Volatile Organic Pollutants Research Articles

Revealing the critical roles of silver species on TNT film for photocatalytic decomposition of volatile organic pollutants under UV or visible light irradiation: From mechanism study to scaled-up test

Ag nanoparticles are commonly employed as co-catalysts to promote photocatalytic reactions. In addition to their apparent roles as electron traps and catalytic active sites, nanoparticulate Ag can also generate hot electrons under visible light irradiation, which endows visible light photocatalytic activity to its supporting material. On the other hand, Ag0 can be easily converted to Ag2O, however, few studies focus on its formation and roles during the photocatalytic process. In this work, we have successfully fabricated and optimized the preparation procedures of titania nanotube (TNT) and Ag species deposited TNT to get the optimum photochemical activities of Ag modified TNT. Specifically, the roles of Ag species on TNT film have been investigated by photoelectrochemical (PEC) measurements and photocatalytic decomposition of volatile organic pollutants under UV or visible light irradiation. Toluene (30 ppm) can be effectively decomposed (∼83.3%) and mineralized (∼70.7%) by Ag species modified TNT in 3 h under UV–visible light irradiation, while the degradation and mineralization ratios are only about 60.0% and 33.3% under visible light irradiation. The results demonstrate that appropriate Ag/Ag2O ratio on TNT film are crucial for improving PEC and photocatalytic performance, and the interconversion between Ag and Ag2O influences the photochemical stability of Ag/TNT film. The scaled-up tests (∼1.0 m3 reactor) on the degradation of low concentration of toluene and formaldehyde prove that the optimized Ag/TNT film can be considered as a promising photocatalyst for indoor air purification.

Response of PM2.5 and O3 to Emission Reductions in Nanjing Based on Random Forest Algorithm

High levels of fine particulate matter (PM2.5) and ozone (O3) in ambient air affect climate change and also endanger human health and ecosystems. Air pollution in Nanjing has been improving since the implementation of the "Air Pollution Prevention and Control Action Plan" in 2013. However, Nanjing still faces PM2.5 and O3 pollution. Evaluating the response of pollutant concentrations to the reductions in precursor emissions is helpful to obtain effective strategies of emission reduction to improve pollution levels. The sensitive simulations of emission perturbation in atmospheric chemistry models directly demonstrate the response of pollution to the reductions in emissions. Nevertheless, these sensitive simulations are limited in computing time and resources. The random forest algorithm was trained by using the simulation results of the atmospheric chemical transport model (GEOS-Chem) in 2015. The changes in daily PM2.5 and daily maximum eight-hour O3 (MDA8 O3) concentrations in Nanjing in 2019 were efficiently predicted under different reduction scenarios of anthropogenic emissions. The simulations showed that the seasonal average of ρ(PM2.5) in Nanjing would decrease by 2-4 μg·m-3 with the reduction in anthropogenic emissions of 10% in 2019 in China. In the case of controlling only local emissions in Nanjing, the concentrations of PM2.5 in Nanjing decreased significantly without local anthropogenic emissions. Additionally, the simulations showed that the annual average of ρ(PM2.5) in Nanjing could be lower than the national secondary limit (35 μg·m-3) when the anthropogenic emission reduction in China was higher than 20% in 2019. For ozone, the equal proportional emission reductions in nitrogen oxides (NOx) and volatile organic pollutants (VOCs) of O3 precursors in China likely led to the increase in seasonal average concentrations of O3 in Nanjing. For the proportional reduction of anthropogenic emissions by 10%-50% in China, the seasonal average of ρ(MDA8 O3) in Nanjing in 2019 would increase by 1-3 μg·m-3 in spring, 1-4 μg·m-3 in autumn, and 3-11 μg·m-3 in winter, respectively, compared with that in the base simulation. With the reduction in anthropogenic NOx emission by 10% and VOCs by 20%, the seasonal average of ρ(MDA8 O3) in Nanjing would decrease by 3-6 μg·m-3. On this basis, further increasing the proportion (30%) of VOCs emission reduction could reduce the annual average of ρ(MDA8 O3) in Nanjing by 7 μg·m-3. However, the annual average of ρ(MDA8 O3) of Nanjing in 2019 increased by 1 μg·m-3, with the local emission reduction of NOx by 10% and VOCs by 30%. Therefore, this showed that the key to alleviate ozone pollution in Nanjing is a reasonable control ratio of ozone precursor emissions and the implementation of regional joint prevention and control. In order to effectively reduce the O3 pollution in Nanjing, the emission reduction ratio of NOx and VOCs in China should be less than 1:2. The response of pollutant concentrations to reductions in precursor emissions were efficiently obtained by the random forest algorithm and GEOS-Chem model. The simulations would provide the scientific basis for the emission control strategy to alleviate air pollution.

A Critical Review on Electric Vehicle Batteries — Based on Life Cycle Assessment Method

Currently, the production of electric vehicles and the lithium batteries that powers them is increasing significantly. Thus, this dissertation combines the literature review approach and the life cycle assessment (LCA) method to investigate the environmental or social impact of lithium batteries for electric vehicles from cradle to grave. According to the literature review, the environmental impacts of lithium batteries include carbon dioxide and harmful electrolyte emissions, water pollution, air pollution, solid waste emissions, gaseous pollutants, volatile organic compounds, nitrogen oxides, heavy metals, organic pollutants, particulate matter and CO2 emissions. Therefore, lithium batteries for electric vehicles pose a great environmental concern. In addition, the confusion surrounding the definition of lithium batteries in LCA can pose a significant concern. The in-depth analysis reveals that there is a lack of uniform data on EV lithium batteries, a low recycling rate of lithium batteries, and a lack of waste stream management. There is no uniformity in the technology and development of lithium batteries among countries such as China, Canada, and the USA. As a result, the secondary data may only represent this region. Besides, the literature consulted covers a long period of time. There is little possibility that the negative environmental impact of earlier technology like the burning of lithium batteries in incinerators can now be improved. Moreover, lithium batteries are still in the development stage. Therefore, there is still room for potential development in the future.

Photocatalytic Performance of Zinc Oxide and Metal‐Doped Zinc Oxide for Various Organic Pollutants

AbstractZinc oxide (ZnO) has a high photocatalytic potential to decompose volatile organic pollutants into CO2 and H2O which depend on their physical properties, such as particle shape and size, band gap, type of dopant, and optical and structural properties. Using 93 references listed in this review, the relationship between metal dopant and synthesis methods to the efficiency of ZnO and composite ZnO‐metal in degrading pollutants for photocatalyst applications is studied. The basic principles of the photocatalyst process is described when the electrons at the valence band of ZnO get the energy from solar spectrum, generate the charge (electron and hole), and then continue to react with superoxide and water, resulting in radical atoms which break the bonds of organic pollutants. Rare earth dopants have the highest efficiency up to 100 % at 15 min irradiation. Conclusions and future prospects of ZnO and metal‐doped ZnO are also discussed. Perspectives and challenges of the future development of ZnO‐based photocatalysts are evaluated.

Sulfur-vacancy-rich ZnS/CdIn2S4 heterojunction for efficient photocatalytic selective oxidation of toluene to benzaldehyde

The conversion of the volatile organic pollutant to industrially valuable chemicals using photocatalysis is a promising endeavor. Herein, ZnS/CdIn2S4 heterojunction with rich sulfur vacancy was constructed via a simple one-pot method for the selective photocatalytic oxidation of toluene to benzaldehyde. ZnS/CdIn2S4 has a suitable band gap and valence band position, thus possessing a mild oxidation ability to generate benzaldehyde while avoiding excessive oxidation. In addition, the presence of tightly bound contact interfaces and sulfur vacancy in ZnS/CdIn2S4 heterojunction facilitates the rapid separation of photogenerated electron-hole. These characteristics of the heterojunction synergistically promoted the selective photocatalytic oxidation of toluene, resulting in ZnS/CdIn2S4 exhibiting the highest benzaldehyde production rate (1025 μmol g−1 h−1) and the highest conversion rate (13.7%), which were 93.1 and 56.9 times higher than those of ZnS and CdIn2S4, respectively. Furthermore, a possible response mechanism has been suggested based on a series of experiments. This study provides new insights into the combination of volatile organic pollutant degradation and high-value chemicals production.

Hydrothermal synthesis of CaFe2O4/Zn2SnO4 composite with its enhanced formaldehyde gas sensing property

Formaldehyde is a harmful volatile organic pollutant to the humans. Here, the CaFe2O4/Zn2SnO4 composite were synthesized by hydrothermal method and the crystal phase, morphologly structures and chemical composition et al. were characterised by XRD, SEM, TEM, BET and XPS. The CaFe2O4/Zn2SnO4 gas sensor displays a high gas response (52), excellent repeatability and selectivity to HCHO at 400 °C. This unique CaFe2O4/Zn2SnO4 composite is available as a potential gas-sensing material to monitor formaldehyde.

In situ confined growth of g-C3N4/pigment compound catalyst in porous diatomite for enhancing photocatalytic nicotine elimination and bacterial inactivation

Humans spend at least 70% of their time indoors, but indoor air pollution has received very little attention compared to outdoor pollution. Indoor air pollutants include inhalable particulate matter, volatile organic pollutants, and biological pollutants. In particular, nicotine in second-hand smoke and pathogenic microorganisms in the air are the most overlooked pollutants, which pose serious threats to human health. Here, low-cost inorganic pigments and diatomite have been selected to modify g-C3N4 to obtain five novel g-C3N4-based photocatalysts, which are intensely colored and show excellent nicotine degradation performance under both simulated sunlight and white LED illumination. Five g-C3N4-based photocatalytic textiles obtained by supporting the colored photocatalysts on low-melting-point skin–core composite polyester (LMPET) still exhibited outstanding photocatalytic degradation performance and cyclability in removing nicotine. Some of the photocatalytic textiles also displayed highly efficient bacterial inactivation towards E. coli and S. aureus under white LED illumination. Mechanistic research has revealed that the combination of inorganic pigments and diatomite effectively promotes the separation of photogenerated electrons and holes. Moreover, •O2-, 1O2, and •OH have been identified as the main active species in the colored photocatalyst systems. Notably, the colored photocatalysts may be used as dyes to make wall coverings, sofa covers, and so on, which could conceivably purify indoor air while playing a decorative role.

Investigation of the presence of volatile organic pollutants (VOCs) in tap water in Ankara provincial districts

Amaç: Su kaynaklarının temizliği ve güvenilirliği konusu halk sağlığı açısından düzenli ve sürekli kontrol altında tutulan bir husustur. Bununla birlikte, düzenli olarak kontrol edilen kimyasal kirleticilerin listesi sınırlıdır ve bölgesel veya zamana bağlı değişikliklerle meydana gelen bazı kirleticilerin varlığının gözden kaçabileceği unutulmamalıdır. Uçucu Organik Bileşikler (UOB), hem havaya buharlaşan hem de suda çözünen organik kimyasallardır. UOB normal günlük hayatımızda sanayide, tarımda, ulaşımda ve birçok işlemde kullanıldığı için günlük yaşamda yaygındır. Yaygın olarak kullanılan UOB çevreye salındığı bilinmekte ve su kaynaklarına ve yer altı sularına ulaştıklarında, birçok UOB kalıcı hale gelebilmekte ve içme suyu tedarik sistemine dahil olabilmektedirler. Bu kimyasalların birçoğu zehirli olup ve içme suyu veya çevrede insan sağlığı veya ekolojik kaygılar oluşturabilmektedirler. Uçucu organik kirleticiler de büyük bir çeşitlilik göstermektedir ve uzun vadeli ve ülke çapında geniş ve yaygın kaynaklara dayalı araştırmalar, su kaynaklarında bazı UOB görüldüğünü göstermektedir. Yöntem: Bu çalışmada Ankara ilindeki musluk sularında bölgesel bir su kirliliği olup olmadığının tespiti için sinyal araştırması yapılmıştır. Ankara ili ilçelerinden musluk suyu numuneleri alınmış olup, UOB miktarı Head Space Gaz Kromatografisi yöntemi ile ölçülmüştür. Bulgular: Formaldehit, n-pentan, tertbutilmetileter, n-hekzan, etilasetat, heptan, 1-butanol, 1,4-dioksan için gerçekleştirilen ölçümler tayin sınırları (LOD) altında kalmıştır. Sonuç: Çalışmanın sonuçları, ilin herhangi bir bölgesinde seçilmiş 8 adet UOB kimyasalı için kirliliğe işaret eden bir sinyal olmadığını göstermektedir.

Study on degradation of cooking fume by compound filter material and UV photodegradation.

Environmental contamination issues have steadily surfaced with the rapid development of the cooking industry. In this paper, the front end of the cooking fume exhaust was filtered by the filter material, and then, the ultraviolet photolysis technology was used for in-depth treatment. The filter material filtration performance of glass fiber, molecular sieve, and composite filter material was studied by the filter efficiency, filter resistance, and quality factor three filter performance indexes. The results show that the filter wind speed has a significant influence on the filter material fume filtration characteristics. The filtration efficiency of the pre-filter material changes the least with the increase of the wind speed when the wind speed is 18m·s-1 and the filter material tilt Angle is 60°; meanwhile, the pressure drop of the two kinds of filter material is reduced, and the quality factor is improved. Under the optimal wind speed and angle, the composite filter material of glass fiber and molecular sieve combined with UV photolysis technology was used to study the treatment of formaldehyde and acrolein, which are two volatile organic pollutants with high content in cooking fume, and the mineralization mechanism of formaldehyde and acrolein under UV light was analyzed. The results showed that the removal rates of formaldehyde and acrolein could reach 99.84% and 99.75%, respectively.

Strong Metal Support Effect of Pt/g-C3N4 Photocatalysts for Boosting Photothermal Synergistic Degradation of Benzene

Catalysis is the most efficient and economical method for treating volatile organic pollutants (VOCs). Among the many materials that are used in engineering, platinized carbon nitride (Pt/g-C3N4) is an efficient and multifunctional catalyst which has strong light absorption and mass transfer capabilities, which enable it to be used in photocatalysis, thermal catalysis and photothermal synergistic catalysis for the degradation of benzene. In this work, Pt/g-C3N4 was prepared by four precursors for the photothermal synergistic catalytic degradation of benzene, which show different activities, and many tests were carried out to explore the possible reasons for the discrepancy. Among them, the Pt/g-C3N4 prepared from dicyanamide showed the highest activity and could convert benzene (300 ppm, 20 mL·min-1) completely at 162 °C under solar light and 173 °C under visible light. The reaction temperature was reduced by nearly half compared to the traditional thermal catalytic degradation of benzene at about 300 °C.

An updated review of indoor pollutant purification by solar photocatalytic ventilation wall: Materials, modelling and performance evaluation

Solar photocatalysis has been an efficient option to eliminate indoor volatile organic pollutants (VOCs) due to its relatively low cost. Moreover, solar ventilation wall is a common heating and ventilating technology that supplies air circulation in a room and expels polluted air under the action of wind pressure. An efficient air purification type ventilation wall that meets indoor pollutant purification, natural ventilation and thermal fully driven by the combination of solar photocatalytic purification technology and natural ventilation wall has been developed by previous research. The aim of this updated review is to explore the development of the solar photocatalytic ventilation wall (SPVW) system and critically analyze the scientific literature on photocatalysts, models, mechanism, parameter analysis and evaluation of this multifunctional system. The review also included the effects of parameters such as initial concentrations of pollutants, ultraviolet (UV) light intensity, relative humidity, channel width, channel height on the solar photocatalytic characteristics and natural ventilation performance, and a brief performance evaluation on natural ventilation, indoor heating and solar photocatalytic degradation. The governing analysis reveals that the daily stability of the SPVW system could be achieved by enhancing the activity of the photocatalyst and decreasing fluctuation of light source in the external input.

Catalytic Performance and Reaction Mechanisms of Ethyl Acetate Oxidation over the Au–Pd/TiO2 Catalysts

The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPdx nanoparticles (NPs) were loaded on TiO2 through the electrostatic adsorption approach to generate the yAuPdx/TiO2 (i.e., 0.35AuPd0.46/TiO2, 0.34AuPd2.09/TiO2, and 0.37AuPd2.72/TiO2; x and y are Pd/Au molar ratio and AuPdx loading, respectively; x = 0.46–2.72; and y = 0.34–0.37 wt%) catalysts, and their catalytic activities for the oxidation of ethyl acetate were determined. The results showed that the 0.37AuPd2.72/TiO2 sample exhibited the best activity (T50% = 217 °C and T90% = 239 °C at SV = 40,000 mL/(g h), Ea = 37 kJ/mol, specific reaction rate at 220 °C = 113.8 µmol/(gPd s), and turnover frequency (TOFNoble metal) at 220 °C = 109.7 × 10−3 s−1). The high catalytic performance of the 0.37AuPd2.72/TiO2 sample was attributed to the good dispersion of AuPd2.72 NPs, the strong redox ability, the large ethyl acetate adsorption capacity, and the strong interaction between AuPdx and TiO2. Acetaldehyde, ethanol, and acetic acid are the main intermediates in the oxidation of ethyl acetate, and the loading of AuPdx NPs effectively reduces the formation of the toxic by-product acetaldehyde. The oxidation of ethyl acetate over the 0.34AuPd2.09/TiO2 sample might occur via the pathway of ethyl acetate → ethanol → acetic acid → acetate → CO2 and H2O. We believe that the obtained results may provide a useful idea for the design of bimetallic catalysts under industrial conditions and for understanding the VOCs oxidation mechanisms.

Impacts of Pollutant Emissions from Typical Petrochemical Enterprises on Air Quality in the North China Plain

Under the state’s key surveillance, petrochemical industries are considered polluting enterprises. Even though large-scale petrochemical enterprises follow the complete treatment of combustion waste gas, process waste gas, and volatile organic waste gas pollutants, the impact of pollutant emissions on the regional air quality is unclear. This study used the atmospheric chemical transport model and adopted the subtraction method to simulate the impacts of air pollutant emissions from four typical petrochemical enterprises on regional air quality of the North China Plain. Results indicated that emissions from petrochemical enterprises on surface PM2.5, SO2, and NO2 concentrations mainly contributed to the nearby area, particularly SO2 and NO2. The pollution can be controlled within the boundaries of the petrochemical plants. Petrochemical enterprises had a small SO2 and NO2 contribution with a maximum of up to 4.65% within a 9 km distance. Emissions from petrochemical enterprises contributed less to surface PM2.5 concentrations (less than 0.5%) within a 9 km distance. Surface O3 concentrations driven by petrochemical enterprises did not show near-source distribution characteristics, which were closely related to its complex precursors and secondary reactions. Contributions of petrochemical enterprises to local pollution decreased significantly with the increase in distance. The SO2 and NO2 pollution contributions to the North China Plain remained around 0.1–0.2%, with the maximum contribution occurring in January and July. The maximum contribution of PM2.5 in this region was in April (0.42%) while it was below 0.1% for other months. The pollutant emission from the four typical petrochemical enterprises in the North China Plain had little impact on the concentration of air pollutants in the North China Plain. However, it had a significant impact on the ambient air quality in the region near the enterprise. This study can be useful in analyzing and refining the influence of enterprises on the region.

Collaborative Purification of Tert-Butanol and N2O over Fe/Co-Zeolite Catalysts.

N2O is a greenhouse gas and a candidate oxidant. Volatile organic pollutants (VOCs) have caused great harm to the atmospheric ecological environment. Developing the technique utilizing N2O as the oxidant to oxidize VOCs to realize the collaborative purification has significant importance and practical value for N2O emission control and VOC abatement. Therefore, the study of N2O catalytic oxidation of tert-butanol based on zeolite catalysts was carried out. A series of molecular sieves, including FER, MOR, ZSM-5, Y, and BEA, were selected as the catalyst objects, and the 1.5% wt Fe and Co were, respectively, loaded on the zeolite catalysts via the impregnation method. It was found that the catalytic performance of BEA was the best among the molecular sieves. Comparing the catalytic performance of Fe-BEA under different load gradients (0.25~2%), it was found that 1.5% Fe-BEA possessed the best catalytic activity. A series of characterization methods showed that Fe3+ content in 1.5% Fe-BEA was the highest, and more active sites formed to promote the catalytic reaction. The α-O in the reaction eventually oxidized tert-butanol to CO2 over the active site. The Co mainly existed in the form of Co2+ cations over Co-BEA samples; the 2% Co-BEA possessing higher amounts of Co2+ exhibited the highest activity among the prepared Co-BEA samples.

Synergistic double doping of Co and Cu constructs multiple active sites to achieve catalyzed degradation of toluene at high humidity

Developing high water resistance, efficient, and stable, functional catalysts under practical working conditions is significant reducing and controlling VOCs (volatile organic compounds). It is a considerable challenge to elucidate the catalytic process and mechanism of VOCs degradation under the action of environmental water. In this study, CoCu-CeO2 trimetallic oxide catalysts are designed to investigate the catalytic performance in the water-toluene complex system by modulating the morphological and structural characteristics of the bimetallic at the multiphase interface. The result indicates that introducing Cu species enhances the electron transfer process from Co3+ to Co2+resulting in improved redox performance. Co species significantly promote the migration and conversion of the Cu species at the nanoscale to achieve lattice atom substitution. The bimetallic substitution enhances the ability of CeO2 to form oxygen defects. In the presence of ambient water, Co-Cu interactions inhibit the oxidation of toluene to benzaldehyde and benzoic acid by-products with enhanced mineralization of toluene. Design defects and multi-metal sites play a crucial role in the O2-H2O-toluene reaction system. The construction of this catalyst system provides scientific guidance in efficiently removing volatile organic pollutants in complex multi-media environments.

Mechanisms of N, N-dimethylacetamide-facilitated n-hexane removal in a rotating drum biofilter packed with bamboo charcoal-polyurethane composite

n-Hexane and N, N-dimethylacetamide (DMAC) are two major volatile organic compounds (VOCs) discharged from the pharmaceutical industry. To enhance DMAC-facilitated n-hexane removal, we investigated the simultaneous removal of multiple pollutants in a rotating drum biofilter packed with bamboo charcoal-polyurethane composite. After adding 800 mg·L−1 DMAC, the n-hexane removal efficiency increased from 59.4 % to 83.1 % under the optimized conditions. The maximum elimination capacity of 10.0 g·m−3·h−1n-hexane and 157 g·m−3·h−1 DMAC were obtained. The biomass of bamboo charcoal-polyurethane and the ratio of protein-to-polysaccharide in extracellular polymeric substances were significantly increased compared with the non-DMAC stage, which is attributed to increased carbon utilization. In addition, Na+ K+-ATPase was positively correlated with increasing electron transport system activity, which was 1.98 and 1.36 times greater. Hydrophilic DMAC improved the bioavailability of hydrophobic n-hexane and benefited bacterial metabolism. Co-degradation of n-hexane and DMAC system can be used for other volatile organic pollutants.

The Chemical Composition Characteristics and Health Risk Assessment of Cooking Fume Condensates from Residential Kitchens in Different Regions of China

The aim of this study was to explore the similarities and differences of volatile organic pollutants (VOCs) in cooking fumes (COF) of residential buildings in different regions of China, as well as to evaluate their potential health risks. COF condensates were collected from 10 representative cities in China and analyzed by a GC-MS method. Their effects on α-glucosidase, acetylcholinesterase (AchE), and lactate dehydrogenase (LDH) activities were then detected to evaluate potential health risks. A total of 174 kinds of VOCs, including aldehydes, esters, hydrocarbons, alcohols, and carboxylic acid, were identified. There were 59 identical compounds in the northern and southern regions, and 56 common compounds in spicy and non-spicy regions. Health risk assessment results showed that COF condensate could inhibit the activity of α-glucosidase to varying degrees (61.73-129.25%), suggesting that it had a potential risk of causing hypoglycemia. Daily and 3 and 6 month intakes of COF in minors, adults, and the elderly had both activated and inhibited effects on AchE. The activated effect in the southern and spicy areas was higher than that in northern and non-spicy areas, revealing that different regions and dietary habits had different effects on the risk of neurological diseases caused by changes in AchE activity. For minors, adults, and the elderly, COF had different degrees of activation of LDH at different exposure times and regions. Activation in the northern and non-spicy areas was higher than that in southern and spicy areas, suggesting that the health risks caused by changes in LDH activity levels were significantly increased.

The urgent need to control volatile organic compound pollution over the Qinghai-Tibet Plateau.

Owing to the impact of the western development of China, there have been signs of air pollution over the Qinghai-Tibet Plateau in recent years. However, monitoring data on atmospheric volatile organic compounds (VOCs) are lacking in plateau areas. Here, VOCs concentrations in urban and background areas in North China and the Qinghai-Tibet Plateau were observed from 2012 to 2014 and 2020 to 2022, respectively. Compared to 2012-2014, the concentration of VOCs increased to 2.5 times in urban areas on the Qinghai-Tibet Plateau, which was equivalent to that in North China. Oil, gas, and solvent evaporation caused by a low atmospheric pressure is the primary factor for the increase in VOCs in plateau areas, and weak VOCs degradation is the secondary factor. Hence, we put forward the VOCs control strategies in plateau areas and point out the defects in the current research.

Nickel Oxide Clusters on TiO2@Carbon Cloth Nanowires for Efficient Photocatalytic Oxidation of Formaldehyde under 420 nm LED Irradiation

AbstractIt is a great challenge to fabricate effective visible‐light‐driven photocatalysts to decompose indoor volatile organic pollutants in the air. Herein, rutile TiO2 nanorods were prepared on carbon cloth by means of a seed assisted hydrothermal method, and NiO clusters were loaded subsequently onto the TiO2 nanorods. Loading of NiO clusters enhances the absorption of visible light due to the surface plasma resonance (SPR) effect at the interface of NiO/TiO2. The degradation efficiency of the optimized sample reaches 94 % for formaldehyde under 420 nm LED irradiation, higher than value of 34 % obtained for TiO2. While under 365 nm LED light, the degradation rate obtained with the same sample compared with TiO2 decreases dramatically since 365 nm light cannot activate the NiO/TiO2 junction and NiO coverage blocks partly light absorption. The SPR effect for NiO/TiO2 facilitates the generation and transfer of photoinduced electron/hole pairs, thus enhancing the photocatalytic oxidation of gaseous formaldehyde under visible‐light irradiation.

Surface Modification of GdMn2O5 for Catalytic Oxidation of Benzene via a Mild A-Site Sacrificial Strategy

Thermal catalytic oxidation technology is an effective way to eliminate refractory volatile organic pollutants, such as Benzene. Nevertheless, a high reaction temperature is usually an obstacle to practical application. Here, GdMn2O5 mullite (GMO-H) catalyst with disordered surface Gd-deficient and oxygen-vacancy-rich concentrations was synthesized via a controllable low-temperature acid-etching route. Results show that the preferentially broken Gd-O bond is conducive to exposing more Mn-Mn active sites, which Gd species covered. The affluent surface oxygen vacancies supply sufficient adsorption sites for oxygen molecules, facilitating the oxygen cycles during Benzene catalytic oxidation. Furthermore, surface exposed Mn3+ species were oxidized to Mn4+, which is beneficial to increase catalytic activity at a lower temperature. Compared with the conventional GdMn2O5, the reaction temperature for removing 90% Benzene over GMO-H was dropped from 405 to 310 °C with WHSV of 30,000 mL g−1 h−1. Significantly, during a 72 h catalytic test, the catalytic activity remains constant at 90% of the Benzene removal at 300 °C, indicating excellent activity stability. This work reported an efficient approach to preparing manganese-base mullite thermal catalyst, providing insight into the catalytic oxidation of Benzene.