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The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from air was investigated in two similar biotrickling filters (BTFs) packed with polyurethane (PU) foam, differing in terms of inoculation procedure (BTF A was packed with pre-incubated PU discs, and BTF B was inoculated via the continuous recirculation of a liquid inoculum). The effects of white rot fungi enzyme extract addition and system responses to variable VOC loading, liquid trickling patterns, and pH were studied. Positive effects of both packing incubation and enzyme addition on biotrickling filtration performance were identified. BFF A exhibited a shorter start-up period (approximately 20 days) and lower pressure drop (75 ± 6 mm H2O) than BTF B (30 days; 86 ± 5 mm H2O), indicating the superior effects of packing incubation over inoculum circulation during the biotrickling filter start-up. The novel approach of using white rot fungi extracts resulted in fast system recovery and enhanced process performance after the BTF acidification episode. Average BTEX elimination capacities of 28.8 ± 0.4 g/(m3 h) and 23.1 ± 0.4 g/(m3 h) were reached for BTF A and BTF B, respectively. This study presents new strategies for controlling and improving the abatement of BTEX in biotrickling filters. [ABSTRACT FROM AUTHOR]

Hypochlorous acid HOCl is an effective disinfectant with a broad spectrum and high rate of microbicidal action. Its use for air treatment can be an effective tool for the prevention and therapy of infectious diseases. In this work, the in vivo study was conducted on 110 Wistar Han rats (12 and 72 weeks old) on the effect of a single inhalation of air containing gaseous HOCl on the activity of antioxidant system enzymes. For this, a special installation was designed to uniformly maintain the concentration of HOCl in the air and regulate it over a wide range. Inhalation exposure was carried out for 4 h at total chlorine concentrations in the air of approximately 2.0 mg/m3 and 5.0 mg/m3, after which the animals were observed for 14 days. The effect of inhalation on the antioxidant system activity varied significantly in animals of different ages. Catalase activity in young rats increased approximately 2-fold on days 1-2 after inhalation, regardless of the HOCl concentration, while in old animals a sharp dose-dependent decrease was initially observed. The glutathione peroxidase activity in animals of both ages increased upon inhalation of air with 5.0 mg/m3 HOCl, and in old animals this was more pronounced; when the HOCl concentration decreased to 2.0 mg/m3, this indicator increased slightly in old rats and remained virtually unchanged in young ones. The glutathione reductase activity when exposed to 2.0 mg/m3 HOCl did not change for both age groups, and with increasing HOCl concentration it increased by 1.5-2.0 times in all animals. [ABSTRACT FROM AUTHOR]

A pilot-scale experiment was implemented in a waste bioreactor with an inner capacity of 1 m3 in order to simulate a real-scale composting process. The waste underwent composting conditions that are typical of the initial bio-oxidation phase, characterised by a high production of volatile organic compounds (VOCs), hydrogen sulphide (H2S) and odorants. The waste bioreactor was fed with an intermittent airflow rate of 6 Nm3/h. The target of this study was to investigate the air treatment performance of three biofilters with the same size, but filled with different filtering media: (1) wood chips, (2) a two-layer combination of lava rock (50%) and peat (50%), and (3) peat only. The analyses on air samples taken upstream and downstream of the biofilters showed that the combination of lava rock and peat presents the best performance in terms of mean removal efficiency of odour (96%), total VOCs (95%) and H2S (77%) concentrations. Wood chips showed the worst abatement performance, with respective mean removal efficiencies of 90%, 88% and 62%. From the results obtained, it is possible to conclude that the combination of lava rock and peat can be considered as a promising choice for air pollution control in waste composting facilities. [ABSTRACT FROM AUTHOR]

Chlorobenzene (CB) and Chloronaphthalene (CN) emissions from cement plant operations pose significant environmental risks. This study investigates the mass transfer effects of chlorinated aromatic Volatile Organic Compounds (VOCs), specifically CB and CN, in the gas phase of a continuous-tangential-flow annular photocatalytic reactor. The experiments involved introducing CB and CN into the reactor, and the degradation kinetics were analyzed using the Langmuir–Hinshelwood (L-H) model. The L-H model was applied to assess the impact of the flow rate, concentration, and relative humidity (% RH) on the degradation rate (DR). The results indicate that both the experimental and simulated degradation rates improved with increased flow rates (1 to 9 m3·h−1) and inlet concentrations (30 to 216 mg·m−3). This enhancement of the DR correlates with the availability of active OH* species on the TiO2 surface. The L-H model emphasizes the role of H2O molecules in VOC removal kinetics. The degradation rates increased with a rising water content (5 to 55%), but adverse effects on VOC conversion were observed beyond a 55% RH. This study reveals a mass transfer effect, with internal diffusional limitations in the TiO2 pores under operational conditions. The kinetics were predominantly controlled by chemical kinetics and catalyst pore availability. Furthermore, this study demonstrates a higher CB degradation than CN in the reactor and experimental conditions. For a concentration of 1.328 mM·m−3, the CB DR ranged from 0.70 to 2.84 µM·m2·s−1, as the flow rate varied from 1 to 9 m3·h−1. The CN DR varied from 0.60 to 2.20 µM·m2·s−1 within the same flow rate range. [ABSTRACT FROM AUTHOR]

The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from air was investigated in two similar biotrickling filters (BTFs) packed with polyurethane (PU) foam, differing in terms of inoculation procedure (BTF A was packed with pre-incubated PU discs, and BTF B was inoculated via the continuous recirculation of a liquid inoculum). The effects of white rot fungi enzyme extract addition and system responses to variable VOC loading, liquid trickling patterns, and pH were studied. Positive effects of both packing incubation and enzyme addition on biotrickling filtration performance were identified. BFF A exhibited a shorter start-up period (approximately 20 days) and lower pressure drop (75 ± 6 mm H2O) than BTF B (30 days; 86 ± 5 mm H2O), indicating the superior effects of packing incubation over inoculum circulation during the biotrickling filter start-up. The novel approach of using white rot fungi extracts resulted in fast system recovery and enhanced process performance after the BTF acidification episode. Average BTEX elimination capacities of 28.8 ± 0.4 g/(m3 h) and 23.1 ± 0.4 g/(m3 h) were reached for BTF A and BTF B, respectively. This study presents new strategies for controlling and improving the abatement of BTEX in biotrickling filters.

The majority of household energy is consumed in heating and air conditioning. Desiccant disks are a way to harvest renewable solar energy or waste heat for air conditioning. In the literature there is a gap in the investigation of start-up of desiccant dehumidifiers, which this paper attempts to covers. For this work, a desiccant disk was designed, manufactured, and tested. To reduce the cost, off-the-shelf components were used as structure materials. And as adsorption material, widely available materials were used. Input heat was simulated by an electrical heater and power to auxiliary motors was provided in the form of DC power. Temperature and humidity were recorded at various locations using DHT11 sensors. The system was turned off and tested at a start of operation mode. The performance of the desiccant disk was quantified by the coefficient of performance and the dehumidification efficiency. Results showed gradual increase of the desiccant disk efficiency with a maximum COP value of 0.4 reached within 10 min of the start of operation. Time delays were attributed to heating of the disk. Further work is required to fully understand the transient operation.

Information on vitamin C—ascorbic acid (AA)—content is important as it facilitates the provision of dietary advice and strategies for the prevention and treatment of conditions associated with AA deficiency or excess. The methods of determining AA content include chromatographic techniques, spectrophotometry, and electrochemical methods of analysis. In the present work, an electrochemical enzyme-free ascorbic acid sensor for a neutral medium has been developed. The sensor is based on zinc oxide nanowire (ZnO NW) arrays synthesized via low-temperature chemical deposition (Chemical Bath Deposition) on the surface of an ITO substrate. The sensitivity of the electrochemical enzyme-free sensor was found to be dependent on the process treatments. The AA sensitivity values measured in a neutral PBS electrolyte were found to be 73, 44, and 92 µA mM−1 cm−2 for the ZnO NW-based sensors of the pristine, air-annealed (AT), and air-annealed followed by hydrogen plasma treatment (AT+PT), respectively. The simple H-plasma treatment of ZnO nanowire arrays synthesized via low-temperature chemical deposition has been shown to be an effective process step to produce an enzyme-free sensor for biological molecules in a neutral electrolyte for applications in health care and biomedical safety. [ABSTRACT FROM AUTHOR]

Abstract The research presents an effective and efficient mechanism for treating air and improving its specifications by designing and manufacturing a portable and small environmentally friendly device that works by an electric reactor to produce negative ions, which vibrate in the air during the discharge of negative charges to work on the association of negative ions with pollutants that carry a positive charge and fall by gravity and oxidize It decomposes and its effect diminishes and the production of small amounts of ozone works to kill pathogens without irritating the respiratory passages and lungs or causing side effects of living organisms.

Chlorobenzene (CB) and Chloronaphthalene (CN) emissions from cement plant operations pose significant environmental risks. This study investigates the mass transfer effects of chlorinated aromatic Volatile Organic Compounds (VOCs), specifically CB and CN, in the gas phase of a continuous-tangential-flow annular photocatalytic reactor. The experiments involved introducing CB and CN into the reactor, and the degradation kinetics were analyzed using the Langmuir–Hinshelwood (L-H) model. The L-H model was applied to assess the impact of the flow rate, concentration, and relative humidity (% RH) on the degradation rate (DR). The results indicate that both the experimental and simulated degradation rates improved with increased flow rates (1 to 9 m3·h−1) and inlet concentrations (30 to 216 mg·m−3). This enhancement of the DR correlates with the availability of active OH* species on the TiO2 surface. The L-H model emphasizes the role of H2O molecules in VOC removal kinetics. The degradation rates increased with a rising water content (5 to 55%), but adverse effects on VOC conversion were observed beyond a 55% RH. This study reveals a mass transfer effect, with internal diffusional limitations in the TiO2 pores under operational conditions. The kinetics were predominantly controlled by chemical kinetics and catalyst pore availability. Furthermore, this study demonstrates a higher CB degradation than CN in the reactor and experimental conditions. For a concentration of 1.328 mM·m−3, the CB DR ranged from 0.70 to 2.84 µM·m2·s−1, as the flow rate varied from 1 to 9 m3·h−1. The CN DR varied from 0.60 to 2.20 µM·m2·s−1 within the same flow rate range.

The immobilization of titanium dioxide, particularly commercial TiO2 P25, on the surface of recycled rubber tiles presents a solution for achieving passive air protection. A completely new purpose for tiles was obtained by addressing air pollution and related health issues. Modified rubber tiles were prepared using a sol–gel method with three different proportions of TiO2 (2, 4, and 10 g) in the solution. The nature of TiO2 nanoparticles and their respective binding on the tile surface was determined using scanning electron microscopy (SEM) equipped with electron dispersion X-ray spectrometry (EDS) and Fourier-transform infrared (FTIR) spectroscopy. The SEM-EDS results showed that the most successful immobilization was achieved with the lowest amount of TiO2 in the sol–gel solution. The FTIR results confirmed a band at 950 cm−1 that was attributed to the Ti-O-Si bond. The stability and environmental impact of the treated rubber substrates were investigated by a leaching test. Photocatalytic oxidation was confirmed by the oxidation of NH3 to N2. Based on the results obtained, rubber substrates with an addition of 2 g of TiO2 have demonstrated prospects for further tests of the photocatalytic degradation of airborne pollutants. [ABSTRACT FROM AUTHOR]

The preparation of anodic TiO2 nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO2 thin layer has been also prepared using the sol–gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N2O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO2 nanotube layers have exhibited the highest N2O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO2 nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h. [ABSTRACT FROM AUTHOR]

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Disposal of copper, manganese and iron is particularly problematic in wastewater of metallurgical and galvanization plants, the electronics industry and agriculture. On the other hand, volatile organic compounds (VOCs), emitted from industrial processes, transportation and consumer products are the main class of air pollutants. The study revealed the potential of waste metal-loaded zeolite, generated through wastewater treatment procedures, to be utilised as an effective VOC removal catalyst for air treatment. In the first step, we have evaluated the sorption performance of natural zeolite clinoptilolite (HEU type), and synthetic zeolite 4A (LTA type) for the simultaneous removal of Cu2+, Mn2+ and Fe3+ species from aqueous solution. By a detailed sorption study, we determined the optimum sorption conditions and maximum metal concentrations in wastewater that can be after treatment disposed of in rivers or municipal plants. The efficiency of both zeolites for metal immobilization was demonstrated for concentrations up to 5 mg metals/1 g zeolite. These waste Cu-, Mn- and Fe-loaded zeolites were thermally treated at 540 °C before the second step, where we evaluated their catalytic performance in removing VOC. The thermally treated waste Cu-, Mn- and Fe-loaded natural zeolite clinoptilolite showed good catalytic performance in total toluene oxidation as a model VOC (conversion rate up to 96% at 510°C) and cycling stability (less than 15% drop in conversion rate in 4 h). In contrast, this is not the case for thermally treated waste Cu-, Mn- and Fe-loaded synthetic zeolite 4A.

Information on vitamin C—ascorbic acid (AA)—content is important as it facilitates the provision of dietary advice and strategies for the prevention and treatment of conditions associated with AA deficiency or excess. The methods of determining AA content include chromatographic techniques, spectrophotometry, and electrochemical methods of analysis. In the present work, an electrochemical enzyme-free ascorbic acid sensor for a neutral medium has been developed. The sensor is based on zinc oxide nanowire (ZnO NW) arrays synthesized via low-temperature chemical deposition (Chemical Bath Deposition) on the surface of an ITO substrate. The sensitivity of the electrochemical enzyme-free sensor was found to be dependent on the process treatments. The AA sensitivity values measured in a neutral PBS electrolyte were found to be 73, 44, and 92 µA mM−1 cm−2 for the ZnO NW-based sensors of the pristine, air-annealed (AT), and air-annealed followed by hydrogen plasma treatment (AT+PT), respectively. The simple H-plasma treatment of ZnO nanowire arrays synthesized via low-temperature chemical deposition has been shown to be an effective process step to produce an enzyme-free sensor for biological molecules in a neutral electrolyte for applications in health care and biomedical safety.

An investigation on TiO 2 /SiO 2 catalysts was performed, covering a wide range of TiO 2 contents (0–100 % wt%) and calcination temperatures (150–1000 °C), which were applied to a continuous gas-solid photocatalytic reactor, irradiated by UV-LED for n -hexane degradation. A series of characterization analyses were conducted and the effects of the operational parameters and the catalyst stability over time were investigated. The TEM images confirmed the results of XRD crystallography, showing the preferential (101) anatase plane, in the form of 4–5 nm nanocrystals. Silica gel delayed the phase transformation from anatase to rutile even after calcination at 750 °C, while the band gap energy decreased from 3.21 to 3.06 eV with increasing calcination temperature from 150 to 1000 °C. The 20 %-TiO 2 material calcined at 450 °C exhibited the best performance among 14 different materials, reaching a conversion rate of 2.7 × 10−7 mol g−1 min−1, n -hexane degradation of 40 %, maintaining its stability even after 20 h of continuous photoreaction, with resistance to TiO 2 leaching and particle breakage. Therefore, the presence of silica significantly enhanced the properties of the catalyst, and contributed to improving its photocatalytic activity, making the use of these materials in gas-solid photoreactors a viable alternative for removing volatile organic compounds. [Display omitted] • 450 °C was the ideal calcination temperature in the range of 150–1000 °C. • The transition from anatase to rutile changed to above 700 °C. • SiO 2 support increases the photoactivity of TiO 2 in a fluidized bed reactor. • The catalyst showed high stability over 20 h of n -hexane photocatalytic degradation. [ABSTRACT FROM AUTHOR]

This paper investigates the valorization potential of two biowaste types resulting from biotrickling filtration of volatile organic compounds (i.e., ethanol) and carbon dioxide from air by co-immobilized microalgae and compost heterotrophs, which were either attached on polypropylene spheres or entrapped within the alginate beads. In this regard, biomass samples from the surface of the packing spheres (S1) and the waste alginate beads (S2) underwent thermal and energy characterization via thermogravimetry and calorimetry techniques as a screening step for establishing some possible biomass valorization pathways. The heat release capacity (HRC) values for the samples S1 and S2 were 95.67 J/(g·K) and 44.11 J/(g·K), respectively, while the total heat release (THR) values were 11.03 kJ/g and 3.64 kJ/g, respectively. The results of this study indicate that the S1 biomass could be suitable for undergoing thermal decomposition processes-based applications, while the S2 biomass could have a potential application for improving flame retardancy of some materials. These findings show that the biowaste issued from such air biotreatment can become a valuable resource for different applications instead of being disposed of. Further research referring to the implementation of these solutions for the development of the final applications is needed. [ABSTRACT FROM AUTHOR]

The main aim of this investigation was an experimental analysis of the air cleaning efficiency in a mock-up next-generation air cleaning device - one-level 8-channel industrial cyclone-separator with quarter-rings - while changing parameters of the inner structure and the assessment of the effects of dispersion of particulate matter. Therefore, the research was carried out in two stages: the first stage covered the analysis of the efficiency of the multi-channel cyclone with particulate matter of

Air desiccant cooling systems are burgeoning. Their major advantage is the use of water alone as a refrigerant. Pairing with efficient solar panels looks promising. Much research is underway to improve the techniques and performances of installations. In this article, we present the results of a calculation code that we developed from experimental data. It studies the conditions of air treatment by desiccation according to three different techniques with wide intervals of climatic conditions in order to point the limits of applicability. The objective is to precisely define the area in which each type of handling system can be used. We started by simulating the treatment of the air in the desiccant handling system (DHU) operating according to four techniques in order to choose one for the Algerian climate. A validation of the results with the experimental data was made. According to our calculations, DHU using Pennington cycle are not able to achieve satisfactory comfort conditions. An improvement in the Pennington cycle is proposed. It consists in adding an exchanger cooled by the water leaving the heating circuit and which is used to cool the fresh air. This solution seems effective and gives clearly acceptable results for the climatic conditions studied. In the last part of this article, we present the calculation results relating to the sensitivity of each technique to variations in temperature and humidity conditions. We have thus successfully delimited the climatic zones of applicability of each system from the process of the evolution of the air inside the building (coefficient ɛ). It has been confirmed that the improved Pennington cycle is the system best suited to Algerian climatic conditions. [ABSTRACT FROM AUTHOR]

The preparation of anodic TiO2 nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO2 thin layer has been also prepared using the sol–gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N2O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO2 nanotube layers have exhibited the highest N2O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO2 nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h.

A comprehensive kinetic model has been developed to address the factors and processes governing the photocatalytic removal of gaseous ethanol by using ZnO loaded in a prototype air purifier. This model simultaneously tracks the concentrations of ethanol and acetaldehyde (as its primary oxidation product) in both gas phase and on the catalyst surface. It accounts for reversible adsorption of both compounds to assign kinetic reaction parameters for different degradation pathways. The effects of oxygen vacancies on the catalyst have been validated through the comparative assessment on the catalytic performance of commercial ZnO before and after the reduction pre-treatment (10% H 2 /Ar gas at 500 °C). The influence of humidity has also been assessed by partitioning the concentrations of water molecules across the gas phase and catalyst surface interface. Given the significant impact of adsorption on photocatalytic processes, the beginning phases of all experiments (15 min in the dark) are integrated into the model. Results showcase a notable decrease in the adsorption removal of ethanol and acetaldehyde with an increase in relative humidity from 5% to 75%. The estimated number of active sites, as determined by the model, increases from 7.34 10−6 in commercial ZnO to 8.86 10−6 mol g cat −1 in reduced ZnO. Furthermore, the model predicts that the reaction occurs predominantly on the catalyst surface while only 14% in the gas phase. By using quantum yield calculations, the optimal humidity level for photocatalytic degradation is identified as 25% with the highest quantum yield of 6.98 10−3 (commercial ZnO) and 10.41 10−3 molecules photon−1 (reduced ZnO) catalysts. [Display omitted] • Kinetic modeling of gas-phase degradation of ethanol by prototype air purifier. • Integration of acetaldehyde as by-product of ethanol oxidation in kinetic modeling. • Incorporation of relative humidity in adsorption and degradation of ethanol. • Investigation of optimal relative humidity for enhancement of quantum yield. • Effect of production of oxygen vacancies on ZnO in ethanol degradation. [ABSTRACT FROM AUTHOR]

The catalytic decomposition of ozone was carried out at 40 °C with a Pd/Al2O3 catalyst, in the presence or absence of nitrogen oxides traces. NOx were produced during the generation of ozone from air. Two set-ups were used to examine the possible effects of NOx poisoning, one fixed bed with a powder catalyst, and another using a monolith coated with the same catalyst. NOx were shown to significantly poison the catalyst, resulting in a decrease of ozone conversion over time on stream. NOx-free ozone feed can lead to the total recovery of the initial catalyst properties indicating a reversible poisoning.

• Bubbling, turbulent and pneumatic regimes applied in the photocatalytic reactor. • Freeboard Elutriation Model successfully applied to the photo reactor. • Solids holdup of 10% and turbulent regime were found as optimum for operation. The fluidization behaviour of a circulating fluidized bed (CFB) photoreactor was varied by applying different flow (Q) and solid feed rates (F s), and the performance of the reactor for the degradation of the target pollutant n -hexane was compared for a wide range of fluidization regimes. The Freeboard Entrainment Model was applied to model and predict the values of solids hold-up (ε s) in the experimental range evaluated. The optimum n -hexane degradation rate for the CFB was found to be 4.0 × 10−4 mol m-3 s-1 operating in turbulent fluidization regime with ε s = 0.10 with the finer solid size distribution, demonstrating that high-velocity fluidization regimes can be used to enhance photocatalytic reaction rates based on better UV-photocatalyst contact. [ABSTRACT FROM AUTHOR]

In this paper, CeO2(30%)/Clinoptilolite was synthesized via HNO3 treatment and co-precipitation methods and then 1% Pt was dispersed over support by ultrasound assisted wet impregnation. The synthesized samples were characterized using XRF, XRD, FESEM, N2 adsorption and FTIR techniques. The obtained results from XRD revealed the main phase in utilized clay is clinoptilolite and also formation of amorphous structure was proved after acid treatment. FESEM micrographs confirmed significant structural changes in clinoptilolite after acid treatment and also formation of ceria nanoparticles. N2 adsorption presented large enough surface area for Pt/CeO2-Clinoptilolite nanostructured catalyst to be used for toluene oxidation. Finally, activity results indicated that synthesized nanostructured catalyst was highly active and stable and could eliminate more than 90% of toluene at 130 °C. Utilizing inexpensive materials in synthesis and assisting ultrasound in dispersion of active phase have made Pt(1%)/CeO2(30%)-Clinoptilolite a nominee to be used for catalytic oxidation of toluene.

In this study, we present an effective solution for the treatment of toxic gases, based on a photocatalytic process as destructive process. The aim of this investigation is to study the efficiency of the photocatalytic Filtering reactor (PFR), for the treatment of cyclohexane which is chosen as target pollutant of anti-gas cartridges of type 'A'. Indeed, the influence the input concentration (a range of Cyclohexane concentrations defined in the values and exposure limits recommended by the different French, European or American standards), residence time in reactor, and type of catalyst were studied in detail. In addition, the conversion rate was controlled under a respiratory flow (standards: ISO / DIS 8996). Moreover, a TiO2 deposed on optical fiber was evaluated in these conditions. The obtained results confirm that this configuration of the reactor can present an extremely promising route for individual protection device as an autonomous cartridge for a gas mask. [ABSTRACT FROM AUTHOR]

It is emphasized that a generalized relationship can be used to predict the ionic nitrogen concentration (i.e., sum of ammonium NH4+, nitrite NO2- and nitrate NO3-) of the scrubbing liquid in a biotrickling filter treating ammonia emissions by measuring the electrical conductivity (EC) of the water directly. From measurements carried out on different water samples from six biotrickling filters in operation in pig husbandries, the generalized relationship is: Σ([NH4+]+[NO2-]+[NO3-]) g N/L = 0.22 EC mS/cm. This equation is valid provided the fresh water feeding the biotrickling filter has a low electrical conductivity (<1 mS cm-1). Moreover, since ammonium, nitrite and nitrate ions are the ultra-majority ions in the liquid phase, the balance between NH4+ and (NO2- + NO3-) was confirmed, and consequently the relationship NH4+ = 0.11 EC mS/cm can also be applied to determine the ammonium concentration from the EC. As a result, EC measurement could be applied extensively to monitor operating biotrickling filters worldwide and used to determine ammonia mass transfer in real time, keeping in mind that the accuracy of the generalized relationship is ±20%. [ABSTRACT FROM AUTHOR]

It was demonstrated that the daily monitoring of electrical conductivity (EC) of scrubbing water can easily be used to determine the performance of biotrickling filters treating ammonia (NH3) emissions, generated by livestock facilities. Two different measurement campaigns were carried out on a pilot-scale biotrickling filter installed at a pig facility. Different phases of the operation were observed for each campaign, in accordance with EC values. For EC ranges of between 5 and 40 mS cm-1 day-1). Due to the correlation established in Part A of this study, the performance of the biotrickling filter can be directly expressed as gN h-1 m-3packing material without gas-phase monitoring. Thus, for an Empty Bed Residence Time of 1 s, the nitrogen accumulation capacity of the biotrickling filter was 24 gN h-1 m-3 packing material. For higher EC values, the ammonia mass transfer slowed down and stopped with EC at around 50-60 mS cm-1 (campaign #1) and 70 mS cm-1 (campaign #2). It was evidenced that the mass transfer stopped due to ammonia mass transfer limitation controlled by the driving force, although biomass inhibition can occur at these levels of nitrogen concentration in the scrubbing liquid. EC monitoring can also be used to assess the ratio of nitrogen accumulated in water φ and amount of ammonia entering the system φmax. Thus φ/φmax ratios of 41% and 27% were recorded for campaign #1 and #2 respectively. [ABSTRACT FROM AUTHOR]

Livestock production is associated with several gaseous pollutant emissions to the environment. These emissions can degrade local and regional air quality, contribute to surface water eutrophication and acid rain, and contribute to the greenhouse gas footprint of the production sector. Modern production systems must balance animal welfare and environmental pollution potential with economic reality, which is a great challenge to maintain as global demand for animal protein increases. Accordingly, gaseous emission technologies were the main target for this research, in which mitigating gas emissions of ammonia, nitrous oxide, and methane from pig production facilities via slurry aeration system was tested. Five treatments with different airflow rates in the test room were examined continuously over a period of 6 weeks and the results were compared with the control room. Test results indicate that the highest mitigation potentials were 12, 57.6, and 10.4% for nitrous oxide, methane, and ammonia, respectively. Subsequently directing exhaust air into a sulfuric acid air scrubber at 3.0 pH further reduced total ammonia emissions by 80 to 87%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Prototype plug-flow photocatalytic reactor was applied for degradation of VOCs. • The impacts of operating parameters on reactions kinetics were established. • Ozone in treated air accelerates VOCs oxidation. • Ozone mixed with VOCs is rapidly decomposed photocatalytically. Airborne volatile organic compounds (VOCs) present an increasingly relevant health hazard addressed by the EU directive 2016/2284 requiring 40-% reduction in emissions of non-methane VOCs by 2030 in comparison to 2005. Advanced oxidation processes (AOPs) provide a solution for the VOC problem in industry. Among AOPs, pulsed corona discharge (PCD) and photocatalytic oxidation (PCO) are of particular interest in their synergy complementing each other's strengths in energy-efficient manner. In the present study, air polluted with 2-methoxyethanol (2ME) was treated by using a prototype 21.3 L photocatalytic reactor for the pollutant degradation at its variable concentrations (6–50 ppm), irradiances (65–119 W m−2) and residence times (12–77 sec). Further combination of PCO reactor with forthcoming PCD requires studies in ozone photocatalytic degradation as a standalone byproduct and in combination with 2ME. The analysis of variable conditions resulted in singling out the PCO major restrictive parameters, also demonstrating the degradation enhancement, when both 2ME and ozone were present in air. The PCO treatment combined with ozone resulted in degradation of 2ME and ozone for 40 % and 95 %, respectively. [ABSTRACT FROM AUTHOR]

• Sequential vs. co-impregnation sono-dispersion of Mn-Cu over clinoptilolite. • Enhanced utilization of ultrasound irradiation in nanocatalyst preparation. • Complete oxidation of toluene at low temperature over synthesized nanocatalyst. • Modeling of the fixed bed reactor using combination of CFD with intelligent genetic accurate algorithm. • Determination of reaction kinetic parameters for the novel synthesized catalysts. A series of manganese-copper oxides on clinoptilolite with various impregnation sequences were synthesized using ultrasonic irradiation. Their properties were characterized by XRD, BET, FTIR, FESEM, and EDX techniques. The XRD patterns confirmed the formation of Mn 2 O 3 /MnO and CuO as the crystalline phase on clinoptilolite. FESEM images confirmed that manganese and copper dispersed on support in nano-range size. EDX results indicated uniform dispersion of the elements. FTIR patterns demonstrated that surface groups of nanocatalysts agree with the patterns of metals and support applied in nanocatalysts synthesis. Catalysts were investigated in the oxidation of toluene from the polluted air. Results showed that bimetallic nanocatalysts are more active than single metal oxide nanocatalysts) Mn 2 O 3 /MnO/CuO(causing the synergism effect of active phases. The highest catalytic activity was observed on the Mn/Cu/CLT nanocatalyst in which excess manganese oxide as active sites existed on the support and led to a decreased complete oxidation temperature of toluene. The result of toluene oxidation from the polluted air demonstrated that the prepared nanocatalyst was very active and stable. Also, the Mars–Van Krevelen kinetic model and the calculated kinetic parameters of this model were used to develop and express the toluene catalytic oxidation reaction rate on newly synthesized catalysts using the combination of CFD method with an intelligent genetic optimization algorithm. All results obtained using this method have an RMSE less than 0.1. Also, the activation energy based on the Arrhenius law for the toluene oxidation reaction using the Mn/Cu/CLT optimal nanocatalyst was calculated by this method equal to 98480 J/mol with RMSE 0.0248. Catalytic oxidation was utilized over a series of manganese-copper oxides on clinoptilolite with different impregnation sequence for removal of toluene from air. The nanocatalysts synthesized by ultrasound irradiation characterized by XRD, FESEM, EDX, FTIR and BET technique and tested for complete oxidation of toluene. Synthesis of catalysts by ultrasound energy led to preparation of nanocatalyst with uniform dispersion of active phase on support. Catalytic performance of nanocatalysts shows effect of impregnation sequence on activity of nanocatalysts. Also, the Mars–Van Krevelen model and the calculated kinetic parameters of this model were used to develop and express the catalytic oxidation rate of toluene of the newly synthesized catalysts using the CFD combination method with the intelligent genetic optimization algorithm. [Display omitted] [ABSTRACT FROM AUTHOR]

Automobile exhaust has become an important source of urban air pollution. Improving vehicle emission standards is one of the key measures to control air pollution. This paper takes Tianjin's implementation of the "National V" motor vehicle emission standard as an example. The study found that this policy is an indispensable condition for improving air quality, which helps to reduce carbon monoxide (CO) and nitrogen dioxide (NO2) in the atmosphere, but the effect on the treatment of atmospheric pollutants such as particulate matter (PM2.5) and respirable particulate matter (PM10) is not significant. It can be seen that while continuously improving the emission standards of motor vehicles, it should also cooperate with the improvement of public transportation systems, the development of new energy vehicles and alternative fuels, and the targeted regulation of air pollution control measures in other high-energyconsuming industries. [ABSTRACT FROM AUTHOR]

Here we report, for the first time, a versatile ZnO:ZnWO 4 heterostructure active for photocatalytic degradation of pollutants in liquid and gaseous media, prepared using a simple hydrothermal method driven by the differences in chemical solubility of the components. This heterostructured material was effective in the oxidation of methylene blue dye, caffeine, and amiloride in aqueous solution, and ethylene gas. High photocatalytic performance was attributed to the spontaneous formation of heterojunctions between ZnO and ZnWO 4 during the synthesis step, increasing electron/hole pair lifetimes. Recycling experiments revealed that the heterostructure was stable over time, indicating the commercial potential of this material. Image 1 • A versatile ZnO:ZnWO 4 heterostructure suitable for photocatalytic degradation was successfully prepared. • The heterostructure was effective in the oxidation of water-soluble and gaseous contaminants. • Recycling experiments revealed that the heterostructure was stable over time. • High photocatalytic performance was attributed to the spontaneous formation of heterojunctions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UV reactors for VOC abatement were modelled using numerical and CFD simulations. • The photochemical reactions mechanisms were elucidated in the whole air domain. • The flow pattern and fluid dynamics was described, presenting the chemical effects. • Several geometries were modelled, comparing them to experiments with good agreement. • Aimed at reactor scale-up, prototype reactors were also simulated with CFD. Abstract The present work focuses on the treatment of VOC emissions from industrial processes, since they represent a very severe environmental hazard. For removing the VOC, an AOP (Advanced Oxidation Process) stage based on UV light and ozone was considered, analyzing the methods for the unit scale-up. An innovative CFD (Computational Fluid Dynamics) model, combining UV irradiation, reaction kinetics and fluid dynamics, describing the behavior of UV reactors in the laboratory scale, was developed. This model was verified against experimental results, displaying good agreement. Therefore, we concluded the CFD model could adequately describe relevant features regarding the performance of UV reactors. After analyzing the laboratory reactors, two designed and scaled up prototypes, were simulated using the CFD model. While the first prototype has a standard lamps configuration, the second presents an innovative lamps distribution. As for the laboratory cases, the most relevant features in terms of irradiation and reaction were described for the prototypes, comparing their performance. We evaluated both the overall VOC conversion and VOC conversion per UV lamp, analyzing the energy efficiency of each configuration with adequately accuracy. Therefore, we conclude the developed CFD model to be an important tool for reactor scale-up as a result of the good prediction of experimental results and the accurate description of the governing phenomena. By using the developed model, the scale-up process of UV reactors can be quickly improved, by screening various configurations with the simulator before testing them, saving significant time and effort in the development of full-scale reactors. [ABSTRACT FROM AUTHOR]

In this study a new approach for aerogel preparation is presented, along with the screening of obtained aerogel towards air decontamination potential. The synthesis method allows the tuning of the porosity degree of the aerogel by changing the amount of the solvent (water), which dictates the physical appearance of the obtained aerogel (compacted or expanded). Experiments have been carried out under dynamic conditions, by using isobutylene (ISB) as model pollutant and activated carbon as a reference sorbent. At low contaminant loading, the obtained aerogels exhibit comparable performance with that observed for activated carbon, otherwise the activated carbon presents the highest performance at higher loadings. The physical appearance of the aerogel appears to influence the ISB removal performance. Influence of gas flowrate and ISB concentration on the performance response is depicted. The obtained results reveal new perspectives in developing and using aerogels (ultralight materials) for the removal of air contaminants in special applications such as those related to gas safety (for example, the gas masks that should assure not only quality, but also comfort). [ABSTRACT FROM AUTHOR]

A range of different studies has been performed in order to design and develop photocatalysts that work efficiently under visible (and near-infrared) irradiation as well as to improve photons absorption with improved reactor design. While there is consensus on the importance of photocatalysis for environmental applications and the necessity to utilized solar irradiation (or visible-light) as driving force for these processes, it is not yet clear how to get there. Discussion on the future steps towards visible-light photocatalysis for environmental application is of great interest to scientific and industrial communities and the present paper reviews and discusses the two main approaches, band-gap engineering for efficient solar-activated catalysts and reactor designs for improved photons absorption. Common misconceptions and drawbacks of each technology are also examined together with insights for future progress. [ABSTRACT FROM AUTHOR]

Heterogeneous photocatalytic oxidation (PCO) is a widely studied alternative for the elimination of volatile organic compounds (VOC) in air. In this context, research on novel photoreactor arrangements to enhance PCO rates is desired. Annular fluidized bed photoreactors (AFBPR) have yielded prominent results when compared to conventional thin film reactors. However, very few works aimed at optimizing AFBPR operation. In this study, TiO2 photocalytic agglomerates were synthesized and segregated in specific size distributions to behave as Geldart groups A, B, C, and D fluidization. The TiO2 agglomerates were characterized by XRD, FTIR spectra, and N2 adsorption. Photocatalyst performances were compared in a 10-mm gapped AFBPR for degrading the model pollutant methyl-ethyl-ketone (MEK), using a 254-nm radiation source. Geldart group C showed to be inadequate for AFBPR operation due to the short operation range between fluidization and elutriation. In all the cases, photocatalytic reaction rates were superior to sole UV photolysis. Group A and group B demonstrated the highest reaction rates. Considerations based on mass transfer suggested that the reasons were enhanced UV distribution within the bed at lower flow rates and superior catalyst surface area at higher flow rates. Results also revealed that groups A, B, and D perform equally per catalyst area within an AFBPR if the fluidization numbers (FN) are high enough. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • C 4 H 8 O removal using (UV-TiO 2 /plasma) + catalytic-bed system is studied. • Specific catalysts are tested for C 4 H 8 O/O 3 removal at pilot scale. • Impacts of operating parameters on process performance are defined. • Highly efficient synergetic association was obtained. • Better performance in mineralization rate via ozone valorization. Abstract This study focuses on Butyraldehyde (C 4 H 8 O) degradation using catalytic ozonation oriented to the optimization of non-thermal plasma/photocatalytic coupled processes. After the first oxidation by non-thermal plasma coupled photocatalytic processes, a second oxidative step leading to the decomposition of the residual Butyraldehyde by Ozone is catalyzed by Mordenite, ZSM-5 and γ-alumina. The Butyraldehyde degradation in the presence of Ozone under operational parameters such as plasma energy, Butyraldehyde inlet concentration, relative humidity and the height of the catalytic bed are reported in detail. The optimum operating conditions found were: Q air = 1 m3 h-1, [C 4 H 8 O] = 100 mg m-3, SIE plasma = 18 JL-1, for Butyraldehyde degradation mediated by ZSM-5. The formation of intermediate by-products was monitored during the degradation of Butyraldehyde in the presence of Ozone and ZSM-5 catalyst to suggest a degradation pathway. The coupling of catalytic ozonation by non-thermal plasma/photocatalysis lead to the total decomposition of Ozone when catalyzed by ZSM-5and presents a positive effect on the mineralization capacity. The pollutants degradation intermediates were identified by GC-MS and the oxidative states on the catalytic bed were characterized by XPS. [ABSTRACT FROM AUTHOR]

Background: Human hair can be used as an inexpensive and accessible adsorbent to remove a variety of pollutants from air. Although several studies have been done on removal of formaldehyde from wastewater by human hair, to date no study has investigated using hair to remove formaldehyde from air. Therefore, the aim of this study was to remove formaldehyde from synthetic contaminated air by a reactor packed with human hair. Methods: Air contaminated with formaldehyde was introduced into a cylindrical reactor packed with human hair at the initial concentration of 8500 mg/L. Formaldehyde concentration was measured in the influent and effluent of the reactor to indicate formaldehyde removal efficiency. Other measurements of parameters effective on formaldehyde removal were taken including amount of human hair and environmental temperature. Results: Results of this study revealed that each gram of human hair was able to remove 0.13 to 0.49 g of formaldehyde from air. Human hair adsorbed 98% of formaldehyde from synthetic contaminated air under 20˚C. These results demonstrate that increased temperature had a negative effect on formaldehyde removal. Conclusion: Results of this study show that human hair can be applied as a simple and inexpensive adsorbent to remove formaldehyde from industrial air exhaust. In addition, results of these tests can be considered as a small step to promote better air quality.

Background and Objectives: Adsorption is one of the most common methods for VOCs elimination from waste air stream. The study on the application of a selective and cheap adsorbent with high efficiency in VOCs removal is important from economic aspects. In this study, the potential of MnO/GAC and MgO/GAC composites was investigated for toluene adsorption from air stream at lab scale. Material and methods: The MnO/GAC and MgO/GAC adsorbents were prepared through Sol-gel method and then were characterized using BET, XRF, and SEM analysis. The effect of operational parameters including; retention time (0.5, 1, 1.5, 2, and 4 S), inlet toluene concentration (100, 200, 300, and 400 ppmv) and the temperature of the air stream (25, 50, 75, and 100 ˚C) were examined on the efficiency of both adsorbents. The efficiency of MnO/GAC and MgO/GAC were determined from the breakthrough time and adsorption capacity and the results were compared statistically. Results: The breakthrough time of MnO/GAC and MgO/GAC adsorbents increased 90% by increasing retention time from 0.5 to 4 S. Adsorption capacity of MgO/GAC and MnO/GAC was increased 39and 61.1% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. Breakthrough time of MgO/GAC and MnO/GAC decreased 65 and 59% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. The efficiency of MgO/GAC and MnO/GAC adsorbents had a direct relationship with the increase of air temperature from 25 to 100 ˚C. Accordingly, the efficiency of MgO/GAC and MnO/GAC was increased 78 and 32% by increasing air temperature, respectively. Conclusion: The results of the study showed that MgO/GAC and MnO/GAC adsorbents had high efficiency in toluene removal from air stream. The difference between the efficiency of MgO/GAC and MnO/GAC adsorbents was significant and MgO/GAC adsorbent showed higher efficiency than MnO/GAC for toluene adsorption from waste air.

It was demonstrated that the daily monitoring of electrical conductivity (EC) of scrubbing water can easily be used to determine the performance of biotrickling filters treating ammonia (NH3) emissions, generated by livestock facilities. Two different measurement campaigns were carried out on a pilot-scale biotrickling filter installed at a pig facility. Different phases of the operation were observed for each campaign, in accordance with EC values. For EC ranges of between 5 and 40 mS cm−1, performance was similar for both campaigns, indicating that the nitrogen accumulated in water (φ) was controlled by the operating conditions and biotrickling filter design (φ = 205 gN day−1 corresponding to 1.71 mS cm−1 day−1). Due to the correlation established in Part A of this study, the performance of the biotrickling filter can be directly expressed as gN h−1 m−3packing material without gas-phase monitoring. Thus, for an Empty Bed Residence Time of 1 s, the nitrogen accumulation capacity of the biotrickling filter was 24 gN h−1 m−3packing material. For higher EC values, the ammonia mass transfer slowed down and stopped with EC at around 50–60 mS cm−1 (campaign #1) and 70 mS cm−1 (campaign #2). It was evidenced that the mass transfer stopped due to ammonia mass transfer limitation controlled by the driving force, although biomass inhibition can occur at these levels of nitrogen concentration in the scrubbing liquid. EC monitoring can also be used to assess the ratio of nitrogen accumulated in water φ and amount of ammonia entering the system φmax. Thus φ/φmax ratios of 41% and 27% were recorded for campaign #1 and #2 respectively.

It is emphasized that a generalized relationship can be used to predict the ionic nitrogen concentration (i.e., sum of ammonium NH4+, nitrite NO2− and nitrate NO3−) of the scrubbing liquid in a biotrickling filter treating ammonia emissions by measuring the electrical conductivity (EC) of the water directly. From measurements carried out on different water samples from six biotrickling filters in operation in pig husbandries, the generalized relationship is: Σ([NH4+]+[NO2−]+[NO3−]) g N/L = 0.22 EC mS/cm. This equation is valid provided the fresh water feeding the biotrickling filter has a low electrical conductivity (−1). Moreover, since ammonium, nitrite and nitrate ions are the ultra-majority ions in the liquid phase, the balance between NH4+ and (NO2− + NO3−) was confirmed, and consequently the relationship NH4+ = 0.11 EC mS/cm can also be applied to determine the ammonium concentration from the EC. As a result, EC measurement could be applied extensively to monitor operating biotrickling filters worldwide and used to determine ammonia mass transfer in real time, keeping in mind that the accuracy of the generalized relationship is ±20%.

The paper presents the results of an analysis of a two-stage pilot plant for the removal of toluene and benzene from the exhaust air of an industrial wastewater treatment plant (WWTP). The two-stage air process combines a water scrubber and a biotrickling filter (BTF) in sequence, and treats air stripped from the liquid phase compartments of the WWTP. During the experimental period, the pilot plant treated an airflow of 600 Nm3h-1. Average concentrations of the waste air stream entering the water scrubber were 10.61 mg Nm-3 benzene and 9.26 mg Nm-3 toluene. The water scrubber obtained medium-high removal efficiencies (averages 51% and 60%, for benzene and toluene, respectively). Subsequent passage through the BTF allowed a further reduction of average concentrations, which decreased to 2.10 mg Nm-3 benzene and to 0.84 mg Nm-3 toluene, thereby allowing overall average removal efficiencies (REs) of 80% and 91% for benzene and toluene, respectively. Results prove the benefits obtained from a combination of different removal technologies: water scrubbers to remove peak concentrations and soluble compounds, and BTFs to remove compounds with lower solubility, due to the biodegradation performed by microorganisms.

Vertically aligned carbon nanotubes array offers unique properties for various applications. Detaching them from the growth substrate, while preserving their vertical structure, is essential. Quartz, a cost-effective alternative to silicon wafers and metal-based substrates, can serve as both a reaction chamber and a growth substrate. However, the strong adhesive interaction with the quartz substrate remains an obstacle for further applications. Herein, we presented a simple and well-controlled exfoliation strategy assisted by the introduction of heteroatoms at root ends of a carbon nanotubes array. This strategy forms lower surface polarity of the carbon fragment to significantly reduce adhesion to the quartz substrate, which contributes to the effortless exfoliation. Furthermore, this scalable approach enables potential mass production on recyclable quartz substrates, enhancing the cost-effectiveness and efficiency. This work can establish a solid foundation for cost-competitive carbon nanotube-based technologies, offering a promising avenue for their widespread applications.