PDTS）and applied to the vacuum membrane desalination.The surface morphology,contact angle and chemical composition of the hydrophobic modified ceramic membrane were characterized.It can be seen that there are a large amount of ZnO nanorods with ideal properties on the surface of the hydrophobic modified ceramic film,such as super hydrophobicity,excellent thermal and mechanical stability,and the contact angle is 160.12°.At the same time,the basic membrane pore structure is also retained.In this thesis,the novel membrane is used in the vacuum membrane distillation（VMD）system to treat the regenerated wastewater from the simulated chlor alkali plant and the desulfurization wastewater from the coal-fired power plant.The hydrophobicity modified ceramic membrane shows excellent self-cleaning performance and good antifouling ability in the utilization of VMD system for high-salinity water desalination.It also maintains a high permeate flux of 27.34-23.66 kg m^-2h^-1and a low conductivity of 5.13-14.32μS cm^-1.The effects of temperature,velocity and vacuum pressure of the permeation flux of hydrophobic modified ceramic membrane were investigated and simulated.Meanwhile,the optimal operation conditions of hydrophobic modified ceramic membrane were obtained during the treatment of desulfurization wastewater:feed temperature:65℃,feed velocity:0.032 m s^-1,vacuum degree:0.080 MPa,continuous operation cycle:40 min.