Crystalline TiO2 nanoparticles were synthesized by hydrolysis of titanium (IV) isopropoxide (TTIP) in the Aerosol OT (AOT)¡Ðcyclohexane microemulsion at controlled temperature. The influence of various reaction conditions, such as mixing energy ( ), [AOT] concentration (W), [TTIP] concentration (R), temperature (T), and aging (t) on the particle size were investigated. The nano-TiO2 particles were characterized for specific surface area (Brunauer-Emmett-Teller, BET) in addition to X-ray diffraction (XRD) and X-ray spectroscopy (XPS) as to determine the particle size, crystalline state, chemical composition, surface charge, and binding energy. The photocatalytic activity was assessed using methylene blue as probe.
Results showed that the particle size was in the range from 13.7 to 31.4 nm based on BET measurements. The size of the particle grows with mixing energy until log ( ) = 2.02; further increase in mixing rate caused particle breakup. In micelle solution, the particle size decreased with increase in W. In true solution the particle size increased with W. However, increase in R increased the particle size which reached a maximum value at a critical value of log R = -0.26, then decreased upon further increase in R. The activation energy (Ea) was calculated using Arrenhius plot and a value of -5.96 and -2.17 kJ mol-1 was obtained. Results of particle size analysis from XRD and BET were consistent with each other. Crystalline pattern was proved to be anatase. Furthermore, the photocatalytic activity appeared to optimum with particle size between 22.0-25.1 nm and best crystalline pattern.
Titanium dioxide (TiO2) synthesized using the thermal hydrolysis method in our laboratory was used as the photocatalyst in this study to degrade low concentration phenol in aqueous solution. A 150 mL batch reactor was used to carry out the degradation of 0.385 mM phenol solution (pH = 6.5) in room temperature (25 oC) with 0.5 g L-1 TiO2 and irradiated with 10.8 mW cm-2 light intensity for 8 hours. Major intermediate products include hydroquinone (HQ) with the highest quantity followed by catechol (CA), p-benzoquinone (BQ), resorcinol (RES); tri-hydroquinone (THQ) is the secondary intermediate. The by-products consist of 6 organic acids including the six-carbon trans, trans-muconic acid (t,t-MA), the four-carbon maleic acid (MA), the three-carbon propionic acid (PA), the two-carbon oxalic acid (OA) and acetic acid (AA) as well as the one-carbon formic acid (FA). Among these acids, oxalic acid is the most abundant followed by formic acid; the six-carbon t,t-MA is one of the by-products with a lagged formation period. The pathway of intermediate product formation was mathematically calculated and simulated using first-order reaction kinetics models. The reaction rate constants were statistically calculated using functions provided in Microsoft Excel 2003; the simulated results show that the predicted and measured concentrations of the reactant and products in samples collected at various times are consistent.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0711107-174937 |
| Date | 11 July 2007 |
| Creators | Liao, Yu-ling |
| Contributors | Cheng-di Dong, T.Y. Yeh, J.H. Chang, Chih-ming Kao, J.J. Lin |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0711107-174937 |
| Rights | off_campus_withheld, Copyright information available at source archive |
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