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Volatile organic compounds (VOCs) emitted from porous wood-based panels with fractal structure severely pollute indoor environment. Different from previous studies which the diffusion type of VOC in building materials is attributed to Fick diffusion, VOC emission from porous wood-based panels belongs to Knudsen diffusion is firstly determined by comparing the pore diameter of internal channel with VOC molecular free path in this paper. Therefore, a time fractional mass transfer model related to the fractal dimension has been proposed to analyze Knudsen diffusion characteristics firstly. This model considers areal porosity has an impact on surface emission. Analytical solution of the present model is obtained for the first time. Furthermore, it is proved that the finite difference scheme is solvable, unconditionally stable, and convergent, and numerical simulation result and experimental data match well. Moreover, the influences of the fractal dimension d f , areal porosity ε, and delay time parameter λ on VOC emission are demonstrated and analyzed; results suggest that the higher ε and d f , and lower λ promote VOC emission, which can provide guidance for improving indoor air quality., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

As one of the major sources of volatile pollutants in indoor air, gaseous emissions from adhesives during interior decoration have attracted increasing concern. Identifying major volatile pollutants and the risk in adhesive gaseous emissions is of great significance, but remains rarely reported. In the present research, we assessed the major volatile pollutants emitted from white emulsion adhesive and silicone adhesive samples (n = 30) from three aspects: chemical composition, odor and health risk contributions. The results showed that a total of 21 volatile pollutants were detected. Significantly, xylene was the most concentrated compound from white emulsion adhesives, accounting for 45.51% of the total concentrations. Butanone oxime was the most concentrated compound in silicone adhesives, accounting for 69.86% of the total concentrations. The trends in odor concentration (evaluated by the odor activity value method) over time were well correlated with the total chemical concentrations. Xylene (58.00%) and butanone oxime (76.75%) showed the highest odor contribution, respectively. Moreover, from an integrated perspective of chemical emissions, odor and health risk contributions, xylene, ethylbenzene, ethyl acetate and benzene were identified as the key volatile pollutants emitted from the white emulsion adhesives, while butanone oxime, butanone, and ethanol were the key volatile pollutants emitted from the silicone adhesives. This study not only identified the key volatile pollutants but also provided characteristics of odor and health risks of gas emitted from adhesives.

Volatile organic compounds (VOCs) emissions are regarded as a worth concerned threat to human health. The UV-Fenton coupled with mass transfer enhanced process shows promising effects on VOCs treatment. However, the detailed mechanism and mathematical model for this method have not been established. This work focuses on the hypothesis and validation of a mathematical model for UV-Fenton removal of VOCs using activated carbon particles to enhance mass transfer efficiency. Based on the mathematical model of reaction-diffusion-mass transfer, a mathematical model is established by using a series of important parameters such as u b , D g , D l , K ial , K l a and hydroxyl radical lifetime. The proposed model in this study introduces the key parameter of synergistic factor, which greatly improves the consistency between the model predicted results and the experimental data (the determination coefficient R 2 distribution range changed from 0.71-0.98 to 0.95-0.98). Moreover, it can also explain reasonably the steady trend of outlet VOC concentration after 30 min of reaction. The mathematical model confirms that the addition of activated carbon during the UV-Fenton reaction ensures mass transfer efficiency and considerably improves (growth from 2% to 54%) the VOCs removal efficiency due to the synergy between UV-Fenton oxidation and mass transfer enhancement. Meanwhile, it provides insight into fruitful utilization of the oxidation capacity in the oxidation reaction,and achieves the purpose of predicting the efficiency of VOC removal in the Fenton process., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Municipal solid waste (MSW) landfills are a source of odorous and toxic compounds. In this work, we present an integrated assessment of the odor concentration and human health risks of volatile compounds to evaluate the environmental quality at a MSW landfill. Air samples were collected seasonally from six areas of the landfill with different functions. The total concentrations of the compounds ranged from 204.0 to 7426.7 μg m -3 , and the concentrations in temporarily and permanently capped areas were 50.3 and 83.4% lower than those in the tipping area, respectively. The odor concentration was greatest at the leachate collection tank (1732-6254 ou E m -3 ) and tipping area (1573-4113 ou E m -3 ) and was mainly caused by hydrogen sulfide (57.9 and 49.1%, respectively). Moreover, the odor concentration was positively correlated with the temperature (r = 0.500, p < 0.05, n = 24). Although the non-carcinogenic (HI) and carcinogenic (R) risks of most compounds were largely below the acceptable levels (HI = 1, R = 1.0E-6), HI values of hydrogen sulfide (2.3), trichloropropane (2.0), and naphthalene (1.2) as well as R values of naphthalene (1.3E-4) and trimethylbenzene (1.2E-4) in the waste areas exceeded acceptable levels. Moreover, the cumulative HI (2.5-5.7) and R (1.0E-04 to 3.4E-04) in the waste areas should receive special attention since they were above acceptable levels during all of the seasons. Aromatic and halogenated compounds dominated the cumulative R, accounting for 79 and 21% of the total, on average, while for the cumulative HI, sulfur compounds contributed the most (67%)., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Abstract Dry building material is a complex porous medium with a fractal structure. A developed fractional mass transfer model can accurately simulate anomalous diffusion in complex media, such as dry building material. In this work, a new time and space fractional diffusion model is first established to study the transport and emission behaviors of volatile organic compounds (VOCs) in a dry building material in an environmental chamber. In this model, the space fractional derivative is expressed by the weight coefficients of the upward and downward transfer probabilities, and the time fractional derivative and areal porosity of the material are introduced to describe anomalous diffusion. With the newly developed finite difference and parameter estimation methods, the present model can describe the early breakthrough and heavy-tailed phenomena well. Furthermore, the results of the present model show good agreement with the experimental data, as the error value (67.44 μg/m3) is much less than that of Deng and Kim's model (190 μg/m3). The advantages of long-term prediction are shown. Moreover, the effects of key parameters on VOC transport are revealed. Highlights • A mass transfer model is built with time and space fractional derivatives. • A modified fractional Fick's law is developed for VOC emissions. • Space fractional derivatives are expressed by different weight coefficients. • The boundary condition of convective mass transfer related porosity is developed. • A parameter estimation method is utilized to optimize the relevant parameters. [ABSTRACT FROM AUTHOR]

For the UV/Fenton treatment of waste gas, low solubility of volatile organic compounds (VOCs) was a significant factor of limiting gas–liquid mass transfer and thus restricted the removal efficiency. In this study, synergistic effect of UV/Fenton oxidation and mass transfer enhancement with addition of activated carbon (AC) was observed through a drastic improvement of n-octane removal in a bubble column reactor. Firstly, the effect of AC on mass transfer was investigated. Result revealed that the addition of AC could change bubble behavior and largely enhance the mass transfer efficiency (volumetric mass transfer coefficient ( k L a ) increased from 0.0057 to 0.14 s −1 as 0–0.1% AC was added) due to the particle shuttle effect. Then AC was introduced into the UV/Fenton reaction system, and the removal efficiency of n-octane had been remarkably improved (maintained above 50% in 60 min with addition of 0.04% AC, compared with below 10% in 20 min for the UV/Fenton alone). Moreover, we comprehensively detected the concentration of residual reactants, intermediates, final products and hydroxyl radicals in the gas and liquid phase. Results indicated that addition of AC could mildly and stably generate hydroxyl radicals (10 −8  M), and the mass balance showed that the mineralization efficiency had increased from 42.4% to 57.9%. For theoretical calculations, the value of the cooperation factor raising from 0.5 to 11.7 in 40 min could offer direct evidence for confirming the synergistic effect. Finally, the reaction pathways of n-octane in UV/Fenton or AC-UV/Fenton were proposed. It can be induced that the latter ones were more likely to first break the C C bond and then oxidize into small molecules acids or CO 2 . [ABSTRACT FROM AUTHOR]

• Core-shell Fe 3 O 4 @C acts as multifunctional microreactor for refractory VOC removal. • High octane removal efficiency and low-level toxic byproduct generation are achieved. • DFT calculation reveals the key role of Fe O C bond during regeneration of Fe(II). • The adsorption process is enhanced by the carbonyl sites. • The advanced oxidation mechanism and the octane degradation pathway are proposed. Volatile organic compound (VOC) elimination technologies have been investigated to alleviate health damage and to reduce serious environmental risks. The degradation of hydrophobic and refractory VOCs calls for advanced oxidation processes with high degradation efficiency and low-level toxic byproduct generation. In this study, core-shell Fe 3 O 4 @C was employed as an advanced oxidation microreactor for hydrophobic and refractory VOC removal during the Fenton process, and octane was chosen as a typical target pollutant. The average octane removal efficiency increased by 41.6%, while the main byproduct concentrations decreased by 65.8% in the initial 60 min compared with Fe 3 O 4. Density functional theory (DFT) calculations revealed the key role of Fe O C bond during the regeneration of Fe(II) species, and the enhanced octane adsorption process by the carbonyl sites. Calculation of mass transfer enhancement factor proved that the carbon shell was critical during mass transfer process. The advanced oxidation mechanism was investigated by detection and measurement of byproducts and hydroxyl radicals and XPS analysis. The synergism and the octane degradation pathway was proposed based on the two main types of reactions. This core-shell Fenton system suggests a promising approach for catalyst and microreactor design in advanced oxidation technologies for refractory VOCs removal. [ABSTRACT FROM AUTHOR]

• The synergistic effect of mass transfer and catalytic oxidation is investigated. • The octane removal efficiency is increased and the byproduct levels is decreased. • The volumetric mass transfer coefficient and the enhancement factor are calculated. • The regional reaction mechanism for yolk-shell Fe 3 O 4 @C/Fenton system is proposed. Volatile organic compound (VOC) emissions are a global environmental concern because of their potential health risks. The removal of refractory VOCs calls for advanced technologies with powerful oxidative ability and high mass transfer efficiency. In this study, a yolk-shell Fe 3 O 4 @C/Fenton system was designed to improve octane removal efficiency. The octane removal efficiency at equilibrium was increased by 24.7% relative to that of the Fe 3 O 4 /Fenton system, and the main intermediate or byproduct levels decreased by 89.4%. The yolk-shell Fe 3 O 4 @C displayed higher catalytic and mass transfer efficiencies for octane degradation than Fe 3 O 4. A synergistic effect of mass transfer enhancement and catalytic oxidation was observed in the yolk-shell Fe 3 O 4 @C/Fenton system. The mechanism of the synergistic effect of mass transfer and octane degradation, a regional reaction theory for the yolk-shell structure, and octane removal pathways were proposed and supported by the octane removal results and byproducts detection and measurement. This yolk-shell Fe 3 O 4 @C/Fenton system provides an effective and advanced way to treat refractory and hydrophobic VOCs, and its preparation can be extended to other high-efficiency core-shell structure catalyst-carbon materials. [ABSTRACT FROM AUTHOR]