Engineering of oxygen vacancy defect in CeO2 through Mn doping for toluene catalytic oxidation at low temperature

Catalytic oxidation is considered a highly effective method for the elimination of volatile organic compounds. Oxygen vacancy defect engineering in a catalyst is considered an effective approach for high-performance catalysts. Herein, a series of doped Mn_xCe_1-xO₂ catalysts (x = 0.05-0.2) with oxygen vacancy defects were synthesized by doping low-valent Mn in a CeO₂ lattice. Different characterization techniques were utilized to inspect the effect of doping on oxygen vacancy defect generation. The characterization results revealed that the Mn_0.15Ce_0.85O₂ catalyst has the maximum oxygen vacancy concentration, leading to increased active oxygen species and enhanced oxygen mobility. Thus, Mn_0.15Ce_0.85O₂ catalyst showed an excellent toluene oxidation activity with 90% toluene conversion temperature (T₉₀) of 197 °C at a weight hourly space velocity of 40,000 mL g^-1 h^-1 as compared to undoped CeO₂ (T₉₀ = 225 °C) and Ce based oxides in previous reports. In addition, the Mn_0.15Ce_0.85O₂ catalyst displayed strong recyclability, water resistant ability and long-time stability. The in situ DRIFT results showed that the Mn_0.15Ce_0.85O₂ catalyst has a robust oxidation capability as toluene is quickly adsorbed and actuated as compared to CeO₂. Thus, the present work lays the foundation for designing a highly active catalyst for toluene elimination from the environment.

Effect of interaction between Pd and Fe in modified red mud on catalytic decomposition of toluene

As an industrial solid waste produced by alumina industry, red mud was modified as support of Pd catalysts for toluene catalytic oxidation in this paper. The xPd/MRM catalysts had high activity for toluene catalytic oxidation, and the 0.3Pd/MRM catalyst showed the best catalytic performance (T₅₀ = 175 °C and T₁₀₀ = 200 °C). The results indicated that the prepared 0.3Pd/MRM catalyst had more ratio of surface-adsorbed oxygen and Fe³⁺, rather than MRM and RM, which benefitted to the toluene oxidation. The excessive Pd species and the growth of the PdO nanoparticles negatively affected the catalytic efficiency of toluene. 0.4Pd/MRM activity decreased because of PdO aggregation in the catalyst, which could be confirmed by TEM analysis. The results of XPS, H₂-TPR, FT-IR, O₂-TPD, and Raman examination revealed that the formation of Pd-O-Fe under the interaction between Fe in MRM and Pd (Pd²⁺ + Fe ²⁺ → Pd⁰ + Fe³⁺) increased the electron transfer and raised the mobility of surface-adsorbed oxygen. Furthermore, in situ DRIFTS and GC-MS were used to detect intermediate products of catalytic reactions, and the reaction mechanism of catalysts was also studied. The catalytic oxidation of toluene on 0.3Pd/MRM catalyst might have two reaction paths simultaneously. The first reaction path would be toluene → species benzyl → benzaldehyde → benzoic acid → long-chain aldehydes or carboxylic acids → CO₂ and H₂O. The second reaction path would be toluene → benzene → phenol → long-chain aldehydes or carboxylic acids → CO₂ and H₂O.

Characterization of products formed from the oxidation of toluene and m-xylene with varying NOx and OH exposure

Aromatic volatile organic compounds (VOCs) are an important precursor of secondary organic aerosol (SOA) in the urban environment. SOA formed from the oxidation of anthropogenic VOCs can be substantially more abundant than biogenic SOA and has been shown to account for a significant fraction of fine particulate matter in urban areas. A potential aerosol mass (PAM) chamber was used to investigate the oxidised products from the photo-oxidation of m-xylene and toluene. The experiments were carried out with OH radical as oxidant in both high- and low-NO_x conditions and the resultant aerosol samples were collected using quartz filters and analysed by GC × GC-TOFMS. Results show the oxidation products derived from both precursors included ring-retaining and -opening compounds (unsaturated aldehydes, unsaturated ketones and organic acids) with a high number of ring-opening compounds observed from toluene oxidation. Glyoxal and methyl glyoxal were the major ring-cleavage products from both oxidation systems, indicating that a bicyclic route plays an important role in their formation. SOA yields were higher for both precursors under high-NO_x (toluene: 0.111; m-xylene: 0.124) than at low-NO_x (toluene: 0.089; m-xylene: 0.052), likely linked to higher OH concentrations during low-NO_x experiments which may lead to higher degree of fragmentation. DHOPA (2,3-dihydroxy-4-oxo-pentanoic acid), a known tracer of toluene oxidation, was observed in both oxidation systems. The mass fraction of DHOPA in SOA from toluene oxidation was about double the value reported previously, but it should not be regarded as a tracer solely for oxidation of toluene as m-xylene oxidation gave a similar relative yield.

Volatile organic compounds measured by proton transfer reaction mass spectrometry over the complex terrain of Quintero Bay, Central Chile

This research provides new evidence regarding the different kinds of air quality episodes, and their underlying mechanisms, that frequently impact the urban area of Quintero Bay in Central Chile, which is located along complex coastal terrain and is surrounded by industries. The monitoring campaign was carried out in January 2022 and encompassed two distinctive meteorological regimes. The first part of the month was dominated by a coastal low centered to the south of Quintero, which resulted in prevailing northerly flow (or weak southerlies) and a deep cloud-topped marine boundary layer. After a 2-3-day transition, the latter collapsed, and a clear-sky regime ensued, which was characterized by a shallow boundary layer and strong southerly winds during the daytime that lasted until the end of the campaign. By using proton transfer reaction time of flight mass spectrometry (PTR-TOF-MS) at a high temporal resolution (1 s), we measured high levels of volatile organic compounds (VOCs) during air quality episodes in real time. The episodes detected were associated with different prevailing meteorological regimes, suggesting that different point sources were involved. In the first episode, propene/cyclopropane, butenes, benzene, toluene and ethylbenzene/xylenes were associated with north and northwesterly weak winds. Complaints associated with hydrocarbon odor were reported. The pollution originated from industrial and petrochemical units located to the north of Quintero, which transport and store natural gas, liquified petroleum gas and oil. The second episode was linked to an oil refinery located south of our measurement site. In this case, high levels of phenol, furan and cresols occurred under strong southwesterly winds. During this event, headaches and dizziness were reported. By contrast, the levels of other aromatic compounds (benzene, toluene, ethylbenzene/xylenes) were lower than in the first air pollution episode.

Association of glutathione-S-transferase polymorphism with genetic damage in paint workers

BACKGROUND

Occupational exposure to toluene causes serious health problems ranging from drowsiness to lethal diseases such as cancer. Paint workers are exposed to toluene through inhalation or the dermal route, which can induce genetcic damage. The increased DNA damage could be linked to genetic polymorphism. Therefore, we evaluated the association of glutathione-S-transferase polymorphism with DNA damage in paint workers.

METHODS

First, we included skilled paint workers (n = 30) as exposed and healthy individuals (n = 30) as control belonging to the same socio-economic strata. The genotoxicity biomarkers, Cytokinesis-block micronucleus (CBMN), and single-cell gel electrophoresis (SCGE)/Comet assay were used to assess genotoxicity while Multiplex-PCR and PCR-RFLP were used to assess polymorphism in glutathione-s-transferase (GST) genes. Using linear curve regression analysis, we assessed the association between genetic damage and polymorphism in the glutathione-s-transferase (GST) gene in the exposed and control subjects.

RESULTS

A significantly higher frequency of CBMN (4.43 ± 1.50) and tail moment (TM) (11.23 ± 1.0) respectively in paint workers as compared to the control(1.50 ± 0.86 and (0.54 ± 0.37) underlined significantly high genetic damage in paint workers.Regression curve analysis reveals that polymorphism in the GST gene is significantly associated with higher MN and TM in paint workers.

CONCLUSION

Overall, our study provides a strong rationale for identifying a clear association between glutathione-S-transferase polymorphism and genetic damage in paint workers.

Short- and long-term effects of chronic toluene exposure on spatial memory in adolescent and adult male Wistar rats

Addiction to toluene-containing volatile inhalants is of significant medical and social concern, particularly among youth. These concerns are underscored by the fact that the majority of adult abusers of toluene started as teenagers. Surprisingly, however, the lasting effects of chronic toluene exposure, especially in various age groups, have not been well investigated. Recently, we reported that adolescent and adult male Wistar rats show differential responses to chronic toluene exposure in recognition memory tasks. Since different cognitive functions may be differentially affected by drugs of abuse, we used the same model to evaluate the short- and long-term effects of chronic toluene on spatial learning and memory using Morris water maze. Daily exposure to toluene (2000 ppm) for 40 days (5 min/day) resulted in age-dependent behavioral changes. For example, only adolescent animals showed a decrease in time and distance travelled to find the hidden platform 24 h after the last toluene exposure. In contrast, only adult rats exhibited a decrease in acquisition time and distance travelled at 90 days' post toluene exposure. Our data provide further support for the contention that age-dependent responses should be taken into consideration in interventional attempts to overcome specific detrimental consequences of chronic toluene exposure.

Liquid-phase benzylation of toluene by benzyl alcohol over micro-mesoporous hierarchical mordenite zeolite

In this work, post-synthetic effective acid (HNO₃) and base (NaOH) etching technique are used to create hierarchical mordenite having different pore structure. The powder X-ray diffraction (P-XRD) technique was used to confirm the crystalline structure of the base-modified and acid-modified mordenite. Field emission-scanning electron microscope (FE-SEM) was employed to confirm the structural morphology of the materials. The modified mordenite was further characterised by inductive coupled plasma-optical emission spectrometry (ICP-OES), N₂ adsorption-desorption isotherms, thermogravimetric analysis (TGA), and acid-base titration, to confirm the structural integrity, presence of active acidic sites, and other vital parameters. The structure was well conserved after the change, as evidenced by the characterisation. The toluene benzylation with benzyl alcohol using hierarchical mordenite and H-mordenite produced mono-benzylated toluene. Comparison between acid treated, base treated, and H-mordenite was done. All samples were catalytically active as proved by the catalytic result in the benzylation reaction. The results show that the base alteration dramatically enhances the mesoporous surface area of H-mordenite. Furthermore, the acid-treated mordenite had the highest benzyl alcohol conversion (75%), but the base-modified mordenite had benzyl alcohol conversion of 73% with the highest mono-benzylated toluene selectivity (61%). The process was further optimised by varying the reaction temperature, duration, and catalyst quantity. Gas chromatography (GC) was used to evaluate the reaction products and gas chromatography-mass spectrometry (GC-MS) was used to confirm them. Introduction of mesoporosity in the microporous mordenite was found to have significant effect on their catalytic activity.

Effects of indoor exposure to low level toluene on neural network alterations during working memory encoding

OBJECTIVE

While high concentrations of toluene are known to affect multiple human organ systems, research concerning the influence of immediate, short-term exposure to toluene indoors and at low concentrations is scarce. Here, we studied effects of indoor toluene exposure on neural network alterations during working memory (WM) encoding.

METHODS

A total of 23 healthy college students were recruited. All participants were situated in a closed environmental chamber with a full fresh air system. Each participant was subjected to four exposure experiments with different toluene concentrations (0, 17.5, 35, and 70 ppb, named Group A, B, C and D, respectively), with at least one week between each experiment. WM Behavioral and 19-channel electroencephalogram (EEG) recordings in a pre-set environmental chamber were conducted simultaneously during each toluene exposure experiment. Neural networks relevant to WM encoding were visualized analyzing the obtained data.

RESULTS

1. No significant difference in WM behavioral performance among the four groups was found. However, a significant increase in whole brain neural network functional connectivity was noted, especially in the frontal region. 2. An outflow directional transfer function (DTF_outflow) revealed higher frontal region values among Group D (the 70 ppb group) as compared to Group A, B and C (the0, 17.5 ppb and 35 ppb groups, respectively), although no differences in frontal region DTF_inflow values among the four groups were noted. 3. The DTF_FZ-F7, DTF_FZ-T5, DTF_FZ-P4, DTF_FZ-P3, DTF_FP2-O2, DTF_P3-T4, DTF_P3-F4, DTF_P4-CZ and DTF_P4-T4 values of Group D were found to be higher as compared to those of Group A and B. Furthermore, DTF_FZ-F7 and DTF_P4-T4 values of Group C were higher as compared to those of Group A. The DTF_FZ-F7 values of Group D were higher as compared to those of the Group C.

CONCLUSION

Short-term toluene exposure significantly influences neural networks during cognitive processes such as WM encoding, even at low concentration.

Effect of A, B-site cation on the catalytic activity of La1-xAxMn1-yByO3 (A = Ce, B = Ni) perovskite-type oxides for toluene oxidation

ABO3-type perovskites (A = La, Ce; B = Mn, Ni) were prepared by sol-gel method, and applied for catalytic oxidation of toluene. The activity test results show that the activity of LaMnO3 can be improved when a small amount of Ce and Ni are doped into the A and B sites of LaMnO3, respectively. The effects of different calcination temperatures and different calcination time on the preparation of La-based perovskites were also investigated. The results illustrate that the toluene conversion of La0.8Ce0.2Mn0.8Ni0.2O3 is the highest when the calcination temperature is 700 °C and the calcination time is 4 h in La1-xCexMn1-yNiyO3 perovskites, and it requires lower reaction temperature when the conversion rate of toluene reaches 100% as compared to other catalysts, the T90 is 295 °C (T90, the temperature corresponding to the 90% of toluene conversion). Importantly, the mechanism of catalytic oxidation was also discussed. Therefore, the catalyst has potential prospects in the volatile organic compounds (VOCs) degradation.

Catalytic removal of toluene using MnO2-based catalysts: A review

Volatile organic compounds (VOCs) have serious hazard to human health and ecological environment. Due to its low cost and high activity, the catalytic oxidation technology considered to be the most effective method to remove VOCs. Toluene is one of the typical VOCs, hence its catalytic elimination is crucial for the regulation of VOCs. Manganese dioxide (MnO₂) has been extensively studied for its excellent redox performance and low-temperature operation conditions. In this review, we summarize the research progresses in the toluene catalytic oxidation of MnO₂-based catalysts, which contain single MnO₂, metal-doped MnO₂ and supported MnO₂ catalyst. In particular, we pay much attention on the relationship between the chemical properties and toluene oxidation performance over MnO₂ catalyst, as well as the catalytic reaction mechanisms. Moreover, the effects of different crystal forms and morphologies on the catalytic toluene reaction were discussed. And the perspective on MnO₂ catalysts for the catalytic oxidation of toluene has been proposed. We expect that the summary of these important findings can serve as an important reference for the catalytic treatment of VOCs.

Ginkgo, fennel, and flaxseed can affect hormone release by porcine ovarian cells and modulate the effect of toluene

Experimental studies have documented the toxic effects of toluene on the mammalian female reproductive processes. The aim of this in vitro study was to examine the potential of functional food plant extracts, namely, of ginkgo, fennel, and flaxseed, in modifying the toluene-induced effects on ovarian hormone release. Porcine granulosa cells were incubated with ginkgo, fennel, or flaxseed extracts (0, 1, 10, or 100 µg/mL) and/or toluene (10 µg/mL). Enzyme immunoassays were used in order to measure the release of progesterone (P), oxytocin (OT), and prostaglandin F (PGF) in the culture media. Toluene suppressed the release of P and enhanced the release of OT and PGF. All tested plant extracts reduced P and increased OT release, while the PGF output was found inhibited by ginkgo and stimulated by fennel and flaxseed. When the cells were incubated with toluene and each one of the plant extracts, toluene was able to prevent their action on P release, as well as those of fennel and flaxseed on OT and PGF release. Moreover, ginkgo enhanced but fennel or flaxseed prevented the toluene-induced effects on OT and PGF release. These observations (i) document novel aspects of the toluene-induced toxicity; (ii) demonstrate the direct influence of ginkgo, fennel, and flaxseed extracts on the ovarian secretory activity; (iii) inform our understanding of the interrelationship between toluene and the tested plant extracts with regard to their effects on ovarian hormone release; (iiii) demonstrate the ability of fennel and flaxseed to prevent adverse effect of toluene on ovarian hormones.

An immobilization of aminopropyl trimethoxysilane-phenanthrene carbaldehyde on graphene oxide for toluene extraction and separation in water samples

A new functionalized Nano graphene with aminopropyl trimethoxysilane-phenanthrene-4-carbaldehyde (NGO@APTMS-PNTCA) as a novel adsorbent was used to extract toluene from water samples by the ultrasound-assisted dispersive solid-phase microextraction procedure (USA-D-SPME). So, 50 mg of NGO@APTMS-PNTCA adsorbent was added to water samples and sonicated for 20 min. After toluene extraction, the NGO@APTMS-PNTCA adsorbent separated from the liquid phase with a Whatman membrane filter (200 nm). Then, the toluene was back-extracted from the adsorbent by 2.0 mL of the acetone/ethanol (1:1, eluent) at 25 °C. Due to the physical properties and structure of toluene, fluorobenzene was used as an internal standard. Finally, the toluene values were measured by a gas chromatography-flame ionization detector (GC-FID). In optimized conditions, the limit of detection (LOD), the working range (WR), and the enrichment factor (EF) were obtained at 2.5 μg L^-1, 0.01-1.2 mg L^-1, and 9.63, respectively (MRSD% = 3.38). Also, the limit of quantification (LOQ) 10 μg L^-1 and extraction recovery of more than 95% was efficiently achieved for toluene. Standard additions of toluene to blank solutions had high recoveries between 95.2% and 104.5% with a relative standard deviation (RSD%) of 0.27-5.2. The absorption capacities of NGO and NGO@APTMS-PNTCA adsorbents for toluene extraction were obtained at 32.8 mg g^-1 and 154.9 mg g^-1, respectively. The USA-D-SPME method was validated by spiking the standard concentrations of toluene. The proposed method demonstrated relevant and suitable statistical results with high accuracy and precision for toluene extraction by a novel adsorbent synthesis.

Modelling toluene sorption in ionic liquid/metal organic framework composite materials

Toluene is a prevalent pollutant in indoor environments and its removal is essential to maintain a healthy environment. Adsorption is one of the best alternatives for organic vapours removal, specially at low indoor concentrations. Metal Organic Frameworks (MOFs) and Ionic Liquids (ILs) are potential materials for this mean. In this work, the synthesis and application of IL/MOF composite materials for toluene removal is reported. Loading [BMIM][CH₃COO] ionic liquid into MIL101 porous structure improves parent materials affinity towards toluene capture by two orders of magnitude (as Henry's constants, attesting to their synergy). MIL101(Cr) and absorption in [BMIM][CH₃COO] IL is best described by Henry's Law, while the Langmuir adsorption model predicts toluene adsorption on [BMIM][CH₃COO]/MIL101(Cr) better than Freundlich and Toth equations. Diffusional and kinetics models revealed that toluene diffusion is the rate limiting step for pristine MIL101. Kinetic and diffusion rates were systematically improved upon the incorporation of the ionic liquid due to shorter toluene hops with the adsorbed IL and the increased hydrophobicity in the composites making the sorption more favourable. This study provides a systematic analysis and modelling of the toluene capture process in IL/MOF composites aiding a better understanding of the sorption process in these novel materials.

Working memory-related alterations in neural oscillations reveal the influence of in-vehicle toluene on cognition at low concentration

Although toluene is a typical in-vehicle pollutant, the impacts of in-vehicle toluene exposure on cognitive functions remain unestablished. Therefore, this study aimed to investigate the effects of short-term toluene exposure in vehicles on working memory based on neural oscillations. In total, 24 healthy adults were recruited. Each subject was exposed to four different concentrations of toluene and divided into 0 ppb, 17.5 ppb, 35 ppb, and 70 ppb groups for self-control studies. After 4 h of exposure to each concentration of toluene, a behavioral test of visual working memory was performed while 19-channel electroencephalogram (EEG) signals were collected. Meanwhile, the power spectral density (PSD) and spatial distribution of working memory encoding, maintenance, and extraction periods were calculated by short-time Fourier transform to clarify the characteristic frequency bands, major brain regions, and characteristic channels of each period. To compare the changes in the characteristic patterns of neural oscillations under the effect of different concentrations of toluene. There was no significant difference in working memory reaction time and correct rate between the groups at different toluene concentrations (p > 0.05). The characteristic frequency band of the working memory neural oscillations in each group was the theta frequency band; the PSD of the theta frequency band was predominantly concentrated in the frontal area, and the characteristic channel was the Fz channel. The whole brain (F = 3.817, p < 0.05; F = 4.758, p < 0.01; F = 3.694, p < 0.05), the frontal area (F = 2.505, p < 0.05; F = 2.839, p < 0.05; F = 6.068, p < 0.05), the Fz channel (F = 3.522, p < 0.05; F = 3.745, p < 0.05; F = 6.526, p < 0.05), and the PSD of working memory in the theta frequency band was significantly increased in the 70 ppb group compared with the other three groups during the coding, maintenance, and retrieval phases of working memory. When the in-vehicle toluene exposure concentration was 70 ppb, the PSD of the characteristic frequency bands of working memory was significantly increased in the whole brain, major brain regions, and characteristic channels.

Wheat straw return can lead to biogenic toluene emissions

As a common practice in agricultural system, straw return has been reported to release a large number of trace gases and attracted much attention. However, the role of straw return in toluene emission remains poorly understood. In this study we measured the emissions of toluene as well as other 50 volatile organic compounds (VOCs) from wheat straw return for 66 days under flooded and non-flooded conditions, respectively. The results showed that substantial toluene was released from the returned wheat straw particularly under flooded condition, and primarily derived from the secondary product. Toluene emissions from the returned wheat straw were 36.8 and 8.45 mg C/kg, sharing 28.0% and 8.6% of total VOCs released, and over 90% of toluene emissions occurred between days 24-56 and 0-17 under flooded and non-flooded conditions, respectively. The emission rates of toluene were relatively high but decreased sharply at the beginning 2 days, and then was steady until 24 days under the two moisture conditions. After the initial decrease these rose again to form one "peak emission window" between days 24-56 under flooded condition, while these were still very low and steady until the end under non-flooded condition. The toluene emission rates significantly positively correlated with microbial biomass C under flooded condition, but negatively associated with bacteria and fungus number, microbial biomass C, and CO₂ flux under non-flooded condition, suggesting that microorganism might play an important role in toluene emissions from wheat straw return. A rough estimate indicated that straw return might be important for biogenic toluene.

Evaluation of environmental and biological monitoring methods for toluene exposure assessment in paint industry

The aim of this study was to assess the exposure to Toluene in paint industry and to evaluate the environmental and biological monitoring techniques for the assessment of occupational exposure to this aromatic hydrocarbon. In this study, personal active and passive air sampling for toluene measurements, blood and urine sampling respectively for B-Tol and HA or U-Tol analyses for eight workers from two paint and thinner production factories were collected during four successive working days. Correlations were analyzed between biological indicators and environmental toluene exposure levels. The concentration of Toluene measured in air samples ranged from 0.2 to 414.0 ppm (mean = 59.8 ppm), with high variability of atmospheric levels between activities and between days. No significant difference was found between airborne toluene concentrations measured by the two sampling methods. The correlation between air concentrations sampled by the diffusive sampling method and the biomarkers was the best for HA (r = 0.902, p < 0.01), followed by B-Tol (r = 0.820; p < 0.01), o-Cr (r = 0.691; p < 0.01) and U-Tol (r = 0.607; p < 0.05). The correlation was better between air concentrations and urinary metabolites HA and o-Cr for exposure levels higher than 50 ppm (r = 0.931; p < 0.01), and lower than 300 ppm (r = 0.827; p < 0.01), respectively. According to our results, workers in the studied industries are highly exposed to Toluene. Given the high correlation found between toluene concentrations in samples taken on dosimeters and those actively sampled on charcoal tubes, it may be assumed that both sampling methods are valuable. Despite the influencing factors, HA was found to be a reliable biological indicator for the monitoring of occupational exposure to toluene for high exposure levels. However, B-Tol seems to be an interesting alternative, since it is more specific and showed the best correlations with airborne toluene levels.

Metagenome analyses of microbial population in geotextile fabrics used in permeable reactor barriers for toluene biodegradation

Toluene is one of the hydrocarbons that contaminate soil and groundwater, and has a high cost to remediate, which makes it an environmental pollutant of concern. This study aimed to find bacterial distribution from nonwoven geotextile (GT) fabric specimens in a pilot-scale permeable reactive barrier (PRB). Upon 167 days of incubation with the addition of toluene, the microbial community on the GT surfaces (n = 12) was investigated by the 16S rRNA metagenome sequencing approach. According to taxonomic classification, the Proteobacteria phylum dominated the metagenomes of all the geotextile samples (80-90%). Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway database search of the toluene degradation mechanism revealed the susceptible toluene-degrading species. For the toluene-to-benzoate degradation, the Cupriavidus genus, particularly C. gilardii, C. metallidurans, and C. taiwanensis, are likely to be functional. In addition to these species, the Novosphingobium genus was abundantly localized in the GTs, in particular Novosphingobium sp. ABRDHK2. The results suggested the biodegradation potential of these species in toluene remediation. Overall, this work sheds light on the variety of microorganisms found in the geotextile fabrics used in PRBs and the species involved in the biodegradation of toluene from several sources, including soil, sediment, and groundwater.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03460-y.

Abatement of VOCs mixture of emerging concern by VUV-PCO process: From lab to pilot scale

As a kind of emerging pollutant, volatile organic compounds (VOCs) are getting increasing attention due to their contribution to the formation of atmospheric haze and O₃. Photocatalytic oxidation under vacuum ultraviolet photocatalytic oxidation (VUV-PCO) presents a promising method for VOCs degradation, but it is seldom studied for VOCs compound and the mechanism is still elusive. Herein, typical VOCs such as toluene and ethyl acetate were degraded separately or together in VUV system and in VUV-PCO system with the designed trifunctional catalyst Mn/TiO₂/ZSM-5. Intermediates were recognized by PTR-TOF-MS. It is found that dual VOCs mixture outperformed single VOCs under both VUV process and VUV-PCO process. Possible degradation mechanisms were proposed. To explore the potential practicality of VUV-PCO technology, scale-up synthesis of Mn/TiO₂/ZSM-5 on ceramic foams was successfully carried out and assembled into a homemade pilot-scale VUV-PCO equipment for the control of simulated VOCs complex (toluene, ethyl acetate, ethanol, and acetone). Pilot-scale catalytic testing with the monolithic catalysts achieved high removal efficiency (over 90 % efficiency after two cycles of regeneration) and confirmed the practical application possibility of VUV-PCO technology in multiple VOCs degradation. This work probes into the VUV-PCO technology applicability from lab scale to pilot scale and promotes the understanding of VUV and VUV-PCO in VOCs complex decomposition.

Anaerobic mineralization of toluene by enriched soil-free consortia with solid-phase humin as a terminal electron acceptor

The anaerobic biodegradation of toluene proceeds very slowly owing to limited electron acceptors in contaminated aquifer. The liquid reagents traditionally used to enhance this process readily migrate away from the contaminated site, and continuous addition would cause secondary pollution. In our previous study, the reduced solid-phase humic substances (humin), which are redox active, were found to act as electron donors to promote the microbial reactions. Here, we provide new evidence that humin can promote the anaerobic biodegradation of toluene as a terminal electron acceptor. When inoculating nitrate-reducing (NR) and iron-reducing (IR) consortia with toluene degradation activities, the average toluene degradation rates reached 21.20 ± 1.18 μmol/(L·d) and 15.43 ± 0.41 μmol/(L·d) in the presence of a sediment humin (HMcj), and 94.69% ± 4.26% and 93.20% ± 3.73% of the electrons released from toluene oxidation to CO₂ could be recovered by the reduction of HMcj, respectively. Spectroscopy analyses revealed that quinone moieties and nitrogen-containing moieties may be the electron-accepting groups of HMcj. Based on 16S rRNA sequencing, Cellulomonas spp. were the possible functional bacteria in the culture with NR consortium as the inoculum, while Azospira spp., Cellulomonas spp. and Bacillus spp. were the possible functional bacteria in the culture with IR consortium as the inoculum. Further Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analyses indicated that toluene oxidation and extracellular electron transfer functions were more abundant in HMcj amended cultures, suggesting a possible enhancement mechanism by HMcj. Additionally, experiments using natural groundwater illustrated that toluene degradation was highly dependent on its concentration, HMcj dosage, pH, and salinity. The study of a column filled with HMcj-coated quartz sand demonstrated a desirable level of toluene degradation in a continuous-flow mode without the presence of other electron acceptors. This study provided an effective and green approach for the remediation of the toluene-contaminated groundwater.

Optimization of photothermal conversion and catalytic sites for photo-assisted-catalytic degradation of volatile organic compounds

Solar energy conversion is a promising strategy to enhance the elimination of volatile organic compounds (VOCs) and minimize power consumption. Herein, non-noble metal WC@WO₃ as cocatalyst was composited with CeO₂ to optimize photochemical and photothermal conversion for the catalytic ozonation of toluene and acetone. The photothermal conversion efficiencies of visible and infrared lights on 20%WC@WO₃-CeO₂ were 2.2 and 10.4 times higher than those on CeO₂, respectively, which indicates that the equilibrium temperature of the catalyst remarkably increased under full-spectrum light irradiation. Moreover, WC@WO₃ transferred electrons to CeO₂ in 20%WC@WO₃-CeO₂ and thus remarkably improved the activity of catalytic sites. The synergy factor of light and O₃ on 20%WC@WO₃-CeO₂ was 5.8, and the reaction rate of toluene and acetone reached 9274.5 and 35779.0 mg/(m³∙min), respectively. This work provides a low-cost and high-efficient catalyst for the utilization of solar energy for VOC control.

Photocatalytic Removal of Toluene Vapour Pollutant from the Air Using Titanium Dioxide Nanoparticles Supported on the Natural Zeolite

Background

The emission of volatile organic compounds (VOCs) in industrial and urban areas has adverse effects on the environment and human health. Toluene, the main pollutant among the VOCs, has wide applications in different industries such as plastics, adhesives, silicone sealant, paint, etc. This study aimed to remove of toluene from the air by using TiO2 nanoparticles supported on the natural zeolite using the photo-catalytic process.

Methods

This is an experimental study that was conducted in 2017 in the Chemical Agents Laboratory of the Occupational Health Engineering Department at Jundishapur University in Ahvaz. Toluene vapour decomposition was carried out using UV/ZE, UV/TiO2, and UV/TiO2-ZE under continuous flows conditions. The effects of toluene initial concentration, retention time, and nanocomposite surface weight on toluene vapour decomposition were also investigated.

Results

When UV/TiO2 and UV/TiO2-ZE systems are performed, increasing the initial toluene concentration reduces the efficiency of photocatalytic decomposition. The SEM images of TiO2-ZE catalyst show that zeolite pores were occupied by titanium dioxide nanoparticles. Moreover, the combination of titanium dioxide nanoparticles and zeolite has an incremental effect on toluene decomposition. Increasing retention time raises toluene decomposition, and the increased nanocomposite surface weight raises decomposition to the maximum level (70%) at 33.68 mg/cm2 weight and then decreases.

Conclusion

The increasing toluene decomposition rate by using the TiO2-ZE nanocomposite can be due to the incremental effect of absorption and photocatalytic decomposition.

Quercetin can affect porcine ovarian cell functions and to mitigate some of the effects of the environmental contaminant toluene

The present in vitro experiments aimed to examine the effects of the plant polyphenol quercetin and the environmental contaminant toluene on basic ovarian cell functions, including the ability of quercetin to be a natural protector against the adverse effects of toluene. The influence of toluene, quercetin, and their combination on proliferation (accumulation of PCNA), apoptosis (accumulation of bax) and release of progesterone, testosterone and insulin-like growth factor I (IGFI) by cultured porcine ovarian granulosa cells was investigated. Toluene stimulated cell proliferation and inhibited progesterone, IGF-I and testosterone release but did not affect apoptosis. Quercetin, when administered alone, inhibited cell proliferation, apoptosis, IGF-I and testosterone release and stimulated progesterone output. When administered in combination with toluene, quercetin mitigated toluene's effects on proliferation and on progesterone release and induced toluene to exhibit a pro-apoptotic effect. These observations demonstrate the direct effects of both quercetin and toluene on basic ovarian functions and a protective effect of quercetin against the effects of toluene. Therefore, quercetin-containing plants could be regulators of porcine reproduction and natural protectors against the adverse effects of the environmental contaminant toluene.

Functionalization of metal organic frameworks by [BMIM][CH3COO] ionic liquid for toluene capture

Indoor exposure to volatile organic compounds (VOCs) is detrimental to the health of the occupants, and their removal is crucial in maintaining good air quality. Novel adsorbents prepared by modifying Metal-Organic Frameworks (MOFs), MIL101 (Cr), UiO-66, and UiO-66-NH₂ with [BMIM][CH₃COO] ionic liquid, were characterized and tested for toluene adsorption. [BMIM][CH₃COO]/MIL101 performed best with a fast sorption rate, large sorption capacity, and good regenerability. It displays synergistic interactions between the IL and MOF. Adding one weight percent [BMIM][CH₃COO] to UiO-66 and UiO-66-NH₂ has a synergistic effect with respective 14% and 5% enhancements sorption over calculated values. The strong interactions between IL and UiO-66 and UiO-66-NH₂, as observed in their thermogravimetric data, results in poor toluene sorption for 10 wt% [BMIM][CH₃COO] loadings. This work provides a basis for IL modification of MOFs for enhanced sorption of VOCs for air treatment.

Effect of nitrogen functional groups on competitive adsorption between toluene and water vapor onto nitrogen-doped spherical resorcinol-formaldehyde resin-based activated carbon

To elucidate the effect of nitrogen functional groups on the competitive adsorption of toluene and water vapor, a series of N-doped resorcinol-formaldehyde resin-based activated carbons using g-C₃N₄ as the nitrogen source were prepared, which possessed different N contents (1.29-6.14%). The competitive adsorption characteristics and mechanisms were investigated by characterizations, dynamic adsorption experiments, adsorption isotherms, and density functional theory calculations. Results showed that the normalized toluene adsorption capacity under 50 RH% was consistent with the N content, revealing that nitrogen functional groups can enhance the competitive adsorption for toluene under a humid atmosphere. Adsorption isotherms analysis suggested that nitrogen functional groups can not only accelerate the adsorption of toluene but also improve the hydrophobicity of carbon surface. Competitive adsorption mechanisms were ascribed to π-π interactions and electrostatic interactions. Specifically, graphitic-N and pyridinic-N enhance competitive adsorption for toluene through reinforced π-π interactions with toluene and weakened electrostatic interactions with water molecule. However, pyrrolic-N improve the competitive adsorption, which is principally attributed to enhanced π-π interactions with toluene. Furthermore, it was found that the reusability of activated carbon could be improved by nitrogen functional groups. This study provides theoretical hints to develop volatile organic compound adsorbents in the presence of water vapor.