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Synthesis Of The Nano-WO3 With High Specific Surface Area And Its Photocatalytic Activity To Degrade Gaseous Formaldehyde

Posted on:2006-12-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:L X ZouFull Text:PDF
GTID:1101360185991680Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Tungstic acid is prepared from Na2WO4 with protonated cation-exchange resin, to synthesize a series of WO3 in different methods, such as: hydrothermal, template in porous anodic oxidation of aluminum(AAO), cavitation in ultrasonic supersonic-centrifuging and microwave radiating at circumfluence. Characteristics of the nano-WO3 like crystalline phases, crystallite sizes, morphological, specific surface area, infrared absorption and light absorption are studied with many effect factors. Their photocatalytic activeities are evaluated through degradation formaldehyde in gas phase as a objective. The result shows: The samples of WO3 exhibit different crystalline phases, morphology absorbance of infrared spectra and photocatalytic activity respectively over thermal treating tungstic acid in different method and at different temperature; Samples over microwave drying have smaller crystallite size, higher degree of crystallization and can be separated and deposited better. The high crystal nanorods WO3 are gained after hydrothermal tungstic acid at 265℃ and microwave desiccation. It had more high photocatalytic activities. The WO3·H2O nanowire array film prepared by sol-gel chemistry in AAO template has an arrayed order with specific surface area 29.6 m2·g-1; Products obtained by hydrothermally treating tungstic acid show a higher degree of crystallization and smaller crystallite size. A nano-H0.10WO3·1.06H2O with microporous and thin lamella is gained passing through cavitations in ultrasonic-centrifuging 7 times. Its specific surface area is 26.16 m2·g-1 and cexpands to 2.4 times large as the one which is ultrasonicd-centrifuged once and the diffuse reflectance spectra can shift to wavelength of 480 nm .A Mesoporous and pore size distribution uniformity and the specific surface area 53.91 m2·g-1 of the cubic-rhombus sample of WO3 ·0.33H2O is prepared by microwave radiating under circumfluence. The specific surface area of sample of WO3·0.33H2O·NiO with doped in NiO is 66.37 m2·g-1 and its light absorptivity wavelength shifts to about 600nm. The photocatalytic activity of WO3 synthesized by microwave radiating under circumfluence is the largest, and the one synthesized by cavitations in ultrasonic-centrifuging is larger than the one synthesized by hydrothermal or template in AAO. The photodegradation efficiency for gas-phase formaldehyde with WO3·0.33 H2O·NiO is 3.4 times large as the WO3 which is prepared by sol-gel chemistry in UV light and is 76.8% in visible light. The photocatalyst WO3·0.33 H2O·NiO is employed 5 times continously in photo-reactor experimentals , and it has not found the obvious phenomenon of photocatalyst deactivation. The photocatalytic characteristic of this ano-WO3 catalyst in visible light exhibits larger application in photocatalytic oxidation for indoor air purification.
Keywords/Search Tags:specific surface area, nano-WO3, photocatalytic, gaseous formaldehyde, microwave radiating
PDF Full Text Request
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