Preparation and Characterization of Porous TiO2 Membrane and Porous Support

• Main Authors: Huang, Chung-Tai, 黃中玳
• Other Authors: Kan-Sen Chou
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/54611527096701174708

碩士 === 國立清華大學 === 化學工程學系 === 85 === The objective of this work is to reduce the pore size and improve the surface roughness of the porous plate for making membranes with smaller pores . The sol-gel method was usually adopted to prepared the membrane for gas separation industries. Cracking ,however, is the major problem to affedt the quality ofthe membrane , and the surface morphology of the support is one of the causes .A membrane often cracks upon drying if the pores are not uniform. TiO2 particles of 0.5um and 30nm were dispersed in water with Darvan 7 and then dipped in sequence onto the support and water was filtrated out by applying vacuum on the down stream side . The first and second intermediate membrane layer were formed with mean pore sizes 0.5um and 30nm, respectively. The main job of this work is to investigate the relationship amoung processing variables - microstructure - properties of the membrane and condition for producing the optimum products. TiO2 particles of 0.5um can be well dispersed in 200ml D.I water with 1ml Darvan 7 (0.654 Vol%) to show about 90% particles around 0.5um from LPA analysis. However , the 30nm particles show about 45% at 50nm indicating agglomeration between particles . The grain growth of the sintered TiO2 particles is affected by sintering temperature and the coordination number amoung the particles .Grain growth will accompany with increasing pore size. The surface roughness ofthe membranes will be greatly improved as shown from SEM , AFM and a-Step analysis .A flat surface will be advantageous to subsequent sol-gel process t o further reduce pore sizes. As for the microstructure ,the membrane thickness is linear with the quantities of TiO2. The mean pore size (0.40→0.125 um) and overall permeability (420x10-7→160x10-7) (mol/sec-Pa-m2)) decreased , while th porosity (23→35%)is increased with thickness . If compared with commercial products , our membrane can offer smaller pore size , yet similar fluxes. When thporous support is tested as a bubble device ,we found that the mass transfer coefficent (KL.a) is higher than commercial products made of sintered glasses , especially in the low gas flux region (Ug < 1cm/sec) .This mainly due to the very small bubble size associated with our porous support. When tested in crossflow operations , both the support and the membrane show decaying flux with time ,suggesting that particles are gradually plugging the support. Nervertheless , the adhesive property between support and membrane is quitesatisfactory.