Development of standardization methods for the performance tests of photocatalytic indoor air purification at high air velocities using a close-loop reactor

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Photocatalytic degradation of azo dye Metanil Yellow: Optimization and kinetic modeling using a chemometric approach

International audienceThe photocatalytic degradation of an azo dye Metanil Yellow was carried out in aqueous solution using TiO2 as photocatalyst under UV irradiation. The decolorization and degradation kinetics were investigated and both followed a pseudo first order kinetic according to Langmuir–Hinshelwood model. Using HPLC/DAD and GC/MS analyses, more than 10 major reaction intermediates were identified and a tentative degradation pathway was proposed. Furthermore, ion chromatography (IC) and TOC measurements revealed a complete mineralization of Metanil Yellow into CO2, N2, H2O and inorganic ions (NH4+, NO3− and SO42−). On the other hand, an experimental design based on the surface response methodology was applied to assess the individual and interaction effects of several operating parameters (dye concentration, TiO2 concentration, pH, light flux, etc.) on the treatment efficiency (dye removal time). Based on the experimental design data, a semi-empirical expression was obtained, permitting to predict and optimize the dye removal time. This model was very consistent with experiment results (correlation factor: 99.5%). Moreover, additional experimental results obtained under near optimal conditions were found to be very close to the predicted values. This work demonstrates well the utility and benefits of the experimental design approach for screening and modeling the reaction parameters. Furthermore, it contributes significantly to the improvement and better understanding of photocatalytic processes

Photocatalytic treatment of indoor air: Optimization of 2-propanol removal using a response surface methodology (RSM)

Vildozo, Daniel Ferronato, Corinne Sleiman, Mohamad Chovelon, Jean-MarcThis paper presents an experimental design methodology for the optimization of the photocatalytic removal of 2-propanol also called isopropyl alcohol (IPA) at indoor air concentration level (ppbv). The response surface methodology (RSM) for the modelization and optimization of the photodegraclation of 2-propanol in the presence of titanium dioxide was used. The effect of four different process parameters on the yield of 2-propanol mineralization was determined. Experiments were performed using an annular flow-through reactor with TiO2 as photocatalyst, 2-propanol as a volatile organic compound (VOC) model, under different ranges of relative humidity (RH: 0-60%), inlet concentration (100-700 ppbv) and flow rate (100-500mL min(-1)), TiO2 loading (5-20 g m(-2)). Analysis of reaction intermediates was conducted using an automated thermal desorption technique coupled with gas chromatography-mass spectrometry (ATD-GC-MS) whereas a gas chromatograph equipped with a pulsed discharge helium photoionization detector (GC-PDHID) was used for on-line measurements of CO and CO2 at ppbv level. RH was found as the principal parameter that affect significantly the mineralization and the formation of acetone, the principal reaction intermediate from the photocatalytic oxidation of 2-propanol. For example an immediate and total removal of 2-propanol at very low % of RH along with a high rate of mineralization without any by-products was found. Many strong interactions between the parameters were also found ([2-propanol]-flow rate, RH-[TiO2], [2-propanol]-RH). The model obtained (R-2 = 0.9965) shows a satisfactory correlation between the values of experimental data and predicted values of 2-propanol mineralization (CO2). (C) 2009 Elsevier B.V. All rights reserved

Reconfiguração socioterritorial e produtiva para o planejamento coletivo da microbacia de Larati

The Bolivian society has experienced episodes of reconfiguration in recent decades, linked to the expansion of urban areas and the decreasing rural agricultural activity. This research aims to analyze the territorial transformation in the peri-urban and rural context of the Larati microbasin (Sacaba, Cochabamba, Bolivia) based on a New Rurality approach, through qualitative methodologies of Research-Action. The findings revealed the accelerated urbanization process that the peri-urban zone of the microbasin is undergoing, to the detriment of agricultural lands and sociocultural aspects of agricultural production, which present a closer connection with market dynamics, while at the same time relegating ancestral practices. This context generates power struggles and conflicts between local organizations and external agents, complexifying the dynamics of territorial self-management and the application of collective productive dynamics for the management of common goods. Given this reality, reflections and prospective guidelines are proposed to strengthen the territorial self-management of social organizations, analyzing central elements such as natural resource governance, territorial planning that considers productive needs and urban development, as well as the proposal of public policies that are in line with the social reality.La sociedad boliviana ha vivido episodios de reconfiguración en las últimas décadas, ligados a la expansión de la mancha urbana y la decreciente actividad agrícola rural. Esta investigación pretende analizar la transformación territorial en el contexto periurbano y rural de la microcuenca Larati (Sacaba, Cochabamba, Bolivia) basada en un enfoque de Nueva Ruralidad, mediante metodologías cualitativas de Investigación Acción Participativa. Los hallazgos obtenidos dilucidaron el acelerado proceso de urbanización que sufre la zona periurbana de la microcuenca, en desmedro de tierras agrícolas y aspectos socioculturales de la producción agrícola, las cuales presentan una conexión más estrecha con las dinámicas mercantiles, mientras a la par relegan prácticas ancestrales. Este contexto genera pugnas de poder y conflictos entre organizaciones locales y agentes externos, complejizando las dinámicas de autogestión territorial y la aplicación de dinámicas productivas colectivas para el manejo de los bienes comunes. Ante esta realidad, se plantean reflexiones y lineamientos prospectivos para fortalecer la autogestión territorial de las organizaciones sociales, analizando elementos centrales como la gobernanza de los recursos naturales, la planificación territorial que contemple las necesidades productivas y el desarrollo urbano, así como el planteamiento de políticas públicas acordes a la realidad social.A sociedade boliviana tem vivido episódios de reconfiguração nas últimas décadas, ligados à expansão da mancha urbana e à diminuição da atividade agrícola rural. Esta pesquisa pretende analisar a transformação territorial no contexto periurbano e rural da microbacia de Larati (Sacaba, Cochabamba, Bolívia) com base em uma abordagem de Nova Ruralidade, por meio de metodologias qualitativas de Investigação-Ação Participativa. Os achados obtidos elucidaram o acelerado processo de urbanização que sofre a zona periurbana da microbacia, em detrimento de terras agrícolas e aspectos socioculturais da produção agrícola, que apresentam uma conexão mais estreita com as dinâmicas mercantis, enquanto relegam práticas ancestrais. Esse contexto gera conflitos de poder e conflitos entre organizações locais e agentes externos, complexificando as dinâmicas de autogestão territorial e a aplicação de dinâmicas produtivas coletivas para o manejo dos bens comuns. Diante dessa realidade, são propostas reflexões e diretrizes prospectivas para fortalecer a autogestão territorial das organizações sociais, analisando elementos centrais como a governança dos recursos naturais, o planejamento territorial que contemple as necessidades produtivas e o desenvolvimento urbano, bem como a proposição de políticas públicas adequadas à realidade social

Analysis of gas phase intermediates and mineralization during the photocatalytic oxidation of organic pollutants: a critical step towards the performance evaluation

AIR:EAU+DCA:DVI:MSL:CFE:LFI:JMCThis work illustrates the capabilities of two advanced analytical methods, Automated Thermal Desorption/Gas Chromatography/Mass Spectrometry, (ATD/GC/MS) and Gas Chromatography, Pulse Discharge Helium Ionization Detector, (GC/PDHID) for a better understanding of the photocatalytic degradation of organic compounds in air at ppb(v) levels. For this purpose two compounds, viz. dichlorvos and 2-propanol were chosen and the influence of relative humidity (RH%) on the oxidation efficiency was investigated. According to the RH levels, different mechanisms of degradation as well as rate of mineralization were proposed. For example at 40% RH, the main reaction intermediates coming from dichlorvos degradation was dichloroacetaldehyde while traces of phosgene were observed. In contrast, at 0% RH, trichloroacetaldehyde was found to be the main intermediate and a higher amount of phosgene was observed. When only the conversion rate was followed, it was impossible to assess the photocatalytic efficiency of the air cleaning system since whatever RH values considered, high rates of conversion were always measured. However using PDHID detector it was possible to calculate the rate of mineralization which varies drastically as a function of RH: a decrease in the mineralization rate with increasing RH is shown. In addition, it was shown that during photocatalytic treatment of bilge water in an aerated reactor, volatile organic compounds (VOCs) were emitted which are potential source of pollution for workers in engine room. In this case, an additional treatment of the gaseous phase would be necessary

STANDARDIZATION METHODS FOR THE PERFORMANCE EVALUATION OF PHOTOCATALYTIC MEDIAS FOR INDOOR AIR APLICATIONS

International @ AIR+DVI:FDA:CFE:EPU:JMC:CGUInternational audienceThe Photocatalytic Oxidation (PCO) seems to be a promising technique for commercial air cleaning applications1. However besides the numerous scientific publications2,3 there are still potential drawbacks inherent with this technology, like the risk of dangerous by-products generations by incomplete reactions. The absence of standard methodologies in order to evaluate the real performance of the process are the main issues that need to be addressed to ensure successful applications. In order to better understand the photocatalytic process in indoor air treatments the Normacat Project was established by two french laboratories (IRCELYON, IPREM) and several industrials. It has as main objectives the development of: i) new experimental approaches, tools and test benches to measure the efficiencies of photocatalytic media under typical indoor air conditions, ii) new photocatalytic materials iii) and to give recommendations to improve materials and systems. The photocatalytic performance of PCO medias were study using two different test benches: a photoreactor designed according to the standard ISO 22197 at realistic low VOCs concentrations (<20 ppbv) and a new experimental close-loop reactor using high air velocities (m s-1 range), equivalent to those encountered in HVAC (heating, ventilation and air conditions) systems. Robust sensitive analytical methods were also developed: for the conversion of the initial VOCs, a chromatograph equiped with a pulsed photoionization detector (GC-PID), for the quantification and identification of the reaction by-products an automated thermal desorption technique coupled with gas chromatography-mass spectrometry (ATD-GC-MS), for the analysis of CO, CO2 at ppbv levels a gas chromatograph equiped with a plasma emission detector (GC-PED) and for the on-line formaldehyde and acetaldehyde detection at low levels a gas chromatograph equiped with a pulsed discharge helium photoionization detector (GC-PDHID). A representative VOC mixture found in buildings (Toluene, n-Heptane, Acetone, Acetaldehyde and Formaldehyde) was used as target pollutants at typical indoor air levels. The influence of the different supports (organic cellulose, glass fibers, quartz fibers, ceramic foam and active carbon) on the photocatalytic activity used by commercial PCO air cleanear systems was studied and evaluated in terms of conversion, mineralization (CO2) and by-products formation. The effects of different parameters (humidity level, residence time, inlet concentrations UV lamps, radiation intensity) will be also discussed

NORMACAT PROJECT Normalized Tests using a Closed-Loop Reactor for the Performance Evaluation of Commercial Photocatalytic Medias for Indoor Air Aplications

International @ AIR+DVI:FDA:EPU:CFE:JMC:CGUInternational audienceSince research found that poor indoor air quality (IAQ) can significantly affect peoples health, comfort, satisfaction and productivity, the reduction of indoor air pollutants by air cleaning/purification devices have received a considerable interest [1]. A new substantial market for removing various indoors contaminants from residences and offices is settled. So far, between the numerous techniques available, photocatalytic oxidation (PCO) technology has shown to be well suited for the purification of indoor air [2-3]. Besides that PCO is still under development, nowadays in the market, numerous PCO cleaners are commercially available and promoted. However, there is limited information available regarding their performance and there are no standard methods for testing the VOCs removal efficiency from PCO air cleaning devices. The evaluation of the performance of the photocatalytic filters used in these air cleaning systems is the key issue of this study. Different TiO2-supported catalysts, from commercial air cleaning devices, based on photocatalytic technology for indoor air treatment, were tested in a new experimental close-loop reactor (Figure 1). The photocatalytic efficiency of the TiO2 catalysts immobilized on various supports (organic cellulose, glass fibers, quartz fibers and active carbon) were evaluated at realistic conditions: low VOCs concentrations (ppbv levels) and high airflow rates (m3h-1 range), equivalent to those encountered in HVAC (heating, ventilation and air conditions) systems. The filters were evaluated in terms of conversion, mineralization (CO2) and by-products formation. For this purpose, robust sensitive analytical methods were also developed: for the conversion of the initial VOCs, a chromatograph equipped with a pulsed photoionization detector (GC-PID), for the quantification and identification of the reaction by-products an automated thermal desorption technique coupled with gas chromatography-mass spectrometry (ATD-GC-MS), for the analysis of CO, CO2 at ppbv levels a gas chromatograph equipped with a plasma emission detector (GC-PED) and for the on-line formaldehyde and acetaldehyde detection at low concentrations a gas chromatograph equipped with a pulsed discharge photoionization detector (GC-PDID) was used. According to the results of this work, if the photocatalytic efficiency of the catalyst was measured only by taking into account the VOC removal capacity, all the filters were considered highly effective. Our results showed that the mineralization (CO2) of the target pollutants and the formation of reaction intermediates have to be considered in order to obtain a relevant evaluation of the photocatalytic activity of the filters

NORMACAT PROJECT: Development of standardization methods for the performance evaluation of photocatalytic medias under realistic indoor air conditions.

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