The combined effect of non-thermal plasma treatment of water and seeds on the rate of germination and plants growth of radish (
Raphanus sativus
), tomato (
Solanum lycopersicum
), and sweet pepper (
...Capsicum annum
) have been investigated using dielectric barrier discharges in air under atmospheric pressure and room temperature. A cylindrical double dielectric barrier discharge reactor is used for water activation and a plate-to-plate double DBD reactor is employed for seed treatment. The activation of water, for 15 and 30 min, lead to acidic solutions (pH 3) with moderate concentrations of nitrate (NO
3
−
) and hydrogen peroxide (H
2
O
2
). Plasma activated water (PAW) has shown a significant impact on germination as well as plant growth for the three types of seeds used. Interestingly, the positive effect, in seed germination and seedling growth, has been observed when the PAW and plasma-treated seeds (10 and 20 min) were combined. In one hand, when the seeds were (tomato and pepper) exposed to 10 min plasma and watered with PAW-15 for first 9 days followed by tap water for 51 days, the stem length is increased about 60% as compared to control sample. On the second hand, for longer exposures of seeds and water to plasma discharges, a negative effect is observed. For instance, plasma-treated seeds watered with PAW-30, the plant growth and vitality were decreased as compared to control sample. These results revealed that the developed cold plasma reactors could be used to significantly improve the seed germination as well as plant growth, nevertheless, the plasma treatment time has to be optimized for each seeds.
Seed germination and plants growth are significantly improvement by combining plasma activated water and plasma treated seeds.
The conversion of CO2 to CH3OH over binary mixed metal oxides of NiO–Fe2O3 is investigated in the study. A series of catalysts, i.e., NiO, Fe2O3, 5% NiO–Fe2O3 (5NF), 10% NiO–Fe2O3 (10NF), and 15% ...NiO–Fe2O3 (15NF), was tested for CO2 conversion and CH3OH selectivity performance. The results show that binary mixed metal oxides are more active in comparison to pure metal oxides. Moreover, increasing NiO mixing leads to the agglomeration of NiO particles. At 200 °C, around 1.5%, 2%, and 3.2% CO2 conversion is achieved for 5NF, 10NF, and 15NF, respectively. Interestingly, when cold plasma was ignited at 200 °C, around 5.4%, 6.2%, and 10.2% CO2 conversion was achieved for the 5NF, 10NF, and 15NF catalysts, respectively. 15NF exhibited the highest CO2 conversion, but produced only CH4. Plasma coupling with the catalyst led to an increase in the CH3OH yield, and around an 5.8-fold enhancement was achieved with 10NF at 200 °C compared to thermal catalysis. We showed that the combination of plasma and thermal heating brings about significant changes to the catalyst morphology, which significantly improved the catalytic activity. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization revealed that plasma treatment leads to the formation of a mixture of spinel compounds (NiO–Fe2O3, NiFe2O4, and Fe3O4).
The conversion of CO
to CH
OH over binary mixed metal oxides of NiO-Fe
O
is investigated in the study. A series of catalysts,
, NiO, Fe
O
, 5% NiO-Fe
O
(5NF), 10% NiO-Fe
O
(10NF), and 15% NiO-Fe
O
...(15NF), was tested for CO
conversion and CH
OH selectivity performance. The results show that binary mixed metal oxides are more active in comparison to pure metal oxides. Moreover, increasing NiO mixing leads to the agglomeration of NiO particles. At 200 °C, around 1.5%, 2%, and 3.2% CO
conversion is achieved for 5NF, 10NF, and 15NF, respectively. Interestingly, when cold plasma was ignited at 200 °C, around 5.4%, 6.2%, and 10.2% CO
conversion was achieved for the 5NF, 10NF, and 15NF catalysts, respectively. 15NF exhibited the highest CO
conversion, but produced only CH
. Plasma coupling with the catalyst led to an increase in the CH
OH yield, and around an 5.8-fold enhancement was achieved with 10NF at 200 °C compared to thermal catalysis. We showed that the combination of plasma and thermal heating brings about significant changes to the catalyst morphology, which significantly improved the catalytic activity. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization revealed that plasma treatment leads to the formation of a mixture of spinel compounds (NiO-Fe
O
, NiFe
O
, and Fe
O
).
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•Simple functionality and small size are the advantages of the phenothiazine to develop a low cost material.•Being simple secondary amine with an amine content of 7.5 % the molecule ...exhibits a CO2 capture capacity of 17 mg/g.•A linear response is obtained for CO2 concentration varied between 0.04 to 15 %, thus, this material can be used for direct CO2 capture from air.
Globally, CO2 levels are rising and thus, dedicated efforts are driven towards CO2 capture and storage. In this work, we have demonstrated for the first time CO2 adsorption and storage by phenothiazine (Pheno) molecule. The amine functionalities of Pheno are exploited for the chemisorption of CO2. A maximum of 0.4 mmol/g of CO2 is adsorbed which equates to 17.6 mg CO2 captured/g of Pheno molecule. This value may seem less but the small size, simplistic functionalities, and cheap cost make this study relevant for CO2 mitigation. The CO2 stored on the Pheno molecule is chemisorbed to form strong carbamide (amide linkage) and thus, difficult to desorb even at a temperature of 150 °C. This shows that CO2 is stored strongly (via chemical bond formation) and safely thus, could reduce the accidents resulting from accidental leakage/desorption of CO2 which could be fatal. Pheno based sorbent shows linear response over various concentrations ranging from atmospheric concentration of CO2, 400 ppm to 15% concentrations of CO2 at ambient conditions. The adsorption efficacy of Pheno exponentially decreases with an increase in temperature above room temperature. However, the adsorption efficiency increases with an increase in relative humidity as non-condensable water molecules further provide an additional site for CO2 dissolution and bicarbonate formation which increases CO2 uptake.
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•Mn-based SCR catalysts with different CuO content were analyzed and tested over TiO2/CNTs composite support for NO conversion.•Effect of CuO and CNTs addition to Mn/Ti catalyst on ...H2O/SO2 resistance was investigated.•Test results depicted that addition of 5 wt% CuO was sufficient to achieve better NO conversion in the temperature regime of 150–350 °C.•Remarkable low temperature SCR activity was achieved with the addition of CuO to Mn/Ti-C catalyst.
A series of titania-carbon nanotubes (TiO2-CNTs) supported MnOx-CuO catalysts were prepared and investigated for NH3-SCR of NO at low temperature. It was observed that the addition of Cu and/or CNTs to Mn/TiO2 has a beneficial effect in improving the activity of the catalyst. In addition, the effect of Cu loading was also studied and found that the catalyst with 5 wt% Cu (Mn-Cu5/Ti-CNTs) exhibited the best NH3-SCR performance. Remarkably, the Mn-Cu5/Ti-CNTs showed excellent resistance to SO2/H2O in comparison to the Mn/TiO2 catalyst. The addition of CNTs has increased the specific surface area, total pore volume, and reduced the average pore size of the catalyst. Meanwhile, the Cu loading has enhanced the Mn4+ species and chemisorbed oxygen species on the surface of the catalyst. Besides, the incorporation of both Cu and CNTs have decreased the catalyst reduction temperature and increased the amount and strength of acidic sites on the catalyst. All these factors contributed to the superior NH3-SCR activity and SO2/H2O resistance of the catalyst.
•Characterization of VOC non-thermal plasma treatment under typical indoor air conditions.•Comparison of continuous and sequential processes with the same packed bed reactor.•Assessment of side ...product generation by both processes at ppb-levels.•Experimental evidence of the lower energy demand of the sequential process.
MnXOY coated glass beads packed bed non-thermal plasma (NTP) reactor has been designed and operated for isopropanol (IPA) removal close to indoor air conditions. The IPA removal efficiency of continuous NTP treatment is compared with the sequential approach, i.e. adsorption of IPA on MnXOY and subsequent regeneration of the saturated MnXOY surface by non-thermal plasma. The comparison between both approaches has been achieved with the same packed bed reactor and model VOC under equivalent indoor air conditions. Firstly, based on carbon mass balance calculations, the continuous treatment has shown better performances from an IPA abatement point of view, as well as from a mineralization point of view. However, the characterization of ppb level side-products evidenced that the continuous treatment leads to a more significant release of organic side products which may impact indoor air quality. Secondly, both processes have been compared in terms of energetic costs regarding (i) IPA removal, and (ii) CO2 formation. Interestingly, it is evidenced that, to treat the same amount of IPA, the sequential approach requires 14.5 times less energy than the continuous NTP treatment process. Similarly, to produce the same amount of CO2, the sequential approach consumes 10 times less energy. This comparison evidences the interest of adsorption combined with subsequent non-thermal plasma regeneration for indoor air effluent treatment.
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► TiO2 adsorbed IPA quantification was performed as a function of air RH. ► Air RH is a key parameter regarding IPA adsorption modes. ► Air RH is a key parameter regarding surface ...plasma regeneration efficiency. ► For air RH>25%, carbon balance recovery exceeds 80% of irreversibly adsorbed IPA.
Environmental regulation on air quality requires the development of energetic efficient volatile organic compounds (VOCs) abatement techniques. Adsorption, photocatalysis, non-thermal plasma and their combinations have been widely studied for VOC treatment. Even if the plasma – material (sorbent or catalyst) association appears as one of the most efficient configuration for VOC removal, it mainly consists in operating continuously the discharge on the material surface as long as the effluent flows across the reactor. This work aims at investigating another approach of plasma – material association for VOC removal: in a first step, the material is used as a sorbent until the complete coverage of adsorption sites; in a second step, once VOC saturation is achieved, the discharge is ignited on the material surface. During both steps, the influence of air relative humidity (RH) is investigated in order to evaluate its impact on the process. The objectives of our approach are: (i) the reduction of energy consumption; (ii) the increase of sorbent life-times by efficient regeneration; (iii) the investigation of plasma interaction with VOC saturated materials; (iv) the investigation of air RH influence on such VOC treatment process.
A packed bed reactor coated with TiO2 has been designed. IPA is used as a model VOC. First, injected power in the packed-bed reactor is characterized as a function of air RH. Complete coverage of TiO2 surface over 35% RH is suggested as a significant parameter. Then, adsorption of IPA on TiO2 was monitored until IPA breakthrough. The amount of IPA adsorbed per TiO2 surface unit is compared to values reported by other authors. The influence of air RH on reversibly and irreversibly adsorbed IPA fractions is investigated. Over 35% RH irreversible adsorption is favored, adsorption modes are discussed. Plasma regeneration of IPA saturated TiO2 surface leads simultaneously to IPA desorption and mineralization. Increasing air RH favors IPA mineralization and diminishes acetone production. Carbon balance obtained after 1h plasma treatment reaches 91% in the presence of 50% RH. A thermal treatment is performed after each plasma treatment in order to evidence plasma insensitive adsorbed species and to restore TiO2 initial surface state. 97% of the carbon balance is collected under 50% RH after thermal treatment. During the thermal step, acetone and CO2 are mainly produced, their formation pathways are discussed.
The
in situ
(direct) and
ex situ
(indirect) nitric oxide (NO) oxidation experiments were carried out at room temperature in an atmospheric pressure multi-pin-to-plane corona discharge reactor. For
in ...situ
oxidation the gas mixture (NO-O
2
-H
2
O-N
2
) was directly treated in the plasma discharge, whereas for the
ex situ
oxidation the plasma reactor was used to generate ozone and other species using the O
2
-N
2
gas mixture and at the outlet of the reactor the NO-N
2
mixture is added. In this study, we have mainly investigated the influence of (i) reactor configuration on discharge morphology and ozone production, (ii) the NO removal efficiency of
in situ
and
ex situ
processes, (iii) input pulse energy deposition on NO oxidation and (iv) the influence of humidity on NO oxidation and NO
2
selectivity. It is demonstrated that the increase of pin density (17 and 57 pins) increased the pulse energy (at a given applied voltage), and significantly decreased streamer branching and the corresponding volume occupied by the plasma channels. Therefore, NO conversion decreased. For
in situ
NO oxidation, at a fixed energy density, the 17 pin reactor was more efficient than the 57 pin reactor. A total NO conversion is obtained by
ex situ
plasma oxidation, whereas only 42% NO conversion is reached for
in situ
corona discharge using the 17 pin reactor at 42.5 mJ per pulse. However, in the
ex situ
plasma oxidation process when the ozone concentration exceeds about 90% of the NO inlet concentration, the NO
2
selectivity dramatically decreases due to the secondary oxidation reaction of NO
2
into NO
3
and further conversion into N
2
O
5
. It is observed that the addition of 5% humidity does not influence the pulse energy deposition, whereas it has improved the NO conversion by 30% and decreased the NO
2
selectivity by increasing HNO
3
and HNO
2
production.
Pin-to-plane corona reactor for NO to NO
2
conversion at ambient conditions.
Comparison of regeneration efficiency of different methods on IPA saturated MnXOY surface regeneration. Display omitted
•MnXOY is used as a sorbent/catalyst to remove IPA from the air stream.•The ...amounts of reversibly and irreversibly adsorbed IPA on MnXOY are quantified.•The regeneration efficiency of three different methods has been investigated.•In-Situ NTP treatment has shown more mineralization than the other studied methods.•Adsorbed IPA oxidation pathway is mainly dependent on IPA adsorption modes.
IPA saturated MnXOY surface regeneration has been investigated under dry air. MnXOY coated glass beads packed-bed reactor has been designed and used for IPA storage under gas-flowing condition at 296K. The coated MnXOY material is characterized by Brunauer–Emmett–Teller (BET), non destructive Optical Profilometer and X-ray diffraction (XRD) techniques. Atmospheric pressure gas phase Fourier Transform Infrared Spectroscopy (FTIR) and online Thermal Desorption coupled with Gas Phase Chromatography and Mass Spectrometry (TD–GC–MS) have been respectively used to quantify and to identify the gas phase species produced during the regeneration processes. This study mainly aims at investigating three different methods to regenerate the IPA saturated MnXOY surface. In this framework, methods have been investigated for IPA saturated MnXOY surface regeneration namely (i) direct thermal treatment (DTT), (ii) ozonolysis and (iii) In-Situ Non Thermal Plasma Treatment (NTP). Among the employed methods, In-Situ NTP treatment has shown better regeneration efficiency, and twice more CO2 selectivity. Notably, dry air In-Situ NTP treatment prior to thermal treatment has significantly improved the mineralization. The order of mineralization efficiency and/or COx selectivity can be written as follows: In-Situ NTP>dry air ozonolysis>dry air DTT.
Evolution of acetaldehyde irreversibly adsorbed fraction (qirr) on TiO2 at 296K as a function of TiO2 surface coverage by NOx− adsorbed species (θ) obtained by preliminary NO2 adsorption on TiO2. ...Display omitted
•Acetaldehyde adsorption parameters on TiO2 are quantitatively determines.•TiO2 surface coverage by NO2 derived adsorbed species has been controlled.•NO2 preliminary adsorption considerably impacts acetaldehyde adsorption parameters.
Titanium dioxide (TiO2) is a widespread metal oxide used in catalysis and photocatalysis, or coupled to non-thermal plasma for volatile organic compound (VOC) oxidation. Adsorption is a key step in the advanced heterogeneous oxidation processes; adsorption is partially addressed in that it is mainly investigated on fresh TiO2 surfaces. However, the treatment of real effluents combines various pollutants with VOCs; among them, NOx are characterized by reactive adsorption properties on TiO2 leading to irreversibly adsorbed species on the surface. The aim of this work is to determine the impact of NO2 preliminary adsorption on the subsequent adsorption of a model VOC: acetaldehyde. Breakthrough methods are used to (i) characterize acetaldehyde adsorption on fresh and NO2 covered TiO2 surface, (ii) control the coverage of TiO2 surface by irreversibly adsorbed NOx(ads)- species. In a first step, acetaldehyde adsorption on TiO2 has been characterized. In a second step, acetaldehyde adsorption has been achieved on TiO2 surface after NO2 exposure corresponding to different surface coverages. Then, acetaldehyde adsorption parameters have been determined. Subsequently, it has been possible to plot the evolution of acetaldehyde reversibly and irreversibly adsorbed quantities, and reversible fraction adsorption constant, as a function of TiO2 surface coverage by NOx(ads)- species, so called TiO2 surface NO2 ageing. Interestingly, both adsorbed acetaldehyde fractions are highly impacted by the presence of NOx(ads)- species on TiO2 surface. The irreversibly adsorbed fraction is considerably decreased since the lowest values of TiO2 surface coverage by NOx(ads)- species. Hypotheses related to competitive adsorption are not sufficient to explain the observed impact, suggesting that NOx(ads)- species modify TiO2 surface chemistry and acetaldehyde reactive adsorption. The reversibly adsorbed fraction of acetaldehyde is highly impacted as well; reversibly adsorbed amounts are decreased since the lowest surface coverage by NOx(ads)- species. The corresponding adsorption constants are abruptly increased as soon as TiO2 surface has been exposed to NO2, suggesting the formation of a new adsorption mode for acetaldehyde on NO2 exposed TiO2 surface. This paper evidences the considerable impact of NO2 on TiO2 adsorption properties regarding VOCs. Considering that NOx may accumulate on TiO2 the long term behaviour of such processes should be investigated further taking into account the NOx vs. VOC interaction for adsorption.
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