Typical Volatile Organic Compounds Research Articles

Portable Mass Spectrometry for On-site Detection of Hazardous Volatile Organic Compounds via Robotic Extractive Sampling.

Various hazardous volatile organic compounds (VOCs) are frequently released into environments during accidental events that cause many hazards to ecosystems and humans. Therefore, rapid, sensitive, and on-site detection of hazardous VOCs is crucial to understand their compositions, characteristics, and distributions in complex environments. However, manual handling of hazardous VOCs remains a challenging task, because of the inaccessible environments and health risk. In this work, we designed a quadruped robotic sampler to reach different complex environments for capturing trace hazardous VOCs using a needle trap device (NTD) by remote manipulation. The captured samples were rapidly identified by portable mass spectrometry (MS) within minutes. Rapid detection of various hazardous VOCs including toxicants, chemical warfare agents, and burning materials from different environments was successfully achieved using this robot-MS system. On-site detection of 83 typical hazardous VOCs was examined. Acceptable analytical performances including low detection limits (at subng/mL level), good reproducibility (relative standard deviation (RSD) < 20%, n = 6), excellent quantitative ability (R2 > 0.99), and detection speed (within minutes) were also obtained. Our results show that the robot-MS system has excellent performance including safety, controllability, applicability, and robustness under dangerous chemical conditions.

In-Depth Understanding of the Oxidative Compatibility of Volatile Organic Compounds with Mn2O3 and Pt-Loaded Catalysts.

Designing suitable catalysts for efficiently degrading volatile organic compounds (VOCs) is a great challenge due to the distinct variety and nature of VOCs. Herein, the suitability of different typical VOCs (toluene and acetone) over Pt-based catalysts and Mn2O3 was investigated carefully. The activity of Mn2O3 was inferior to Pt-loaded catalysts in toluene oxidation but showed superior ability for destroying acetone, while Pt loading could boost the catalytic activity of Mn2O3 for both acetone and toluene. This suitability could be determined by the physicochemical properties of the catalysts and the structure of the VOC since toluene destruction activity is highly reliant on Pt0 in the metallic state and linearly correlated with the amount of surface reactive oxygen species (Oads), while the crucial factor that affects acetone oxidation is the mobility of lattice oxygen (Olat). The Pt/Mn2O3 catalyst shows highly active Pt-O-Mn interfacial sites, favoring the generation of Oads and promoting Mn-Olat mobility, leading to its excellent performance. Therefore, the design of abundant active sites is an effective means of developing highly adaptive catalysts for the oxidation of different VOCs.

Biofiltration of toluene in the presence of ethyl acetate or n-hexane: Performance and microbial community.

This study describes the operation of two independent parallel laboratory-scale biotrickling filters (BTFs) to degrade different types of binary volatile organic compound (VOC) mixtures. Comparison experiments were conducted to evaluate the effects of two typical VOCs, i.e., ethyl acetate (a hydrophilic VOC) and n-hexane (a hydrophobic VOC) on the removal performance of toluene (a moderately hydrophobic VOC) in BTFs ''A" and ''B", respectively. Experiments were carried out by stabilizing the toluene concentration at 1.64 g m-3 and varying the concentrations of gas-phase ethyl acetate (0.85-2.8 g m-3) and n-hexane (0.85-2.8 g m-3) at an empty bed residence time (EBRT) of 30 s. In the presence of ethyl acetate (850 ± 55 mg m-3), toluene exhibited the highest removal efficiency (95.4 ± 2.2%) in BTF "A". However, the removal rate of toluene varied from 48.1 ± 6.9% to 70.1 ± 6.8% when 850 ± 123 mg m-3 to 2800 ± 136 mg m-3 of n-hexane was introduced into BTF "B". The high-throughput sequencing data revealed that the genera Pseudomonas and Comamonadaceae_unclassified are the core microorganisms responsible for the degradation of toluene. The intensity of the inhibitory or synergistic effects on toluene removal was influenced by the type and concentration of the introduced VOC, as well as the number and activity of the genera Pseudomonas and Comamonadaceae_unclassified. It provides insights into the interaction between binary VOCs during biofiltration from a microscopic perspective.

Experimental and theoretical studies on effective synergistic low-temperature removal of NO and typical volatile organic compounds (VOCs) from flue gas based on Cu@VWTi catalyst

The transition metal-modified VWTi structural catalysts hold great promise for simultaneously removing nitrogen oxides (NOx) and volatile organic compounds (VOCs) from industrial flue gases. A series of Cu@VWTi catalysts were prepared to investigate their synergistic low-temperature removal performance towards NO and typical VOCs, including toluene, benzene, chlorobenzene (CB), p-chlorotoluene (p-CT), and dichloromethane (DCM). The copper-enhanced samples prepared via ultrasound-assisted impregnation exhibited irregular globular and varying crystallinity. The catalysts displayed a typical anatase crystal structure with high TiO2 content or high dispersion of V and W species along with a certain adjustment effect on the morphology. Various controlling factors affecting the synergistic removal of NO and VOCs were evaluated. It was observed that the presence of VOCs in flue gas has weak impact on NO removal, except for the waste incineration using the Cu@VWTi catalyst. However, a high initial NO concentration had an adverse effect on VOCs removal. Impressively, the optimized copper-doped catalyst (5wt% Cu loaded of smelting plant and coal-fired power plant used catalyst) exhibited excellent performance for p-CT, toluene and DCM removal of 95.0%, 99.6% and 100% at 300 °C, respectively. The toluene and p-CT conversion efficiencies were highest over the catalyst used in the smelting plant after Cu loading, surpassing the benzene conversion efficiency. Cu@VWTi demonstrated excellent performance for p-CT, toluene, and DCM removal at 250 °C. Although 5wt% Cu loading on the catalysts significantly enhanced the stability and anti-jamming of VOCs removal, as well as their tolerance to both SO2 and water vapor. The enhanced mechanism of Cu decoration attributed to the enhanced intensity of acid sites and the stable relative proportion of Oads/Olatt species in the used 5% Cu loaded catalyst due to the redox cycles of Cu and V species. Compared with Brønsted acid, which primarily adsorbs NH4+, Lewis acid mainly adsorbs gas phase acid and forms coordinated NH3 in gas phase. The bonding between toluene and the Cu site was enhanced with an adsorption energy of -130.9 kJ·mol-1, as well as the cracking adsorption of the CH2Cl2 on the Ti site with a bonding energy of -436.7 kJ·mol-1, both indicating strong chemical adsorption. The first step of dechlorination and demethylation was thermodynamically and kinetically favorable for DCM and toluene decomposition.

Promotion of toluene catalytic oxidation by M−La/CoOx catalysts directly prepared from Co-MOFs precursors

Volatile organic compounds (VOCs) are identified as volatility and toxicity, and have become major pollutants in the atmosphere. The development of low-energy and high-efficiency environmentally friendly VOCs purification technologies is urgent. Therefore, in this paper, a series of M−La/CoOx (M = La addition) catalysts with different La additions were synthesized by a combination of impregnation and calcination using Co-MOFs as precursors. It was shown that the catalytic activity of the constructed 0.012-La/CoOx catalyst was unexpectedly improved (T90% = 227 °C) under optimal reaction conditions (catalyst mass-air velocity = 60000 mL/(g•h)), initial toluene concentration = 1000 ppm) when employing gaseous toluene (C7H8) as typical target VOCs. Among the La-doping catalysts, the catalysts containing La on the surface have smaller grain sizes as well as more homogeneous grain distributions than the pure Co3O4-MOF catalysts. 0.012-La/CoOx displayed the highest activity, which is attributed to its smaller particle size, larger specific surface area (SSA), richer content of Co3+ and surface Oads, which could enhance the oxygen mobility and the redox performance. The possible degradation mechanism of toluene on 0.012-La/CoOx was revealed using in-situ DRIFTS. This work might provide guidance for the development of efficient and environmentally friendly catalytic oxidation of toluene.

Comprehensive investigation on non-volatile and volatile compounds in Auricularia auricula from different regions by UPLC-MS/MS-based metabolomics and GC-IMS

Auricularia auriculata from two regions of China were studied for their metabolite fingerprints, metabolic pathways, and volatile organic compounds (VOCs) using UPLC-MS/MS and GC-IMS techniques in conjunction with multivariate statistical analysis approaches. A total of 881 metabolites were identified by UPLC-MS/MS, of which 39 compounds displayed significant differences. Acetyl-l-carnitine, N-acetyl-l-alanine, PC (18:3(9Z,12Z,15Z)/0:0), 4-fumaryl-acetoacetate, S-2-hydroxybutanedioic acid, and 4-guanidinobutyric acid belonged to the characteristic non-volatile metabolites. The umami-tasted amino acid, essential amino acid was abundant in Heilongjiang and Shaanxi province, respectively. KEGG pathway analysis indicated that differential metabolites were mainly enriched in lipid and amino acid metabolism. The GC-IMS study revealed 64 different types of VOCs, including acids, alcohols, aldehydes, esters, ketones, and other compounds. A. auricula from Shaanxi province was abundant in 2,3-pentanedione, 1-octen-3-one (dimer), 2-acetylfuran, beta-pinene (monomers, dimers) and alpha-pinene. While the primary distinctive VOCs of A. auricula from Heilongjiang province were butyl acetate, methyl acetate and propyl acetate. PCA and OPLS-DA allowed for clear differentiation between the A. auricula samples from the two regions. This research established foundations for investigating potential biomarkers for A. auricula and has important applications values for the creation and implementation of traceability systems within the edible mushroom industry.

Xylene adsorption behaviors of Co-MOF-74(X) synthesized from Co(II) salt with different anions

Xylene, a typical volatile organic compound (VOC) and primary raw material in the chemical industry, has been found to be a key component in ozone formation. Metal organic frameworks (MOFs) containing open metal sites are capable of binding to xylene. To recover xylene from waste solvent and to mitigate the environmental risks associated with it, three 1D coordination polymers (CPs), Co-MOF-74(X) (X = OAc–, Cl–, or NO3–), were synthesized using various cobalt salts of Co(OAc)2·4H2O, CoCl2·6H2O and Co(NO3)2·6H2O to investigate the influence of anions. Moreover, the liquid phase adsorptive performance for xylene was evaluated. The morphology features and structure differences of the resulting Co-MOF-74(X) were determined by SEM-EDS, XRD, N2/CO2 adsorption, FTIR and XPS. In situ DRIFT was applied to further distinguish the adsorption performance of Co-MOF-74(X) for xylene. The results indicated that Co-MOF-74(X) exhibits a different morphology. Co-MOF-74(OAc–) is flaky and agglomerated severely, while both Co-MOF-74(Cl–) and Co-MOF-74(NO3–) are hexagonal rod–like crystals. All of Co-MOF-74(X) showed microporous structures with high specific surface areas. A small amount of Cl– was retained in Co-MOF-74(Cl–), forming a Co–Cl bond with Co(II), and the active site of adsorption increased. Co-MOF-74(Cl–) shows the highest adsorption capacity of 1317.65 mg/g for the xylene mixture with excellent cyclic stability reported so far, which is 2.17 or 2.78 times more than Co-MOF-74(NO3–) or Co-MOF-74(OAc–). Therefore, it is anticipated to be a highly efficient adsorbent for removal or recovery of xylene.

Advances in Adsorption, Absorption, and Catalytic Materials for VOCs Generated in Typical Industries

In recent years, atmospheric composite pollution has become increasingly serious, and accelerating VOC governance has become the focus of and difficulty in atmospheric governance. Volatile organic compounds (VOCs) come from a wide range of sources, and industrial sources are the main source of anthropogenic VOC emissions in China. Chemicals, oil refining, and solvents are three typical VOC-emitting industries, and their control is an important part of accelerating and optimizing VOC governance. It can be controlled by source control, process control, and pipe end treatment; among these, pipe end treatment is divided into recovery technology and destruction technology. In pipeline end treatment, with the key materials of adsorption, absorption, catalytic oxidation, and catalytic combustion, the research and development of adsorbents, absorbents and catalysts has become a hot spot in recent years. This paper summarizes the chemical materials used in typical VOC pipe end-treatment technology (including adsorbents used in the adsorption method, absorbents used in the adsorption method, and catalysts used in the catalytic oxidation and catalytic combustion methods), summarizes the advantages and disadvantages of various materials and their application range, and looks forward to the direction of future developments.

Establishment of a headspace-thermal desorption and gas chromatography-mass spectrometry method (HS-TD-GC-MS) for simultaneous detection of 51 volatile organic compounds in human urine: Application in occupational exposure assessment

Volatile organic compounds (VOCs) are a group of ubiquitous environment pollutants especially released into the workplace. Assessment of VOCs exposure in occupational populations is therefore a crucial issue for occupational health. However, simultaneous biomonitoring of a variety of VOCs is less studied. In this study, a simple and sensitive method was developed for the simultaneous determination of 51 prototype VOCs in urine by headspace-thermal desorption coupled to gas chromatography-mass spectrometry (HS-TD-GC-MS). The urinary sample was pretreated with only adding 0.50 g of sodium chloride to 2 mL of urine and 51 VOCs should be determined with limits of detection (LODs) between 13.6 ng/L and 24.5 ng/L. The method linearity ranged from 0.005 to 10 μg/L with correlation coefficients (r) of 0.991 to 0.999. The precision for intraday and inter-day, measured by the variation coefficient (CV) at three levels of concentration, was below 15 %, except for 4-isopropyl toluene, dichloromethane, and trichloromethane at low concentration. For medium and high levels, recoveries of all target VOCs were within the standard range, but 1,1-dichloropropene and styrene, which were slightly under 80 % at low levels. In addition, the proposed method has been used to determine urine samples collected in three times (before, during and after working) from 152 workers at four different factories. 41 types of prototype VOCs were detected in workers urine. Significant differences (Kruskal-Wallis chi-squared = 117.18, df = 1, P < 0.05) in the concentration levels of VOCs between the exposed and unexposed groups were observed, but not between the three sampling times (Kruskal-Wallis chi-squared = 3.39, df = 2, P = 0.183). The present study provides an alternative method for biomonitoring and assessing mixed exposures to VOCs in occupational populations.

Experimental and mechanistic studies on the thermo-electric synergistic catalytic oxidation of acetone over MnO2/TiO2-Ni foam catalyst

Volatile organic compounds (VOCs) cause serious environmental and human health risks and must be efficiently removed. In this work, a metal-structured catalyst of Ni foam loaded Mn/Ti oxides was used for the oxidation of acetone, a typical VOC compound. The catalyst was in-situ joule heated when applying an electric current and produced the thermo-electric synergistic oxidation (TEO) effect. Compared with conventional thermal oxidation (CTO), the oxidation rate of acetone significantly increased by 124.19 % and the energy consumption of per unit complete oxidation rate was reduced by 66.67 % in TEO reaction with a 12 A electric current at 200 °C. The efficiency gradually improved (from 16.12 % to 36.14 %) and the energy consumption of per unit complete oxidation rate decreased (from 2.85 W/% to 0.95 W/%) with the increase of electric current. Besides, the thermal (including the catalyst thermal effect and reaction gas thermal effect) and electric effects in TEO reaction were analyzed by the statistical analysis method. With the temperature increasing from 200 °C to 400 °C, the proportion of electric effect slightly decreased while that of reaction gas thermal effect increased from 5.2 % to 18.1 %. It proved that the TEO method has the advantage of improving low-temperature catalytic activity. Furthermore, the mechanism of electric effect was investigated, in which it enhances the conversion of lattice oxygen in TiO2 to surface-adsorbed oxygen species and promotes the oxidation of Mn oxides, sequentially improving the oxidation of acetone.

Single AgNF@ZIF-8 nanoparticle for deep learning assisted SERS detection of gaseous molecule

Random nanogaps between plasmonic nanoparticles formed by the surface tension of solution bring a great challenge in the application of Surface Enhanced Raman Spectroscopy (SERS) technique. Meanwhile, due to its natural nanogaps on the surface, single plasmonic nanoflower exhibits a unique charm for avoiding random gaps in the quantitative analysis of SERS. Herein, a single core-shell plasmonic nanoparticle consisting of an Ag nanoflower (AgNF) core and zeolite imidazolate frame-8 (ZIF-8) shell is synthesized for SERS detection of the gaseous molecule. Benefiting the porous shell of ZIF-8 to capture gaseous molecules and natural nanogaps on the surface of AgNF to enhance Raman intensity, SERS spectra of the gaseous molecule are successfully collected with high sensitivity at 10−6 M, which also exhibit high SERS stability with RSD at 2.29 % for single nanoparticle and 9.86 % for multiple single nanoparticles. In addition, two levels of automatic identification based on deep learning (DL) are also implemented in this work, whose data demonstrate artificial neural network (ANN) algorithm could identify gaseous glutaraldehyde (GA) as typical volatile organic compounds (VOCs) with high accuracy at 97.5 %. This single core-shell plasmonic MOF nanoparticle overcomes the limitations of traditional SERS detection in nanoparticle aggregating and realizes the detection of gaseous molecules, which enlarges the application of SERS technique.

Catalytic Oxidation of Benzene over Atomic Active Site AgNi/BCN Catalysts at Room Temperature.

Benzene is the typical volatile organic compound (VOC) of indoor and outdoor air pollution, which harms human health and the environment. Due to the stability of their aromatic structure, the catalytic oxidation of benzene rings in an environment without an external energy input is difficult. In this study, the efficient degradation of benzene at room temperature was achieved by constructing Ag and Ni bimetallic active site catalysts (AgNi/BCN) supported on boron-carbon-nitrogen aerogel. The atomic-scale Ag and Ni are uniformly dispersed on the catalyst surface and form Ag/Ni-C/N bonds with C and N, which were conducive to the catalytic oxidation of benzene at room temperature. Further catalytic reaction mechanisms indicate that benzene reacted with ·OH to produce R·, which reacted with O2 to regenerate ·OH. Under the strong oxidation of ·OH, benzene was oxidized to form alcohols, carboxylic acids, and eventually CO2 and H2O. This study not only significantly reduces the energy consumption of VOC catalytic oxidation, but also improves the safety of VOC treatment, providing new ideas for the low energy consumption and green development of VOC treatment.

Characterization and sources of volatile organic compounds (VOCs) during 2022 summer ozone pollution control in Shanghai, China

An experimental study was conducted to evaluate the effectiveness of the measures for controlling ozone (O3) pollution in Jinshan District, Shanghai, China during the summer months of June 2022–August 2022. The study period was divided into a control period (CP) when measures were enforced and a non-control period (NCP) without interventions. The concentrations of volatile organic compounds (VOCs) were compared between the two periods, with the ranking of various types of identical VOCs, in which alkanes exhibited the highest (39.48%) concentrations, followed by aromatics (24.35%), halohydrocarbons (19.94%) and alkenes (16.23%). Compared to NCP, the mean levels of VOCs were 32.67% lower in CP, indicating the control measures significantly reduced the concentrations of VOCs during the months when control measures were in effect. The typical bimodal O3 pattern was eliminated during CP along with the absence of peak VOC levels between 10:00 Hrs and 16:00 Hrs, which surpassed the level of 40 μg/m3 during NCP. The analyses of O3 formation potential (OFP) and rate of loss of OH radicals (LOH) indicated that alkenes and aromatics were the most chemically active VOCs driving the production of O3. Following six types of sources were determined for VOCs using positive matrix factorization (PMF): (1) solvent use (8.2%); (2) fuel evaporation (25.1%); (3) petrochemical plant (17.3%); (4) LPG (20.1%); (5) industrial process (16.1%); (6) vehicular emissions (13.2%). Emissions from vehicles and solvent use declined by 19.21% and 15.43%, respectively, underscoring their importance as controllable VOC sources in Shanghai, China. Overall, the study demonstrated the effectiveness of regional control measures in improving air quality by reducing the production of O3 and related VOCs.

Volatile organic compounds and odor emissions from typical building materials and air sample storage time analysis

Building materials are the main sources of indoor volatile organic compounds (VOCs) and odors, which significantly impact indoor air quality and perceived air quality. In this study, gas chromatography-mass spectrometry was used to measure VOC emissions from 34 building materials, while an untrained panel assessed odor intensity (OI) and acceptability (ACC). The total VOC (TVOC) concentrations ranged from 156.5 to 3572.0 μg/m3, with alkanes identified as the predominant types of VOCs. Formaldehyde and n-hexane were found to be the most abundant compounds. Aldehydes are the dominant odorants, with hexanal being the most prevalent one according to the odor activity value (OAV). OI ranged from 2.35 to 4.69, while ACC ranged from −0.49 to 0.36. Adhesives exhibited both the highest TVOC concentration as well as a strong odor compared to other building materials; furniture boards emitted the lowest TVOC concentrations; wall coverings emitted minimal levels of odors. The effects of storage time on VOC concentrations and odor assessments were analyzed after sample collection for different durations: 6 h, 24 h or 48 h. A storage time period of 24 h was determined to be sufficient for assessing OI and ACC whereas shorter durations may be required when analyzing VOC concentrations or OAV values. The data provided in this study could help regulate VOC and odor emissions from building materials, as well as facilitate developing a model correlating subjective assessment results of OI and ACC with objective measurements of VOC concentrations and OAV.

Enhanced VOC emission with increased temperature contributes to the shift of O3-precursors relationship and optimal control strategy

Assessing the impact of anthropogenic volatile organic compounds (VOCs) on ozone (O3) formation is vital for the management of emission reduction and pollution control. Continuous measurement of O3 and the major precursors was conducted in a typical light industrial city in the YRD region from 1 May to 25 July in 2021. Alkanes were the most abundant VOC group, contributing to 55.0% of TVOCs concentration (56.43 ± 21.10 ppb). OVOCs, aromatics, halides, alkenes, and alkynes contributed 18.7%, 9.6%, 9.3%, 5.2% and 1.9%, respectively. The observational site shifted from a typical VOC control regime to a mixed regime from May to July, which can be explained by the significant increase of ROx production, resulting in the transition of environment from NOx saturation to radical saturation with respect to O3 production. The optimal O3 control strategy should be dynamically changed depending on the transition of control regime. Under NOx saturation condition, minimizing the proportion of NOx in reduction could lead to better achievement of O3 alleviation. Under mixed control regime, the cut percentage gets the top priority for the effectiveness of O3 control. Five VOCs sources were identified: temperature dependent source (28.1%), vehicular exhausts (19.9%), petrochemical industries (7.2%), solvent & gasoline usage (32.3%) and manufacturing industries (12.6%). The increase of temperature and radiation would enhance the evaporation related VOC emissions, resulting in the increase of VOC concentration and the change of ROx circulation. Our results highlight determination of the optimal control strategies for O3 pollution in a typical YRD industrial city.

Volabolomic Fingerprinting for Post-Mortem Interval Estimation: A Novel Physiological Approach.

Death is a multifaceted process wherein each individual cell and tissue has a metabolic homeostasis and a time of functional cessation defined by the dying process as well as by intrinsic and extrinsic factors. Decomposition is physiologically associated with the release of different types of volatile organic compounds (VOCs), and these form volaboloma mortis. The main purpose of this study was to record the volabolomic fingerprint produced by volatile molecules during the physiological decomposition process of human tissue and muscle cells. The volatile chemical signature has important implications for an open issue in forensics and pathology, namely the estimation of the postmortem interval (PMI), which decreases in accuracy with the passage of time. Volatile metabolites emitted from human tissues and muscle cells at 0, 24, 48, and 72 h were recorded in real time with an electronic nose sensor device. The key findings were the continuous sampling of VOCs emitted from tissues and cells. These showed a common behavior as time progressed; particularly, after 48 h the distributions became dispersed, and after 72 h they became more variable. Volabolomic fingerprinting associated with time progression relevant to the study of PMIs was reconstructed. Additionally, there may be broader applications, such as in dog training procedures for detecting human remains, and perhaps even for studying scavenger and insect attractants.

Control of odorants in swine manure and food waste co-composting via zero-valent iron /H2O2 System

Odors have posed challenges to the advancement of aerobic composting. This work aims to identify the primary components responsible for odors and assess the effectiveness and mechanisms of the zero-valent iron/H2O2 system controlling various odorants in aerobic composting. Swine manure and food waste were used as composting materials, with the addition of zero-valent iron and hydrogen peroxide to mitigate odor emissions. Results revealed that odorants included ammonia, hydrogen sulfide, and 22 types of volatile organic compounds (VOCs), with ethyl acetate, heptane, and dimethyl disulfide being predominant. Among the odorants emitted, ammonia accounted for 75.43%, hydrogen sulfide for 0.09%, and identified VOCs for 24.48%. The ZVI/H2O2 system showed a significant reduction in ammonia and VOCs emission, with the reduction of 51% (ammonia) and 41.3% (VOCs) respectively, primarily observed during the thermophilic period. The occurrence of Fenton-like reactions and changes in key microbial populations were the main mechanisms accounting for odor control. The occurrence of Fenton-like reaction was confirmed by X-ray photoelectron spectroscopy and reactive oxygen detection, showing the oxidation of zero-valent iron by H2O2 to higher valence elemental iron, and the simultaneous production of ·OH. Microbial analysis indicated that an enrichment of specific microorganisms with Bacillus contributed to feammonx and Bacillaceae contributed to organic biodegradation. Redundancy analysis highlighted the role of key microbial species (Bacillaceae, Bacillus, and Ureibacillus) in effectively reducing the level of ammonia and volatile organic compounds. These novelty findings illustrated that the potential of this system is promising for controlling the emission of odorants and aerobic composting reinforcement.

Using Machine Learning to Overcome Interfering Oxygen Effects in a Graphene Volatile Organic Compound Sensor.

Discriminating between volatile organic compounds (VOCs) for applications including disease diagnosis and environmental monitoring, is often complicated by the presence of interfering compounds such as oxygen. Graphene sensors are effective at detecting VOCs; however, they are also known to be highly sensitive to oxygen. Therefore, the combined effects of each of these gases on graphene sensors must be understood. In this work, we use graphene variable capacitor (varactor) sensors to examine the cross-selectivity of oxygen at 3 concentrations and 3 VOCs (ethanol, methanol, and methyl ethyl ketone) at 5 concentrations each. The sensor responses exhibit distinct shapes dependent on the relative concentrations in mixtures of oxygen and VOCs. Because the entire response shape is therefore informative for distinguishing between each gas mixture, a classification algorithm that utilizes entire sequences of data is needed. Accordingly, a long short-term memory (LSTM) network is used to classify the mixtures and VOC concentrations. The model achieves 100% accurate classification of the VOC type, even in the presence of varying levels of oxygen. When the VOC type and VOC concentration are classified, we show that the sensors can provide VOC concentration resolution within approximately 200 ppm. Throughout this work, we also demonstrate that an effective gas mixture classification can be achieved, even while the sensors exhibit varied drift patterns typical of graphene sensors. This is made possible due to the data analysis and machine learning methods employed.

Comparison of Cr and Sr doping into TiO2 for photocatalytic removal of gaseous 1,2 dichloroethane

1,2-dichloroethane/DCE, a volatile organic compounds (VOCs), can carry out damage to human health and be emitted from various industrial activities. Therefore, development of an eco-friendly process for removal of DCE is critical to improve the air quality index and further protect human health. Photocatalytic activity has been recognized as an efficient strategy in removing various types of VOCs. Owing to its compatibility to be conducted under mild condition, photocatalytic reaction is also favorable. Performance of TiO2, a widely applied photocatalyst, can be improved by the doping of various metal elements, like Sr and Cr. Besides, the doping process might also promote the suitability of photocatalyst to be operated under visible light. This study explored performance of various ratios of Sr/TiO2 and Cr/TiO2 under illumination of UV light. 0.01 %Sr/TiO2 achieved the best DCE removal and was further applied examination using various temperatures, along with concentration of DCE and O2. The presence of O2 played an important role during the photocatalytic reaction. Characterization, reaction kinetics study, and analysis of byproducts were also investigated in this study. A short-extended assessment was also applied to examine the performance under blue light and white light illumination. Contrary, Cr performed the best DCE photocatalytic removal under the supply of visible light.

Self-aspiration sampling design for rapid analyses of volatile organic compounds based on atmospheric pressure chemical ionization/photoionization combined ionization source mass spectrometry.

Development of combined mass spectrometry ionization sources has enabled expansion of the application and scope of mass spectrometry. A novel hybrid ionization system combining vacuum ultraviolet (VUV) and atmospheric pressure chemical ionization (APCI) was constructed. Gaseous samples were self-aspirated into an ionization zone through a capillary by negative pressure, generated by high-speed airflow based on the Venturi effect. Compared with APCI mode alone, the signal-to-noise ratio (S/N) in APCI/VUV mode was increased by about 276-times. To increase the ionization efficiency further, correlated experimental conditions were optimized. Four types of volatile organic compounds (VOCs) were tested to evaluate the performance of the APCI/VUV ion source. Excellent linearity and limit of detection were achieved for compounds in mixed solutions. Quantitative analyses of four VOCs (toluene, cyclohexanone, styrene and ethylbenzene) using APCI/VUV-MS were done, and the relative standard deviations (RSDs) were 1.57%, 6.30%, 4.49% and 8.21%, respectively, indicating that the APCI/VUV ionization source had excellent reproducibility. Our results demonstrated that the developed method was promising for analyzing VOCs as well as being rapid, simple, and easy to operate.