Kinetic Modeling of VOC Photocatalytic Degradation Using a Process at Different Reactor Configurations and Scales

International audienceThis work investigated the performance of isovaleraldehyde (3-methylbutanal) removal from gas streams in photocatalytic reactors at room temperature. The feasibility of pollutant removal using the up-scaled reactor was systematically assessed by monitoring the removal efficiency at different operational parameters, such as geometries of reactor, air flow rate and inlet concentration. A proposal modeling for scaling up the photocatalytic reactors is described and detailed in this present study. In this context, the photocatalytic degradation of isovaleraldehyde (Isoval) in gas phase is studied. In fact, the removal rate has been compared at different continuous flow reactors: a photocatalytic tangential reactor (PTR), planar reactor and P5000 pilot. The effects of the inlet concentration, flow rate, geometries and size of reactors on the removal efficiency are also studied. A kinetic model taking into account the mass transfer step is developed. The modeling is done by introducing an equivalent intermediate (EI) formed by the photo-oxidation of Isoval. This new approach has substantially improved the agreement between modeling and experiments with a satisfactory overall description of the mineralization from lab to pilot scales

Study of synergetic effect by surface discharge plasma/TiO2 combination for indoor air treatment: sequential and continuous configurations at pilot scale

International audienceThis work investigated the performance of butyraldehyde decomposition with the help of dielectric barrier discharge (DBD) plasma coupled with photocatalysis (TiO2+UV) at room temperature. Effects of flow rate and initial butyraldehyde concentration on the decomposition and the distribution of byproducts were examined and discussed. The combination of these two technologies led to an enhancement of butyraldehyde abatement compared to the separate systems at pilot scale from 5 to 10 m3.h−1 of flowrate. The synergy factor due to combination processes ranged from 1.13 to 1.27. In the same way, CO2 selectivity was significantly improved when compared to the DBD plasma alone. In this research, DBD plasma system and an immobilized TiO2 photocatalysis system is sequentially combined to oxidize the target pollutant. Indeed, different ways to combine sequentially DBD plasma with photocatalytic materials are listed. Results at pilot scale showed that when photocatalyst is placed in the post discharge, the performance of sequential coupling plasma–photocatalyst process is improved in term of decomposition, by-products formation and energy yiel

Use of DBD plasma, photocatalysis, and combined DBD plasma/photocatalysis in a continuous annular reactor for isovaleraldehyde elimination - Synergetic effect and byproducts identification

International audienceRemoval 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 OHradical dot 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%

Removal of trimethylamine and isovaleric acid from gas streams in a continuous flow surface discharge plasma reactor

International audienceThe removal of isovaleric acid (IVA) and trimethylamine (TMA) using nonthermal plasma (NTP) in a continuous surface discharge reactor is investigated. The influence of the energy density shows that its increment is accompanied by the increase of the removal rate. At flowrate equal to 2 m3 h−1, when energy density extends three times, the removal rates of IVA and TMA are increased from 5 to 15 mmol m−2 h−1 and from 4 to 11 mmol m−2 h−1, respectively. The impact of relative humidity (RH) is also studied. An increase in % RH (up to 20%) leads to a decrease of the removal rate. Additionally, the formation of by-products in the surface discharge reactor and the plausible reaction mechanism of the two VOC were also detected and discussed. Moreover, a kinetic model taking into account the mass transfer step is developed in order to represent the experimental results. The model shows a good agreement with experimental results

Modeling and simulation of VOCs removal by nonthermal plasma discharge with photocatalysis in a continuous reactor: Synergetic effect and mass transfer

International audienceThis 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

Photocatalytic degradation of indole–4-methylphenol mixture in an aqueous solution: optimization and statistical analysis

International audienceThe photocatalytic degradation of indole and 4-methylphenol mixture, using ZnO, was studied. The optimal conditions for the degradation were determined using response surface methodology. We showed that in, our experimental domain, the quasi-complete degradation of the mixture’s organic constituents is possible. Moreover, we note that the effects of the entire variables are not linear. Indeed, the optimum removal conditions were determined. Thus, the optimal conditions for indole degradation were 1.5 mg/L catalyst concentration, 2.5 L/min airflow, and 7.16 pH. For 4-methylphenol, they were 1.37 mg/L of catalyst concentration, 2.38 L/min airflow, and 6.96 pH. Under optimized conditions, the complete photocatalytic degradation was obtained at 30 μL/L 4-methylphenol and 10 mg/L indole concentration. Similarly, the optimized correlation coefficients R2 and for a quadratic model was satisfactorily evaluated as 99.5 and 99.1%, respectively with indole and 99.7 and 99.4%, respectively, with 4-methylphenol. Our results reveal that the tested ZnO photocatalyst can be employed as a powerful tool for the pollutant degradation in wastewater

Abatement of 3-methylbutanal and trimethylamine with combined plasma and photocatalysis in a continuous planar reactor

International audienceThis paper deals with the 3-methylbutanal ((CH3)2CHCH2COH) removal with the help of a nonthermal surface plasma discharge coupled with photocatalysis. The capability of this process for gas treatment was studied. A planar reactor system was developed in order to perform the effect of adding photocatalytic material in plasma surface discharge barrier dielectric (SDBD) zone on (i) 3-methylbutanal removal, (ii) selectivity of CO2 and CO, (iii) byproducts formation such ozone formation. It was found that the influence of the UV light generated by SDBD reactor was very low. The activation of the photocatalyst media could be negligible. Whereas, the introduction of external UV light to the process improves significantly the removal efficiency of 3-methylbutanal (3MBA) and the mineralization. A synergetic effect was observed by combining plasma SDBD and photocatalysis from all experiments and with other pollutant such as trimethylamine (N(CH3)3). Moreover, the byproducts of 3MBA were identified and evaluated with plasma SDBD, photocatalysis and plasma SDBD/photocatalysis combination

Review on discharge Plasma for water treatment: mechanism, reactor geometries, active species and combined processes

Owing to the water crisis, the development of innovative and clean advanced oxidation processes to decompose a variety of harmful organic compounds in wastewater becomes the main challenge for many research teams. Cold discharge plasma is one of the most widely studied and developed processes, owing to its low energy cost and easy to operate. The impact of different factors on the decontamination effectiveness of discharge plasma are detailed in this review. The generation and reaction mechanisms of reactive species in discharge plasma systems have also gained a significant interest and hence discussed. Several potentials and laboratory-scale reactor design recently reported are discussed and schematically presented. The recent combination of discharge plasma decontamination and other processes in both post and pre-treatment configuration are reported. Some applications of water treatment based on discharge plasma at the pilot scale have been addressing

Synthesis of novel biocomposite powder for simultaneous removal of hazardous ciprofloxacin and methylene blue: Central composite design, kinetic and isotherm studies using Brouers-Sotolongo family models

Over the past decades, extensive efforts have been made to use biomass-based-materials for wastewater-treatment. The first purpose of this study was to develop and characterize regenerated-reed/reed-charcoal (RR-ChR), an enhanced biosorbent from Tunisian-reed (Phragmites-australis). The second aim was to assess and optimize the RR-ChR use for the removal of binary ciprofloxacin antibiotic (CIP) and methylene blue dye (MB), using Central Composite Design under Response Surface methodology. The third purpose was to explain the mechanisms involved in the biosorption-process. The study revealed that the highest removal-percentages (76.66 % for the CIP and 100 % for the MB) were obtained under optimum conditions: 1.55 g/L of adsorbent, 35 mg/L of CIP, 75 mg/L of MB, a pH of 10.42 and 115.28 min contact time. It showed that the CIP biosorption mechanism was described by Brouers–Sotolongo-fractal model, with regression-coefficient (R2) of 0.9994 and a Person’s Chi-square (X2) of 0.01. The Hill kinetic model better described the MB biosorption (R2 = 1 and X2 = 1.0E-4). The isotherm studies showed that the adsorbent surface was heterogeneous and the best nonlinear-fit was obtained with the Jovanovich (R2 = 0.9711), and Brouers–Sotolongo (R2 = 0.9723) models, for the CIP and MB adsorption, respectively. Finally, the RR-ChR lignocellulosic-biocomposite-powder could be adopted as efficient and cost-effective adsorbent