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Title: The preparation and characterization of inorganix membranes
Other Titles: Wu ji mo de zhi bei he biao zheng
Authors: Shi, Li (施力)
Department: Dept. of Biology and Chemistry
Degree: Doctor of Philosophy
Issue Date: 2000
Publisher: Dept. of Biology and Chemistry, City University of Hong Kong
Subjects: Membranes (Technology)
Notes: CityU Call Number: TP159.M4 S54 2000
Includes bibliographical references (leaves 137-142).
Thesis (Ph.D.)--City University of Hong Kong, 2000
x, 144 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: Recently, much attention has been focused on inorganic membranes which are superior to the organic ones in respect of their thermal, chemical and mechanical stabilities and resistance to microbial degradation. Among various methods used for preparation of inorganic membranes, the sol-gel approach is most practical in making thin ceramic membrane with top layers in microscale, pore diameter in nanoscale, and narrow pore-size distribution. Supported and unsupported γ-alumina membranes and composite membranes of alumina and titania were prepared using sol-gel method. In the course of preparation, effects of acid concentration, type of acid, alkoxide and binder on particle size and pore size of the membrane were investigated by thermal analysis (TG and DTA), N2 physisorption and light scattering techniques. Since alumina is a slit-shaped pore model, its particle size does not affect the pore size largely. Polyvinyl alcohol (PVA) was added as a binder to the boehrnite precursor to improve the quality of the membrane. This resulted in only a less critical but better controllable drying and calcining procedure. Different mole ratios of alumina and titania could produce composite membranes with different pore sizes from 3.2 to 4.8 nm and surface areas retained above 100 m²/g. In sol-gel method, hydrolysis condition is one of the important factors. Hydrolysis time and geometry of the substituent group in metal alkoxide directly affect particle size of the sol. Textural stability of titania and zirconia membranes prepared with sol-gel method has been studied using thermal analysis, X-ray diffraction (XRD), Rarnan spectroscope, scanning electron microscopy (SEM) and N2 physisorption techniques. Remarkable characteristics of the 3 mol% yttria-doped titania membrane were observed and improvement in its thermal stability was achieved by retarding the anatase-rutile phase transformation to at least 200 ºC . From the XRD results, it was found that pure and yttria-doped titanias transformed to more than 90% of rutile after 600 and 800ºC, respectively. But the yttria doping has no effect on embryo crystallization formation from the amorphous state. Yttria-doped zirconia and pure zirconia membranes were prepared with sol-gel method using zirconium oxychloride octahydrate (ZrOC12.8H2O) as starting material. Stable tetragonal phase and pore structure in yttria-doped zirconia membranes were observed at 400-700ºC. And, phase transformation temperature can be lowered to 300ºC. As a result, yttria doping can be developed as a method to secure the membrane from cracking in preparation process and high temperature applications. Commercial as well as potential uses of inorganic membranes multiply rapidly in recent years as a result of the continuous improvement and optimization of the manufacturing technologies, and applications development for these membranes. In this work, raw soy souce was refined and bacteria removal of sea water in Hong Kong Piers was tested using inorganic membranes. E. Coli can be 100% rejected in water treatment.
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