Search

The CO 2 level is rising in the atmosphere and has reached well above 400 ppm. Thus, there is growing concern about increasing CO 2 levels in the atmosphere as it is a greenhouse gas, constituting 20–25 % of total greenhouse gas emissions. CO 2 is quite a resilient molecule and is a by-product of any combustion-driven process. The CO 2 conversion is a non-spontaneous process due to its strong stability. The IEA and IPCC constantly mandate laws to monitor and regulate CO 2 emissions in the atmosphere. One efficient way is to scrub off CO 2 coming out of the exhaust. Several technologies have been developed around this concept, like adsorption and absorption. In this work, we have used zeolite for CO 2 adsorption. Four different zeolites with a Si/Al ratio of one, which possess varied pore diameters of 3 Å, 4 Å, 5 Å and 10 Å are tested for CO 2 adsorption. The zeolite with the pore diameter of 5 Å exhibited the best performance, which adsorbed 0.3 mmol/g (13.203 mg/g) of CO 2. The adsorption capacity of zeolites is further enhanced by creating oxygen vacant sites and loading sodium (Na) promotor. The creation of oxygen vacancy ∼11 % for MZE600 sample raises the CO 2 adsorption by 1.6 times compared to the ZE. Various concentrations of Na promotor are loaded on zeolite namely 5,10,15,20,25,35 %. About 11.97 mmol/g (527 mg/g) of CO 2 adsorption was observed for 25 % loading of Na promotor on zeolite (M25NaZE). With the sequential increase in promotor loading (up to 25 %), CO 2 adsorption increases. Further increase in loading reduces the CO 2 adsorption, attributed to blockage of pores on sorbent and plausible agglomeration of the promotor. The M25NaZE sample is stable for a minimum of 10 regeneration cycles and exhibits linear response to variation in CO 2 concentration from 2.5 % to 16 % and feed flow rate of 50–500 mL/min. • Pore diameter impacts CO 2 capture. The 5 Å diameter has the highest capture efficiency at 0.31 mmol/g. • Zeolite thermal treatment in a reduced atmosphere generates oxygen vacancies (10% H 2 +90% N 2) at temperatures ranging from 300 ºC to 600 ºC, which can capture CO 2 in addition to the porous network. • Zeolite thermal treatment in a reduced atmosphere at 600 ºC with 11% oxygen vacancy increases CO 2 capture by 1.5 times (~0.5 mmol/g) due to enhancement of the Lewis basic character. • The loading of alkali sodium promotors leads to profound enhancement in CO 2 capture. • M25ZENa zeolite captures 11.97 mmol/g CO 2 at ambient conditions, with stability over 10 cycles. [ABSTRACT FROM AUTHOR]

Weed seedbank was assessed and an integrated weed management package was developed to control Parthenium hysterophorus in vegetable capsicum. Field experiments were conducted simultaneously in a Parthenium-site (PS) and Parthenium-free site (PFS) during two consecutive seasons in a split-plot design replicated three times. Primary tillage (ploughing and manual weeding) were the main plots and sub-plots consisted of post-tillage practices; (a) Oxyfluorfen applied two-days before transplanting the crop (180 g a.i. ha −1 ), (b) gliricidia leaf mulch applied soon after transplanting (6 t ha −1 , 68% moisture), and (c) control. After transplanting, all weeds in PS, except P. hysterophorus , were removed manually in all plots bi-weekly, while weeds were not controlled in PFS. Parthenium hysterophorus in PS and Cyperus rotundus in PFS dominated the soil seedbank in upper 0–5 cm. Soil seedbank of P. hysterophorus in PS was higher in season-1 (March–August) than in season-2 (September–February) and viable even when buried 15 cm deep. Interaction between primary and post-tillage practices was not significant (P > .05) on plant height, canopy width, and yield of the crop. Capsicum yield in PFS was 40% higher in season-1 and 9.5% higher in season-2 compared to those of PS, due to lower weed competition and higher crop growth in the former. Manual weeding or ploughing as primary tillage followed by mulching with gliricidia leaves as a post-tillage practice suppressed P. hysterophorus effectively and enhanced growth and yield of vegetable capsicum. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mn X O Y is used as a sorbent/catalyst to remove IPA from the air stream. [•] The amounts of reversibly and irreversibly adsorbed IPA on Mn X O Y 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. [ABSTRACT FROM AUTHOR]

Highlights: [•] A quantitatively assessed adsorption mechanism of NO2 and TiO2 is proposed. [•] Quantitative ratio between adsorbed NO2, produced NO3 and evolved NO is 3:2:1. [•] NO initial formation time is controlled by TiO2 surface coverage. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

• NTP discharge initiates the CO 2 dissociation to CO. • NiO nano catalyst assist the hydrogenation of CO on the catalyst surface. • NTP discharge enhances the CO 2 to CH 4 formation at 250 °C. • High operating temperature assist the water gas shift reaction and partial oxidation of CH 4 to CO. • Several hours of plasma discharge does not change the catalyst morphology. Modernization, deforestation and overwhelmingly growing world population are significantly increasing the atmosphere CO 2 level. The conversion of CO 2 to other products has attracted much more attention, especially atmospheric pressure cold plasma for CO 2 conversion to CH 4. In this study the hydrogenation of CO 2 to CH 4 was carried out using Ni/γ-Al 2 O 3 nanocatalyst coupled non-thermal plasma dielectric barrier discharge reactor (NTP-DBD). The effect of temperature, plasma input power on CO 2 conversion rate and CH 4 selectivity have been studied. It was evidenced that, compared to conventional thermal catalysis (300 °C), plasma-catalysis has shown temperature shift (T shift) of 50 °C (250 °C). Furthermore, at 250 °C, 10wt.%Ni/γ-Al 2 O 3 nanocatalyst has shown about 40% CO 2 conversion and 70% CH 4 selectivity with 340 J.L−1 specific input energy (SIE). At low operating temperature, increase in SIE increases the CO 2 conversion and CH 4 selectivity by about 10%. The SEM and EDX analysis evidenced that NiO is homogeneously dispersed on the alumina beads surface. The TEM analysis before and after catalytic experiments showed that the average "NiO" particle size is 10–12 nm and 12–15 nm, respectively. The plasma discharge slightly increases the Ni particle size, however, it does not affect neither CO 2 conversion and nor CH 4 selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-based SCR catalysts with different CuO content were analyzed and tested over TiO 2 /CNTs composite support for NO conversion. • Effect of CuO and CNTs addition to Mn/Ti catalyst on H 2 O/SO 2 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 (TiO 2 -CNTs) supported MnOx-CuO catalysts were prepared and investigated for NH 3 -SCR of NO at low temperature. It was observed that the addition of Cu and/or CNTs to Mn/TiO 2 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-Cu 5 /Ti-CNTs) exhibited the best NH 3 -SCR performance. Remarkably, the Mn-Cu 5 /Ti-CNTs showed excellent resistance to SO 2 /H 2 O in comparison to the Mn/TiO 2 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 NH 3 -SCR activity and SO 2 /H 2 O resistance of the catalyst. [ABSTRACT FROM AUTHOR]