•The removal of isovaleraldehyde by surface plasma discharge was studied.•Operating parameters are tested at pilot scale with high flow rate.•The scale-up of plasma reactors were discussed.•Plasma ...process was successfully extrapolated at larger scale.
This work investigated the performance of Isovaleraldehyde (3-methylbutanal) removal from gas streams using continuous flow surface discharge plasma at room temperature. The feasibility of pollutant removal using up-scaled reactor was systematically assessed by monitoring removal efficiency and mineralization at different operational parameters, such as specific energy, air flow rate and inlet concentration. Results show that increasing flow rate lead to improve the removal capacity. For example, when flow rate extends two times, the removal capacity varies from 0.6 to 1.1gh−1. Moreover, when specific energy increased, both removal capacity and mineralization were enhanced. Additionally, a comparison between laboratory and pilot scales using surface discharge plasma system was carried out. A methodology of scaling up the surface discharge plasma system was proposed. In this context, removal capacities were compared for different continuous reactors: two reactors at laboratory scale (planar and cylindrical reactor), and pilot unit. The results suggest that the plasma reactor scale-up for pollutant removal can be feasible.
In this work, a solution for the treatment of toxic gases based on a photocatalytic process using TiO2 coated on a cellulosic support, has been investigated. Here, cyclohexane was chosen as the ...reference for testing its removal efficiency via a continuous front flow reactor as type A anti-gas filters. The photocatalytic support was firstly characterized by EDX, to confirm its elemental composition. Then, the experiments were carried out, starting with a batch reactor in order to evaluate the degradation efficiency of the photocatalytic media, as well as the monitoring of the photocatalytic process which allowed the establishing of a carbon mass balance corresponding to the stoichiometric number of our target pollutant. The transition to a continuous treatment with a front flow reactor aims to highlight the influence of the input concentration (0.29–1.78 mM m−3) under different flow rates (12, 18 and 36 L min−1). The relative humidity effect was also investigated (from 5 to 90% of humidity) where an optimum rate was obtained around 35–45%. In addition, the mineralization rate was monitored. The major rates obtained were for a cyclohexane input concentration of 0.29 mM m−3 in wet condition (38%) at an air flow rate of 18 L min−1, where the CO2 selectivity reached 77% for an abatement of 62%. In order to understand the limiting steps of the photocatalytic process, a model considering the reactor geometry and the hydraulic flow was developed. The obtained results showed that the mass transfer must be considered in the photocatalytic process for a continuous treatment. The Langmuir-Hinshelwood bimolecular model was also developed to represent the influence of the humidity.
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•Influence of key operating parameters for the elimination of Cyclohexane.•Monitoring of carbon mass balance of the degradation process.•Simulation of degradation including mass transfer step in continuous reactor.•Simulation of relative humidity effect of reactor performance.
General scheme for combined NTP and photocatalysis. Display omitted
•A synergetic effect was observed by combining plasma SDBD and photocatalysis.•A model based on chemical and mass transfer steps ...was developed.•The model describes successfully the degradation of isovaleraldehyde by each process.•By-products formation was well simulated by the model.•Synergetic effect is taken into account by acting on the mass transfer coefficient.
This paper deals with photocatalysis (TiO2+UV), nonthermal plasma (NTP) and their combinations. These processes have been widely studied for isovaleraldehyde (Isoval) treatment. Isoval removal, selectivity of CO2 and CO, and ozone formation are investigated in order to evaluate the performance of the combined process. The results show that the performance of the process has enhanced and a synergetic effect is observed.
On the other hand, this work aims at investigating kinetic modeling of combined process with taking into account the mass transfer step. The model is based on mass balances in three types of region: bulk region, discharge zone and solid phase which contains the photocatalyst. The oxidation in discharge and solid phases is described in two stages. Firstly, the removal of Isoval gives an equivalent intermediate (EI). Secondly, EI is oxidized into carbon dioxide (CO2) and carbon monoxide (CO). This simplified approach of removal allows for an agreement between modeling and empirical data in terms of degradation and mineralization. It also allows for the simulation of NTP and photocatalytic kinetics without knowing the plausible pathway. Moreover, the synergetic effect can be represented correctly by increasing mass transfer constant.
A scale-up procedure was assessed in this study to predict the fixed bed adsorption behaviors with aging granular activated carbon (GAC) for various micropollutants (pesticides, pharmaceuticals). Two ...assumptions of this upscaling methodology (i.e., involving equal adsorption capacities and surface diffusivities between the batch test and the fixed bed) were studied for the first time to investigate the aging effect on the adsorption capacity and kinetics of carbon at full scale. This study was conducted in natural waters (the Seine River) treated by Veolia Eau d’Ile de France in Choisy-Le-Roi, a division of Syndicat des Eaux d’Ile de France, aiming to monitor real industrial conditions. The isotherms showed that the adsorption capacity for most compounds was significantly affected by aging. For the mass transfer coefficients (i.e., as determined by the homogeneous surface diffusion model (HSDM)), different patterns of adsorbate/adsorbent behaviors were observed, suggesting different competition mechanisms. The model predictions (i.e., HSDM) performed with all parameters obtained during the batch tests tended to overestimate the full-scale pilot adsorption performance. This overestimation could be compensated for by applying a scaling factor. Finally, an empirical pseudo-first order function was used to model the impact of the GAC service time on the characteristic adsorption parameters. Thus, our scale-up procedure may enable the prediction of long-term fixed bed adsorption behaviors and increase the model efficiency for practical implementation.
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•Adsorption capacities of the GAC reduced seriously after the 6 months of use.•Ds reached maximum after several months of use followed by a decrease.•An SF was required to predict the adsorption behaviors of the fixed bed.•A new pseudo-first order function was employed to model the impact of GAC aging on the adsorption parameters.
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•Titania applied onto cellulosic paper was used as a photocatalyst.•Salinity and dual pollution of organic and mineral was monitored.•Optimization of textile effluent removal was ...performed using RSM approach.•Zinc contributed in free hydroxyl radicals generation that enhanced dye degradation.•Possible degradation mechanisms were discussed.
In the present research, the optimization of the photocatalytic degradation of simulated textile effluent containing two pollutants (Methylene blue (MB) and Zinc) consisted of studying the variation of four parameters, namely initial MB concentration (MBI, mg/L), zinc concentration (Zn2+I, mg/L), sodium chloride concentration (NaClI, M) and flow rate (Q, mL/min) through a design of experiment using the response surface methodology approach. Results showed that MB degradation depends by order of importance on NaCl concentration > MB concentration > ionic zinc concentration > flowrate. Modeling results presented a good concordance between predicted and experimental values with acceptable correlation coefficients (R2 = 0.9879 and R2 (adjusted) = 0.9773). Desirability function was applied on the second-order polynomial equation to determine the optimal experimental condition for fastest total photocatalytic degradation and it was identified as follows: For a maximal target of 85.91% and a desirability of d = 1.0, MB = 75 mg/L, Zn2+ = 45 mg/L, NaCl = 0.125 M and Q = 500 mL/min. Moreover, results showed that zinc had a good affinity to cellulose material and contributed on enhancing the photocatalytic activity in terms of degradation. Mineralization of the dye was assessed for the optimal conditions using the TOC method. Moreover, special attention was also paid to better understand the effect of inorganic pollutant, scavenging effects of different molecules such as EDTA, isopropyl alcohol and CCl4 were examined and discussed.
A hybrid system combining plasma with photocatalysis for treatment of refrigerated food chambers.
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•A possible way to treat the air in refrigerated food chambers is ...proposed.•Non-thermal plasma was coupled to photocatalysis for indoor air treatment.•The impact of the operating parameters on performance of the process are tested.•The removal of propionic acid and benzene each alone and in mixture are studied.•Poisoning and catalyst regeneration capacity with non-thermal plasma is studied.
The purpose of this study is to evaluate the efficiency of non-thermal plasma (NTP) and heterogeneous photocatalytic processes for indoor air treatment of refrigerated food chambers. Propionic acid and benzene were chosen as target pollutants to simulate odors inside a fridge. Firstly, the microstructure of the used catalyst was investigated by transmission electron microscopy (TEM). The influence of operating parameters such as pollutant concentration, type of system (mono-compound or bi-compound system), duration of photocatalytic degradation and relative humidity in the indoor air were investigated. Our findings show a synergetic effect between NTP and photocatalysis for malodors removal. Additionally, the mineralization of pollutant is directly controlled by the amount of ozone produced by the plasma discharge then it decomposes on the TiO2-based catalytic surface. Our results highlight also the key role of the generated reactive oxygen species (hydroxyl radials and atomic oxygen) in (i) propionic acid and benzene removal, (ii) selectivity of CO2 and CO, (iii) by-products formation such as ozone formation. Moreover, the recovery of the initial photocatalytic activity was explored in details. A significant poisoning occurred when photocatalysis was carried out alone for the degradation of propionic acid and benzene. Results confirm that NTP plasma enhanced the photocatalytic activity. We also showed the effect of NTP plasma on the regeneration of the photocatalytic surface.
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•Adsorbent/Photocatalysis coupling configuration with integrated regeneration system was developed for mustard gas simulants.•Mass and Energy balances have been carried out to explore ...the process efficiency.•Continuous coupling configuration for CWA simulant treatment has been investigated.•Process validation under real environmental conditions.
This investigation and optimization of the adsorption and photocatalysis coupling process for treating chemical warfare agents (CWAs) were performed with a compact cartridge based on activated carbon felt (AF) and TiO2 photocatalyst deposited on luminous textiles. The target pollutants were simulants of the chemical warfare agent (yperite), methyl salicylate, diethyl sulfur (a simulant of sulfur mustard gas), and cyclohexane, which is the benchmark for type A gas filtration tests. To take better advantage of this new configuration, an optimization of the photocatalytic process was highlighted with an improvement of the regeneration process by implementing the integrated compactness of desorption by the Joule effect (in situ). In the case of methyl salicylate treatment, the recovery of the adsorption capacity of the AF were about 95% and a working time of 85% compared to initial adsorbent performance. For the second cycle regeneration, the recovered adsorption capacity was about 88% compared to initial capacity. We note also that the working time decrease by 15% for each regeneration step. The evaluation of the new coupling configuration aimed at highlighting the influence of a sulfur compound was encouraging, with a regeneration rate of the adsorbent of about 80%. Compared to MS, the regeneration seems to be more difficult. This is due to by-products (SO2, MSH) formation which is highlighted by the degradation pathway proposed. The removal efficiency of the coupling system (UV-LED/AF) under continuous process, was equal to 36%. This leads an increase in filter working time of 50 min over that of a conventional adsorption process. Special attention was paid to validating the coupling system performance in real conditions. The system was placed on a humanlike seated thermal manikin used to simulate an occupant of a chamber of 30 m3 with the realistic condition of applying chemical, biological, radiological, and nuclear (CBRN) agent protection. The time protection was 60 and 30 min for respective concentrations of about 150 and 300 mg.m−3.
This global investigation addressed how to overcome the scientific barriers to designing a compact, self-contained filtration cartridge for personal protection in CBRN emergency response and management in accordance with the United Nations Sustainable Development Goals (SDGs).
This study investigates and provides a solution for optimizing the photocatalytic treatment of toxic gases based on the use of TiO2 media deposited on luminous textiles. The target was the ...cyclohexane referent for the type A gas filtration tests. The photocatalytic supports were characterized by scanning electron microscopy. Then, the experiments conducted on a batch reactor showed that the TiO2-coated optical fiber media (in situ illumination configuration) performs better than conventional configuration (cellulosic TiO2 with external radiation "UV lamp". To take advantage of the new optical fiber media configuration, an intensification study was carried out by increasing the amount of TiO2 in the media and UV intensities of LED. Increasing these two parameters leads to an approximately fourfold increase in the degradation rate. The continuous treatment allowed the study to highlight the efficiency of the new configuration of the front flow reactors developed (PFR-LED) compared to the conventional configuration. This increased efficiency is demonstrated by the fourfold increase in the specific degradation rate of the optimized PFR-LED compared to the conventional reactor. The performance evaluation of the compact and optimized configurations of the frontal flow reactor (PFR-LED Optimized) aimed to highlight the influence of the inlet concentration under different flow rates. Furthermore, the effect of the number of optical fiber supports shows that the degradation rate and selectivity are enhanced. The results were obtained using four photocatalytic media (4OF/4UV-LED) for 1.19 mmol.m and#xfffd; 3 of cyclohexane input concentration at 18 L. min-1 of flow rate under optimal humidity conditions (38 %), constituting the ultimate rate of CO2 selectivity achieved (31 %) for an abatement of 59 %. This global investigation has allowed for the design of a new version of a compact reactor.This reactor provides an economical and efficient way to eliminate gaseous pollutants, which clearly meets the main aims of the UN Sustainable Development Goals (UN SDGs).
The selection of a proper sorbent for a given application is a complex problem. The design and efficiency of adsorption processes require an equilibrium adsorption model. Linear transformation is one ...of the methods available to estimate the adjustable parameters of isotherm models but possesses limitations compared to nonlinear regressions. A different approach to calculate predicted equilibrium isotherm values leading to an alternative nonlinear regression is presented in this paper and compared with usual regression methods. Adsorption isotherm data of gaseous THT onto three activated carbon materials constitute an experimental basis for the discussion. Assessment of the goodness-of-fit of the Langmuir model is supported by different selected test functions. The new nonlinear approach did not obtain the best results for each test function, but raises questions about the inherent combined error in regression procedures.
•Isovaleraldehyde elimination by DBD plasma and photocatalysis is studied.•Effects of some operating parameters on performance of each process are tested.•A synergetic effect is observed by coupling ...plasma DBD and photocatalysis.•The byproducts of isovaleraldehyde are identified and evaluated.•A possible pathway of isovaleraldehyde removal is proposed.
Removal of isovaleraldehyde from air was investigated experimentally by three processes: dielectric barrier discharge (DBD) plasma, photocatalysis and a DBD plasma/photocatalysis combination. The latter led to a synergetic effect.
Many operating parameters were investigated in this study such as the specific energy of discharge, the inlet concentration of isovaleraldehyde and the relative humidity. The UV light generated by the DBD plasma reactor did not activate the photocatalytic medium. Thus, its contribution to the removal of isovaleraldehyde by photocatalysis could be ignored. On the other hand, the use of external UV light significantly improved the removal efficiency.
Using a photocatalytic reactor in the presence of water vapor, in small amounts, had a promoting effect on the degradation due to the formation of OH radicals. The same phenomenon has been observed in other processes for small amounts of water in air.
The identified and analyzed byproducts were classified into four groups: intermediate products (propionic acid, acetic acid and acetone), carbon monoxide, carbon dioxide and ozone. The carbon balance on carbon products was achieved at about 90%.
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