Browsing by Author "Lo, Pin-han"

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ENVR 173-Photoactivity of TOPO-capped TiO2 nanocrystals toward the degradation of endocrine disrupting chemicals
(2007-08-19)
Chang, Sue-min
;
Lo, Pin-han
;
Hou, Chieh-Yao
;
環境工程研究所
;
Institute of Environmental Engineering
Photocatalytic behavior of TOPO-capped TiO(2) nanocrystals for degradation of endocrine disrupting chemicals
(2009-09-28)
Chang, Sue-min
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, we investigated the photocatalytic kinetics and mechanisms of trioctylphosphine oxide-capped titanium dioxide (TOPO-capped TiO(2)) for degradation of two endocrine disrupting chemicals (EDCs), phenol and bisphenol A, which contained different hydrophobicity, chemiadsorbability, and degradable capacity. The TOPO-capped TiO(2) exhibited high partition coefficients of 2.00 x 10(-4) and 3.42 x 10(-3) l/mg for phenol and bisphenol A, respectively. In addition, the bonded TOPO introduced substantial amounts of trapped holes at the surface. The high affinity toward the target compounds and stabilized charge carriers resulted in high photocatalytic activity of the modified TiO(2). The TOPO-capped TiO(2) exhibited 12- and 3-fold higher photocatalytic activities than P25 for decomposition of bisphenol A and phenol, respectively. The presence of the hydrophobic modifier inhibited the generation of hydroxyl radicals and led to the photocatalysis undergoing mainly from partition followed by chemisorption and interfacial charge transfer. Partition and interfacial charge transfer were the rate determining steps for the degradation of phenol and bisphenol A, respectively. According to the Langmuir-Hinshelwood model, the adsorption coefficient (K,) and intrinsic rate constant (k(r)) for phenol were 4.17 x 10(-2) l/mg and 5.60 x 10(-2) mg-g/l-min-m(2), respectively, while they were 2.91 x 10(-2) l/m and 2.18 x 10(-1) mg-g/l-min-m(2), respectively for bisphenol A degradation. The product of the k(r) and k(a) for bisphenol A was 2.7 times higher than that for phenol, revealing that the modified TiO(2) favored decomposition of the compound which contains high chemiadsorbability and direct photocatalytic tendency in their individual systems. In contrast, the high degradable capability of phenol resulted in its preferential degradation in the competitive system. (C) 2009 Elsevier B.V. All rights reserved.
Photocatalytic behavior of TOPO-capped TiO2 nanocrystals for degradation of endocrine disrupting chemicals
(2009-09-28)
Chang, Sue-min
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, we investigated the photocatalytic kinetics and mechanisms of trioctylphosphine oxide-capped titanium dioxide (TOPO-capped TiO2) for degradation of two endocrine disrupting chemicals (EDCs), phenol and bisphenol A, which contained different hydrophobicity, chemiadsorbability, and degradable capacity. The TOPO-capped TiO2 exhibited high partition coefficients of 2.00 x 10(-4) and 3.42 x 10(-3) l/mg for phenol and bisphenol A, respectively. In addition, the bonded TOPO introduced substantial amounts of trapped holes at the surface. The high affinity toward the target compounds and stabilized charge carriers resulted in high photocatalytic activity of the modified TiO2. The TOPO-capped TiO2 exhibited 12- and 3-fold higher photocatalytic activities than P25 for decomposition of bisphenol A and phenol, respectively. The presence of the hydrophobic modifier inhibited the generation of hydroxyl radicals and led to the photocatalysis undergoing mainly from partition followed by chemisorption and interfacial charge transfer. Partition and interfacial charge transfer were the rate determining steps for the degradation of phenol and bisphenol A, respectively. According to the Langmuir-Hinshelwood model, the adsorption coefficient (K,) and intrinsic rate constant (k(r)) for phenol were 4.17 x 10(-2) l/mg and 5.60 x 10(-2) mg-g/l-min-m(2), respectively, while they were 2.91 x 10(-2) l/m and 2.18 x 10(-1) mg-g/l-min-m(2), respectively for bisphenol A degradation. The product of the k(r) and k(a) for bisphenol A was 2.7 times higher than that for phenol, revealing that the modified TiO2 favored decomposition of the compound which contains high chemiadsorbability and direct photocatalytic tendency in their individual systems. In contrast, the high degradable capability of phenol resulted in its preferential degradation in the competitive system. (C) 2009 Elsevier B.V. All rights reserved.
Preparation of phosphated Zr-doped TiO(2) exhibiting high photocatalytic activity through calcination of ligand-capped nanocrystals
(2009-07-25)
Chang, Sue-min
;
Hou, Chieh-yao
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
We incorporated phosphate and pyrophosphate species into the surface lattice of Zr-doped TiO(2) via calcination (>550 degrees C) of triocylphosphine oxide (TOPO)-capped nanocrystals that had been prepared using a non-hydrolytic sol-gel method. The phosphated Zr-doped TiO(2) calcined at 550-750 degrees C exhibited 2.88-5.28-fold higher photocatalytic activities for decomposition of bisphenol A (BPA) than did P25. Moreover, the sample prepared through calcination at 950 degrees C performed an extraordinary activity which was 40.3 times higher than that of P25. The high surface reactivities were resulted from co-doing of TiO(2) surface with Zr(4+) and phosphate/pyrophosphate species. Calcination enhanced the reactivity at elevated temperatures because it changed the microstructures and surface properties of phosphated Zr-doped TiO(2). The average crystallite size increased dramatically from 10.2-10.8 to 16.1 nm when the temperature increased from 750 to 950 degrees C. This change was associated with the formation of pyrophosphate species through condensation of the concentrated phosphate species. Dehydration resulted in substantial amounts of oxygen vacancies (O(M)/M(S) = 1.38) and Ti(3+) ions in the surface layers of the phosphated Zr-doped TiO(2) calcined at 950 degrees C. The dehydrated TiO(2) displayed high affinity toward BPA with a maximum adsorption capacity of 5.35 mg/g. The appearance of signals for Ti(4+)-O(2)(-) in the EPR spectrum of the modified TiO(2) in the dark indicated its high capability for the chemisorption of O(2). In addition, the remarkable decrease in the intensities of trapped electrons in the sample under an O(2) atmosphere revealed that efficient charge transfer occurred from the trapped sites to the electron scavenger. Thus, the phosphated Zr-doped TiO(2) calcined at high temperatures exhibit improved adsorbability toward reactants and enhanced interfacial charge transfer, resulting in outstanding photocatalytic activity. (C) 2009 Elsevier B.V. All rights reserved.
Preparation of phosphated Zr-doped TiO2 exhibiting high photocatalytic activity through calcination of ligand-capped nanocrystals
(2009-07-25)
Chang, Sue-min
;
Hou, Chieh-yao
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
We incorporated phosphate and pyrophosphate species into the surface lattice of Zr-doped TiO2 via calcination (>550 degrees C) of triocylphosphine oxide (TOPO)-capped nanocrystals that had been prepared using a non-hydrolytic sol-gel method. The phosphated Zr-doped TiO2 calcined at 550-750 degrees C exhibited 2.88-5.28-fold higher photocatalytic activities for decomposition of bisphenol A (BPA) than did P25. Moreover, the sample prepared through calcination at 950 degrees C performed an extraordinary activity which was 40.3 times higher than that of P25. The high surface reactivities were resulted from co-doing of TiO2 surface with Zr4+ and phosphate/pyrophosphate species. Calcination enhanced the reactivity at elevated temperatures because it changed the microstructures and surface properties of phosphated Zr-doped TiO2. The average crystallite size increased dramatically from 10.2-10.8 to 16.1 nm when the temperature increased from 750 to 950 degrees C. This change was associated with the formation of pyrophosphate species through condensation of the concentrated phosphate species. Dehydration resulted in substantial amounts of oxygen vacancies (O-M/M-S = 1.38) and Ti3+ ions in the surface layers of the phosphated Zr-doped TiO2 calcined at 950 degrees C. The dehydrated TiO2 displayed high affinity toward BPA with a maximum adsorption capacity of 5.35 mg/g. The appearance of signals for Ti4+-O-2(-) in the EPR spectrum of the modified TiO2 in the dark indicated its high capability for the chemisorption of O-2. In addition, the remarkable decrease in the intensities of trapped electrons in the sample under an O-2 atmosphere revealed that efficient charge transfer occurred from the trapped sites to the electron scavenger. Thus, the phosphated Zr-doped TiO2 calcined at high temperatures exhibit improved adsorbability toward reactants and enhanced interfacial charge transfer, resulting in outstanding photocatalytic activity. (C) 2009 Elsevier B.V. All rights reserved.