A Research On The Preparation And Hydrophilic Modification Of Inorganic Ceramic Membrane

This paper aims to adopt sol-gel method to get Al₂O₃ membrane based on using aluminium nitrate as raw material and introducing different additives.The results of the characterized analysis like viscosity,Zeta potential,TG-DTG,IR,XRD,SEM and BET to analyze thermal stability,crystal phases,surface morphology of Al₂O₃ sample,demonstrate that:（1）Considering viscosity,zeta potential and membrane formation,methyl cellulose was selected as the additive,with the addition of 20%（mass fraction）;（2）Heat treatment of Al₂O₃ membrane is as follows:the gel are dried at 60℃,relative humidity of 70%,and heated to 800℃at a rate of 0.5℃/min in a muffle furnace and insulated for 2 hrs,meanwhile heated slowly when mass lost sharply and insulated appropriately,finally cooled to room temperature,then got complete Al₂O₃ membranes.This system can effectively solve membrane cracking.（3）The results of TG-DTG,XRD and IR showed that the crystal structure changed fromγ-AlOOH toγ-Al₂O₃ and then toα-Al₂O₃,after 800℃heat treatment was mainlyγ-Al₂O₃.（4）The results of SEM and BET showed that the surface of Al₂O₃ membrane is flat and has pore structure,the particles are arranged closely and with regular shape.The membrane has a specific surface area and a narrow pore size distribution,which belongs to mesoporous materials.Next in importance,adopting sol-gel method TiO₂ membrane was prepared by using tera butyl titanate as raw material.By changing its heat treatment temperature,light treatment,also adjusting the thickness of the membrane,adding PEG as thetemplate,preparing TiO₂-SiO₂ composite membrane to enhance hydrophilicity.After these methods,the results of the characterized analysis like TG-DTG,IR,XRD,SEM,BET and contact angle measurements to analyze thermal stability,organic functional group structure,pore size and specific surface area,as well as effects of different factors on the surface wettability,demonstrate that:（1）Heat treatment are as follows:TiO₂ gel are dried at 30℃,relative humidity of 60%,and heated to 750℃at a rate of 0.5℃/min in a muffle furnace and insulated for 3 hrs,meanwhile heated slowly at 280℃and 420℃also insulated appropriately,finally cooled to room temperature.TiO₂-SiO₂ composite gel are dried at 50℃,relative humidity of 60%,and heated to 650℃at a rate of 0.5℃/min in a muffle furnace and insulated for 3 hrs,meanwhile heated slowly at 230℃and 420℃also insulated appropriately,finally cooled to room temperature then got complete membranes and this system can effectively protect membrane from cracking.（2）The results of TG-DTG,XRD and IR showed that the crystal structure of TiO₂ changed from anatase to rutile at 500℃;SiO₂ component in TiO₂-SiO₂ composite membrane was amorphous and the Ti-O-Si bond formed after heat treatment,explaining the formation was chemical bonding.（3）The results of SEM and BET showed that the structure of TiO₂ membrane was dense and the particles were aggregated.When polymer PEG was as the thetemplate,its surface became rough and had mesopores and macropores.TiO₂-SiO₂ composite membrane has a relatively uniform internal structure with high porosity and an average pore diameter of50.20 nm.（4）The results of contact angle measurements showed that:a.The higher content of anatase TiO₂,the better wettability of the membrane surface,and the stronger hydrophilicity;b.Hydrophilicity was positively correlated with TiO₂ membrane thickness in the range of coating times.The best hydrophilicity was contact angle with 5.3°when the relative thickness was 7L.c.Under ultraviolet light,the hydrophilicity of anatase TiO₂ was suitable;while in visible light,the hydrophilicity of composite crystalline TiO₂ was better.d.When PEG was used as template,the hydrophilicity increased with increasing molecular weight and the amount of PEG until membrane surface was cracked.When the templating agent was PEG2000 and the addition amount was 5%,the surface wettability was better.e.The addition of SiO₂ in the TiO₂-SiO₂ composite membrane promoted the surface acidity to adsorb more hydroxyl and showed stronger hydrophilicity.In the present experiment,when the TiO₂:SiO₂（mol/mol）was 3:2,the hydrophilicity of the composite membrane was more better.