VOC Pollution Research Articles

Vocs pollution and respiratory exposure in commercial and residential underground parking garages

The indoor air quality in Underground Parking Garages (UPGs) has deteriorated significantly, primarily due to the high concentrations of particulate matter and volatile organic compounds (VOCs) emitted by idling or low-speed motor vehicles. However, the compositional characteristics and respiratory exposure to VOCs in UPGs have not been quantitatively analyzed. To establish a method for investigating the respiratory exposure to VOCs among different populations in UPGs, a three-dimensional dynamic diffusion model of indoor pollutants was developed based on monitoring data from 116 components in various UPGs in a large city in northern China. The results indicated that air pollution in underground spaces poses significant health risks to workers and children. Furthermore, a comprehensive approach is essential for improving ventilation capacity and air quality in underground transportation spaces.

Fabrication and adsorption properties of hierarchical NaY zeolite with mesopores in the range of 2–5 nm

Adsorption is one of the most effective methods for controlling the concentration of VOCs pollution. In this work, the hierarchical NaY zeolites with size-controlled mesopores in the range of 2–5 nm are obtained via NH4HF2-etching and surfactant-templating process. By using the different cationic surfactant (CnTAB), we fabricate the surfactant-templated zeolite with controllable mesopores, and improve its adsorption capacity for toluene. In addition, the modified zeolite’s hydrophobicity is enhanced, and it maintains a high adsorption capacity in a complex humid environment.

Characteristics and Source Analysis of VOCs Pollution During Emergency Response in Tianjin

To elucidate the characteristics of VOCs chemical components during heavy pollution episodes, hourly online VOCs data derived from 11 heavy pollution events in Tianjin from 2019 to 2020 were employed. The positive matrix factorization （PMF） and conditional bivariate probability function （CBPF） were employed to analyze the sources of VOCs during heavy pollution episodes. The results indicated that the average VOCs volume fraction during these episodes was recorded at 35.7×10-9. Furthermore, it was observed that during the winter emergency response period, there was a discernible increase in the volume fraction of VOCs when compared to that during the autumn season. Specifically, there was a notable upswing of 48% in the olefins category, whereas alkanes registered a 4% increase. Additionally, the VOCs component structure changed significantly during the heavy pollution episodes. During the orange warning period, the proportion of alkanes increased by 36%, and the proportion of acetylene decreased by 32%. During the yellow warning period, the proportion of alkanes increased by 14%, and the proportion of acetylene decreased by 5%. During the emergency response period, motor vehicle emission sources, natural gas evaporative sources, and solvent use sources were the main contributors of VOCs in environmental receptors, contributing 17.5%, 15.4%, and 15.2%, respectively. Compared with that during the period antecedent to the emergency response, the contribution of vehicle emission sources and diesel volatile sources to VOCs in environmental receptors decreased by 2.0% to 5.5% and 2.1% to 6.6%, respectively, and the contribution of solvent use sources decreased by 0.2% to 2.4% during the yellow warning period. During the orange warning period, the contribution of motor vehicle emission sources was reduced by 0.1% to 8.3%, and the contribution of solvent use sources was reduced by 0.5% to 6.2%.

Challenging design of highly active Pt/CeO2–TiO2/ZSM-5 catalysts for VOCs low-temperature removal

Four Pt/CeO2–TiO2/ZSM-5 catalysts with different Pt species dispersion states and acidic properties were designed, and key factors affecting the oxidation activity of various VOCs (benzene, DCE, ethyl acetate and acetonitrile as typical organic compounds of aromatic hydrocarbon and halogen/oxygen/nitrogen-containing VOCs, respectively) were identified in the present work. The strength of the acid and oxidation sites on the surface of catalysts and their synergistic interaction play a crucial role. Highly dispersed Pt species and its strong redox ability promote low-temperature oxidation of benzene. A synergistic interaction between the acid and oxidation sites is required to achieve high DCE oxidation activity. An abundance of surface acid sites (particularly strong acid sites) favors the adsorption and dechlorination to form vinyl chloride of DCE, and the strong redox ability of oxidation sites would accelerate the deep oxidation of intermediates (such as vinyl chloride and acetic acid, etc.). For ethyl acetate or acetonitrile oxidation, the strong acidic property of the catalyst plays a prior role for their catalytic oxidation, which facilitates the low-temperature hydrolysis of ethyl acetate or acetonitrile. This work provides a significant thought to design and synthesize high activity catalysts for low-temperature oxidation of various VOCs pollutants.

Oxygen-deficient WO3 for stable visible-light photocatalytic degradation of acetaldehyde within a wide humidity range

Indoor VOCs pollution has attracted broad attention for its harm to mankind’s health recent years. Photocatalytic degradation of indoor VOCs holds great prospects in addressing these health concerns in daily life. However, traditional photocatalysts have a large recombination rate of charge carriers and a decrease of the photocatalytic degradation efficiency under high relative humidity. Herein, uniform tungsten oxide nanoparticles with enriched oxygen vacancies (WO3-U) were synthesized by a direct annealing method with urea addition, which exhibited superior performance in the visible-light photocatalysis. The reaction rate constant value of photocatalytic acetaldehyde degradation over WO3-U catalyst was above 3 times higher than that of pristine WO3 sample. More importantly, the WO3-U catalyst maintained stable and excellent photocatalytic performance at relative humidity range of 25–100 %. Except for the enhanced photogenerated charges separation, abundant oxygen vacancies could effectively accelerate O2 activation to generate •O2−, which accounted mainly for the initial conversion of acetaldehyde. Then the subsequent transformation of •O2− into •OH to promoted the final mineralization of acetaldehyde. In addition, the presence of oxygen vacancies also facilitated H2O dissociation to form surface hydroxyl groups, which increased the adsorption of acetaldehyde, resulting in the consistent photocatalytic performance of WO3-U catalyst within a wide humidity range. This work provides guidelines to design visible-light responsive photocatalysts with efficient activity at high humidity conditions for indoor VOCs degradation.

Volatile acetic acid selective adsorption by biomass-derived activated carbon with humidity-resistance: Tunable implanting and activation approach of activator

The selective adsorption and capture of polar organic acid gas by activated carbon (AC) absorbent could solve the challenge of irritant volatile organic compound discharge. However, volatile acid gas selective adsorption by traditional activated carbon with humidity resistance remains challenged. In this study, we developed an innovative one-step chemical synthesis method using discarded banana peels as a carbon source to create porous carbon materials. The selection of activators including sodamide and potassium hydroxide along with tunable implanting means of activator under different activated temperatures were modulated to optimize the fabrication of activated carbon. The results reveal that the low dosage of NaNH2 activator (NaNH2/carbon precursor = 1) implanted into carbon precursor through one-step ball-milling could contribute an excellent structural properties, and higher activated temperature makes the mesoporous behavior of activated carbon more obvious. Based on various optimization conditions, the optimal sample, BAC900, displays remarkable structural features (SBET = 2302 m2/g, Vtotal = 1.968 cm3 g−1, V>2nm = 1.474 cm3 g−1), achieving exceptional acetic acid adsorption efficiency (24.105 mmol g−1). Comparative analysis under various synthetic conditions revealed a close linear relationship between the structural characteristics (total pore volume) of adsorbent and acetic acid adsorption efficiency. We further explored the role of mesopores in facilitating acetic acid adsorption at relatively high pressures and their contribution to enhancing the hydrophobicity of the adsorbent. Additionally, we employed the Differential Isothermal Heat (DIH) technique to predict adsorption selectivity at varying relative humidity, revealing the higher adsorption heat (57 kJ mol−1) of acetic acid compared to water vapor (36 kJ mol−1). This comprehensive study emphasizes the outstanding adsorption selectivity of adsorbent for acetic acid, even in humid environments. Furthermore, the low adsorption heat of the BAC900 indicates good reversibility and reusability, paving the way for the practical application of biomass-derived functional biochar adsorbents in the environmental management of threatening acid VOCs pollutants.

Release characteristics of volatile organic compounds at residential garbage collection points: a case study of Hangzhou, China.

With the implementation of garbage classification, perishable waste has become increasingly concentrated. This has led to a significant change in the VOC release characteristics at residential garbage collection points, posing a potential risk with unknown characteristics. This study investigated the release characteristics, odor pollution, and health risks of VOCs at garbage collection points under different classification effectiveness, seasons, garbage drop-off periods, and garbage collection point types. The results showed that the average concentration of VOCs released from the garbage sorting collection points (SPs) was 341.43 ± 261.16 μg/m3, and oxygenated compounds (e.g., ethyl acetate and acetone) were the main VOC components. The VOC concentration increased as the community classification effectiveness improved, and it was higher in summer (followed by spring, autumn, and winter). Moreover, the VOC concentrations were higher in the evenings than in the mornings and at centralized garbage collection points (CPs) than at SPs. Further, odor activity value (OAV) assessments indicated that acrolein, styrene, and ethyl acetate were the critical odorous components, with an average OAV of 0.87 ± 0.85, implying marginal odor pollution in some communities. Health risk assessments further revealed that trichloroethylene, benzene, and chlorotoluene were the critical health risk substances, with an average carcinogenic risk (CR) value of 10-6-10-4, and a non-carcinogenic risk (HI) value < 1. These results indicated that HIs were acceptable, but potential CRs existed in the communities. Therefore, VOC pollution prevention and control measures should be urgently strengthened at the garbage collection points in high pollution risk scenarios.

Investigation on ozone formation mechanism and control strategy of VOCs in petrochemical region: Insights from chemical reactivity and photochemical loss

To investigate disparities in VOCs pollution characteristics, O3 generation activity, and source apportionment outcomes resulting from photooxidation, online monitoring of 106 VOCs was conducted in Jinshan District, Shanghai from April to October 2020. The observed VOCs concentrations (VOCs–obs) were 47.1 ppbv and 59.2 ppbv for clear days (CD) and O3-polluted days (OPD), respectively. The increase in daytime concentrations of alkenes is a significant factor contributing to the enhanced atmospheric photochemical activity during the OPD period, corroborated by VOCs-loss, ozone formation potential (OFP), propy-equiv concentration, and LOH. The sensitivity analysis of O3–NOx–VOCs indicated that O3 formation was in a transitional regime towards NOx-limited conditions. The results of positive matrix factorization (PMF) demonstrated that refining and petrochemicals (20.8–25.0 %), along with oil and gas evaporation (15.6–16.7 %) were the main sources of VOCs concentrations. Notably, source apportionment based on VOCs–obs underestimated the contributions from sources of reactive components. It is worth highlighting that the sunlight impact & background source was identified as the major contributor to LOH (21.6 %) and OFP (25.3 %), signifying its significant role in O3 formation. This study reiterates the importance of controlling reactive VOC components to mitigate O3 pollution and provides a scientific foundation for air quality management, with emphasis on priority species and controlling sources.

Adoption of SIFT-MS for VOC Pollution Monitoring in South Korea

Adoption of SIFT-MS for VOC Pollution Monitoring in South Korea

Characteristics Analysis of Volatile Organic Compounds Pollution in Residential Buildings in Northeast China Based on Field Measurement

A total of 8 mechanically ventilated residential buildings and 8 naturally ventilated residential buildings were selected to analyze the pollution characteristics of indoor VOCs under different ventilation modes in the severe cold area of northeast China. On typical meteorological days in each season, VOCs were detected on site, and ventilation modes were investigated by long-term online monitoring. The test results showed that the TVOC (total volatile organic compounds) concentrations varied greatly in different seasons or different functional rooms, and the TVOC concentration was the highest in winter, with a value of 0.994 mg/m3. The kitchen was the place with the most serious VOC pollution, and the TVOC concentration could reach 1.403 mg/m3. Benzene series and methylsiloxane had the highest detection rates, but the detected concentrations were low, and the average concentrations were 0.025 mg/m3 and 0.013 mg/m3 respectively. Among the VOC types with a detection rate greater than 50%, the average proportions of aldehydes, alkanes, and benzene series were 18.7%, 15.39%, and 14.38%, respectively. And their mass ratios were also high, which were 14.90%, 30.85%, and 15.70%, respectively. The annual daily average ventilation duration of mechanically ventilated residential buildings was 7.84 h longer than that of naturally ventilated residential buildings. The median TVOC concentrations of mechanically ventilated residential buildings and naturally ventilated residential buildings were 0.621 mg/m3 and 0.707 mg/m3, respectively. The fresh air system was applicable in the severe cold area of northeast China.

S-scheme construction boosts highly active self-supporting CeO2/Cu2O photocatalyst for efficient degradation of indoor VOCs

Photocatalyst-governing degradation of VOCs emitted from household products is promising due to its high performance and long-term durability. In this study, unique hierarchical CeO2/Cu2O nanowire arrays with S-scheme construction grow on a Cu mesh through a simple wet chemical method. Abundant oxygen vacancies on CeO2 work as adsorption sites, and the effective separation of photogenerated carriers driven by built-in electric field in the S-scheme CeO2/Cu2O heterojunction generates mobile reactive oxygen radicals for oxidizing target VOCs. Spectra of Kelvin probe force microscopy (KPFM) reveal that the potential difference at the CeO2/Cu2O interface grows from 9 mV in dark to 29 mV under irradiation, demonstrating a powerful force for driving the migration of photoelectrons. Therefore, under simulated sunlight exposure, 50 ppm of toluene, xylene and formaldehyde can be completely degraded in 70, 50 and 6 min by 15 cm2 CeO2/Cu2O mesh, respectively. The elimination of actual indoor VOCs confirms the practicability of the self-supporting CeO2/Cu2O catalyst, which figures out new ideas for designing efficient photocatalysts for the removal of VOCs pollutants.

Versatile polydopamine-mediated growth of N and C co-doped hollow porous TiO2 spheres with oxygen vacancies for visible-light-driven oxidation of acetaldehyde

Developing visible-light-responsive TiO2-based photocatalysts provides a promising avenue for addressing VOCs pollution. Herein, polydopamine (PDA) template pyrolysis waste was in-situ up-cycled for simultaneous growth of N and C co-doped hollow porous TiO2 microreactors (H-NT-0.2) in air. The resulting H-NT-0.2 with a highly intact hollow structure, thin spherical shell (∼ 13 nm) and high porosity possesses the highest N and C co-doping ratio and largest oxygen vacancies (OVs) amount, leading to the highest concentration of reactive oxygen species (ROS) among all H-NT-x. A crucial role of OVs in enhancing H2O adsorption for the generation of hydroxyl radicals (⋅OH) has been revealed by DFT calculations. As a result, H-NT-0.2 shows the highest photocatalytic oxidation (PCO) efficiency of flowing acetaldehyde gas (90%) under visible light irradiation, which exceeds 3.5 times of commercial TiO2 (P25)), and outperforms most of the reported photocatalysts. The growth mechanism, as well as the photocatalytic reaction pathways, were analyzed based on TG-MS and in-situ DRIFTS results, respectively. This work provides an economical, green and feasible strategy to develop advanced visible-light-responsive photocatalysts for aldehydes VOCs abatement in practical applications.

Literature Review on the Indoor Air VOCs Purification Performance of Metal–Organic Frameworks

Controlling the indoor air (volatile organic compound) VOCs concentration plays an important role in creating a healthy and comfortable living environment. Comparing several VOCs purification measures, solid adsorption is found to be a promising air cleaning method for civil buildings, which have diverse VOCs pollutants. For solid adsorption technology, absorbance is the key to its air-cleaning performance. Compared with traditional adsorbent materials, (metal–organic frameworks) MOFs have excellent physical parameters and are promising adsorbent materials. In this paper, the synthesis and adsorption mechanisms underlying several metal–organic frameworks are summarized. The exploration and experiment measurements of VOCs adsorption performance according to the metal–organic frameworks are summarized. The exploration of these materials’ stability during air cleaning is reviewed. Finally, some application examples of metal–organic frameworks for VOCs adsorption are given. This literature review demonstrates that metal–organic frameworks can be promising adsorbents for indoor air cleaning. The green synthesis methods, stability, adsorption performance under low concentration and diverse VOCs conditions, and application methods for metal–organic frameworks should be further researched before their large-scale application.

Controlled synthesis of bimetallic Nb-Fe composite oxides with high thermal stability for catalytic degradation of binary VOCs pollutants

A string of niobium-iron composite oxides with varying Nb/Fe ratios and calcination temperatures were produced and utilized to remove mixed contaminants (500 ppmv chlorobenzene and 500 ppmv toluene in air), and the structure/texture of catalytic materials were systematically characterized. The findings of the structure-performance study revealed that the physicochemical qualities of Nb2O5-Fe2O3 were greatly enhanced than pure metal oxide. The presence of iron oxide hindered the crystallization of niobium oxide, which aided in the uniform dispersion of niobium-iron components into each other. Forming FeNbO4 at Nb/Fe molar ratio of 1/2 effectively improved the thermal stability of catalyst, withstood short-time thermal shock below 850 °C. The formation of niobium-iron composite oxides improved the specific surface area, optimized the pore size distribution, increased surface acid centers, enhanced reduction/oxidation cycle, and promoted metal-metal interaction for the Nb-Fe-O catalysts. At 320 °C, the catalytic degradation efficiency of 1Nb2Fe-500 could approach 90% for chlorobenzene and 85% for toluene, and it could sustain this efficiency for at least 80 h without evident deactivation, with a high CO2 selectivity of 86%. Furthermore, the Nb-Fe-O catalysts met the environmentally benign and low-cost requirements for environmental catalysis.

A review of prospects and challenges of photocatalytic decomposition of volatile organic compounds (VOCs) under humid environment

AbstractVolatile organic compounds (VOCs) are harmful for humans and the surrounding ecosystem. Emissions from these pollutants have caused a significant reduction in air quality, which has an effect on people's health. Alkanes, alkenes, alcohols, aromatics, and other VOC pollutants have all been broken down by TiO2 photocatalytic processes. Due to several operating inefficiencies and deactivation issues in humid environments, the practical application of photocatalysis has not been realized on a broader scale. The effectiveness of photo‐oxidation of VOCs is impacted by a variety of environmental conditions. In the photocatalytic oxidation of the VOCs, relative humidity (RH) is critical. Therefore, it is important to review the recent findings on how humidity affects the photocatalytic breakdown of VOCs in air. To satisfy this need, this work provides a critical review of the related literature with focus on the fundamentals of photocatalysis, photocatalytic degradation of air pollutants, and the influence of humidity on the photocatalytic process degradation for selected air pollutants. It also highlights the kinetic models and typical photocatalytic reactor and supports for VOC removal.

Pt-modified 3D MnCoOx nanocages as effective catalysts for toluene oxidation

The hollow structural MnCoOx catalysts were prepared by self-assemble method using metal−organic frameworks as sacrificial template. Compared with MnCoOx nanoparticles synthesized by co-precipitation method, the hollow MnCoOx nanocages showed higher performance toward toluene oxidation, which was attributed to the high surface area, more active sites and better redox ability. After the addition of Pt species, the catalytic performance of hollow Pt/MnCoOx-H nanocages were greatly boosted, which was superior to the contrast Pt/MnCoOx-N catalyst. It revealed that the synergistic effect between Pt and support mainly contributes to improved activity, as well as the enhanced surface-active oxygen and low-temperature redox ability. In addition, the superior thermal stability was also demonstrated under dry or moisture conditions. This further promotes a potential application in the mitigation of VOCs pollution.

A Different Perspective on Air Pollution Measurements

This study aims to determine the air pollution in Karabük province. For this purpose, a new equipment has been designed. The equipment can measure the SO2, CO2, CO, CH4, NOX, O3, PM2.5, and VOC pollution alongside with many atmospheric parameters. The measurement period has been decided to be one year starting from June 2021. The measurement period was one year, starting from June 2021. The measurements were taken at fifty points with 8 portable intermittent equipment. Then hourly and monthly averages were calculated. The calculation of the averages depends on many statistical analyses. The mean (geometric, harmonic, root, interquartile, Winsorized), median, midrange, Skewness, and Kurtosis analyses were done to obtain correct daily, and monthly averages. These analyses are necessary to comment on the intermittent measurement averages. The analyses of the collected data showed that the concentrations are changing considerably through the measurement period. The highest concentration was observed for the SO2, CO, NOX, and PM2.5 with respective values of 186.4, 170, 204.9, and 265 µg/m3. All these values are dangerous for human health. Elevation, temperatures, atmospheric pressure, and wind are sensitive parameters for atmospheric pollution. In Karabük province, most of the measurement points are affected by multi-pollution sources. The scatter diagrams also support this fact. During winter months, the pollution increases instantly. However, O3 and VOC parameters show different trends as compared to other pollutants. The concentration of these two parameters, namely O3 and VOC, increases during spring months. The O3 and VOC increase by 78.1%, and 43.2%, respectively due to photochemical reactions in the atmosphere in spring.

Research Progress on Indoor VOC Pollution and Control

Abstract: Nowadys, indoor air pollution is harming human health and has become a global problem. Therefore, research on indoor air pollution is necessary. This paper systematically reviews the research progress of indoor air pollution in recent years, mainly including indoor pollutant types and sources, indoor pollutant detection methods and equipment, pollutant release simulation models and quality standards, indoor air treatment technologies, and points out the problems that exist in current researches. Furthermore, it proposes the direction of future research work.

Dispersion of PM and VOC pollutants from open burning of municipal solid wastes on host communities: emission inventory estimation and dispersion modelling study

This study focused on the dispersion of PM and VOC pollutants from the open burning of solid waste on the Sokoto-Aiyekale dump site in Ilorin, Nigeria, owing to the scarcity of information on pollutants' impact on onsite workers and the population surrounding the dump site.

A Novel Sustainable Semiconductor/Metal-organic Framework Coated Electret Filter for Simultaneous Removal of PM2.5 and VOCs

A MIL-125-NH2 metal-organic framework (MOF) coated electret filter, named E-MOFilter, was previously developed to simultaneously remove PM2.5 (particulate matter less than 2.5 mm in aerodynamic diameter) and volatile organic compounds (VOCs, e.g., toluene). This E-MOFilter captures toluene primarily through physical adsorption, however, degradation of the adsorbed VOCs is desired for increasing the service life of the filter. In this study, photocatalytic nanosheets Bi2WO6/BiOCl (p-BWO) were synthesized, grafted on the MIL-125-NH2 to be p-BWO@MIL, and then coated to the electret filter to form a new filter named PE-MOFilter. The physical characterizations, including size, morphology, crystal structure, optical properties, and surface area for the semiconductor p-BWO nanosheets, p-BWO@MIL and PE-MOFilter were first examined to find out the optimal p-BWO to MIL ratio and coating wt% of p-BWO@MIL particles on the electret filter. Results demonstrated that the p-BWO nanosheets were successfully coated on the surface of MIL and the p-BWO@MIL retained the surface area and micropore volume of the MIL-125-NH2. The capability of the PE-MOFilter on adsorption and degradation of VOCs and the removal efficiency of PM2.5 was examined. The results showed that this novel PE-MOFilter not only captured but also effectively photodegraded VOC pollutants via the synergistic action of adsorption and photocatalytic oxidation (PCO). The photodegradation efficiency was found to be as high as 68.7% and it depended on the ratio of p-BWO to MIL. The PM2.5 removal efficiency also demonstrated that the coating of p-BWO@MIL particles had a negligible influence on the degradation of fiber charge. This research sheds light on the development of semiconductor@MOF coated electret media to simultaneously remove particulate and gaseous pollutants to improve indoor air quality with low energy consumption.