| In this paper,tubular alumina ceramic membrane support with ?-Al2O3 as aggregate was prepared by extrusion-forming method,and its properties was characterized;membrane suspensions was prepared by sol-gel method based on using TEOS and aluminum isopropoxide,investigating the effect of the ratio of TEOS/Et OH and reaction temperature on the properties of Si O2 membrane suspensions;they were combined by dip-coating method toughly to prepared porous ceramic composite membrane which was dried and sintered though specific dry system and firing system.The properties of porous ceramic composite membrane was characterized by porous ceramic composite membrane(SEM)and automatic mercury porosimeter.(1)Tubular alumina ceramic membrane support which was prepared with ?-Al2O3 has the performance below: porosity of 33.75%,pure water flux of 3097.6L/m2 h,flexural strength of 106.476 MPa,acid/alkali corrosion mass loss of 0.86%/0.92%.Preprocessing support according to the following steps: 150 # ~ 400 # sandpaper to polish support,then in dilute acid and ethanol mixed solution soak for 6 hours,after washing with distilled water repeatedly,ultrasonic cleaning for 1 h.(2)While the membrane suspensions have high coating liquid viscosity and high solid content,it is not conducive to coating on the support.To ensure the performance of Si O2 membrane suspensions,the ratio of TEOS/Et OH and reaction temperature has been improved.Eventually choose TEOS/Et OH/H2O/HCl=1:5:7:0.085(molar ratio)hydrolysised under 60? as the best condition to obtain membrane suspensions,with viscosity of 3.27 m Pa·s,gelation time for 27 d.With the same time,Al2O3-Si O2 membrane suspensions with viscosity of 1.98 m Pa·s,gelation time of 34 d was prepared.At the frequency of 40 k Hz and temperature of 20?,membrane suspensions was dispersed for 1h.Set aside.(3)In order to get composite membrane,support and membrane suspensions which have being pre-processed were used.The experiment steps were impregnation,desiccation,impregnation,desiccation and sintering.The process parameters are as follows: dipping three times,each dipping time for 20 s,pull rate of 1 mm/s,under the condition of 50%RH,40? to dry,and sintered.Eventually composite membrane without crack was prepared.The suitable sintering system of porous Si O2 composite membrane is: heating at a uniform heating rate of 0.25,0.5,0.5,1?/min respectively in room temperature to 120?,120~200?,200~400?,400~800?,and insulating 120 min respectively at 120,200,400 and 800?,and then cooling to room temperature.The suitable sintering system of porous Al2O3-Si O2 composite membrane is: heating at a uniform heating rate of 0.25,0.5,1?/min respectively in room temperature to 150?,150~350?,350~800?,and insulating 120 min respectively at 150,350 and 800?,and then cooling to room temperature.(4)Adhesion of coats has tested and shows that: combination of support and composite suspension is good,not easy to fall off;in the coating process,adhesion of coats did not have chemical reaction with the supports significantly.Si O2 composite membrane has the most probable aperture of 62.91 nm and 1289.34 nm respectively,and Al2O3-Si O2 composite membrane was 19.98 nm and 899.19 nm respectively.They have narrow pore size distribution,good pore structure,favourable permeability,uniform surface structure,continuous membrane layer,and excellent performance. |
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