Degradation Of NO2 Research Articles

Photocatalytic Degradation of Vehicle Exhaust by Nano-TiO2 Cement Slurry: Experimental Factors and Field Application

Nano-TiO2 combined with cement slurry can be utilized to degrade nitrogen oxides (NOx) in vehicle exhaust, making it an excellent photocatalytic material for air purification. In practice, environmental factors can significantly affect the photocatalytic performance. In this study, a vehicle exhaust test system was developed, and the test methods and evaluation criteria for the degradation test are provided. This study investigated the photocatalytic degradation of NO2 using nano-TiO2 cement slurry through laboratory tests. The effects of temperature, relative humidity, ultraviolet (UV) radiation flux, cement slurry thickness, surface dust adherence, and the number of water rinsing cycles were examined. Additionally, nano-TiO2 cement slurries were applied to an expressway toll station. The results showed that the efficiency of photocatalytic degradation was significantly influenced by temperature and UV radiation flux, while the thickness of the cement slurry had minimal impact. The photocatalytic degradation efficiency was negatively correlated to the relative humidity, when the relative humidity of the cement slurry specimens was high. This is because the excess water (H2O) competes with NO2 for adsorption. The photocatalytic performance of the samples was significantly reduced by surface dust and rain erosion, as both led to a decrease in the amount of nano-TiO2 participating in the reaction. Furthermore, the photocatalytic material has wide-ranging potential applications. The findings of this study would support the promotion of environmentally friendly roads as a strategy to combat air pollution.

Tungsten Trioxide and Its TiO2 Mixed Composites for the Photocatalytic Degradation of NOx and Bacteria (Escherichia coli) Inactivation

The increased air pollution and its impact on the environment and human health in several countries have caused global concerns. Nitrogen oxides (NO2 and NO) are principally emitted from industrial activities that strongly contribute to poor air quality. Among bacteria emanated from the fecal droppings of livestock, wildlife, and humans, Escherichia coli is the most abundant, and is often associated with the health risk of water. TiO2/WO3 heterostructures represent emerging systems for photocatalytic environmental remediation. However, the results reported in the literature are conflicting, depending on several parameters. In this work, WO3 and a series of TiO2/WO3 composites were properly synthesized by an easy and fast method, abundantly characterized by several techniques, and used for NOx degradation and E. coli inactivation under visible light irradiation. We demonstrated that the photoactivity of TiO2/WO3 composites towards NO2 degradation under visible light is strongly related to the WO3 content. The best performance was obtained by a WO3 load of 20% that guarantees limited e−/h+ recombination. On the contrary, we showed that E. coli could not be degraded under visible irradiation of the TiO2/WO3 composites.

Degradation of pollutants in solid and gas states using waterborne acrylic nanocomposite paints

In this study, TiO2/SiO2 nanoparticles were synthesized using titanium tetraisopropoxide and tetraethoxysilane in a two-step sol-gel route. FTIR, XRD, UV–Vis, and XPS techniques were used to characterize the synthesized nanoparticles. Fe-SEM was utilized to evaluate the particle size of the synthesized nanoparticles (30.35 ± 4.52 nm). Photo-degradation of rhodamine B (Rh.B) as a solid pollutant model and NO2 as a typical gaseous pollutant was assessed on the surface of the waterborne-acrylic coatings containing TiO2/SiO2 nanoparticles (TSC.La) under direct sunlight irradiation and accelerated weathering conditions and the results were compared with a P25–TiO2 nanoparticle (UT.La) embedded coating samples.To evaluate the degradation of Rh.B, color coordinates (L*a*b*) were measured, while the degradation of NO2 was determined in a batch-designed photocatalytic reactor by measuring the reduction in gas concentration. For the TSC.La-sample exposed to accelerated weathering conditions, the changes in a* parameter (Δa*) were about 60%, which was 44 times greater than the changes in this parameter for the sample exposed to sunlight. The surface morphology of the exposed samples to the accelerated weathering conditions was evaluated using AFM and BET measurements. The AFM results indicated that TiO2/SiO2 nanoparticles lead to less surface degradation of the paints compared to the commercial TiO2 nanoparticles. NO2 concentration decreased steadily in the reactor from 30 to 27 ppm, at an RH%<20 in the presence of UT.La or TSC.La-samples after 45 and 60 min of UV exposure. This reduction in gas concentration is equivalent to photocatalytic power of 6 and 8 mLm−2h−1, for the two samples, respectively.

Applicability of TiO2‐Laden Asphalt Pavements in Reducing the Vehicular Pollution of Chandigarh, India

AbstractVehicular emissions play a significant role in urban‐environmental pollution. Therefore, in the present investigation, efforts are made to estimate the applicability of Titanium dioxide (TiO2)‐laden asphalt pavements in degrading the ambient Nitrogen Dioxide (NO2) in Chandigarh, India. In this regard, an artificial environment is created, and experiments are designed to degrade NO2 and Sulfur dioxide (SO2) using photocatalysis. Further, the process parameters, viz., concentration of TiO2 emulsion (25 to 125 mL m−2), Ultraviolet UV‐A irradiance (1 to 5 mW cm−2), and proportion of bitumen (4 to 6%), are optimized to achieve the maximum degradation of NO2 and SO2. Results reveal that maximum degradation of NO2 and SO2, that is, 61.91 and 55.39%, respectively, is achieved at 81.67 mL m−2 of TiO2 emulsion, 5 mW cm−2 of UV‐A irradiance, and 5.78% of bitumen. The optimized conditions of photocatalytic application are further used to treat the ambient NO2 of Chandigarh, India. Analysis of the ambient air data of Chandigarh, India, from 2005 to 2015, depicts significant contribution of vehicular emissions. It is also predicted that by 2031 the ambient concentration of NO2, may exceed the permissible limits. However, layering of asphalt payments with TiO2 could prevent such situation by 2114.

Assessing the Applicability of Photocatalytic-Concrete Blocks in Reducing the Concentration of Ambient NO2 of Chandigarh, India, Using Box–Behnken Response Surface Design Technique: A Holistic Sustainable Development Approach

Anthropogenic emissions, such as industrial, vehicular, biomass burning, and coal combustion, play a significant role in degrading the atmospheric conditions of India. Therefore, in the present study, applicability of the photocatalytic-concrete blocks was estimated in improving the ambient environment of Chandigarh, India. The photocatalytic-concrete blocks were prepared by mixing the TiO2 particles with cement. All the experiments, designed in accordance with the Box–Behnken approach, in combination with response surface methodology, were performed in a batch reactor. Further, the process parameters, namely, concentration of TiO2 (1 to 5 g), UV-A irradiance (1 to 5 mW/cm2), and relative humidity (RH) (10 to 70%), were optimized to achieve maximum degradation of NO2. Outcomes of batch experiments depicted that the maximum degradation of NO2, that is, 68.32%, was attained at 3.35 g of TiO2, 5 mW/cm2 of UV-A irradiance, and 64.60% RH. The findings of batch experiment were further theoretically applied to degrade the ambient NO2 concentration of Chandigarh, India. It was estimated that using the photocatalytic concrete for construction of Chandigarh’s pavements may reduce the ambient NO2 concentration of Chandigarh, India, to an average of 5.80 μg/m3. Afterwards, reusability of photocatalytic-concrete blocks was also assessed, and it was made evident that after five cycles, their efficiency was reduced by only 7.15%. Subsequently, it was revealed that hydrogen peroxide-based treatment of photocatalytic-concrete blocks could completely regenerate its treatment efficiency. Therefore, it is expected that the findings of this study may prove beneficial in urban planning, as it may assist scientific auditory in identifying the applicability of TiO2-based photocatalysis in mitigating the impacts of vehicular emissions.

Reactive uptake of NO2 on volcanic particles: A possible source of HONO in the atmosphere

The heterogeneous degradation of nitrogen dioxide (NO2) on five samples of natural Icelandic volcanic particles has been investigated. Laboratory experiments were carried out under simulated atmospheric conditions using a coated wall flow tube (CWFT). The CWFT reactor was coupled to a blue light nitrogen oxides analyzer (NOx analyzer), and a long path absorption photometer (LOPAP) to monitor in real time the concentrations of NO2, NO and HONO, respectively. Under dark and ambient relative humidity conditions, the steady state uptake coefficients of NO2 varied significantly between the volcanic samples probably due to differences in magma composition and morphological variation related with the density of surface OH groups. The irradiation of the surface with simulated sunlight enhanced the uptake coefficients by a factor of three indicating that photo-induced processes on the surface of the dust occur. Furthermore, the product yields of NO and HONO were determined under both dark and simulated sunlight conditions. The relative humidity was found to influence the distribution of gaseous products, promoting the formation of gaseous HONO. A detailed reaction mechanism is proposed that supports our experimental observations. Regarding the atmospheric implications, our results suggest that the NO2 degradation on volcanic particles and the corresponding formation of HONO is expected to be significant during volcanic dust storms or after a volcanic eruption.

Designed air purifier reactor for photocatalytic degradation of CO2 and NO2 gases using MWCNT/TiO2 thin films under visible light irradiation

The air purifier reactor was designed and fabricated to develop the photocatalytic treatment of CO2 and NO2 gases under visible light irradiation based on multi-walled carbon nanotubes/titanium dioxide (MWCNT/TiO2) thin films. MWCNT/TiO2 thin films were synthesized by a simple dip-coating method on the glass substrate. Structural properties were characterized by SEM, EDX, XRD and optical properties by UV–Vis absorption spectroscopy. The XRD patterns showed the presence of anatase phase. The absorption spectrum of MWCNT/TiO2 revealed a redshift in the optical absorption edge due to carbon doping. For the first time, to evaluate the visible light photocatalytic activity, concentration reduction of CO2 and NO2 gases were measured by Ion Mobility Spectrometry(IMS) analyzer. The designed reactor indicated a high visible light photocatalytic activity for CO2 and NO2 degradation. The calculation of the Photocatalytic reaction by the Langmuir-Hinshelwood model showed that it followed the pseudo-first-order rate law.

A visible-light-responsive TaON/CdS photocatalytic film with a ZnS passivation layer for highly extraordinary NO2 photodegradation.

Recently, TaON has become a promising photoelectrode material in the photocatalytic field owing to its suitable band gap and superior charge carrier transfer ability. In this work, we prepared a TaON/CdS photocatalytic film using a CdS nanoparticle-modified TaON film by the successive ionic layer adsorption and reaction (SILAR) method. For the first time, the ZnS nanoparticles were deposited on the TaON/CdS film using the same method. We found that pure TaON had a nanoporous morphology, thus resulting in high specific surface area and better gas adsorption capacity. Furthermore, the TaON/CdS/ZnS film displayed a highly efficient NO2 photodegradation rate under visible light irradiation owing to its stronger visible light response, photocorrosion preventive capacity, and the high separation efficiency of photo-induced electrons and holes. Interestingly, the promising TaON/CdS/ZnS film also possessed remarkable recyclability for NO2 degradation. Therefore, we suggest that the TaON/CdS/ZnS photocatalytic film might be used for the photocatalytic degradation of other pollutants or in other applications. We also put forward the feasible NO2 photocatalytic degradation mechanism for the TaON/CdS/ZnS film. From the schematic diagram, we could further obtain the photo-generated carrier transport process and NO2 photodegradation principle in detail over the ternary photocatalytic film. Moreover, the trapping experiment demonstrates that ·O2− and h+ all play significant roles in NO2 degradation under visible light irradiation.

Dual modification of TiO2 nanorod arrays with SiW11Co and Ag nanoparticles for enhanced photocatalytic activity under simulated sunlight.

Well-organized TiO2 nanorod arrays (TNRs) have increasingly attracted our attention in recent years due to their excellent photocatalytic properties. However, it is of great importance to prepare more efficient photocatalysts using a facile method towards their more widespread use. In this work, K6SiW11O39Co(ii)(H2O) (SiW11Co) and Ag nanoparticles were introduced into TNRs using spin-coating and chemical bath deposition methods. It was found that TNRs/SiW11Co/Ag composite films with an active area of only 1 cm2 exhibit highly efficient and sustainable properties for the photodegradation of NO2 and display a significant enhancement compared with P25 and pure TNRs. Photocatalytic measurements demonstrated that both SiW11Co and Ag synergistically improve the light absorption and charge separation efficiency, thus obtaining the most efficient photocatalytic performance. In addition, the probable photocatalytic mechanism and the dominating active species for NO2 photodegradation were also proposed, in order to testify the effectively enhanced photocatalytic ability of the TNRs/SiW11Co/Ag composite. Hence, the design of these polyoxometalate and metal particle co-modified TNRs may provide a new tactic for developing promising materials for photocatalytic degradation.

Impact of Nano-TiO2 on the NO2 degradation and rheological performance of asphalt pavement

This research carried out the NO2 degradation performance and asphalt pavement performance of SBS modified asphalt with different content (0%, 1%, 2%, 5%, 10%) of nano-TiO2, and the impact of cationic surfactant were evaluated as well. The nano-TiO2 modified asphalt was prepared for Dynamic Shear Rheometer (DSR) test, Bending Beam Rheometer (BBR) test, Rolling Thin Film Oven Test (RTFOT) and Pressure Aging Vessel (PAV) test. And the high temperature performance, low temperature performance and aging properties were evaluated. Results show that the nano-TiO2 increased the rutting resistance of asphalt in high-temperature especially when the content increased from 0% to 1%, and it did not have a significant impact on low temperature cracking resistance. Secondly, this research developed an innovative photo-reactive and measuring system, and simulated the NO2 degradation environment based on field data of varies typical roadway sections. Then, this research conducted photo-catalytic degradation test of NO2 for asphalt mixture with 5% nano-TiO2 content. The analysis shows that there are reversible reaction between NO2 and N2O4, and results indicated that the asphalt mixture has exhibited NO2 degradation effects. This research provided a deep understanding for the road performance and engineering application of nano-TiO2 modified asphalt mixture.

Enhanced photocatalytic performance of bismuth vanadate assisted by polyoxometalates and phthalocyanine

H3PW12O40 (PW12) and binuclear phthalocyanine (bi-CoPc) modified nanofilms PW12–BiVO4–bi-CoPc were prepared. Under illumination of visible light, PW12–BVO–bi-CoPc nanofilm exhibits a 3-fold enhancement in photocatalytic degradation of NO2.

Development of gas flow reactor with on-line monitoring system for nitrogen dioxide removal

In this work, a new flow system was developed for investigating the efficiency of synthesized TiO2 photocatalysts for NO2 degradation. The system consists of two parts: the gas flow reactor and an on-line NO2 monitoring system. The latter is based on the conversion of NO2(g) to NO2−(aq) with subsequent spectrophotometric detection of the nitrite anion by the Griess-Saltzman reaction. Simplex optimization was employed to obtain the required sensitivity for the NO2 monitoring. The developed flow system was employed to measure the catalytic efficiency of photodegradation of NO2 by various types of TiO2-based synthesized photocatalysts and a commercial TiO2 photocatalyst, ‘P25’. The TiO2 photocatalysts were synthesized using titanium isopropoxide (TTIP), tetrabutyl orthotitanate (TBOT) and titanium oxysulfate (TiOSO4) as precursors. Glass beads, coated with the TiO2 photocatalyst, were packed in a quartz tube reactor. Standard NO2 gas mixture (50ppmv) was continuously flowed through the reactor under UV radiation. Residual NO2 from the outlet of the reactor was measured using the on-line NO2 monitoring system which employs a gas diffusion unit and an acceptor stream of triethanolamine solution. The NO2(g) was converted into NO2−(aq) which was measured spectrophotometrically at 540nm using the Griess-Saltzman reaction. The photocatalytic efficiency of the synthesized photocatalysts was compared. The effects of oxygen and humidity were also studied in order to investigate the mechanism of photodegradation of NO2by the TiO2 catalyst. We observed that at low humidity (12% RH), the OH• radical generated from moisture plays an important role for photooxidation process of NO2.

Ralstonia solanacearum uses inorganic nitrogen metabolism for virulence, ATP production, and detoxification in the oxygen-limited host xylem environment.

ABSTRACTGenomic data predict that, in addition to oxygen, the bacterial plant pathogen Ralstonia solanacearum can use nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), and nitrous oxide (N2O) as terminal electron acceptors (TEAs). Genes encoding inorganic nitrogen reduction were highly expressed during tomato bacterial wilt disease, when the pathogen grows in xylem vessels. Direct measurements found that tomato xylem fluid was low in oxygen, especially in plants infected by R. solanacearum. Xylem fluid contained ~25 mM NO3−, corresponding to R. solanacearum’s optimal NO3− concentration for anaerobic growth in vitro. We tested the hypothesis that R. solanacearum uses inorganic nitrogen species to respire and grow during pathogenesis by making deletion mutants that each lacked a step in nitrate respiration (ΔnarG), denitrification (ΔaniA, ΔnorB, and ΔnosZ), or NO detoxification (ΔhmpX). The ΔnarG, ΔaniA, and ΔnorB mutants grew poorly on NO3− compared to the wild type, and they had reduced adenylate energy charge levels under anaerobiosis. While NarG-dependent NO3− respiration directly enhanced growth, AniA-dependent NO2− reduction did not. NO2− and NO inhibited growth in culture, and their removal depended on denitrification and NO detoxification. Thus, NO3− acts as a TEA, but the resulting NO2− and NO likely do not. None of the mutants grew as well as the wild type in planta, and strains lacking AniA (NO2− reductase) or HmpX (NO detoxification) had reduced virulence on tomato. Thus, R. solanacearum exploits host NO3− to respire, grow, and cause disease. Degradation of NO2− and NO is also important for successful infection and depends on denitrification and NO detoxification systems.

Study of solid/gas phase photocatalytic reactions by electron ionization mass spectrometry.

This paper describes a novel methodology for the real-time study of solid-gas phase photocatalytic reactions in situ. A novel reaction chamber has been designed and developed to facilitate the investigation of photoactive materials under different gas compositions. UV irradiation in the wavelength of ranges 376-387 and 381-392 nm was provided using specially designed high efficiency light emitting diode arrays. The experiments used air containing 190 ppm NO2 in a moist environment with a relative humidity of 0.1%. Photocatalytic samples consisting of pressed pellets of rutile and anatase crystalline forms of TiO2 were monitored over a period of 150 min. An ultra-high vacuum right angled bleed valve allowed a controlled flow of gas from the main reaction chamber at atmospheric pressure to a residual gas analyser operating at a vacuum of 10(-5) mbar. The apparatus and methodology have been demonstrated to provide high sensitivity (ppb). The rate of degradation of NO2 attributed to reaction at the TiO2 surface was sensitive to both crystal structures (anatase or rutile) and wavelength of irradiation.

Photocatalytic property of Ag modified nano-TiO2/carbon nanotube composites for NO2 degradation under visible light

The photocatalytic property for NO2 degradation under visible light was improved through Ag modification and multiwalled carbon nanotubes (MWCNTs). Test results showed that the combined efficacy of Ag and MWCNTs was much larger than the efficacy of MWCNTs, and Ag and carbon nanotube had a synergistic effect on nano-TiO2 when they are doped together. Moreover, the enhancement mechanism was analysed through ultraviolet–visible and SEM methods.

Synthesis of Ni/Diatomite catalysts for direct NO2 decomposition

Diatomite-supported Ni catalysts were synthesized via the simple immersion of diatomite in Ni(NO3)2 solution and the reduction with H2 in the tube furnace. The activity of synthesized catalysts was evaluated by the degradation of NO2. Various factors such as Ni amount, calcinations temperature, calcinations time, degradation reaction temperature were investigated in order to prepare the catalyst with the best activity for NO2 decomposition. The results indicated that Ni metal was highly dispersed onto the diatomite substrate and the best catalyst was the sample prepared with the Ni/diatomite ratio of 1 %, calcined at 500°C for 5 hours which showed the best NO2 conversion of 70% with NO2 fow rate of 0,067mmol/min for 0,25g catalyst.

Relationship Between Photocatalytic Activity and Structure of TiO2 Thin Film

TiO2 thin films with different crystalline structures were prepared by the CVD method. The relationship between photocatalytic activity of a TiO2 thin film and its crystalline type was investigated. These films were characterized by XRD and AFM. Their photocatalytic properties were tested by the degradation of NO2-. The results showed that the crystalline structures of TiO2 thin films are primary anatase and/or rutile when the preparation temperatures were less than 573 K and higher than 773 K respectively. When the preparation temperature was around 623 K, the structures of TiO2 thin films were mixed crystalline structure, which showed the highest catalytic activity. When the ratio of rutile to anatase in TiO2 thin films fell between 0.5 and 0.7, the highest catalytic activity for the degradation of NO2- was found.