Volatile organic compounds (VOCs) are significant atmospheric pollutants that cause environmental and health risks. Waste gases polluted with multiple VOCs often need to be purified simultaneously in ...biofilters, which may lead to antagonistic, neutral, or synergistic effects on removal performance. Antagonism limits the application of biofilters to simultaneous treatment of multiple VOCs, while synergism has not yet been fully exploited. We review the interactions among multiple target pollutants and the changes in the bioavailability and biodegradability of substrates that are responsible for substrate interactions. Potential strategies for enhancing biofilter performance are then discussed. Finally, we propose further efforts to alleviate antagonism by enhancing bioavailability and biodegradability, and discuss possible challenges to take advantage of synergism.
The structure of microbial populations plays an important role in the interactions between hydrophobic and hydrophilic VOCs, and the application of specific single species or mixed microorganisms may alter substrate interactions and consequently enhance removal performance.
Enhancing the bioavailability of reluctant VOCs can better offset the negative interactions exerted by the cosubstrates.
Strategies to alleviate the negative interactions among multiple VOCs will make it possible to employ biofilters for full-scale removal of multiple VOCs.
Biofilter performance for hydrophobic VOCs can be enhanced by exploiting the synergistic interactions of hydrophilic substrates. Regulating operational parameters, such as changing the feeding loading rate for every component and alternating the use of some hydrophilic compounds, may be promising strategies.
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•Cu-Mn-Ce mesoporous catalysts were prepared on ceramic bases.•Oβ was increased and Oγ was decreased when Cu-Mn-Ce oxides were synergistic.•Activation temperature of synergistic ...catalyst will be reduced.•VOCs were removed effectively via microwave catalytic combustion with filtration.
Cu-Mn-Ce mesoporous catalysts with different aperture distribution were prepared on ceramic bases by the impregnation method. The degradation process of volatile organic compounds (VOCs) (toluene, ethyl acetate, acetone, and their mixture) with different catalysts under microwave catalytic combustion was studied, and the synergistic mechanism of Cu-Mn-Ce matters during catalysis were identified. Under the condition of microwave power of 300 W and gas flow rate of 200 ml min−1, the TVOC removal efficiency of toluene (810.38 ± 24.05 mg m−3), ethyl acetate (759.55 ± 12.84 mg m−3), and acetone (795.35 ± 42.76 mg m−3) were 93.09%, 85.41%, and 97.14%, respectively, and their removal efficiencies could reach almost 100%. After 10 cycles (2100 mins), the Cu-Mn-Ce mesoporous catalysts still had adsorption and filtration effects, and the best catalyst showed excellent stability with a removal efficiency of 91.40% for the mixed TVOC. The reasons for the high catalytic performance of Cu-Mn-Ce mesoporous ceramic base catalyst include: 1) The catalyst was highly dispersed on the mesoporous carrier, and cerium further promotes catalyst dispersion. 2) Composite metal oxides could effectively react with each other in the synergistic process. 3) Composite metal oxides catalyst increased the Oβ and decreased the Oγ after synergizing with each other. 4) The hydrogen reduction temperature was significantly lower after metal oxide synergy. 5) The composite catalysts could work together to effectively maintain the unpaired electrons on the catalyst surface and replace the internal structural elements thus forming various defects. The trace amount of residual organics were less harmful to the environment.
Emission of volatile organic compounds (VOCs) is one of the major contributors to air pollution. The main sources of VOCs are petroleum refineries, fuel combustions, chemical industries, ...decomposition in the biosphere and biomass, pharmaceutical plants, automobile industries, textile manufacturers, solvents processes, cleaning products, printing presses, insulating materials, office supplies, printers etc. The most common VOCs are halogenated compounds, aldehydes, alcohols, ketones, aromatic compounds, and ethers. High concentrations of these VOCs can cause irritations, nausea, dizziness, and headaches. Some VOCs are also carcinogenic for both humans and animals. Therefore, it is crucial to minimize the emission of VOCs. Among the available technologies, the catalytic oxidation of VOCs is the most popular because of its versatility of handling a range of organic emissions under mild operating conditions. Due to that fact, there are numerous research initiatives focused on developing advanced technologies for the catalytic destruction of VOCs. This review discusses recent developments in catalytic systems for the destruction of VOCs. Review also describes various VOCs and their sources of emission, mechanisms of catalytic destruction, the causes of catalyst deactivation, and catalyst regeneration methods.
•Common VOCs, their sources and impacts.•Alternative techniques for VOCs destruction/separation.•Catalytic oxidation of VOCs.•Mechanism of catalytic oxidation of VOCs.•Recent development of VOCs oxidation catalysts.
Chemical sensing in vertebrates is crucial in their lives, and efforts are undertaken towards deciphering their chemical language. Volatile organic compounds (VOCs) are a group of chemicals believed ...to play an essential role in a wide variety of animal interactions. Therefore, understanding what animals sense themselves and untangling the ecological role of their volatile cues can be accomplished by analysing VOC emissions. A proton‐transfer‐reaction time‐of‐flight mass spectrometer (PTR‐TOF‐MS) is an instrument that measures VOCs in real‐time in an air sample. Since this technique acts as a hyper‐sensitive ‘nose’ it has a similar potential in deciphering the chemical language of vertebrates.
Here, we validate the use of PTR‐TOF‐MS as a tool to measure VOCs from vertebrates, which in turn will help resolve vertebrate interactions through VOCs. The instrument monitors and records the full spectrum of VOCs emitted by an individual with a high accuracy and low detection limit, including transient VOC emissions. We propose and test diverse measuring configurations that allow for measurement of VOC emissions from different vertebrates and their exudates: full body, specific parts of the body, urine and femoral pores. In addition, we test configurations for sudden and short‐lasting processes as VOCs emitted during adder skin shedding as well as the emissions of skin secretions upon mechanical and physiological stimulation in amphibia. Our configurations work in tandem with gas chromatography–mass spectrometry (GC‐MS) to allow compound structure verification.
We discuss the configurations and methodologies used and conclude with recommendations for further studies, such as the choice of chamber size and flow. We also report the results of the measurements on vertebrates—that are novel to science—and discuss their ecological meaning.
We argue that PTR‐TOF‐MS has a high potential to resolve important unanswered questions in vertebrate chemical ecology with great adaptability to a wide range of experimental set‐ups. If combined with a structure verification tool, such as GC‐MS, the creative deployment of PTR‐TOF‐MS in various future study designs will lead to the identification of ecologically relevant VOCs.
Bij vele vertebraten is de reukzin een belangrijk zintuig, en dus worden er volop stappen ondernomen om de chemische taal van deze dieren te ontcijferen. Wellicht vormen vluchtige organische moleculen (Eng. Volatile organic compounds, VOCs) een prominent onderdeel van die taal. Door de uitstoot aan VOCs te analyseren, kunnen we een idee krijgen van de stoffen die dieren waarnemen, en van de ecologische rol die deze verbindingen spelen. De Proton‐Transfer Reaction Time‐of‐Flight Mass Spectrometer (PTR‐TOF‐MS) is een apparaat dat toelaat om VOCs in een luchtmonster, in real time, te meten. Het is als het ware een hypergevoelige neus, met een grote potentiële waarde voor studies naar de chemische taal van vertebraten.
In deze bijdrage gaan we na of PTR‐TOF‐MS kan gebruikt worden om de rol van volatiele moleculen in de chemische communicatie tussen gewervelde dieren te bestuderen. Het toestel volgt en registreert het volledige spectrum aan VOCs geproduceerd door een individueel dier. Dit gebeurt met hoge precisie en met een zeer lage detectielimiet, en zo kunnen zelfs kortstondige en instabiele emissies geanalyseerd worden. We tonen en testen verschillende opstellingen waarbij VOC‐emissies van verschillende vertebraten en hun secreties gemeten worden. De metingen betreffen het volledige lichaam, specifieke lichaamsdelen, klieren en urine. Daarnaast testen we opstellingen voor het meten van plotse, kortstondige VOC‐uitstoten, zoals die zich voordoen bij vervellende slangen en chemische of fysiologische stimulatie van amfibieën. De opstellingen werden gekoppeld aan gas‐chromatografie massa‐spectrometrie (GC‐MS) om de structuur van de verbindingen te verifiëren.
We bespreken de verschillende gebruikte opstellingen en methoden en geven suggesties aangaande hun gebruik bij toekomstige studies, bijvoorbeeld qua grootte van de meetkamer en de doorstroming. We geven ook de (nieuwe) resultaten van onze metingen op verschillende vertebraten weer en bespreken hun ecologische relevantie.
We besluiten dat PTR‐TOF‐MS een veelbelovende techniek is die kan bijdragen aan het beantwoorden van de vele vragen die nog bestaan over de chemische ecologie van vertebraten. Mits gecombineerd met hulpmiddelen ter verificatie van de structuur van verbindingen (vb. GC‐MS), zal het creatief inzetten van PTR‐TOF‐MS in toekomstige studies leiden tot de identificatie van ecologisch relevante VOCs.
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•Hydrophobic coating formed on activated carbon by vapor deposition of PDMS.•Modified temperature has two different effects on VOCs adsorption capacity of AC.•Morphology and ...functional groups of AC changed after hydrophobic modification.•PDMS-deposited AC maintains large VOCs adsorption capacity in humid condition.
In engineering applications, moisture is inevitable in waste gas containing VOCs, which leads to the problem of poor adsorption performance of activated carbon under humid conditions. To improve the adsorption selectivity of VOCs, walnut based activated carbon was modified by polydimethylsiloxane (PDMS) and characterized by FTIR analysis, SEM&EDS and the static water contact angle. Dynamic adsorption column experiments were conducted and Yoon-Nelson (Y-N) model was used to identify adsorption effect for benzene on ACs when relative humidity was 0%, 30%, 60%, 90%. The results show that the activated carbon modified by PDMS increases Si and O elements and forms a hydrophobic coating on the surface in the form of Si-O-Si group. The hydrophobicity changed positively with the increase of modification temperature, but the collapse and blockage of pores were more serious. Adsorption capacity of hydrophilic Bare-AC decreased by 55.9% when the relative humidity increased from 0% to 90%. However, the activated carbon covered with PDMS modified at 200 °C decreased by only 19.3%. Changes in the mass transfer rate of benzene during adsorption under different conditions have also been discovered. This study provides a method to solve the problem of serious deterioration of adsorption capacity of adsorbents in wet environment.
•Y@St-DVB composites with hydrophobicity were synthesized successfully.•Samples had excellent the toluene adsorption capacity at dry and humid condition.•Y@St-DVB-12h exhibited excellent the ...adsorption and desorption performance.•A new class of zeolites and polymer core-shell composites could be prepared.
Zeolites with high specific surface area and good stability are considered ideal adsorbent for volatile organic compounds (VOCs) adsorption. However, the hydrophilicity of zeolites surface limits their practical application because of the competitive adsorption between water and VOCs. In this work, we reported a strategy to synthesise Y zeolite and hydrophobic organic polymer core-shell composites (Y@St-DVB), which significantly improved the hydrophobicity and toluene adsorption capacity of Y zeolite. The TEM results showed that hydrophobic organic polymer was uniformly coated on the external surface of Y zeolite through the bridging effect of phenylsilane. The adsorption capacity of Y@St-DVB-12h was 69.9% higher than that of Y zeolite at dry condition, and increased about 96% under 90% relative humidity (RH). It also exhibited excellent adsorption and desorption performance under 60% RH, which was suitable for the practical application. In addition, such composite strategy was suitable for other zeolites (EMT, ZSM-5, and Beta zeolite) to realise hydrophobic modification, which increased the adsorption capacity under wet conditions. This work not only proposes a new hydrophobic zeolite-based VOCs adsorbent, but also provides a new idea for the preparation of a series of hydrophobic adsorbents.
The complex juvenile/maturity transition during a plant's life cycle includes growth, reproduction, and senescence of its fundamental organs: leaves, flowers, and fruits. Growth and senescence of ...leaves, flowers, and fruits involve several genetic networks where the phytohormone ethylene plays a key role, together with other hormones, integrating different signals and allowing the onset of conditions favorable for stage progression, reproductive success and organ longevity. Changes in ethylene level, its perception, and the hormonal crosstalk directly or indirectly regulate the lifespan of plants. The present review focused on ethylene's role in the development and senescence processes in leaves, flowers and fruits, paying special attention to the complex networks of ethylene crosstalk with other hormones. Moreover, aspects with limited information have been highlighted for future research, extending our understanding on the importance of ethylene during growth and senescence and boosting future research with the aim to improve the qualitative and quantitative traits of crops.
Many volatile organic compounds (VOCs) associated with industry cause adverse health effects, but less is known about the physiological effects of biologically produced volatiles. This review focuses ...on the VOCs emitted by fungi, which often have characteristic moldy or "mushroomy" odors. One of the most common fungal VOCs, 1-octen-3-ol, is a semiochemical for many arthropod species and also serves as a developmental hormone for several fungal groups. Other fungal VOCs are flavor components of foods and spirits or are assayed in indirect methods for detecting the presence of mold in stored agricultural produce and water-damaged buildings. Fungal VOCs function as antibiotics as well as defense and plant-growth-promoting agents and have been implicated in a controversial medical condition known as sick building syndrome. In this review, we draw attention to the ubiquity, diversity, and toxicological significance of fungal VOCs as well as some of their ecological roles.
Surface enhanced Raman scattering (SERS) based on chemical mechanism (CM) attracts tremendous attention for great selectivity and stability. However, low enhancement factor (EF) limits its practical ...applications for trace detection. Here, a novel sponge‐like Cu‐doping SnO2‐NiO p‐n semiconductor heterostructure (SnO2‐NiOx/Cu), was first created as a CM‐based SERS substrate with a significant EF of 1.46×1010. This remarkable EF was mainly attributed to the enhanced charge‐separation efficacy of p‐n heterojunction and charge transfer resonance resulted from Cu doping. Moreover, the porous structure enriched the probe molecules, resulting in further SERS signals magnification. By immobilizing CuPc as an inner‐reference element, SnO2‐NiOx/Cu was developed as a SERS nose for selective recognition of multiple lung cancer related VOCs down to ppb level. The information of VOCs was recorded in a barcode, demonstrating practical potential of a desktop SERS device for biomarker screening.
A sponge‐like Cu‐doping SnO2‐NiO p‐n semiconductor heterostructure (SnO2‐NiOx/Cu), was created as a CM‐based SERS substrate with a significant EF >1010. SnO2‐NiOx/Cu was then developed as a SERS nose for selective recognition of multiple lung cancer related VOCs down to ppb level. The information of VOCs recorded in a barcode demonstrated practical potential of a desktop SERS device for biomarker screening.
Measurements of volatile organic compounds (VOCs) were performed as well as other pollutants in Shanghai in winter. The whole measurements were classified into three types of periods, including ...particulate pollution episodes (PPE), VOC pollution episodes (VPE), and relatively clean periods based on the pollution characteristics. Of these types, PPE have the highest fine particulate matter (PM2.5) mass concentrations and second-highest VOC concentrations, mainly impacted by the regional transport of aged air masses from the northwest. VPE generally concern long-lasting high concentrations of VOCs under stagnant atmospheric conditions due to the accumulation of local emissions. Five sources of VOCs were identified by the positive matrix factorization (PMF) model, and furthermore, the analysis of VOCs concentration weighted trajectory (CWT) was employed to investigate the potential source region and even to validate the source identification to some extent. As a result, VOCs in Shanghai in winter were mainly from solvent usage (23.9%), vehicle emissions mixed with some petrochemical emissions (24.7%), natural gas and background (23.6%), combustion-related to regional transport (22.1%), and secondary formation (5.7%). The regional transport, usually with large combustion sources, played more important roles (41.9%) in VOCs during PPE compared to VPE and clean periods. The contribution of local emissions like vehicle exhaust and petrochemical emissions increased during VPE compared to PPE and clean periods. Clean periods have low PM2.5 and low VOC concentrations, with a large contribution from the regional background. The present study highlighted the regional transport of VOCs should be taken into account for policymakers when making the city scale controlling measures.
•Meteorological conditions strongly influenced VOCs characteristics in winter.•PPE and VPE were two kinds of typical pollution episodes in winter.•Regional transport-related combustion from the northwest played important roles during PPE.•Local emissions dominated the increase of VOCs during VPE.
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