| Summary: | 碩士 === 逢甲大學 === 環境工程與科學學系 === 101 === In this research, preparation of porous ceramic filter with the ability of visible-light-driven photocatalysis by sol-gel method was studied. This study utilized the mixing of alumina and silica to benefit alumina’s high specific surface area and porous properties.
The study investigated the effects of adding alumina at different calcination temperatures and synthesis of filter materials using co-hydrolysis (CH) and separately peptized (SP). In addition, XRD, SEM, BET, and TGA were used to characterize the composite powder of alumina-silica mixtures doped with bismuth oxide.
The experiments in this study have showed that the volume ratio of alumina to silica at 1:1 using SP method had the best result at a fixed calcination temperature of 450 ℃ and its specific surface area could achieve as high as 395.85 m²/g. Alumina-silica mixtures via the two sol–gel methods as mentioned did not have significant effects on optical properties and crystal-phase structures as observed by XRD. Compared to CH method, SP could result in higher surface area and smaller pore size. According to SEM and BET analyses, aggregation of particles had decreased specific surface area and enlarged pore size when calcination temperature exceeded 300 ℃.
Specific surface area of the composite powder was 538.23 m²/g when the calcination temperature was performed at 450 ℃. Doping with bismuth oxide could effectively increase the harvesting of visible light and, therefore, lowered the direct band gap to 2.4 eV for the alumina-silica mixtures. XRD analysis results of the composite powder synthesized at temperatures of 300~450 ℃ has showed the formation of mixed phases of tetragonal β-Bi2O3 and tetragonal Bi2O2.33. TGA analysis indicated that the exothermic peak appeared at 300 ℃. This peak was demonstrated by the result from XRD analysis. XRD investigations indicated that prepared bismuth oxide were polycrystalline and multiphase. Thus, calcination temperature plays a key role in the composition and optical properties.
Suspensions using 30 vol.% of solids (composite powder and sucrose) and 70 vol.% of liquids (isopropyl alcohol and PVP) were mixed and grinded in a jar. This mixture was coated onto a stainless steel sieve of 210 μm mesh and calcined at 250 ℃ to form a porous ceramic filter. The as-synthesized filter was tested for flux test run and the flux rate was stabilized at 45 LMH after 15 to 20 minutes.
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