•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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•Proposal of a potential method of treating indoor air in hospitals.•Degradation of VOCs in a binary mixture system by TiO2 on Luminous textile.•Testing the impacts of key parameters ...on the photocatalytic performance.•Kinetic modelling and mass transfer limitation were investigated.
Indoor air pollution is a complex problem that involves a wide range and diversity of pollutants that threaten human health. In this context, significant efforts must be made to improve the quality of indoor air. It is therefore important to start controlling the sources of indoor pollution. However, where eliminating or minimizing sources of emissions is not technically feasible, technologies to reduce them should be used. The present work deals with the photocatalytic depollution of hospitals indoor air, using a continuous photocatalytic process. In order to get closer to real conditions, two model pollutants representing the indoor air of hospitals were chosen as targets; chloroform (CHCl3) and glutaraldehyde (C5H8O2). The photocatalytic oxidation of VOCs alone and their mixture (binary mixing system) has been studied on a pilot scale. Indeed, the experiments were carried out in a continuous planar reactor using a new technology based on the TiO2/optical fiber photocatalyst.
The effects of experimental conditions such as air flow rate (4–12 m3.h−1), VOCs inlet concentration (4–40 mg.m−3) and humidity levels (5–90%) were pointed out. The photocatalytic effect of the OF-TiO2 composite was found to be improved under UV irradiation as compared to TiO2. The presence of water molecules in small amounts (less than RH = 30%) can promote the degradation process due to the formation of •OH radicals. Biomolecular Langmuir-Hinshelwood model including mass transfer step has been developed to represent the process behavior. Reusability test show that the optical fiber -based photocatalysts presented good photocatalytic activities towards CHCl3/C5H8O2 removal.
Odor monitoring plays a crucial role in implementing suitable odor mitigation strategies at composting plants. Odor activity value (OAV) analysis is an instrumental-based approach that could simplify ...and reduce costs of odor monitoring by dynamic olfactometry; yet, the relationship between both methodologies has not been fully explored. In this study, the OAV feasibility to predict odor concentration (OC in OUE m−3) was assessed during the active composting phase of six solid wastes and three digestates at pilot scale. To this end, 92 gas samples were analyzed by analytical methods (i.e., GC/MS) and dynamic olfactometry (EN 13725). For 22 quantified odorants, OAV was calculated as the ratio of a compound's chemical concentration to its corresponding odor detection threshold (ODT). OAVs were then correlated to OC by simple linear and partial least squares (PLS) regressions. The sum of all OAVs in the gas samples (OAVsum) and the maximum OAV (OAVmax) yielded moderately strong linear correlations against OC (R2: 0.67–0.73), thus providing overall insight into OC trend along composting. A PLS model consisting of weighted OAVs of 10 odorants enhanced OC predictions. OAVs explained from 76% to 74% of the OC variance throughout the PLS model validation. Furthermore, OC values regressed by the PLS model were less underestimated (7%) than those predicted by OAVmax and OAVsum (11–13%). Based on results from the OAVmax and PLS regression analysis, hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide were highlighted as the major odor contributors during composting of organic substrates.
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•Gas emissions from composting were analyzed by sensory and analytical methods.•OAVs provide overall insight into OC trend (R2: 0.67–0.73).•A PLS regression model enhanced OC predictions through OAVs (R2: 0.74–0.76).•Volatile sulfur compounds were the major odor contributors during composting.
An hybrid system of combined plasma with photocatalysis for treatment of hospital indoor air.
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•A possible way for treatment of air from hospitals and swimming pools is proposed.•The ...destruction of CVOC in air by photocatalysis and plasma and coupling is studied.•The synergistic effect of the combined system is observed.•The effects of operating parameters on the performance of each process are tested.•TiO2 + UV showed high performance in the mineralization and ozone elimination.
The purpose of this study is to evaluate the efficiency of non-thermal plasma and heterogeneous photocatalysis processes for indoor air treatment using cylindrical continuous reactor at pilot scale and high flow rates. Trichloromethane (CHCl3) also called chloroform was chosen as a model pollutant representing hospital indoor air. This pollutant is considered as carcinogenic, mutagenic and reprotoxic agent. The effect of several parameters such as inlet pollutant concentrations (25–300 mg m−3), flow rates (2–8 m3 h−1), relative humidity of the effluent (5, 30, 50 and 90%) as well as input of the plasma discharge (9–21 kV) on the photodegradation of trichloromethane is investigated.
Our findings show that the increase of flow rate leads to a reduction of degradation efficiency, while the humidity promotes the degradation in the case of photocatalysis process due to the formation of OH radicals.
Moreover, the addition of a photocatalyst under UV radiation in the discharge zone enhances the reduction of ozone and CO gases compared to plasma process alone.
The combination of plasma DBD and photocatalysis enhances the removal efficiency with a synergetic effect, leading to removal efficiency higher than 10% if we consider the sum of the contribution of each process separately.
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Photograph of prototype combining plasma and photocatalysis in situ.
•Isovaleraldehyde removal by plasma and photocatalysis is studied at pilot scale.•A synergetic effect is confirmed ...at high value of flowrate.•A real pollution from animal quartering centers has been treated.•The associated system seems to be a potential method in removing air pollutants.
In this study, a continuous process combining plasma and photocatalysis, at pilot scale, has been investigated on pollution treatment.
The degradation efficiency and by-products formation has been monitored through the variation of multiple parameters such as inlet concentration, specific energy, and residence time. Results show that process combination leads to an enhancement of pollutant degradation compared to the separate systems even at high flow rate (250m3h−1). Synergy factor due to this association ranged from 1.10 to 1.17. Furthermore, CO2 selectivity has significantly improved when comparing the combined system to that with plasma alone. Moreover, we note that adding a photocatalyst in the discharge zone leads to a reduction of ozone and CO formation compared to plasma process alone.
Based on this investigation, a methodology of scaling up the combined system was proposed. Indeed, as a practical application, an industrial reactor has been developed and tested for treating a real pollution from animal quartering centers. This investigation indicates that the combined system of photocatalysis with plasma is a promising method for removing air pollutants.
•The removal of isovaleric acid and trimethylamine by nonthermal plasma was studied.•The influences of injected energy and flowrate were tested.•A model based on chemical and mass transfer steps was ...developed.•The byproducts of isovaleric acid and trimethylamine were identified and evaluated.•The degradation pathways of the two VOCs were discussed.
The 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 2m3h−1, when energy density extends three times, the removal rates of IVA and TMA are increased from 5 to 15mmolm−2h−1 and from 4 to 11mmolm−2h−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.
Disinfection by-products (DBPs) are formed in swimming pools by the reactions of bather inputs with the disinfectant. Although a wide range of molecules has been identified within DBPs, only few ...kinetic rates have been reported. This study investigates the kinetics of chlorine consumption, chloroform formation and dichloroacetonitrile formation caused by human releases. Since the flux and main components of human inputs have been determined and formalized through Body Fluid Analogs (BFAs), it is possible to model the DBPs formation kinetics by studying a limited number of precursor molecules. For each parameter the individual contributions of BFA components have been quantified and kinetic rates have been determined, based on reaction mechanisms proposed in the literature. With a molar consumption of 4 mol Cl2/mol, urea is confirmed as the major chlorine consumer in the BFA because of its high concentration in human releases. The higher reactivity of ammonia is however highlighted. Citric acid is responsible for most of the chloroform produced during BFA chlorination. Chloroform formation is relatively slow with a limiting rate constant determined at 5.50 × 10−3 L/mol/sec. L-histidine is the only precursor for dichloroacetonitrile in the BFA. This DBP is rapidly formed and its degradation by hydrolysis and by reaction with hypochlorite shortens its lifetime in the basin. Reaction rates of dichloroacetonitrile formation by L-histidine chlorination have been established based on the latest chlorination mechanisms proposed. Moreover, this study shows that the reactivity toward chlorine differs whether L-histidine is isolated or mixed with BFA components.
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In this study, the treatment of petroleum wastewater has been investigated by applying heterogeneous photocatalytic process using a recirculating annual reactor. An attempt has been made to study the ...effect of operating parameters such as TiO
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load, initial concentration of the pollutant, emitted photonic flux, and pH of the solution. The degradation efficiency of toluene and benzene, as target molecules, was studied. In fact, result showed that the toluene is better degraded alone than when it is in a mixture. The rate of elimination of toluene separately was 89.5%, while it was 76.19 and 79.55% in the binary (toluene/benzene) and the ternary mixtures (toluene/benzene/xylene), respectively. Moreover, the mineralization of the solution decreased more rapidly when toluene was pure with a rate of 83.13% compared to binary and ternary mixtures. A mathematical model is proposed taking into account the parameters influencing the process performances. The mass transfer step, the degradation, and the mineralization kinetics of the pollutants were defined as model parameters. To build the model, mass balances are written in bulk region and catalyst phase (solid phase). The degradation mechanism on solid phase is divided in two stages. Firstly, the removal of toluene gives an equivalent intermediate (EI). Secondly, EI is oxidized into carbon dioxide (CO
2
). This approach gives a good agreement between modeling and empirical data in terms of degradation and mineralization. It also allows for the simulation of toluene kinetics without knowing the plausible chemical pathway. A satisfactory fit with experimental data was obtained for the degradation and mineralization of toluene.
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