A nonthermal plasma surface discharge (NPSD) coupled with photocatalysis.
Display omitted
•Removal of pollutant in air mixture by photocatalysis and plasma is investigated.•Synergetic effect of ...combined system is explored.•The by-products of each binary mixture were identified and evaluated.•Monitoring of mineralization and ozone has been done at pilot scale.
This paper mainly deals with the isovaleraldehyde degradation with the help of a nonthermal plasma surface discharge (NPSD) coupled with photocatalysis. The efficiency of NPSD reactor, for gas treatment, was studied for different binary mixtures: (1) mixture of aldehydes (Isovaleraldehyde and Butyraldehyde) and (2) mixture of aldehyde and amine (Isovaleraldehyde and Trimethylamine). A planar continuous reactor is used to investigate the effect of addition of another pollutant on the performance of oxidation process.
A synergetic effect was observed by combining NPSD and photocatalysis for the degradation of mixture of pollutants. In addition, combined NPSD/photocatalysis has significantly enhanced the CO2 selectivity, as compared to NPSD alone. This is attributed to the formation of more reactive species due to the presence of TiO2 in the plasma discharge zone. Moreover, ozone and UV light on TiO2, produced by plasma, have activated the surface leading to enhanced mineralization. In addition, the byproducts of each binary mixture were identified and evaluated.
A proposal for scaling-up the photocatalytic reactors is described and applied to the coated catalytic walls with a thin layer of titanium dioxide under the near ultraviolet (UV) irradiation. In this ...context, the photocatalytic degradation of isovaleraldehyde in gas phase is studied. In fact, the removal capacity is compared at different continuous reactors: a photocatalytic cylindrical reactor, planar reactor, and pilot unit. Results show that laboratory results can be useful for reactor design and scale-up. The flowrate increases lead to the removal capacity increases also. For example, with pilot unit, when flowrate extends four times, the degradation rate varies from 0.14 to 0.38 g h⁻¹ mcₐₜ ⁻². The influence of UV intensity is also studied. When this parameter increases, zboth degradation rate and overall mineralization are enhanced. Moreover, the effects of inlet concentration, flowrate, geometries, and size of reactors on the removal capacity are also studied.
Display omitted
•Butyraldehyde removal by plasma and photocatalysis is studied at pilot scale.•Effects of some operating parameters on performance of each process were tested.•A synergetic effect is ...confirmed by plasma and photocatalysis combined.•Sequential and continuous configurations of TiO2/MnO2 with plasma were tested.•Intermediates by-products of butyraldehyde has been identified.
Coupling nonthermal plasma with other processes has been studied over the past few years and promising results were obtained concerning VOCs removal for atmospheric pollution control. In this work, butyraldehyde (BUTY) removal by a dielectric barrier discharge (DBD) plasma coupled with different (photo) catalysts based on TiO2 and MnO2 was studied. DBD plasma system and an immobilized TiO2 and MnO2 at different percentages are continually and sequentially combined in order to decompose residual ozone. Indeed, different ways of combination are listed. Effects of relative humidity and initial BUTY concentration on its conversion rate and the distribution of byproducts were examined and discussed. Results with pilot scale showed that combination of plasma and photocatalysis led to an enhancement of BUTY abatement compared to the separate systems. When 100% of MnO2 catalyst was placed in the post discharge zone, the performance of sequential DBD/MnO2 combined system is improved in terms of decomposition and conversion rate of the pollutant. In the same way, CO was reduced and CO2 selectivity was significantly improved when compared to the DBD plasma alone. Intermediate byproducts were identified and BUTY removal pathways are suggested.
•PSS composting and storage gas samples were determined by chemical and olfactory analyses.•For gas samples, correlations between the chemical composition and its OC was investigated.•OAVMAX assumed ...that OC was equal to the sample’s highest OAV value.•OAVSUM assumed that OC was equal to the sum of all OAV for sample.•The 3 most odorant compound offered a good prediction of the olfactory results.
The objective of this study was to correlate the chemical composition and the odor concentration of emissions produced during storage and composting of pig slaughterhouse sludge (PSS). Seven experimental conditions were monitored using composting reactors with forced aeration and cells designed to simulate storage. Sixty-six gas samples were collected and characterized by both GC–MS and olfactometry. Two types of correlation were investigated between the chemical composition and the odor concentration (OC) of every gas sample. The odor activity value for a given emitted compound (OAV) was computed as the ratio of its chemical concentration to its odor detection threshold (ODT). The correlation OAVMAX considered that the OC of a gas sample was equal to its highest OAV whereas the correlation OAVSUM considered that the odor of the gas sample was equal to the sum of the OAV of every compound contained in the gas sample. As per Standard EN 13725, both OAVMAX and OAVSUM were compared using a confidence level for OC defined as OC/1.65 to 1.65×OC. Whereas OAVMAX values were within the confidence level of OC for 62% of the 66 gas samples, OAVSUM values were within this confidence level for only 53%. Validating OAVMAX as a satisfying correlation between chemical composition and OC, only three compounds among the 66 identified namely trimethylamine, hydrogen sulfide and methanethiol, accounted for the prediction of OC measured during composting and storage of PSS.
More stringent legislation on dissolved organic matter (DOM) urges the drinking water industry to improve in DOM removal, especially when applied to water with high dissolved organic carbon (DOC) ...contents and low turbidity. To improve conventional processes currently used in drinking water treatment plants (DWTPs), the performances of a hybrid membrane bioreactor containing fluidised activated carbon were investigated at the DWTP of Rennes. Preliminary results showed that the residual DOC was the major part of the non-biodegradable fraction. In order to increase the global efficiency, an upstream oxidation step was added to the process. Ozone was chosen to break large molecules and increase their biodegradability. The first step consisted of carrying out lab-scale experiments in order to optimise the necessary ozone dose by measuring the process yield, in terms of biodegradable dissolved organic carbon (BDOC). Secondly, activated carbon adsorption of the DOC present in ozonated water was quantified. The whole process was tested in a pilot unit under field conditions at the DWTP of Rennes (France). Lab-scale experiments confirmed that ozonation increases the BDOC fraction, reduces the aromaticity of the DOC and produces small size organic compounds. Adsorption tests led to the conclusion that activated carbon unexpectedly removes BDOC first. Finally, the pilot unit results revealed an additional BDOC removal (from 0.10 to 0.15
mg
L
−1) of dissolved organic carbon from the raw water considered.
Display omitted
•The removal of butyraldehyde by surface plasma discharge was studied.•Operating parameters are tested at pilot scale with high flow rate.•The byproducts of butyraldehyde are ...identified and evaluated.•Effect of relative humidity was modeled and simulated.
The purpose of this paper is to study the butyraldehyde (Buty) conversion using dielectric barrier discharge (DBD) in a continuous reactor at pilot scale. One of the focused-on parameters in this study is relative humidity, which effect on (i) butyraldehyde removal (ii) selectivity of CO2 and CO, and (iii) intermediate byproducts and ozone formation was investigated using a DBD reactor with planar configuration. The results showed that at pilot scale, adding a small amount of water vapor in air enhances the processes performance and 10% increase in Buty removal efficiency was observed.
A kinetic degradation model was also proposed, which takes into account the relative humidity influence. Active species due to water dissociation are integrated in the model.
To represent the chemical degradation pathway, we supposed, in a first step, that an equivalent intermediate compound (EI) is formed directly from Buty. Then, in a second step, this EI is oxidized by active species into CO2 and CO in the discharge zone. This approach that also considers the competition effect between actives species improved the concordance between simulated results and experiments with a satisfactory overall description of the degradation and byproducts formation.
•Effect of UV generated by plasma SDBD on TiO2 was investigated.•The removal of 3-methylbutanal and trimethylamine was studied.•The byproducts of 3-methylbutanal were identified and evaluated.•The ...degradation pathways of 3-methylbutanal were discussed.•A synergetic effect was observed by combining plasma SDBD and photocatalysis.
This 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.
The presence of pharmaceutical residues in water resources is a critical issue for the production of drinking water, even though trace concentrations are mostly encountered. The adsorption of eight ...micropollutants, in mixture, onto a microporous activated carbon fibre cloth was investigated. For each compound, the kinetics and isotherms of adsorption were studied in batch reactors with ultrapure water, groundwater and half-diluted groundwater. Experimental data were generated and compared to values calculated by the association of Ideal Adsorbed Solution Theory (IAST) model and the Homogeneous Surface Diffusion Model (HSDM). The impact of the nature and the content of Natural Organic Matter (NOM) was modelled considering an Equivalent Background Compound (EBC). The presence of NOM in the groundwater is largely detrimental for the adsorption of trace micropollutants.
This study focuses on the removal of gas-phase ammonia (NH₃) and hydrogen sulfide (H₂S) in a continuous reactor. Photocatalysis and surface dielectric barrier discharge (SDBD) plasma are studied ...separately and combined. Though the removal of volatile organic compounds by coupling plasma and photocatalysis has been reported on a number of studies in laboratory scale, this is as far as we know the first time that it is used to remove inorganic malodorous pollutants. While each separate process is able to degrade ammonia and hydrogen sulfide, a synergetic effect appears when they are combined at a pilot scale, leading to removal capacity higher than the sum of each separate process. The removal capacity is higher when the gas circulates at a higher flow rate and when pollutant concentration is higher. The presence of water vapor in the gas is detrimental to the efficiency of the process. Operating conditions also influence the production of nitrogen oxides and ozone.
► Comparison between two types of reactors (cylindrical and planar) on VOCs photocatalytic degradation. ► Influence of the mass transfer step on the reactor performance. ► All the by-products were ...identified.
An investigation of isovaleraldehyde (ISOV) photocatalytic oxidation was conducted at initial concentrations ranging from 25 to 150mg/m3 and different relative humidities (5–90% RH) in order to characterize the process performances close to indoor air conditions. Experiments were carried out in two different reactors: cylinder and flat-plate photoreactor (planar reactor) at different air gap (20–60mm) and gas residence times (0.67–5.0s). A plug flow reactor system was developed in order to perform kinetic studies of (i) isovaleraldehyde removal, (ii) selectivity of CO2, (iii) by-products formation and removal. It appears that ISOV removal efficiencies increased with lower inlet concentrations, lower air gap and higher gas residence times.
In small amounts, the presence of water vapor has a promoting effect on the degradation due to the formation of OH radicals.
Evaluating different kinetic models by least squares analysis, it was shown that the Langmuir-Hinshelwood (L-H) model could give a good correlation with the experimental results. Thus, the effect of ISOV gas-phase concentration, air gap and light intensity on chemical conversion rates is discussed.
A kinetic model based on Langmuir-Hinshelwood (L-H) approach and taking into account the mass transfer step was developed. This allows us to determine L-H constants regardless of the transfer aspect. This last is estimated by semi-empirical correlation. The separation between the mass transfer and the chemical reaction steps is obtained. The effect of UV light intensity is also considered.
PDF
