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Comparison of aqueous photoreactions with TiO2 in its hydrosol solution and powdery suspension for light utilization / Tong-xu Liu in Industrial & engineering chemistry research, Vol. 50 N° 13 (Juillet 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7841–7848 Titre : Comparison of aqueous photoreactions with TiO2 in its hydrosol solution and powdery suspension for light utilization Type de document : texte imprimé Auteurs : Tong-xu Liu, Auteur ; Yuan Liu, Auteur ; Zhao-ji Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. 7841–7848 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Radiation  chemistry  Photochemistry  photographic  Reprographic  processes Résumé : In aqueous photoreaction systems, the existence of gradient light intensity throughout the reaction solution is one of the important restrictions to the efficiency of the overall photoreaction, which highly relies on the optical properties of the catalyst such as light absorption and scattering effects, the particle size of the catalyst, and the degree of agglomeration in its slurry. In this study, both synthesized TiO2 hydrosol and commercial TiO2 powder, Degussa TiO2 P25, were used as catalysts for comparison, in which their particulate and optical properties in aqueous solution/suspension were investigated. The characteristic results showed that the TiO2 hydrosol had smaller crystal sizes and particle sizes, but a lower degree of crystallinity compared to the P25 powder. As TiO2 hydrosol solution had the much lower light extinction coefficient than P25 suspension, the attenuation of light intensity gradient in the reaction solution containing more transparent TiO2 hydrosol was greatly eliminated. However, both types of catalysts demonstrated similar effects of significant light scattering in their solution/suspension. The photocatalytic activities of two catalysts were then evaluated in two sets of experiments for methyl orange (MO) and methylsulfonic acid (MSA) degradations, respectively. The much higher reaction rates of MO and MSA degradations were found in the TiO2 hydrosol solution than in the P25 suspension, because TiO2 hydrosol catalyst with much finer particles and higher transparency allowed the photoreactor system to work at a higher catalyst loading than the conventional TiO2 powdery catalyst. A new kinetic model considering three main factors of (i) the volumetric rate of photon absorption, (ii) effective reaction volume, and (iii) the effective surface area of catalyst in a cylindrical photoreactor was also established. This new model summarizes that the catalyst with a higher surface area, a lower light extinction coefficient, and a lesser light scattering effect would achieve better light utilization within the photoreactor system and is beneficial to achieve a higher efficiency of overall photoreaction. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102584j [article] Comparison of aqueous photoreactions with TiO2 in its hydrosol solution and powdery suspension for light utilization [texte imprimé] / Tong-xu Liu, Auteur ; Yuan Liu, Auteur ; Zhao-ji Zhang, Auteur . - 2011 . - pp. 7841–7848. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7841–7848 Mots-clés : Radiation  chemistry  Photochemistry  photographic  Reprographic  processes Résumé : In aqueous photoreaction systems, the existence of gradient light intensity throughout the reaction solution is one of the important restrictions to the efficiency of the overall photoreaction, which highly relies on the optical properties of the catalyst such as light absorption and scattering effects, the particle size of the catalyst, and the degree of agglomeration in its slurry. In this study, both synthesized TiO2 hydrosol and commercial TiO2 powder, Degussa TiO2 P25, were used as catalysts for comparison, in which their particulate and optical properties in aqueous solution/suspension were investigated. The characteristic results showed that the TiO2 hydrosol had smaller crystal sizes and particle sizes, but a lower degree of crystallinity compared to the P25 powder. As TiO2 hydrosol solution had the much lower light extinction coefficient than P25 suspension, the attenuation of light intensity gradient in the reaction solution containing more transparent TiO2 hydrosol was greatly eliminated. However, both types of catalysts demonstrated similar effects of significant light scattering in their solution/suspension. The photocatalytic activities of two catalysts were then evaluated in two sets of experiments for methyl orange (MO) and methylsulfonic acid (MSA) degradations, respectively. The much higher reaction rates of MO and MSA degradations were found in the TiO2 hydrosol solution than in the P25 suspension, because TiO2 hydrosol catalyst with much finer particles and higher transparency allowed the photoreactor system to work at a higher catalyst loading than the conventional TiO2 powdery catalyst. A new kinetic model considering three main factors of (i) the volumetric rate of photon absorption, (ii) effective reaction volume, and (iii) the effective surface area of catalyst in a cylindrical photoreactor was also established. This new model summarizes that the catalyst with a higher surface area, a lower light extinction coefficient, and a lesser light scattering effect would achieve better light utilization within the photoreactor system and is beneficial to achieve a higher efficiency of overall photoreaction. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102584j

Development of a photocatalytic wet scrubbing process for gaseous odor treatment / Tong-xu Liu in Industrial & engineering chemistry research, Vol. 49 N° 8 (Avril 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp.3617–3622 Titre : Development of a photocatalytic wet scrubbing process for gaseous odor treatment Type de document : texte imprimé Auteurs : Tong-xu Liu, Auteur ; Xiang-Song Li, Auteur ; Fang-bai Li, Auteur Année de publication : 2010 Article en page(s) : pp.3617–3622 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Photocatalytic  Wet  Scrubbing  Gaseous  Odor Résumé : In this study, methyl mercaptan (CH3SH) gas was used to prepare synthetic odorous gases, and a photocatalytic wet scrubbing process as a new approach was developed for treating such odorous gases. In this process, gaseous CH3SH is first absorbed by the solution, and the dissolved CH3SH/CH3S− is then adsorbed onto the solid surface of TiO2 particles and oxidized under UV illumination in the aqueous phase. Experiments were conducted under different reaction conditions of CH3SH loading, TiO2 dosage, and pH. The reaction kinetics of CH3SH reduction indicates that the pH of the reaction solution greatly influences the rate of CH3SH absorption by the solution. At pH < 11.5, CH3SH absorption by the solution is the rate-determining step (RDS), whereas at pH > 11.5, the photoreaction becomes the RDS in such a system. The experiments demonstrated that the efficiency of CH3SH degradation determined by two methyl mercaptan sensors and the ratio of odor removal determined by olfactometry measurements can be well maintained at high levels of >95% for a CH3SH loading of 10 g m−3 h−1. The main intermediates and final products from CH3SH degradation were identified by GC/MS and ion chromatography, and a pathway for CH3SH degradation with three routes is proposed and discussed. Odor samples to simulate real foul gases were also prepared and treated with this new process. An electronic nose technique was applied to indentify the patterns of odor characteristics before and after treatment. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1000295?prevSearch=Development%2Bof%2Ba%2B [...] [article] Development of a photocatalytic wet scrubbing process for gaseous odor treatment [texte imprimé] / Tong-xu Liu, Auteur ; Xiang-Song Li, Auteur ; Fang-bai Li, Auteur . - 2010 . - pp.3617–3622. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp.3617–3622 Mots-clés : Photocatalytic  Wet  Scrubbing  Gaseous  Odor Résumé : In this study, methyl mercaptan (CH3SH) gas was used to prepare synthetic odorous gases, and a photocatalytic wet scrubbing process as a new approach was developed for treating such odorous gases. In this process, gaseous CH3SH is first absorbed by the solution, and the dissolved CH3SH/CH3S− is then adsorbed onto the solid surface of TiO2 particles and oxidized under UV illumination in the aqueous phase. Experiments were conducted under different reaction conditions of CH3SH loading, TiO2 dosage, and pH. The reaction kinetics of CH3SH reduction indicates that the pH of the reaction solution greatly influences the rate of CH3SH absorption by the solution. At pH < 11.5, CH3SH absorption by the solution is the rate-determining step (RDS), whereas at pH > 11.5, the photoreaction becomes the RDS in such a system. The experiments demonstrated that the efficiency of CH3SH degradation determined by two methyl mercaptan sensors and the ratio of odor removal determined by olfactometry measurements can be well maintained at high levels of >95% for a CH3SH loading of 10 g m−3 h−1. The main intermediates and final products from CH3SH degradation were identified by GC/MS and ion chromatography, and a pathway for CH3SH degradation with three routes is proposed and discussed. Odor samples to simulate real foul gases were also prepared and treated with this new process. An electronic nose technique was applied to indentify the patterns of odor characteristics before and after treatment. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1000295?prevSearch=Development%2Bof%2Ba%2B [...]