Formaldehyde in the Indoor Environment
TL;DR: Adverse health effects from exposure to formaldehyde in prefabricated houses, especially irritation of the eyes and upper airways, were first reported in the mid-1960s and a guideline value of 0.1 ppm was proposed in 1977 by the former German Federal Agency of Health to limit human exposure in dwellings.
Abstract: 1.1. History
Formaldehyde was described in the year 1855 by the Russian scientist Alexander Michailowitsch Butlerow. The technical synthesis by dehydration of methanol was achieved in 1867 by the German chemist August Wilhelm von Hofmann. The versatility that makes it suitable for use in various industrial applications was soon discovered, and the compound was one of the first to be indexed by Chemical Abstracts Service (CAS). In 1944, Walker published the first edition of his classic work Formaldehyde.(1) Between 1900 and 1930, formaldehyde-based resins became important adhesives for wood and wood composites. The first commercial particle board was produced during World War II in Bremen, Germany. Since 1950, particle board has become an attractive alternative to solid wood for the manufacturing of furniture. Particle board and other wood-based panels were subsequently also used for the construction of housing. Adverse health effects from exposure to formaldehyde in prefabricated houses, especially irritation of the eyes and upper airways, were first reported in the mid-1960s. Formaldehyde emissions from particle boards bonded with urea formaldehyde resin were soon identified as the cause of the complaints. As a consequence, a guideline value of 0.1 ppm was proposed in 1977 by the former German Federal Agency of Health to limit human exposure in dwellings. Criteria for the limitation and regulation of formaldehyde emissions from wood-based materials were established in 1981 in Germany and Denmark. The first regulations followed in the United States in 1985 or thereabouts. In Germany and the United States, large-scale test chambers were used for the evaluation of emissions. Although the chamber method is very reliable, it is also time-consuming and expensive. This meant there was a strong demand for simple laboratory test methods.(2)
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TL;DR: For the first time, a direct g-C3N4-TiO2 Z-scheme photocatalyst without an electron mediator was prepared by a facile calcination route utilizing affordable P25 and urea as the feedstocks and will provide new insights into the design of high-performance Z-Scheme photoc atalysts for indoor air purification.
Abstract: Formaldehyde (HCHO) is a major indoor pollutant and long-term exposure to HCHO may cause health problems such as nasal tumors and skin irritation. Photocatalytic oxidation is considered as the most promising strategy for the decomposition of HCHO. Herein, for the first time, a direct g-C3N4–TiO2 Z-scheme photocatalyst without an electron mediator was prepared by a facile calcination route utilizing affordable P25 and urea as the feedstocks. Photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic oxidation decomposition of HCHO in air. It was shown that the photocatalytic activity of the prepared Z-scheme photocatalysts was highly dependent on the g-C3N4 content. At the optimal g-C3N4 content (sample U100 in this study), the apparent reaction rate constant was 7.36 × 10−2 min−1 for HCHO decomposition, which exceeded that of pure P25 (3.53 × 10−2 min−1) by a factor of 2.1. The enhanced photocatalytic activity could be ascribed to the formation of a g-C3N4–TiO2 Z-scheme photocatalyst, which results in the efficient space separation of photo-induced charge carriers. Considering the ease of the preparation method, this work will provide new insights into the design of high-performance Z-scheme photocatalysts for indoor air purification.
1,112 citations
TL;DR: In this article, a single-crystalline α-MnO2 nanowires with exposed high-index {310} facets were synthesized via a facile hydrothermal route with the assistance of a capping agent of oxalate ions.
Abstract: The activity of exposed crystal facets directly determines its physicochemical properties. Thus, acquiring a high percentage of reactive facets by crystal facet engineering is highly desirable for improving the catalytic reactivity. Herein, single-crystalline α-MnO2 nanowires with major exposed high-index {310} facets were synthesized via a facile hydrothermal route with the assistance of a capping agent of oxalate ions. Comparing with two other low-index facets ({100} and {110}), the resulting α-MnO2 nanowires with exposed {310} facets exhibited much better activity and stability for carcinogenic formaldehyde (HCHO) oxidation, making 100% of 100 ppm of HCHO mineralize into CO2 at 60 °C, even better than some Ag supported catalysts. The density functional theory (DFT) calculations were used to investigate the difference in the catalytic activity of α-MnO2 with exposed {100}, {110}, and {310} facets. The experimental characterization and theoretical calculations all confirm that the {310} facets with high ...
418 citations
TL;DR: The 3D-Co 3 O 4 has the best performance of formaldehyde oxidation due to the three-dimensional porous channel structure, larger specific surface area, abundant active surface oxygen species and active Co 3+ cationic species on the exposed (2.2.0) crystal face as discussed by the authors.
Abstract: 2D-Co 3 O 4 and 3D-Co 3 O 4 catalysts were prepared by the hard template method, and nano-Co 3 O 4 was synthesized by precipitation method. The catalytic activity for the oxidation of formaldehyde over various types of catalysts was investigated. The 3D-Co 3 O 4 catalyst attained a 100% conversion rate of formaldehyde at 130 °C with a space velocity of 30,000 mL/(g h), while the 2D-Co 3 O 4 catalyst oxidized formaldehyde completely at 150 °C in the same space velocity conditions. The difference in activity is due to the clear channel structure of the mesoporous Co 3 O 4 prepared by the hard template method, which has large specific surface area and surface active species that allows the reactant to diffuse and undergo surface reactions. The 3D-Co 3 O 4 had the best performance of formaldehyde oxidation due to the three-dimensional porous channel structure, larger specific surface area, abundant active surface oxygen species and active Co 3+ cationic species on the exposed (2 2 0) crystal face. Complete conversion of formaldehyde had remained the same after 3D-Co 3 O 4 was observed for 160 h. Therefore, the 3D-Co 3 O 4 catalyst has the best catalytic activity and stability for formaldehyde, which might be a non-noble catalyst for catalytic removal of formaldehyde in practical application.
391 citations
TL;DR: This overview has reviewed the literature about the effects of extended exposure to low humidity on perceived IAQ, sensory irritation symptoms in eyes and airways, work performance, sleep quality, virus survival, and voice disruption, and research is needed about particle, bacteria and virus dynamics indoors for improvement of quality of life and with more focus on the impact of absolute humidity.
365 citations
TL;DR: In this article, a layered-structure MnO2 was designed with different amounts of manganese vacancy (VMn) for catalytic oxidation of formaldehyde (HCHO), and the content of VMn was determined by the ratio of Mn/O and coordination number of Mn-Mn edge sharing structure.
Abstract: Catalytic reaction active site tends to be the structural defects, such as edges, corners, ribs and other position that has low coordination number. Here, the potassium (K+) type birnessite (i.e. a layered-structure MnO2) was designed with different amounts of manganese vacancy (VMn) for catalytic oxidation of formaldehyde (HCHO). The content of VMn was determined by the ratio of Mn/O and coordination number of Mn–Mn edge-sharing structure. The VMn showed a dramatic promotion effect on the activity of birnessite for HCHO oxidation. The specific rate at 30 °C over the birnessite with the highest content of VMn was highest (0.052 μmol/m2 min) under 40 ppm of HCHO, 120,000 mL/g h of GHSV and ∼ 80% of relative humidity. The presence of VMn induced unsaturated oxygen species and K+ locating nearby VMn sites for charge balance facilitated the formation of active oxygen species, accordingly the activity for HCHO oxidation was greatly improved. This finding reveals a way to enhance the catalytic activity of metal oxides via adjusting metal vacancies.
341 citations
References
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TL;DR: A chronology of key events leading up to and including the birth of Bonnichsen, R. K. & Bonner, J. (1952).
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2,290 citations
TL;DR: The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.
Abstract: Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacols, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18−30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.
1,188 citations
TL;DR: The theory of operation is described and the response of the instrument to be described for different operating conditions is described, including the results obtained in fresh and aged forest-fire and urban plumes.
Abstract: Proton-transfer-reaction mass spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed.
987 citations