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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]

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.

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

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]

[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]

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]

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.

Air pollution from volatile organic compounds (VOCs) is one of the most important environmental hazards. Advanced oxidation processes (AOPs) with UV systems have been showing high potential for the abatement of VOCs. This work is aimed at modeling UV reactors for scaling-up AOPs from lab-scale to full-scale. The proposed model has a novel approach coupling the UV fluence rate to the photo-kinetic mechanism, for a robust understanding of the phenomena involved. The results show that the 185 nm wavelength is deeply absorbed within few centimeters by oxygen, while the 254 nm wavelength is weakly absorbed by the ozone generated in the reactor. Based on the fluence rate calculations, the reactions of ozone generation and depletion were modeled. The ozone net concentration was compared to the experimental results, for model verification. The model accurately predicts the effect of the airflow rate and reactor diameter for the tested cases. The acetaldehyde oxidation reaction was modeled using a simplified kinetic mechanism, using the experimental data of VOC conversion for a further model verification. The suggested reactor models accurately predicted the effect of airflow rate, while exhibiting limitations for the effect of different reactor diameters. Therefore, a computational fluid dynamics (CFD) investigation is needed for an accurate modeling of the VOCs oxidation reaction, implementing the developed analytical expression for reducing the computational workload. By combining the developed model with a CFD simulator, it would be possible to simulate several reactors, also at full-scale, for predicting their performance and identifying optimal configurations. [ABSTRACT FROM AUTHOR]

In this paper, CeO2(30%)/Clinoptilolite was synthesized via HNO3 treatment and coprecipitation 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. [ABSTRACT FROM AUTHOR]

Decahedral anatase titania particles (DAPs) immobilized on zeolites (zeolite/DAP hybrids), have been prepared by the first time. DAPs have been synthesized from titanium chloride (TiCl4) through a gas-phase reaction process by rapid heating and quenching. DAPs with well-defined {101} and {001} facets were synthetized and dispersed onto the zeolites. The incorporation of an 8wt% of DAPs into the zeolites has been achieved by means of the freezing-drying technique. Two types of zeolites (ZSM-5 and zeolite Y) with different SiO2/Al2O3 contents have been selected as adsorbents. The photocatalytic properties for the degradation of representative volatile organic compounds (VOC), i.e. acetaldehyde, formaldehyde or trichloroethylene were analyzed under batch and continuous flow reactors. Raw materials and composites were characterized by SEM, N2 adsorption-desorption, UV-vis spectroscopy, XRD, zeta potential and the amount of VOC adsorbed was measured at dynamic conditions. Zeolite/DAP hybrids combine the textural and crystalline properties of zeolite and DAPs phases. The zeolite type (crystal structure, SiO2/Al2O3 ratio and surface net charge) play a relevant role in the dispersion of DAPs. Zeolite/DAP composites show better photocatalytic performance than those prepared with commercial TiO2 due to the presence of {001} facets in the former. The composites prepared with hydrophobic ZSM-5 and DAPs, are the most versatile materials for photooxidation of aldehydes and organochloride compounds, with substantially less formation of non-desirable reaction products respect to those based on benchmark TiO2. [ABSTRACT FROM AUTHOR]

V2O5-TiO2 mixed oxide nanotube (NT) layers were successfully prepared via the one-step anodization of Ti-V alloys. The obtained samples were characterized by scanning electron microscopy (SEM), UV-Vis absorption, photoluminescence spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), and micro-Raman spectroscopy. The effect of the applied voltage (30-50 V), vanadium content (5-15 wt %) in the alloy, and water content (2-10 vol %) in an ethylene glycol-based electrolyte was studied systematically to determine their influence on the morphology, and for the first-time, on the photocatalytic properties of these nanomaterials. The morphology of the samples varied from sponge-like to highly-organized nanotubular structures. The vanadium content in the alloy was found to have the highest influence on the morphology and the sample with the lowest vanadium content (5 wt %) exhibited the best auto-alignment and self-organization (length = 1 _m, diameter = 86 nm and wall thickness = 11 nm). Additionally, a probable growth mechanism of V2O5-TiO2 nanotubes (NTs) over the Ti-V alloys was presented. Toluene, in the gas phase, was effectively removed through photodegradation under visible light (LEDs, λmax = 465 nm) in the presence of the modified TiO2 nanostructures. The highest degradation value was 35% after 60 min of irradiation. V2O5 species were ascribed as the main structures responsible for the generation of photoactive e- and h+ under Vis light and a possible excitation mechanism was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A UV-LED photocatalytic reactor was developed for the VOC degradation. • TiO 2 /rGO showed significant photocatalyst improvement activity compared to bare TiO 2. • Immobilizing the photocatalyst on porous substrate improved photocatalytic activity. • UV-LED reactor with porous photocatalyst provides a promising air treatment method. The aim of this study was to experimentally investigate the application of ultraviolet light-emitting diodes (UV-LEDs) for removing volatile organic compounds (VOCs) from air. For this purpose, a 365 nm UV-LED and a photocatalyst were used in a batch reactor to study the photocatalysis of toluene as the representative pollutant. It was demonstrated that combining reduced graphene oxide (rGO) with titanium dioxide (TiO 2) and immobilizing the catalyst on the porous substrate could significantly improve the photocatalytic activity compared with the pristine TiO 2 catalyst on a solid substrate. Photocatalyst deactivation was also studied by running cyclical tests. The photocatalytic crystal structure remained intact, but catalytic activity declined more than 80% after five consecutive photocatalytic tests for treating relatively high toluene concentrations. The adsorbed intermediates of toluene photocatalysis, such as benzoic acid, benzaldehyde, and benzyl alcohol, were identified, and the deactivation mechanism was proposed. It was shown that the deactivated photocatalyst can be effectively regenerated by UV-LED irradiation of 38.5 mW/cm2 irradiance within two hours. Overall, it was concluded that the UV-LED with a TiO 2 on porous support provides an effective method for practical air purification applications. [ABSTRACT FROM AUTHOR]

A lab-scale biofilter packed with mixed packing materials was used for degradation of toluene. Different empty bed residence times, 148.3, 74.2 and 49.4 s, were tested for inlet concentration ranging from 0.2 to 1.2 g/m3. The maximum elimination capacity of 36.0 g/(m3 h) occurred at an inlet loading rate of 45.9 g/(m3 h). The contribution of the lower layer was higher than other layers and always had the highest elimination capacity. The carbon dioxide production rate and distribution of micro-organisms followed toluene elimination capacities. The results of this study indicated that mixed packing materials could be considered as a potential biofilter carrier, with low pressure drop (less than 84.9 Pa/m), for treating air streams containing VOCs.