Mixture Of Volatile Organic Compounds Research Articles

Effect of Beaded Activated Carbon Fluidization on Adsorption of Volatile Organic Compounds

This research investigates the effect of adsorbent bed configuration on volatile organic compounds (VOCs) adsorption with beaded activated carbon (BAC). Five-cycle adsorption/desorption tests using a single VOC (1,2,4-trimethylbenzene) and a mixture of nine VOCs were completed using fixed and fluidized bed adsorber configurations. Adsorption tests were completed with full loading of the adsorbent. All regeneration tests were completed in the fixed bed arrangement. The adsorption capacity of the BAC was not affected by the adsorption bed’s configuration in case of reaching full breakthrough. For the VOC mixture, however, 30% less heel buildup was observed for the fluidized bed configuration. Higher accumulation of heavy adsorbates was found in fixed bed as opposed to fluidized bed, explaining the higher heel buildup in the former. On the other hand, improved mass transfer was found across the entire fluidized bed as a result of better gas-particle contact. These results show that, besides the expected engi...

Odorant receptors and antennal lobe morphology offer a new approach to understanding olfaction in the Asian longhorned beetle.

The Asian longhorned beetle Anoplophora glabripennis (Motchulsky) is an exotic forest pest that has repeatedly invaded North America and Europe from Asia, and has the potential to kill millions of trees and cause billions of dollars in damage. Traps baited with an attractive mixture of volatile organic compounds from hosts have been of limited success in monitoring invasion sites. We propose that lures might be improved through studying the olfactory system of adult beetles, especially the gene family of odorant receptors (ORs) and the structure of the antennal lobes of the brain. Here, we report identification of 132 ORs in the genome of A. glabripennis (inclusive of one Orco gene and 11 pseudogenes), some of which are orthologous to known pheromone receptors of other cerambycid beetles. We also identified three ORs that are strongly biased toward expression in the female transcriptome, and a single OR strongly biased toward males. Three-dimensional reconstruction of the antennal lobes of adults suggested a male-specific macroglomerulus and several enlarged glomeruli in females. We predict that functional characterization of ORs and glomeruli will lead to identification of key odorants in the life history of A. glabripennis that may aid in monitoring and controlling future invasions.

Influence of Adsorbent Nature on the Dynamic Headspace Study of Insect Semiochemicals

In chemical ecology studies (insect–insect, insect–plant relationships), it is important to choose the appropriate sampling methods and the correct optimization of sampling by using dynamic systems. In the present work, different adsorbents were evaluated in a dynamic system that presents a stream of purified air flowing through an aeration chamber containing a mixture of volatile organic compounds, mainly insect semiochemicals such as α-pinene, sulcatone, β-linalool, menthone, isomenthone, methyl salicylate, grandlure I, grandlure II, grandlure III, grandlure IV, eugenol, and α-ionone. Traditional adsorbents such as Tenax TA, Porapak Q, Hayesep Q, and activated charcoal were evaluated; further, alternatives such as Porapak Rxn RP, HLB, SCX, and silica gel, among others were proposed owing to their lower cost. The results demonstrated that Porapak Q and Porapak Rxn RP, despite their different chemical composition, were able to produce similar ratios of compounds to that of the reference solution and, moreover, with the highest recovery yields. However, it is important to emphasize the adsorption selectivity provided by SCX for eugenol and α-ionone. When Porapak Rxn RP was used in the analysis of Eucalyptus globulus volatiles, excellent results were obtained, and these agree with reported data from a hydrodistillation method.

Faster health deterioration among nail technicians occupationally exposed to low levels of volatile organic compounds.

The study has aimed at investigating the subjective assessment of an individual's health status and comparing the prevalence of selected work-related symptoms among nail technicians occupationally exposed to volatile organic compounds (VOCs) to the one among control subjects. Associations between occupational exposure to VOCs and the incidence of adverse health effects were also analyzed. The study involved 145 female nail technicians and 152 control subjects. Data on the prevalence of adverse health effects was collected using the researcher- made questionnaire and then analyzed by means of survival analysis methods. Only 22% of nail technicians as compared to 45% of control subjects described their current health status as "excellent" or "very good" (odds ratio (OR) = 0.4, 95% confidence interval (CI): 0.2-0.6, p < 0.00005). In general, 61% of nail technicians confirmed to have experienced any out of all symptoms considered in the study since the commencement of the job, which was significantly higher as compared to 17% of control subjects (adjusted OR = 2.8, 95% CI: 2.1-3.7, p < 0.0001). Estimated median length of the employment period free of investigated symptoms was significantly shorter among nail technicians as compared to controls (12 years vs. 33 years, p < 0.0001), consistent with almost 4-times increased hazard of the occurrence of such symptoms among the technicians (hazard ratio (HR) = 3.9, 95% CI: 2.7-5.7, p < 0.0001). Cox proportional hazard regression modeling revealed almost 5-times increased hazard of the occurrence of any symptoms among nail technicians exposed to higher levels of the mixture of VOCs as compared to those exposed to lower levels (HR = 4.9, 95% CI: 1-24.1, p = 0.05). All outcomes combined together indicate that nail technicians are subject to faster health deterioration, which may be assumed to be caused by occupational exposure to low levels of VOCs. Int J Occup Med Environ Health 2017;30(3):469-483.

High pressure mass spectrometry of volatile organic compounds with ambient air buffer gas.

There are many chemical measurement scenarios that would benefit from hand portable mass spectrometry tools including forensics, environmental monitoring, and safety and security. High pressure mass spectrometry (HPMS) facilitates miniaturization by significantly reducing vacuum system requirements. Previous work demonstrated HPMS using helium buffer gas, but HPMS conducted using ambient air would further reduce the size and weight of a portable instrument while also reducing logistical demands by eliminating the need for a helium supply. Mass spectrometry was performed at pressures exceeding 1Torr with ambient air as the buffer gas. A glow discharge electron ionization source and a miniature cylindrical ion trap mass analyzer with a radius of 0.5mm were used. Mass analysis was possible at these pressures with increased radiofrequency (RF) drive frequencies (10MHz) compared with commercial ion traps (~1MHz). A differentially pumped chamber was used so that mass spectrometry could be performed at high pressures and detection performed at low pressures with an electron multiplier. HPMS with air buffer gas was demonstrated using a suite of volatile organic compounds (VOCs). The glow discharge ionization source was optimized for operation using air. Mass spectral peak widths increased a factor of 8 compared with helium, as expected, but useful chemical information was still acquired. A mixture of VOCs was detected with ambient air as the buffer gas, showing that valuable mass information can be gained using HPMS without the requirement of an onboard buffer gas source. HPMS significantly reduces the pumping requirements required for miniature mass spectrometers and the use of ambient air buffer gas further reduces size, weight, and logistics requirements. Mass analysis at high pressures of ambient air is another important step for the development of hand portable mass spectrometers. Copyright © 2016 John Wiley & Sons, Ltd.

Quantification of the plant terpenome: predicted versus actual emission potentials

Plant essential oils are complex mixtures of volatile organic compounds, which play indispensable roles in communication, defense, and adaptive evolution. The complete chemical library produced by a plant is referred to as its terpenome. The potential biological information stored in essential oil composition data can provide an insight into the silent language of plants, as well as roles of terpene emissions in direct and indirect defense, and for playing a crucial role in adaptive evolution. In this work, we have attempted to measure the plant terpenome from a global perspective. One way of measuring the terpenome is to observe and record actual emissions in natural conditions, and this has been in practice for over a century through variously evolving methods of comprehensive GC–MS and HPLC. An alternative method is a knowledge-based prediction of the terpenome, and this method has gained popularity in recent years, with the advent of large-scale genome sequencing technologies. Over the past decade, our laboratory has been involved in compilation and investigation of the plant terpenome using both these methods and this has offered us the opportunity to compare and contrast data from actual and potential emissions, in order to better understand the terpenome and its roles in primary, secondary and adaptive metabolism. We have used emission data in conjunction with genomic data in order to understand how a plant creates the so-called final terpenome, specific to itself, and whether or not plants tap the complete potential for terpene biosynthesis at their disposal according to their genomes. For measuring actual emissions, we have used EssOilDB (the ESSential OIL DataBase), the largest contextual web resource for phytochemicals and for measuring the total plant potential for emissions, we have used TERZYME, an automated algorithm for identification and analysis of genes and proteins involved in isoprenoid biosynthesis.

Abatement robustness of volatile organic compounds using compact trickle-bed bioreactor: Biotreatment of styrene, ethanol and dimethyl sulfide mixture in contaminated airstream

A wide range of volatile organic compounds (VOCs) chemical characteristics (aromatic, sulfur-containing organics and alcohol) were selected to demonstrate a prospective potential of the biotrickling technology in practical applications through the appropriate selection and combination of biological ‘agents’. The principal objective of this study was to specify operating boundaries of parameters at which the sampled microorganisms were most effective in the biodegradation of gaseous streams containing styrene, ethanol and dimethyl sulfide mixture at dynamic variations of pollutant load. The average conversion factor for the 3-component VOCs mixture was higher than 95% at lower range of the individual pollutant load and basically fell to 80% at middle range vs. 55% at the higher contaminant loads; however, the effectiveness of ethanol biodegradation is stable at the entire investigated range of the mass load. The consequences of an unexpected pollutant overload (media clogging) and the time necessary for the subsequent regeneration of the microbial community and restoring the process stability were investigated as well.

Modelling of a biofiltration process of volatile organic compound mixtures in a biofilter

ABSTRACTCurrently, different methods for air clean-up from chemical pollutants are applied worldwide: adsorption, absorption, and thermal and catalytic oxidation. One of the most promising methods is biological air cleaning. The aim of this study was to test the performance of a developed biofilter with packing material of activated pine bark for biological air cleaning and to mathematically model the biofiltration processes. Comparative analysis of the modelling results for individual pollutants (butyl acetate, butanol and xylene) showed strongest dependence of the efficiency of xylene removal from the air on the amount and ratio of other substances (from 20% to 70%). Thus, the process of removal of pollutants (butanol and butyl acetate) that are easier to biologically decompose was obtained to be influenced to a lesser extent by the amount and ratio (%) of other components. The results also showed that the efficiency of butyl acetate removal mostly depended on the ratio of other substances in the mixture (from 15% to 100%), whereas the efficiency of butyl acetate and xylene removal mostly depended on the amount of other substances in the mixture (from 20% to 100%). With the parameters of the biofilter (height of packing material, incoming air flow velocity) and the pollutants to be removed known, the mathematical expression of the filter efficiency was found, which would allow to make theoretical calculation and selection of the most appropriate parameters of the device as well as to achieve maximum efficiency of air cleaning.

Volatile organic compounds emitted by Trichoderma species mediate plant growth.

BackgroundMany Trichoderma species are applied as biofungicides and biofertilizers to agricultural soils to enhance crop growth. These filamentous fungi have the ability to reduce plant diseases and promote plant growth and productivity through overlapping modes of action including induced systemic resistance, antibiosis, enhanced nutrient efficiency, and myco-parasitism. Trichoderma species are prolific producers of many small metabolites with antifungal, antibacterial, and anticancer properties. Volatile metabolites of Trichoderma also have the ability to induce resistance to plant pathogens leading to improved plant health. In this study, Arabidopsis plants were exposed to mixtures of volatile organic compounds (VOCs) emitted by growing cultures of Trichoderma from 20 strains, representing 11 different Trichoderma species.ResultsWe identified nine Trichoderma strains that produced plant growth promoting VOCs. Exposure to mixtures of VOCs emitted by these strains increased plant biomass (37.1–41.6 %) and chlorophyll content (82.5–89.3 %). Trichoderma volatile-mediated changes in plant growth were strain- and species-specific. VOCs emitted by T. pseudokoningii (CBS 130756) were associated with the greatest Arabidopsis growth promotion. One strain, T. atroviride (CBS 01-209), in our screen decreased growth (50.5 %) and chlorophyll production (13.1 %). Similarly, tomatoes exposed to VOCs from T. viride (BBA 70239) showed a significant increase in plant biomass (>99 %), larger plant size, and significant development of lateral roots. We also observed that the tomato plant growths were dependent on the duration of the volatile exposure. A GC–MS analysis of VOCs from Trichoderma strains identified more than 141 unique compounds including several unknown sesquiterpenes, diterpenes, and tetraterpenes.ConclusionsPlants grown in the presence of fungal VOCs emitted by different species and strains of Trichoderma exhibited a range of effects. This study demonstrates that the blend of volatiles produced by actively growing fungi and volatile exposure time in plant development both influence the outcome of volatile-mediated interactions. Only some of our growth promoting strains produced microbial VOCs known to enhance plant growth. Compounds such as 6-pentyl-2H-pyran-2-one were not common to all promoting strains. We found that biostimulatory strains tended to have a larger number of complex terpenes which may explain the variation in growth induced by different Trichoderma strains.

Arabidopsis thaliana as Bioindicator of Fungal VOCs in Indoor Air

In this paper, we demonstrate the ability of Arabidopsis thaliana to detect different mixtures of volatile organic compounds (VOCs) emitted by the common indoor fungus, Aspergillus versicolor, and demonstrate the potential usage of the plant as a bioindicator to monitor fungal VOCs in indoor air. We evaluated the volatile production of Aspergillus versicolor strains SRRC 108 (NRRL 3449) and SRRC 2559 (ATCC 32662) grown on nutrient rich fungal medium, and grown under conditions to mimic the substrate encountered in the built environment where fungi would typically grow indoors (moist wallboard and ceiling tiles). Using headspace solid phase microextraction/gas chromatography-mass spectrometry, we analyzed VOC profiles of the two strains. The most abundant compound produced by both strains on all three media was 1-octen-3-ol. Strain SRRC 2559 made several terpenes not detected from strain SRRC 108. Using a split-plate bioassay, we grew Arabidopsis thaliana in a shared atmosphere with VOCs from the two strains of Aspergillus versicolor grown on yeast extract sucrose medium. The VOCs emitted by SRRC 2559 had an adverse impact on seed germination and plant growth. Chemical standards of individual VOCs from the Aspergillus versicolor mixture (2-methyl-1-butanol, 3-methyl-1-butanol, 1-octen-3-ol, limonene, and β-farnesene), and β-caryophyllene were tested one by one in seed germination and vegetative plant growth assays. The most inhibitory compound to both seed germination and plant growth was 1-octen-3-ol. Our data suggest that Arabidopsis is a useful model for monitoring indoor air quality as it is sensitive to naturally emitted fungal volatile mixtures as well as to chemical standards of individual compounds, and it exhibits relatively quick concentration- and duration-dependent responses.

Gene-specific 5’-UTR methylation vs. promoter methylation in leukocytes from workers exposed to different levels of VOCs.

Introduction: As a result of exposure to toxic substances, different human and animals cells have displayed either global DNA hypomethylation or gene-specific hypermethylation. Specifically in occupational volatile organic compound (VOC) exposure, we previously found hypermethylation in TOP2A, SOD1 and TNF-a promoter area in leukocytes from people exposed to a complex VOC mixture, while participants exposed to a single VOC did not show any differences compared to controls. The aim of this study was to analyze the methylation pattern in the 5’-UTR region, considered for some authors as an “internal/alternative promoter area” in people occupationally exposed to a single VOC compared to VOC mixtures exposure as well as a reference, non-exposed group. Methods: PCR-pyrosequencing was performed in order to analyze methylation status in CpG’s located at the 5’-UTR region of the TOP2A, SOD1, IL6, TNF-a and CYP2E1 genes in leukocytes from Mexican workers laboring at three different scenarios with VOC exposure compared to a reference group. Results: 5’-UTR region from IL6 and TOP2A genes showed hypomethylation for two populations exposed to a VOC mixture, while TNF-a showed hypermethylation; methylation in the SOD1 gene did not show differences between groups. DNA obtained from the reference group showed hypermethylation in the 5’-UTR region from the CYP2E1 gene compared to all exposed subgroups. Conclusions: 5’-UTR region in certain genes is more prone to undergo epigenetic modifications compared to promoter area as a result of VOC exposure. 5’-UTR methylation status must be considered in a near future as an early biomarker of effect in human chemical toxicity.

Dissociation against oxidation kinetics for the conversion of VOCs in non-thermal plasmas of atmospheric gases

The kinetics of four volatile organic compounds (VOCs) (propene, propane, acetaldehyde, acetone) were studied in plasmas of atmospheric gases using a photo-triggered discharge (homogeneous plasma) or a dielectric barrier discharge (filamentary plasma). It was shown for the homogeneous plasma that quenchings of nitrogen metastable states, A 3 Ʃ + u and the group of singlets a' 1 Ʃ - u , a 1 Π g and w 1 ∆ u , are important processes for the decomposition of such molecules. Recent measurements of the H 2 concentration produced in the N 2 /C 3 H 6 mixture emphasize that the hydrogen molecule can be an exit route for propene dissociation. It is also found that H 2 and CO molecules are efficiently produced following the dissociation of CH 3 COCH 3 and the subsequent chemical reactivity induced by radicals coming from acetone. Addition of oxygen to a N 2 /VOC mixture can change drastically the kinetics. However, the quenching processes of N 2 metastables by the VOC are always present and compete with oxidation reactions for the conversion of the pollutant. At low temperature, oxidations by O or by OH are not always sufficiently effective to induce an increase of the molecule decomposition when oxygen is added to the mixture. In particular, the presence of O 2 has a detrimental effect on the acetone removal. Also, as evidenced for acetaldehyde and propane, some kinetic analogies appear between filamentary and homogeneous plasmas.

Molar fraction stability in dynamic preparation of reference trace gas mixtures

Volatile Organic Compounds (VOC) at trace level are common indicators for climate change and ambient air quality. The calibration of detection systems at trace level needs VOC mixtures at nmol/mol level with 5% uncertainty, the dynamic preparation can fulfil it. A source of uncertainty for dynamic generation is the stability of the VOC molar fraction averaged on the sampling time. A general method for the calculation of the relevance of the stability contribution to the total uncertainty is here proposed. VOC molar fraction is here considered as a composed quantity. Threshold values for stability contribution were set to consider it either as negligible and relevant. The stability of the operative quantities of a device, for the dynamic preparation of accurate VOC reference mixtures, was measured at the working conditions by the Allan deviation algorithm. Stabilities of operative quantities were composed to calculate the VOC molar fraction stability and their contribution to total uncertainty of VOC molar fraction. The stability of the air inlet pressure gave the main stability contribution. The stability contribution to the total uncertainty resulted to be negligible for observation times below 60 min for VOC molar fraction uncertainty of 2% at 30 nmol/mol level.

Phytotoxic and antimicrobial activity of volatile and semi-volatile organic compounds from the endophyte Hypoxylon anthochroum strain Blaci isolated from Burseralancifolia (Burseraceae).

To evaluate the phytotoxic, antifungal and antioomycete activity; and, determine the chemical composition of the volatile organic compounds (VOCs) and semi-volatile metabolites produced by the endophyte Hypoxylon anthochroum strain Blaci isolated from Bursera lancifolia. Based on its macro- and micro-morphological features, the strain Blaci was identified as Nodulisporium sp.; partial analysis of its ITS1-5.8-ITS2 ribosomal gene sequence revealed the identity of the teleomorphic stage of the fungus as H.anthochroum. Phytotoxic and antimicrobial activities of VOCs, and culture medium and mycelium organic extracts from H.anthochroum Blaci were determined by simple and multiple antagonism bioassays, and gas phase and agar dilution bioassays respectively. The volatile and semi-volatile metabolites were identified by gas chromatography-mass spectrometry. VOCs from a 5-day H.anthochroum strain Blaci culture caused the inhibition of seed germination, root elongation and seedling respiration on Amaranthus hypochondriacus, Panicum miliaceum, Trifolium pratense and Medicago sativa. In addition, extracts, phenylethyl alcohol and eucalyptol main compounds present in the VOCs and extract displayed a high phytotoxic activity, inhibiting the three physiological processes on the four test plants in a concentration-dependent manner. The results revealed that H.anthochroum strain Blaci produces a mixture of VOCs. These VOCs showed a strong phytotoxic activity on seed germination, root elongation, and seedling respiration of four plants and slightly affected the growth of phytopathogenic fungi and oomycetes. Also, the culture medium and mycelium extracts of H.anthochroum showed a high phytotoxic activity on the four test plants and, generally, the culture medium extract was more phytotoxic than the mycelium extracts. This work firstly reports the phytotoxic activity of volatile and semi-volatile compounds produced by the endophyte H.anthochroum strain Blaci on seed germination, root elongation, and seedling respiration of four different plants; consequently, these compounds could be useful in biocontrol of weeds and plant pathogens.

Predicting the lifetime of organic vapor cartridges exposed to volatile organic compound mixtures using a partial differential equations model

ABSTRACTIn this study, equilibria, breakthrough curves, and breakthrough times were predicted for three binary mixtures of four volatile organic compounds (VOCs) using a model based on partial differential equations of dynamic adsorption coupling a mass balance, a simple Linear Driving Force (LDF) hypothesis to describe the kinetics, and the well-known Extended-Langmuir (EL) equilibrium model. The model aims to predict with a limited complexity, the BTCs of respirator cartridges exposed to binary vapor mixtures from equilibria and kinetics data obtained from single component. In the model, multicomponent mass transfer was simplified to use only single dynamic adsorption data. The EL expression used in this study predicted equilibria with relatively good accuracy for acetone/ethanol and ethanol/cyclohexane mixtures, but the prediction of cyclohexane uptake when mixed with heptane is less satisfactory. The BTCs given by the model were compared to experimental BTCs to determine the accuracy of the model and the impact of the approximation on mass transfer coefficients. From BTCs, breakthrough times at 10% of the exposure concentration t10% were determined. All t10% were predicted within 20% of the experimental values, and 63% of the breakthrough times were predicted within a 10% error. This study demonstrated that a simple mass balance combined with kinetic approximations is sufficient to predict lifetime for respirator cartridges exposed to VOC mixtures. It also showed that a commonly adopted approach to describe multicomponent adsorption based on volatility of VOC rather than adsorption equilibrium greatly overestimated the breakthrough times.

Dual-channel microcantilever heaters for volatile organic compound detection and mixture analysis.

We report on novel microcantilever heater sensors with separate AlGaN/GaN heterostructure based heater and sensor channels to perform advanced volatile organic compound (VOC) detection and mixture analysis. Operating without any surface functionalization or treatment, these microcantilevers utilize the strong surface polarization of AlGaN, as well as the unique heater and sensor channel geometries, to perform selective detection of analytes based on their latent heat of evaporation and molecular dipole moment over a wide concentration range with sub-ppm detection limit. The dual-channel microcantilevers have demonstrated much superior sensing behavior compared to the single-channel ones, with the capability to not only identify individual VOCs with much higher specificity, but also uniquely detect them in a generic multi-component mixture of VOCs. In addition, utilizing two different dual channel configurations and sensing modalities, we have been able to quantitatively determine individual analyte concentration in a VOC mixture. An algorithm for complete mixture analysis, with unique identification of components and accurate determination of their concentration, has been presented based on simultaneous operation of an array of these microcantilever heaters in multiple sensing modalities.

Study of the Vapor Phase Over Fusarium Fungi Cultured on Various Substrates.

The compositions of volatile organic compounds (VOCs) emitted by Fusarium fungi (F. langsethiae, F. sibiricum, F. poae, and F. sporotrichioides) grown on two nutritive substrates: potato sucrose agar (PSA) and autoclaved wheat kernels (WK) were investigated. The culturing of fungi and study of their VOC emissions were performed in chromatographic vials at room temperature (23 - 24 °C) and the VOCs were sampled by a solid-phase microextraction on a 85 μm carboxen/polydimethylsiloxane fiber. GC/MS was performed using a 60-m HP-5 capillary column. Components of the VOC mixture were identified by electron impact mass spectra and chromatographic retention indices (RIs). The most abundant components of the VOC mixture emitted by Fusarium fungi are EtOH, AcOH, (i) BuOH, 3-methylbutan-1-ol, 2-methylbutan-1-ol, ethyl 3-methylbutanoate, terpenes with M 136, sesquiterpenes with M 204 (a total of about 25), and trichodiene. It was found that the strains grown on PSA emit a wider spectrum and larger amount of VOCs compared with those grown on wheat kernels. F. langsethiae strain is the most active VOC producer on both substrates. The use of SPME and GC/MS also offers the potential for differentiation of fungal species and strains.

Effect of a Ternary Mixture of Volatile Organic Compounds on Degradation of TCE in Biotrickling Filter Systems

The primary goal of this research was to evaluate the effect of a ternary mixture of toluene, methanol, and trichloroethylene (TCE) on the elimination of TCE in a biotrickling filter. Two biotrickling filters—Biofilter I and Biofilter II—were run in parallel, each with a different toluene/methanol/TCE loading ratio of 3:2.7:1 and 1.9:0.9:1, respectively. Both systems were seeded with fungal strains grown on diatomaceous earth media and were run at pH 4 maintained by formate buffer. To control excess biomass growth, the systems were “starved” for 2 days a week and run continuously for the rest of the week. TCE loading rates for each system ranged from 1.61 to 6.44 g/m3 h−1 across three phases while toluene and methanol were loaded at rates corresponding to the influent composition ratios. More than 95 % methanol was removed from the gaseous streams throughout, while TCE removal was a function of the influent organic ratio and the corresponding concentrations. At and above loading rates of 3.22 g/m3 h−1, elimination capacities obtained from Biofilter II surpassed those from Biofilter I due to a lower feed of bio-accessible carbon (toluene and methanol) offering reduced competition to TCE removal. While over 90 % toluene was removed from both systems, its elimination capacities dropped as the phases progressed due to competition and TCE cytotoxicity. Most carbon was converted to CO2 and biomass, and no TCE oxidation by-products were detected.

Performance and microbial analysis of a biotrickling filter inoculated by a specific bacteria consortium for removal of a simulated mixture of pharmaceutical volatile organic compounds

Biotrickling filters (BTFs) could not achieve satisfactory performance for some recalcitrant volatile organic compounds (VOCs) because of slow microbial adaptation and growth. The treatment of a model mixture of pharmaceutical VOCs containing toluene, o-xylene and dichloromethane in a specific BTF was investigated. The BTF was inoculated with specified strains of Zoogloea resiniphila HJ1 and Methylobacterium rhodesianum H13 to improve the removal of recalcitrant VOCs. The BTF showed a fast start-up with over 96.5% removal for each pollutant from day 17 onwards. During the operation, the BTF maintained removal efficiency of 96–100% for a net influent concentration (Cinlet) of 450–600mgm−3 at an empty bed retention time (EBRT) of 30–75s. The maximum elimination capacity (EC) of 114.3gm−3h−1 was achieved at an inlet loading rate (LR) of 135mgm−3h−1. A high carbon mineralization of 80% implied a nearly complete biodegradation of the removed VOCs. Both 16S rRNA gene clone library and 454 pyrosequencing were used to verify the evolution of the added strains during the operation of the BTF. Clones 1 and 11 had a 100% similarity with Zoogloea resiniphila HJ1 and Methylobacterium rhodesianum H13, respectively, confirming the persistent existence of the inoculated specialized strains. According to the pyrosequencing results, Zoogloea and Methylobacterium had higher relative abundances than other bacterial genera in the BTF, implying their dominance during the operation. The persistence and dominance of the added strains were possibly responsible for the improved performance of the BTF. Overall, the results of this study open new possibilities for biotrickling filters of recalcitrant VOCs.

Gas-phase photocatalytic oxidation of refractory VOCs mixtures: Through the net of process limitations

Photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) presents an effective means of indoors air treatment. Shortcomings, however, include relatively low oxidation rate, sometimes formation of toxic by-products and catalyst deactivation. These obstacles are to be surmounted via synthesis of active catalytic materials and efficient catalyst regeneration at properly chosen process parameters. The article describes the photocatalytic performance of a novel flame aerosol synthesised nano-structured titania F3 and the method of accelerated photocatalyst activity restoration using small amounts of ozone. The experimental research into PCO abating VOCs in mixtures was undertaken following the performance of F3 compared to the benchmarking commercially available photocatalyst P25. The mixture containing acrylic acid, acrylonitrile and toluene was degraded at F3 and P25 photocatalysts, whereas the mixture of acrylonitrile, styrene and toluene—at P25 with admixtures of ozone; ozone was also used for regeneration of P25. The contact time, VOCs and ozone concentration in mixtures, temperature, and air humidity varied. In the experimental conditions, the novel photocatalyst showed activity substantially surpassing the one of the benchmark: within the experimental conditions, F3, contrary to P25, showed no symptoms of deactivation, emitting only trace amounts of toxic HCN product. The novel photocatalyst thus confirmed its promising efficiency in abatement of VOCs mixtures. Ozone appeared to be effective aid in both PCO of VOCs and the photocatalyst activity restoration dramatically shortening the photocatalyst regeneration time.