Gaseous formaldehyde removal: A laminated plate fabricated with activated carbon, polyimide, and copper foil with adjustable surface temperature and capable of in situ thermal regeneration

Formaldehyde is one of the most common indoor air pollutants in Chinese residences. This study introduces a novel laminated plate with adjustable surface temperature to remove gaseous formaldehyde. The plate is fabricated with activated carbon, polyimide, and copper foil via thermal compression. The plate can be regenerated in situ by applying a direct current to the copper foil. Adsorption-regeneration cycle tests were conducted to evaluate the plate's formaldehyde removal performance. The overall removal efficiency of the fabricated laminated plate with glue mass fraction of 25% and thickness of 1.5 mm was about 30% at the face velocity of 0.8-1.2 m/s. The pressure drop was about 5 Pa. Its removal ability can be regenerated in situ in 8 minutes by increasing the surface temperature to 80°C. The fabricated laminated plate showed good durability after 52 cycles of adsorption-regeneration tests. The results indicate that the proposed laminated plate can enhance the purifying efficiency and enlarge the life span of ordinary, cheap sorbents. It makes cheap materials with low performance suitable for air purification.

Characterization and adsorption capacity of potassium permanganate used to modify activated carbon filter media for indoor formaldehyde removal

This study examined the effect of potassium permanganate (KMnO₄)-modified activated carbon for formaldehyde removal under different face velocities and different initial formaldehyde concentrations in building environment. We chose the coconut shell activated carbon due to their high density and purity. Moreover, they have a clear environmental advantage over coal-based carbons, particularly in terms of acidification potential. The chemical properties were characterized by FTIR to show the functional groups, EDS to calculate each component of their energy bands to know how the ratio is. Also, the morphology of the surface was examined with scanning electron microscopy (SEM). The BET determines specific surface area, pore size, and pore volume. It was found that where the initial formaldehyde concentration and the face velocity are low, adsorption capacity is high. The adsorption isotherms of formaldehyde on modified activated carbon are well fitted by both Langmuir and Freundlich equations. The rate parameter for the pseudo-first-order model, pseudo-second-order model, and intraparticle diffusion model was compared. The correlation coefficient of pseudo-second-order kinetic model (0.999 > R² > 0.9548) is higher than the coefficient of pseudo-first-order kinetic model (0.5785 < R² < 0.8755) and intraparticle diffusion model (0.9752 < R² < 0.9898). Thus, pseudo-second-order kinetic model is more apposite to discuss the adsorption kinetic in this test, and the overall rate of the modified activated carbon adsorption process appears to be influenced by more than one step that is both the intraparticle diffusion model and membrane diffusion.

Indoor levels of volatile organic compounds and formaldehyde from emission sources at elderly care centers in Korea

The objective of this study is to characterize indoor and outdoor levels of volatile organic compounds (VOCs) and formaldehyde (HCHO) and identify indoor emission sources in thirty elderly care centers (ECCs) located in the Seoul metropolitan city and Gyeonggi province in Korea. Air monitoring samples from indoor and outdoor environments were collected from January to December in 2007. Statistical analyses of indoor and outdoor VOCs and HCHO levels in three rooms (a bedroom, living, and dining rooms) of each ECC were performed, and these were compared to identify environmental factors associated with an increase of indoor pollution levels. Total volatile organic compounds (TVOC) levels were significantly (p<0.05) different between indoor (230.7±1.7 μg/m3) and outdoor (137.8±1.9 μg/m3) environments, with an I/O ratio of 1.67. The indoor HCHO level (20.1±1.6 μg/m3) was significantly (p<0.05) higher than the outdoor level (8.1±1.9 μg/m3), with an I/O ratio of 2.48. Indoor VOCs and HCHO levels in the bedrooms were significantly (p<0.05) higher than those in the living and dining rooms. Furthermore, indoor levels of VOCs and HCHO at ECCs were significantly (p<0.05) different depending on environmental factors such as the use of carpet, paint, and wooden furniture. In multiple regression analysis, indoor VOCs and HCHO levels at ECCs were significantly (p<0.05) correlated with two micro-environmental factors: the use of carpet and paint. This study confirmed that indoor VOCs and HCHO levels were significantly higher than those in outdoor environments. These air pollutants were mainly emitted from indoor sources, such as carpet, paint, and construction materials at the ECCs in Korea.

E-cigarettes can emit formaldehyde at high levels under conditions that have been reported to be non-averse to users

E-cigarette aerosol emission studies typically focus on benchmarking toxicant levels versus those of cigarettes. However, such studies do not fully account for the distinct chemical makeup of e-liquids and their unique properties. These approaches often conclude that there are fewer and lower levels of toxins produced by e-cigarettes than by cigarettes. In 2015, we reported the discovery of new hemiacetals derived from the reaction of formaldehyde and the e-liquid solvents. The main finding was that they constituted a significant proportion of potentially undetected formaldehyde. Moreover, unlike gaseous formaldehyde, the hemiacetals reside in the aerosol particulate phase, and thus are capable of delivering formaldehyde more deeply into the lungs. However, the findings were criticized by those claiming that some of the results were obtained under conditions that are averse to vapers. A "reinvestigation" of our study was recently published addressing this latter issue. However, this reinvestigation ignored major details, including no mention of the formaldehyde hemiacetals. Herein, we isolated both gaseous formaldehyde and formaldehyde hemiacetals at an intermediate power level claimed, in the "reinvestigation", to be relevant to "non-averse," "normal" usage. The results were that both gaseous formaldehyde and formaldehyde from hemiacetals were produced at levels above OSHA workplace limits.

The use of charcoal in modified cigarette filters for mainstream smoke carbonyl reduction

Carbonyls are harmful and potentially harmful constituents (HPHCs) in mainstream cigarette smoke (MSS). Carbonyls, including formaldehyde and acrolein, are carcinogenic or mutagenic in a dose-dependent manner. Past studies demonstrate significant reduction of HPHCs by charcoal filtration. However, limits of charcoal filtration and cigarette design have not yet been investigated in a systematic manner. Objective data is needed concerning the feasibility of HPHC reduction in combustible filtered cigarettes. This systematic study evaluates the effect of charcoal filtration on carbonyl reduction in MSS. We modified filters of ten popular cigarette products with predetermined quantities (100-400 mg) of charcoal in a plug-space-plug configuration. MSS carbonyls, as well as total particulate matter, tar, nicotine, carbon monoxide (TNCO), and draw resistance were quantified. Significant carbonyl reductions were observed across all cigarette products as charcoal loading increased. At the highest charcoal loadings, carbonyls were reduced by nearly 99%. Tar and nicotine decreased modestly (<20%) compared to reductions in carbonyls. Increased draw resistance was significant at only the highest charcoal loadings. This work addresses information gaps in the science base that can inform the evaluation of charcoal filtration as an available technological adaptation to cigarette design which reduces levels of carbonyls in MSS.

Removal of organic phosphorus and formaldehyde in glyphosate wastewater by CWO and the lime-catalyzed formose reaction

Glyphosate (PMG) wastewater with 40-600 mg/L organic phosphorus (OP) and 1-4% CH2O was treated by catalytic wet oxidation (CWO) and the lime-catalyzed formose reaction to remove total phosphorus (TP) and improve biodegradability. Activated carbons (ACs) modified by H2O2 oxidation and thermal treatment with melamine were used as CWO catalysts and characterized by N2 adsorption/desorption and XPS. The CWO experiments were performed in an autoclave reactor at 110-130 °C and 1.0 MPa. The modified AC showed higher catalytic activity than the parent AC due to the introduction of nitrogen-containing functional groups, exhibited over 90% OP removal for various real PMG wastewaters, and had good stability for 20 consecutive CWO runs. The CWO effluents were further treated by lime at 80 °C to remove TP and CH2O. The treated effluents, containing 0.5-12 mg/L TP and 20-60 mg/L CH2O, showed good biodegradability with a BOD5/COD ratio of 0.31-0.41. The combination of CWO and lime is an effective treatment method prior to biological treatment for solving the problems of OP and CH2O encountered by the glyphosate industry.

Effect of endophytic Bacillus cereus ERBP inoculation into non-native host: Potentials and challenges for airborne formaldehyde removal

Phytoremediation could be a cost-effective, environmentally friendly approach for the treatment of indoor air. However, some drawbacks still dispute the expediency of phytotechnology. Our objectives were to investigate the competency of plant growth-promoting (PGP) endophytic Bacillus cereus ERBP (endophyte root blue pea), isolated from the root of Clitoria ternatea, to colonize and stabilize within Zamioculcas zamiifolia and Euphorbia milii as non-native hosts without causing any disease or stress symptoms. Moreover, the impact of B. cereus ERBP on the natural shoot endophytic community and for the airborne formaldehyde removal capability of non-native hosts was assessed. Non-native Z. zamiifolia was effectively inoculated with B. cereus ERBP through soil as the most efficient method of endophyte inoculation. Denaturing gradient gel electrophoresis profiling of the shoot endophytic community verified the colonization and stability of B. cereus ERBP within its non-native host during a 20-d fumigation period without interfering with the natural shoot endophytic diversity of Z. zamiifolia. B. cereus ERBP conferred full protection to its non-native host against formaldehyde phytotoxicity and enhanced airborne formaldehyde removal of Z. zamiifolia whereas non-inoculated plants suffered from formaldehyde phytotoxicity because their natural shoot endophytic community was detrimentally affected by formaldehyde. In contrast, B. cereus ERBP inoculation into non-native E. milii deteriorated airborne formaldehyde removal of the non-native host (compared to a non-inoculated one) as B. cereus ERBP interfered with natural shoot endophytic community of E. milii, which caused stress symptoms and stimulated ethylene biosynthesis. Non-native host inoculation with PGP B. cereus ERBP could bear potentials and challenges for airborne formaldehyde removal.

A Novel Optimization Technique to Improve Gas Recognition by Electronic Noses Based on the Enhanced Krill Herd Algorithm

An electronic nose (E-nose) is an intelligent system that we will use in this paper to distinguish three indoor pollutant gases (benzene (C₆H₆), toluene (C₇H₈), formaldehyde (CH₂O)) and carbon monoxide (CO). The algorithm is a key part of an E-nose system mainly composed of data processing and pattern recognition. In this paper, we employ support vector machine (SVM) to distinguish indoor pollutant gases and two of its parameters need to be optimized, so in order to improve the performance of SVM, in other words, to get a higher gas recognition rate, an effective enhanced krill herd algorithm (EKH) based on a novel decision weighting factor computing method is proposed to optimize the two SVM parameters. Krill herd (KH) is an effective method in practice, however, on occasion, it cannot avoid the influence of some local best solutions so it cannot always find the global optimization value. In addition its search ability relies fully on randomness, so it cannot always converge rapidly. To address these issues we propose an enhanced KH (EKH) to improve the global searching and convergence speed performance of KH. To obtain a more accurate model of the krill behavior, an updated crossover operator is added to the approach. We can guarantee the krill group are diversiform at the early stage of iterations, and have a good performance in local searching ability at the later stage of iterations. The recognition results of EKH are compared with those of other optimization algorithms (including KH, chaotic KH (CKH), quantum-behaved particle swarm optimization (QPSO), particle swarm optimization (PSO) and genetic algorithm (GA)), and we can find that EKH is better than the other considered methods. The research results verify that EKH not only significantly improves the performance of our E-nose system, but also provides a good beginning and theoretical basis for further study about other improved krill algorithms’ applications in all E-nose application areas.

Three-Dimensional Ordered Mesoporous MnO2-Supported Ag Nanoparticles for Catalytic Removal of Formaldehyde

Three-dimensional (3D) ordered mesoporous Ag/MnO2 catalyst was prepared by impregnation method based on 3D-MnO2 and used for catalytic oxidation of HCHO. Ag nanoparticles are uniformly distributed on the polycrystalline wall of 3D-MnO2. The addition of Ag does not change the 3D ordered mesoporous structure of the Ag/MnO2, but does reduce the pore size and surface area. Ag nanoparticles provide sufficient active site for the oxidation reaction of HCHO, and Ag (111) crystal facets in the Ag/MnO2 are active faces. The 8.9% Ag/MnO2 catalyst shows a higher normalized rate (10.1 nmol·s(-1)·m(-2) at 110 °C) and TOF (0.007 s(-1) at 110 °C) under 1300 ppm of HCHO and 150 000 h(-1) of GHSV, and its apparent activation energy of the reaction is the lowest (39.1 kJ/mol). More Ag active sites, higher low-temperature reducibility, more abundant surface lattice oxygen species, oxygen vacancies, and lattice defects generated from interaction Ag with MnO2 are responsible for the excellent catalytic performance of HCHO oxidation on the 8.9% Ag/MnO2 catalyst. The 8.9% Ag/MnO2 catalyst remained highly active and stable under space velocity increasing from 60 000 to 150 000 h(-1), under initial HCHO concentration increasing from 500 to 1300 ppm, and under the presence of humidity, respectively.

A Short Review on Photocatalytic Degradation of Formaldehyde

Nowadays, it is a great challenge to eliminate toxic and harmful organic pollutants from air and water. This paper reviews the role of TiO2 as a photocatalyst, light source and photoreactor in the particular case of removal of formaldehyde using the photocatalytic reaction by titanium dioxide (TiO2) in aqueous and gaseous systems. The reaction mechanisms of the photocatalytic oxidation of gaseous formaldehyde are given. We also present a detailed review of published articles on photocatalytic degradation of formaldehyde by modified titanium dioxide doped with foreign species such as metal and non-metal components. We point out the most prospective developments of the photocatalyst compositions for the future potential commercial applications.

Foliar uptake and translocation of formaldehyde with Bracket plants (Chlorophytum comosum)

The foliar uptake and transport of formaldehyde into Bracket plants from air via leaves and roots to external water was investigated in an air-plant-water system. The results indicated that formaldehyde could be quickly taken up by plant tissues, and that formaldehyde accumulated in leaves could be released rapidly back into air when the formaldehyde level in air was diminished. This rapid reversible translocation of formaldehyde between plant leaves and air resulted in high formaldehyde concentrations in leaf dews, depending upon exposure levels of formaldehyde in air. Meanwhile, formaldehyde could be transported from air to plant rhizosphere solution through downward transport. The concentration of formaldehyde in rhizosphere solutions increased with exposure time and the formaldehyde level in air. The efficiency of the leaf extracts to break down formaldehyde increased, probably because of an increase in oxidative potential of the leaf extracts. Taken together, the main mechanism of formaldehyde loss in air can be attributed to the accumulation by (or breakdown in) plant tissues; the removal rate of formaldehyde from air reached 135 μg h(-1) plant(-1) in the experimental condition.

Highly active mesoporous ferrihydrite supported pt catalyst for formaldehyde removal at room temperature

Ferrihydrite (Fh) supported Pt (Pt/Fh) catalyst was first prepared by combining microemulsion and NaBH4 reduction methods and investigated for room-temperature removal of formaldehyde (HCHO). It was found that the order of addition of Pt precursor and ferrihydrite in the preparation process has an important effect on the microstructure and performance of the catalyst. Pt/Fh was shown to be an efficient catalyst for complete oxidation of HCHO at room temperature, featuring higher activity than magnetite supported Pt (Pt/Fe3O4). Pt/Fh and Pt/Fe3O4 exhibited much higher catalytic activity than Pt supported over calcined Fh and TiO2. The abundance of surface hydroxyls, high Pt dispersion and excellent adsorption performance of Fh are responsible for superior catalytic activity and stability of the Pt/Fh catalyst. This work provides some indications into the design and fabrication of the cost-effective and environmentally benign catalysts with excellent adsorption and catalytic oxidation performances for HCHO removal at room temperature.

Removal of formaldehyde over Mn(x)Ce(1)-(x)O(2) catalysts: thermal catalytic oxidation versus ozone catalytic oxidation

Mn(x)Ce(1)-(x)O(2) (x: 0.3-0.9) prepared by Pechini method was used as a catalyst for the thermal catalytic oxidation of formaldehyde (HCHO). At x=0.3 and 0.5, most of the manganese was incorporated in the fluorite structure of CeO(2) to form a solid solution. The catalytic activity was best at x=0.5, at which the temperature of 100% removal rate is the lowest (270°C). The temperature for 100% removal of HCHO oxidation is reduced by approximately 40°C by loading 5wt.% CuO(x) into Mn(0.5)Ce(0.5)O(2). With ozone catalytic oxidation, HCHO (61 ppm) in gas stream was completely oxidized by adding 506 ppm O₃over Mn(0.5)Ce(0.5)O(2) catalyst with a GHSV (gas hourly space velocity) of 10,000 hr⁻¹ at 25°C. The effect of the molar ratio of O(3) to HCHO was also investigated. As O(3)/HCHO ratio was increased from 3 to 8, the removal efficiency of HCHO was increased from 83.3% to 100%. With O(3)/HCHO ratio of 8, the mineralization efficiency of HCHO to CO(2) was 86.1%. At 25°C, the p-type oxide semiconductor (Mn(0.5)Ce(0.5)O(2)) exhibited an excellent ozone decomposition efficiency of 99.2%, which significantly exceeded that of n-type oxide semiconductors such as TiO(2), which had a low ozone decomposition efficiency (9.81%). At a GHSV of 10,000 hr⁻¹, [O(3)]/[HCHO]=3 and temperature of 25°C, a high HCHO removal efficiency (≥ 81.2%) was maintained throughout the durability test of 80 hr, indicating the long-term stability of the catalyst for HCHO removal.

Experimental investigation of the formaldehyde removal mechanisms in a dynamic botanical filtration system for indoor air purification

Botanical filtration has been proved to be effective for indoor gas pollutant removal. To understand the roles of different transport, storage and removal mechanism by a dynamic botanical air filter, a series of experimental investigations were designed and conducted in this paper. Golden Pothos (Epipremnum aureum) plants was selected for test, and its original soil or activated/pebbles root bed was used in different test cases. It was found that flowing air through the root bed with microbes dynamically was essential to obtain meaningful formaldehyde removal efficiency. For static potted plant as normally place in rooms, the clean air delivery rate (CADR), which is often used to quantify the air cleaning ability of portable air cleaners, was only ∼ 5.1m(3)/h per m(2) bed, while when dynamically with air flow through the bed, the CADR increased to ∼ 233 m(3)/h per m(2) bed. The calculated CADR due to microbial activity is ∼ 108 m(3)/h per m(2) bed. Moisture in the root bed also played an important role, both for maintaining a favorable living condition for microbes and for absorbing water-soluble compounds such as formaldehyde. The role of the plant was to introduce and maintain a favorable microbe community which effectively degraded the volatile organic compounds adsorbed or absorbed by the root bed. The presence of the plant increased the removal efficiency by a factor of two based on the results from the bench-scale root bed experiments.

BioArena system for knowing and understanding the biological world: a review with new experimental results

A simple observation is the basis of the development of BioArena system: according to the first observations during the biological incubation after inoculation there is formaldehyde (HCHO) emission from the chromatographic spots; in this emission process, the level of HCHO molecules decreases time dependently. In fact, the antibiotic effect of an antibiotic-like compound decreases in parallel with the HCHO emission. The investigations demonstrated clearly a unique function and role of endogenous HCHO and its one main reaction product, ozone (O3), in the antiproliferative (e.g., antimicrobial) effect of different molecules with diverse chemical structures. The results in BioArena can be extended for in vivo conditions (e.g., greenhouse experiments), as well. For the pretreatment with different doses of inducers (immunostimulation-inducing molecules) there are always four bioequivalent immunostimulating response ranges (quadruple bioequivalent immune response system) in plants. The inducers (e.g., N-methylated basic amino acids, salicylic acid, cinnamic acid, and trace elements) do not participate directly in the induction of the immunostimulating effect. These new findings support a statement that HCHO and its reaction products (mainly O3), as bioreactive small molecules, are responsible for the immunostimulating activity (in vivo conditions), as well.

Enhanced performance of NaOH-modified Pt/TiO2 toward room temperature selective oxidation of formaldehyde

Pt/TiO(2) catalysts with various Pt loadings (0.05-2 wt %) were prepared by a combined NaOH-assisted impregnation of titania with Pt precursor and NaBH(4)-reduction. The thermal catalytic activity was evaluated toward catalytic decomposition of formaldehyde (HCHO) vapor in the presence of toluene under ambient conditions. HCHO could be selectively oxidized into CO(2) and H(2)O over Pt/TiO(2) catalysts and toluene had no change. Pt/TiO(2) catalysts prepared with the assistance of NaOH showed higher HCHO oxidation activity than those without NaOH due to the introduction of additional surface hydroxyl groups, the enhanced adsorption capacity toward HCHO, and larger mesopores and macropores facilitating diffusion and transport of reactants and products. The as-prepared Pt/TiO(2) catalysts with an optimal Pt loading of 1 wt % exhibited high catalytic stability. Considering the versatile combination of noble-metal nanoparticles and supports, this work will provide new insights to the design of high-performance catalysts for indoor air purification.

[Analyses of cosmetic sanitary quality in Hunan Province in 2010]

OBJECTIVE

To establish a scientific foundation for cosmetic supervision and administration based on the analysis of the sanitary quality of cosmetics in Hunan Province during 2010.

METHODS

According to Cosmetic Sanitary Standards (set by the Ministry of Health, People's Republic of China), 150 random samples of cosmetics in Hunan were assayed both for microbial items (including total plate count, fungus and yeast, fecal coliform, staphylococcus aureus, pseudomonas aeruginosa) and chemical items (including 17 kinds of prohibited substances and 14 kinds of restricted substances).

RESULTS

The total rate of cosmetics failing to meet the standards was 22.0% of the 150 samples; specific rates for failing perfumes, skin care products (eye cream) and deodorant products were, relatively, 70.6%, 60.00%, and 44.4%. Four kinds of prohibited substances, including diethyl phthalate, acrylamide, asbestos and neodymium, as well as 2 kinds of restricted substances, including triclosan and formaldehyde, were found to exceed standards. None of microbial items exceeded standard levels.

CONCLUSION

The sanitary quality control of cosmetics is lax. Administrative departments should not only reinforce their post-production supervision with respect to cosmetics, but also consolidate their control over the process of cosmetic production in order to solve the problem of toxic residues or illegal and intentional adulterations.

Pilot-scale UV/H2O2 advanced oxidation process for surface water treatment and downstream biological treatment: effects on natural organic matter characteristics and DBP formation potential

The effects of the advanced oxidation process (AOP) of ultraviolet radiation in combination with hydrogen peroxide (UV/H2O2) on the structure and biodegradability of dissolved natural organic matter (NOM) and on the formation of disinfection by-products (DBPs) through the post-UV/H2O2 chlorination were investigated using UV reactors equipped with either low-pressure amalgam lamps or medium-pressure mercury vapour lamps. With electrical energy doses and H2O2 concentrations typically applied in full-scale UV systems for water remediation, the UV/H2O2 AOP partially oxidized NOM, reducing its degree of aromaticity and leading to an increase in the level of biodegradable species. Also, when combined with a downstream biological activated carbon (BAC) filter, UV/H2O2 AOP reduced the formation of DBPs by up to 60% for trihalomethanes and 75% for haloacetic acids. Biological activated carbon was also shown to effectively remove biodegradable by-products and residual H2O2.

Simultaneous removal of formaldehyde and benzene in indoor air with a combination of sorption- and decomposition-type air filters

Urgent measures for indoor air pollution caused by volatile organic compounds are required in urban areas of China. Considering indoor air concentration levels and hazardous properties, formaldehyde and benzene should be given priority for pollution control in China. The authors proposed the use of air-cleaning devices, including stand-alone room air cleaners and in-duct devices. This study aimed to find the best combination of sorption and decomposition filters for the simultaneous removal of formaldehyde and benzene, employing four types of air filter units: an activated charcoal filter (ACF), an ACF impregnated with a trapping agent for acidic gases (ACID), a MnO2 filter (MDF) for oxidative decomposition of formaldehyde at room temperature and a photocatalyst filter (PHOTO) coupled with a parallel beam ultraviolet (UV) irradiation device. The performance of the combined systems under air flow rates of 35-165 m3 h(-1) was evaluated in a test chamber (2 m3) with a constant gas generation system. The experimental results and data analysis using a kinetic approach showed the combined system of ACF, PHOTO and MDF significantly reduced both concentrations of formaldehyde and benzene in air without any unpleasant odours caused by the UV-induced photocatalytic reaction. The system was then evaluated in a full-size laboratory (22 m3). This test proved the practical performance of the system even at full scale, and also suggested that the filters should be arranged in the order of PHOTO/ACF/MDF from upstream to downstream. The proposed system has the potential of being used for improving indoor air quality of houses and buildings in China.

The roles of various plasma species in the plasma and plasma-catalytic removal of low-concentration formaldehyde in air

The contributions of various plasma species to the removal of low-concentration formaldehyde (HCHO) in air by DC corona discharge plasma in the presence and absence of downstream MnO(x)/Al(2)O(3) catalyst were systematically investigated in this study. Experimental results show that HCHO can be removed not only by short-living active species in the discharge zone, but also by long-living species except O(3) downstream the plasma reactor. O(3) on its own is incapable of removing HCHO in the gas phase but when combined with the MnO(x)/Al(2)O(3) catalyst, considerable HCHO conversion is seen, well explaining the greatly enhanced HCHO removal by combining plasma with catalysis. The plasma-catalysis hybrid process where HCHO is introduced through the discharge zone and then the catalyst bed exhibits the highest energy efficiency concerning HCHO conversion, due to the best use of plasma-generated active species in a two-stage HCHO destruction process. Moreover, the presence of downstream MnO(x)/Al(2)O(3) catalyst significantly reduced the emission of discharge byproducts (O(3)) and organic intermediates (HCOOH).

Modeling and simulations of the removal of formaldehyde using silver nano-particles attached to granular activated carbon

A combined reaction, consisting of granular activated carbon (GAC) adsorption and catalytic oxidation, has been proposed to improve the removal efficiencies of formaldehyde, one of the major indoor air pollutants. In this study, silver nano-particles attached onto the surface of GAC (Ag-GAC) using the sputtering method were evaluated for the simultaneous catalytic oxidation and adsorption of formaldehyde. The evolution of CO(2) from the silver nano-particles indicated that formaldehyde was catalytically oxidized to its final product, with the oxidation kinetics expressed as pseudo-first order. In addition, a packed column test showed that the mass of formaldehyde removed by the Ag-GAC was 2.4 times higher than that by the virgin GAC at a gas retention time of 0.5s. However, a BET analysis showed that the available surface area and micro-pore volume of the Ag-GAC were substantially decreased due to the deposition of the silver nano-particles. To simulate the performance of the Ag-GAC, the homogeneous surface diffusion model (HSDM), developed for the prediction of the GAC column adsorption, was modified to incorporate the catalytic oxidation taking place on the Ag-GAC surface. The modified HSDM demonstrated that numerical simulations were consistent with the experimental data collected from the Ag-GAC column tests. The model predictions implied that the silver nano-particles deposited on the GAC reduced the adsorptive capacity due to decreasing the available surface for the diffusion of formaldehyde into the GAC, but the overall mass of formaldehyde removed by the Ag-GAC was increased due to catalytic oxidation as a function of the ratio of the surface coverage by the nano-particles.

Formaldehyde removal by potted plant-soil systems

Formaldehyde is a major indoor air pollutant. Formaldehyde removal from indoor air conduces to decrease the health risk for urban inhabitants. In this study, a dynamic chamber technique was employed to investigate formaldehyde removal by potted spider plant (Chlorphytum comosum), aloe (Aloe vera) and golden pothos (Epipremnum aureum) with potted soils. The results showed that the potted plant-soil systems could remove formaldehyde from air in a long time. The spider plant-soil system had the highest formaldehyde removal capacity compared with others. Higher metabolisms in plants and microorganisms in daytime may give a reasonable explanation for higher formaldehyde removal capacities for plant-soil systems in daytime. The order of formaldehyde removal capacity for the three plant species agreed well with the sequence of formaldehyde dehydrogenase activities from plant leaves. Formaldehyde removal by plant may be diffusion-limited rather than reaction-limited since the detached formaldehyde dehydrogenase activities from the leaves of the three plant species were higher than in vivo metabolic capacities. Formaldehyde in air can be largely absorbed and metabolized by the microorganisms in the potted soils indicating that further elevating formaldehyde removal capacity for plant-soil system will be realized by increasing exposed surface of potted soil.

Formaldehyde removal by potted plant-soil systems

Formaldehyde is a major indoor air pollutant. Formaldehyde removal from indoor air conduces to decrease the health risk for urban inhabitants. In this study, a dynamic chamber technique was employed to investigate formaldehyde removal by potted spider plant (Chlorphytum comosum), aloe (Aloe vera) and golden pothos (Epipremnum aureum) with potted soils. The results showed that the potted plant-soil systems could remove formaldehyde from air in a long time. The spider plant-soil system had the highest formaldehyde removal capacity compared with others. Higher metabolisms in plants and microorganisms in daytime may give a reasonable explanation for higher formaldehyde removal capacities for plant-soil systems in daytime. The order of formaldehyde removal capacity for the three plant species agreed well with the sequence of formaldehyde dehydrogenase activities from plant leaves. Formaldehyde removal by plant may be diffusion-limited rather than reaction-limited since the detached formaldehyde dehydrogenase activities from the leaves of the three plant species were higher than in vivo metabolic capacities. Formaldehyde in air can be largely absorbed and metabolized by the microorganisms in the potted soils indicating that further elevating formaldehyde removal capacity for plant-soil system will be realized by increasing exposed surface of potted soil.

Study on activated carbon derived from sewage sludge for adsorption of gaseous formaldehyde

The aim of this work is to evaluate the adsorption performances of activated carbon derived from sewage sludge (ACSS) for gaseous formaldehyde removal compared with three commercial activated carbons (CACs) using self-designing adsorption and distillation system. Formaldehyde desorption of the activated carbons for regeneration was also studied using thermogravimetric (TG) analysis. The porous structure and surface characteristics were studied using N2 adsorption and desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that ACSS has excellent adsorption performance, which is overall superior to the CACs. Adsorption theory indicates that the ACSS outperforms the CACs due to its appropriate porous structure and surface chemistry characteristics for formaldehyde adsorption. The TG analysis of desorption shows that the optimum temperature to regenerate ACSS is 75°C, which is affordable and economical for recycling.

Biotreatability of wastewater generated during machinery washing in a wood-based industry: COD, formaldehyde and nitrogen removal

This paper describes biotreatability tests for treating a wastewater stream generated by wood-floor industries after cleaning and washing of machinery used to apply urea-formaldehyde resins onto wood-fiber boards. A biological system consisting of an anaerobic-intermittently aerated reactor in lab-scale was constructed. Since the investigated wastewater is intermittently generated, the system was designed to operate in batch mode. The treatment focused on removal of formaldehyde and COD, as well as the efficiency of nitrification-denitrification. The proposed cheap and relatively simple-to-operate biological system achieved COD and formaldehyde removal rates of 65+/-11% and 93+/-4% respectively. In spite of anaerobic ammonium removal and denitrification, the intermittently-aerated reactor showed poor performance for nitrification. Therefore, a better understanding of constraints for the process improvement is necessary. Regardless the constraints faced during the investigation, the proposed system can be considered feasible to partially reduce a great amount of biodegradable compounds in urea-formaldehyde-based wastewaters. However, to comply with strict threshold limits for industrial effluent discharges, the use of biological treatment combined with more advanced processes is needed to achieve a better quality of the final effluent.

[Isolation, identification and conditions of bacterial strain capable to metabolize high concentrations of formaldehyde]

One bacterial strain capable to degrade and metabolize formaldehyde as a sole carbon source was isolated from soil. Based on the results of standard morphological identification, physiological and biochemical characters, and 16S rDNA sequence analysis, the strain was identified as Pseudomonas putida. After single factor test and orthogonal test, the optimal condition for formaldehyde degradation was determined as the follows: peptone 1.2 g/L, KH2PO4 4 g/L, K2HPO4 3 g/L, MgSO4 x 7H2O 0.2 g/L, trace elements solution 0.1 mL/L, temperature 30 degrees C, pH 8. Under the optimal conditions, the strain tolerance of original formaldehyde concentration was up to 6 g/L and 86% of formaldehyde was consumed after 54 h. It completely consumed 5 g/L formaldehyde after 46 h and degraded 100% of 4 g/L formaldehyde after 35 h.

Formaldehyde biofiltration as affected by spider plant

The kinetic process of formaldehyde biodegradation in a biofilter packed with a mixture of compost, vermiculite powder and ceramic particles was investigated in this study. The results showed that more than 60% of formaldehyde was removed by the first 5 cm high biofilter bed at 406 Lh(-1) flowrate within the range of 5-207 mgm(-3) inlet concentrations. A macrokinetic model was applied to describe the kinetic process of formaldehyde biodegradation and the experimentally determined elimination capacity for the biofilter agreed well with the model predicted values. The data on the effect of spider plant (Chlorophytum comosum L.) on formaldehyde removal indicated that formaldehyde biofiltration might be stimulated by spider plant since formaldehyde was assimilated by spider plant roots and microbial formaldehyde degradation was enhanced by the root exudates.

Formaldehyde removal from air by a biodegradation system

A biodegradation system was used for the treatment of formaldehyde-polluted air. Air pressure dropped 12 mm water in the trickling biofilter during the experiment of about 4 months. In the range 20-300 mg m(-3) influent formaldehyde, this biodegradation system obtained 4.0-40.0 mg h(-1) degradation capacity, with 100%-66.7% degradation efficiency. The amount of formaldehyde degraded by the trickling biofilter was more than that by the activated sludge bioreactor below 200 mg m(-3) influent gaseous formaldehyde while the amount by the trickling biofilter was less than that by the activated sludge bioreactor over 200 mg m(-3) influent gaseous formaldehyde.

The removal of formaldehyde from concentrated synthetic wastewater using O3/MgO/H2O2 process integrated with the biological treatment

The catalytic advanced oxidation process (CAOP) of O(3)/MgO/H(2)O(2) was integrated with a sequencing batch reactor (SBR) system to completely treat concentrated formaldehyde wastewater, demonstrating that this combination is an effective method for treating such wastewaters. The influence of several operational variables--including pH, MgO powder dosage, and the concentrations of H(2)O(2) and O(3)--was investigated for the O(3)/MgO/H(2)O(2) degradation of a 7000 mg/L formaldehyde wastewater. The optimum conditions were found to be a pH of 8, 5 g/L dose of MgO powder, 0.09 mole/L concentration of H(2)O(2), and 0.153 g/L min dose of O(3). The formaldehyde and COD concentrations were reduced 79% and 65.6%, respectively, in the CAOP for 120 min of reaction time under the optimum condition stated above. The remaining concentrations of formaldehyde and COD were 1500 mg/L and 3200 mg/L, respectively, in the effluent. The degradation of formaldehyde in CAOP was determined to be a first-order reaction with a constant of 0.015/min, and radical oxidation was the predominant degradation mechanism. This effluent was post-treated in SBR system for a total cycle time of 24h. The SBR completely removed the formaldehyde and removed 98% of the COD, reducing the COD concentration to lower than 60 mg/L. Therefore, the integrated O(3)/MgO/H(2)O(2) and SBR process is demonstrated as a promising technology for the complete treatment of wastewater with high concentrations of toxic and inhibitory compounds such as formaldehyde.

A study on a combined process for the treatment of phenolic resin plant effluents

The removal of phenol and formaldehyde from phenolic resin plant effluents has been studied by using a combined process. In the first step, phenol was removed from effluent by solvent extraction. Special attention was paid to the effluent with a low content of phenol, which was treated by non-dispersive solvent extraction in hollow fibres. It was found that a single module of Liqui-Cel 2.5in. x 8in. membrane contactor allowed processing approximately 24 L/h of effluent with 0.4-0.7 g/L phenol and attaining values as low as 0.5 mg/L in the raffinate. Formaldehyde, which was left in phenolic resin plant effluent after the removal of phenol, has been treated with hydrogen peroxide in alkaline medium and also in acidic medium (Fenton process). In alkaline medium, formaldehyde was oxidized with hydrogen peroxide to formate ion, which was recovered by solvent extraction. The oxidation of formaldehyde with Fenton process was also studied under several operating conditions. It was found that a large amount of hydrogen peroxide (i.e. mole ratio H(2)O(2):HCHO>6) was necessary to mineralize more than 90% HCHO in 1-2h, at atmospheric pressure and 25 degrees C. The combination of pressure and high temperature strongly increased the kinetics of the process and allowed achieving a very high overall efficiency of the treatment under moderate H(2)O(2) dosage.

[Removal of formaldehyde with novel packed air purifier and its computational simulation]

A novel air purifier was designed for the removal of indoor formaldehyde. The air purifier was filled with glass beads (3 mm) coated with TiO2. The removal efficiency of this air purifier was examined in an airtight room. The results showed that 87.0%-93.8% of the formaldehyde was removed for the initial formaldehyde concentration of 0.727-1.815 mg/m3. The reaction rate equation of the air purifier was developed. The simulation of single device of the air purifier suggested the uniformity of the air flow in the device. Besides, a mathematical model to simulate the variation of formaldehyde in a room was constructed, in which there was continuous formaldehyde emission source and the air purifier was operated. The simulation result was also proved by the experimental data. The results revealed that using the air purifier at intervals could steadily keep the formaldehyde concentration below the National Air Quality Standard of China, i.e. 0.1 mg/m3.

Removal of formaldehyde, methanol, dimethylether and carbon monoxide from waste gases of synthetic resin-producing industries

The removal of mixtures of gas-phase pollutants released from formaldehyde- and formaldehyde resin-producing industries was studied in different bioreactor systems. The waste gases contained formaldehyde, methanol, dimethylether and carbon monoxide. The use of a hybrid two-stage bioreactor, composed of a biotrickling filter and a conventional biofilter connected in series, led to very high elimination capacities and removal efficiencies close to 100% for overall pollutant loads exceeding 600g m(-3)h(-1). The presence of low concentrations of dimethylether in the gaseous mixture did not have a significant effect on the removal of formaldehyde or methanol under our operating conditions, although moderate concentrations of these compounds did negatively affect the biodegradation of dimethylether. When a mixture of all four compounds, at concentrations around 100, 100, 50 and 50mg m(-3) for formaldehyde, methanol, carbon monoxide and dimethylether, respectively, was fed to a conventional biofilter, removal efficiencies higher than 80% were obtained for the first three pollutants at empty bed retention time values above 30s. On the other hand, dimethylether was removed to a lower extent, although its reduced environmental impact allows to conclude that these results were satisfactory.

Allergens in corticosteroid vehicles

BACKGROUND

Whereas allergy to vehicle ingredients (ie, excipients and preservatives) in topical steroid vehicles is well recognized, there are no data regarding which vehicle ingredients are in common use or on which vehicles and active molecules are associated with which ingredients.

OBJECTIVE

To produce descriptive data on the use of allergenic vehicle ingredients in prescription topical corticosteroids.

METHODS

The package insert for every steroid in widespread use in the United States was obtained from the manufacturer and used to generate an ingredient list for the product.

RESULTS

There are seven vehicle ingredients that are commonly used in topical corticosteroid vehicles that are well-known allergens: propylene glycol, sorbitan sesquioleate, formaldehyde-releasing preservatives, parabens, methylchloroisothiazolinone/methylisothiazolinone, lanolin, and fragrance. Of 166 topical corticosteroids, 128 (including all creams) had at least one of these vehicle ingredients. More generic products were free of allergens than were branded products. Solutions and ointments were the least allergenic vehicles. The most commonly present potential allergens were propylene glycol and sorbitan sesquioleate.

CONCLUSIONS

Most prescription topical corticosteroids have the potential to cause allergic contact dermatitis owing to vehicle ingredients. Dermatologists should be aware of this possibility and should consider prescribing agents that do not contain potentially allergenic vehicle ingredients.

Effect of key parameters on the removal of formaldehyde and methanol in gas-phase biotrickling filters

The effect of some important operation parameters, as pH, pollutant load and composition of the nutrient media, on the biodegradation of a mixture of formaldehyde and methanol in a gas-phase biotrickling filter was studied. pH proved to affect the degradation of both compounds at moderately acidic values. Replacing ammonium with nitrate as nitrogen source in the liquid solution led to a slight decrease in performance, though this difference was not really significant. A slight decrease in the elimination rate was also observed when reducing the N-NO(3)(-) concentration to 60% of its original value. No interactions between the two pollutants were found under our working conditions.

Effectiveness of photocatalytic filter for removing volatile organic compounds in the heating, ventilation, and air conditioning system

Nowadays, the heating, ventilation, and air conditioning (HVAC) system has been an important facility for maintaining indoor air quality. However, the primary function of typical HVAC systems is to control the temperature and humidity of the supply air. Most indoor air pollutants, such as volatile organic compounds (VOCs), cannot be removed by typical HVAC systems. Thus, some air handling units for removing VOCs should be added in typical HVAC systems. Among all of the air cleaning techniques used to remove indoor VOCs, photocatalytic oxidation is an attractive alternative technique for indoor air purification and deodorization. The objective of this research is to investigate the VOC removal efficiency of the photocatalytic filter in a HVAC system. Toluene and formaldehyde were chosen as the target pollutants. The experiments were conducted in a stainless steel chamber equipped with a simplified HVAC system. A mechanical filter coated with Degussa P25 titania photocatalyst and two commercial photocatalytic filters were used as the photocatalytic filters in this simplified HVAC system. The total air change rates were controlled at 0.5, 0.75, 1, 1.25, and 1.5 hr(-1), and the relative humidity (RH) was controlled at 30%, 50%, and 70%. The ultraviolet lamp used was a 4-W, ultraviolet-C (central wavelength at 254 nm) strip light bulb. The first-order decay constant of toluene and formaldehyde found in this study ranged from 0.381 to 1.01 hr(-1) under different total air change rates, from 0.34 to 0.433 hr(-1) under different RH, and from 0.381 to 0.433 hr(-1) for different photocatalytic filters.

Purification of pharmaceutical excipients with supercritical fluid extraction

Supercritical fluid extraction (SFE), with carbon dioxide as the solvent, was tested for its ability to remove common reactive impurities from several pharmaceutical excipient powders including starch, microcrystalline cellulose (MCC), hydroxypropylcellulose (HPC), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Extraction of the small molecule impurities, formic acid and formaldehyde, was conducted using SFE methods under conditions that did not result in visible physical changes to polymeric excipient powders. It could be shown that spiked, largely surface-bound, impurities could be removed effectively; however, SFE could only remove embedded impurities in the excipient particles after significant exposure times due to slow diffusion of the impurities to the particle surfaces. Attempts at hydrogen peroxide extraction were hindered by its low solubility in CO2, thereby effectively precluding SFE for removal of hydrogen peroxide from excipients. This work suggests that SFE will only be commercially useful for removal of low molecular weight impurities in polymeric excipients when migration of the impurities to the particle surfaces is sufficiently rapid for extraction to be completed in a reasonable time frame.

[Development of the new desiccator system for measuring the removal effect of the formaldehyde as an indoor air pollutant by the adsorbent]

The new desiccator system with measures for the prevention of dew drops and the processing of the formaldehyde (FA) gas discharged from the final desiccator was produced, and the FA removal rate for various adsorbents was examined. For the prevention of dew drops in the desiccator, a hygroscopic bottle containing silica gel was used next to the FA gas generator, and humidity was adjusted by adjusting the interval between the FA gas outlet (a) and the desiccant (b). The removal of the harmful FA gas discharged from the final desiccator (n=5) is an important in the environmental preservation. To solve this problem, the FA gas was passed through an oxidation bottle containing KMnO(4)-H(2)SO(4) solution, and it was possible to confirm the complete decomposition of the FA by increase of the CO(2) and elimination of the FA. For the determination of the FA concentration in the desiccator, 100 ml air was beforehand collected using a gas collector into a 100 ml vial bottle containing 2 ml distilled water, and 50 ml of air from each desiccator was injected using a glass syringe. This was left under a slightly reduced pressure for 20 min, and the FA concentration was determined by the AHMT method. The FA removal rate after 1 h for each adsorbent (0.5 g) was 50% or more for chitin, KIMCO and silica gel. The removal efficacy for activated carbon was higher for fine particles than for coarse particles, and a dose-response relationship was established.

Electrochemical treatment of industrial wastewater

This paper presents the results of the treatment of phenolic compounds containing wastewater generated from phenol-formaldehyde resin manufacturing, oil refinery and bulk drug manufacturing industries by electrochemical method. Experiments were conducted at a fixed current density of 5.4 A/dm2 using Ti/TiO2-RuO2-IrO2 electrode and an undivided reactor. During the various stages of electrolysis, parameters such as COD and TOC concentrations were determined in order to know the feasibility of electrochemical treatment. Adsorbable organic halogens (AOX) were detected at high concentrations during the electrolytic treatment of the effluents. However, it was observed that increasing the electrolysis time bring down the AOX concentration to lower levels. Energy consumption and current efficiency during the electrolysis were calculated and presented. The present study proves the effectiveness of electrochemical treatment for highly concentrated bio-refractory organic pollutants present in the industrial wastewater.

Formaldehyde and urea removal in a denitrifying granular sludge blanket reactor

Simultaneous formaldehyde biodegradation, urea hydrolysis and denitrification in anoxic batch assays and in a continuous laboratory anoxic reactor were investigated. In batch assays, the initial formaldehyde biodegradation rate was around 0.7 g CH(2)Og VSS(-1)d(-1) and independent of the urea concentration (90- 370 mg N-NH(2)CONH(2)l(-1)). Urea was completely hydrolyzed to ammonium in the presence of 430 mg l(-1) formaldehyde and complete denitrification took place in all cases (125 mg N-NO(-)(3)l(-1)). Formaldehyde removal efficiencies above 99.5% were obtained in a lab-scale denitrifying upflow sludge blanket reactor at organic loading rates between 0.37 and 2.96 kg CODm(-3)d(-1) (625-5000 mg CH(2)Ol(-1)). The urea loading rate was increased from 0.06 to 0.44 kg Nm(-3)d(-1) (100-800 mg N-NH(2)CONH(2)l(-1)) and hydrolysis to ammonium was around 77.5% at all loading rates. The denitrification process was always almost complete (100-800 mg N-NO(3)(-)l(-1)), due to the high COD/N ratio of 6.7 in the influent. A minimum value of 3.5 was found to be required for full denitrification. The composition of the biogas indicated that denitrification and methanogenesis occurred simultaneously in the same unit. A good granulation of the sludge was observed.

[Study on the acquiring data time and intervals for measuring performance of air cleaner on formaldehyde]

OBJECTIVE

The measuring time and measuring intervals to evaluate different type of air cleaner performance to remove formaldehyde were provided.

METHODS

The natural decay measurement and formaldehyde removal measurement were conducted in 1.5 m3 and 30 m3 test chamber.

RESULTS

The natural decay rate was determined by acquiring formaldehyde concentration data at 15 minute intervals for 2.5 hours. The measured decay rate was determined by acquiring formaldehyde concentration data at 5 minute intervals for 1.2 hours. When the wind power of air cleaner is smaller than 30 m3/h or measuring performance of no wind power air clearing product, the 1.5 m3 test chamber can be used. Both the natural decay rate and the measured decay rate are determined by acquiring formaldehyde concentration data at 8 minute intervals for 64 minutes.

CONCLUSION

There were different measuring time and measuring intervals to evaluate different type of air cleaner performance to remove formaldehyde.

[Validation of a method for discrimination of formaldehyde processing in textile products]

It is important to investigate a cause of formaldehyde contamination exceeding a regulation limit value in a textile product. If formaldehyde was released from a textile product itself by treatment or processing with formaldehyde, an administrative guidance is given to a manufacture. On the other hand, when the formaldehyde migrated from other textile products or a furniture stand during displaying, an improvement instruction is performed to the store. Iwama et al. [Ann. Rep. Nagoya City Public Res. Inst., 42, 11-16 (1996)] developed a method for distinguishing fabric processing and migration by additional hydrolytic extraction using hydrochloric acid solution. This study was to confirm the reliability and stability of the method for knowing formaldehyde processing on textiles. Five laboratories evaluated three samples: unprocessed textile, processed textile and unprocessed but formaldehyde-migrated textile. For a processed textile sample, amounts of formaldehyde increased by additional extractions with acidic solution, so all laboratories judged that the sample had been treated with formaldehyde. In the cases of the other two samples, such increases were not observed in the extracts using acidic solution. All laboratories reported that these samples were not processed using formaldehyde but had absorbed a different level of formaldehyde by migration. In a series of experiments, the judgement about the existence of formaldehyde processing or migration is comparatively consistent among all laboratories. This validation study concluded that the distinguishing method adopting additional extractions with acidic solution is useful to find formaldehyde processing of textile, and to deal with processing and migration separately as a cause of formaldehyde contamination.

Study of effect of adsorptive building material on formaldehyde concentrations: development of measuring methods and modeling of adsorption phenomena

In this paper, a method is developed to assess the performance of adsorptive building materials that are used for reducing indoor pollutant concentrations. Mass transfer has a great influence on the materials' performance. To control the mass transfer rate precisely in the performance test, the authors have developed the Boundary-Layer-Type Small Test Chamber in which airflow along the test materials can be controlled precisely. A new index of adsorption performance, the equivalent ventilation rate (Q(ads)), is defined that corresponds to the mass transfer coefficient when the surface pollutant concentration is zero. Modeling and experimental verification of adsorption were done, demonstrating the pollutant concentration decrease caused by adsorptive building materials. The pollutant reduction phenomena were modeled, including pollutant degradation by chemical reaction and adsorption in building materials. Adsorption tests of gypsum board containing a substance that decomposes HCHO within the board are reported. The adsorption rate of the gypsum board predicted by numerical analysis (CFD, Computational Fluid Dynamics) corresponds well with experimental results.

PRACTICAL IMPLICATIONS

Development and verification of a method to measure the decrease in indoor pollutant concentration caused by an adsorptive building material are reported. Mass transfer has a great influence on the material's performance. The equivalent ventilation rate (Q(ads)) of the adsorption performance is defined as a new index that corresponds to the mass transfer coefficient. The equivalent ventilation rate (Q(ads)) can be used directly to compare the effect of pollutant concentration decrease via adsorption with the effect of ventilation.

[Oxidation treatment of formaldehyde-containing wastewater by electro-Fenton method]

The mechanisms of affecting factors in treating formaldehyde-containing organic wastewater by electro-Fenton reactor which had granular carbon as the filled electrode were investigated. The optimal operating conditions determined by orthogonal experiments and individual factor experiments were as following: 90 min, 25 V, 30 degrees C-40 degrees C, insulating carbon content 40%, Fe2+ concentration 300 mg/L at pH < 3.5. Formaldehyde degradation mechanisms were proposed after analyzing the oxidation products with UV absorbance spectrum. Experiment of treating the actual wastewater using this method were also performed. The removal rates of formaldehyde and CODCr were about 90%, 30%, respectively. In addition, the operating cost was 42.3% less than that of treatment by Fenton method.

Photocatalytic production of hydrogen in single component and mixture systems of electron donors and monitoring adsorption of donors by in situ infrared spectroscopy

The photocatalytic production of hydrogen using aqueous Pt/TiO2 suspension has been investigated in single component and mixture systems of electron donors (pollutants). The reaction systems consisted of oxalic acid, formic acid and formaldehyde, respectively. The adsorption of these donors on TiO2 was also monitored by in situ attenuated total reflection infrared spectroscopy (ATRIR). In the single component systems, the efficiency order of electron donors is as follows: H2C2O4 > HCOOH > HCHO. The order is consistent with the order of adsorption affinity of the electron donors on TiO2 determined by ATRIR, which suggests a link between the strength of surface interaction and the efficiency of photocatalytic hydrogen evolution. In the binary mixture systems, competitive inhibition kinetics is observed. When a donor adsorbed strongly on TiO2 in a state of saturated adsorption in a binary system, the overall rate of the hydrogen evolution is consistent with that of decomposition of the donor, and the system can be treated as a single component system.

Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater

Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification. In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass. The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium. Neither urea hydrolysis nor inhibition of nitrification was observed. Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1). The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea. Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates. In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9. Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio. The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios. A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification. Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.

Formalin removal from archival tissue by critical point drying

The extraction of high-quality nucleic acid may be problematic in formalin-fixed tissues because of cross-linking between proteins and DNA. Old fixed tissue specimens do produce fragmented DNA (<1.2 kb), which is only used for PCR amplification. Here we show that high molecular weight DNA (>194 kb) can be successfully extracted from fixed tissue samples (16-70 years old) by gradual dehydration and critical point drying. The reliability of extracted DNA was measured by its ability to serve as a template for the amplification of mtDNA fragments (403 and 1198 bp) and an nDNA fragment (1844 bp). In addition, fingerprinting analysis was performed using DNA from fixed human tissue to ensure the ability of extracted DNA to hybridize with the DNA probe. DNA derived by this method can be subject to amplification, complete digestion by restriction endonuclease, and hybridization.

Infrared spectrum of the complex of formaldehyde with carbon dioxide in argon and nitrogen matrices

The complex of formaldehyde with carbon dioxide has been studied by infrared spectroscopy in argon and nitrogen matrices. The shifts relative to the free species show that the complex is weak and similar in argon and nitrogen. The results give evidence for T-shaped complexes, which are isolated in several configurations. Some evidence is also presented which indicates that, in addition to the two well-known sites in argon, carbon dioxide can be trapped in a third site.

Comparison of the indoor air quality in mould damaged and reference buildings in a subarctic climate

The purpose of this study was to search for objective parameters most relevant to indicate microbial problems of buildings in cold climate. Various indoor characteristics were compared in nine buildings with known history of moisture problems and visible mould (index) and in nine matched reference buildings. The concentrations of airborne viable fungal had a clear difference between the two groups of buildings. In this study, airborne concentrations of viable bacteria, formaldehyde, total volatile organic compounds (TVOC) and the occurrence of house dust mites in these index buildings were compared with the levels of the pollutants in matched reference buildings. Fungal growth and flora on moist building materials were also studied. The concentrations of TVOC were slightly higher in the index buildings than in the reference buildings. However, the differences in the concentrations or appearance of any of the studied pollutants were not significant. These parameters do not seem to be relevant indicators of microbial growth or surrogates of microbial exposure. Thus, fungal concentration and composition of fungal genera in the air still seems to be the best indicator for moisture problems among the studied pollutants. In the moist building materials, some fungal genera, such as Ulocladium and Chaetophoma were detected that were not found in indoor air showing that building material samples give additional information on the microflora of the building.

Simultaneous supercritical fluid derivatization and extraction of formaldehyde by the Hantzsch reaction

A study where the Hantzsch reaction is used to produce the chemical derivatization of formaldehyde in a supercritical medium is presented in this paper. Pressure, temperature and other parameters such as static and dynamic extraction time must be optimized to increase the yield of this kinetically controlled reaction. A 2(5-1) (resolution V) factorial design was used to study the significant parameters affecting the supercritical process in terms of resolution and sensitivity. A subsequent central composite design was employed to find the conditions of maximum response. Ultraviolet-visible spectrophotometry was used as the detection technique. The optimum conditions were used for the determination of formaldehyde in real finger-paints by means of the previous addition of known quantities of this analyte to the paint. Results were compared with those obtained with supercritical fluid extraction and subsequent chemical derivatization and an improvement of sensitivity as well as a reduction of time of analysis, solvent waste and reagents consumption were observed.

Formaldehyde prepared from paraformaldehyde is stable

For critical histological investigations, tissue fixation is sometimes carried out in formaldehyde freshly prepared from paraformaldehyde by heating. The purity of formaldehyde produced in this way is superior to that of commercial stock solutions. We studied the stability of freshly prepared formaldehyde solutions by determination of pH and titration of acid, which reflect the formation of formic acid. It was found that very small amounts of acid are produced during the heating of paraformaldehyde. Prolonged heating or storage of freshly prepared formaldehyde for up to 8 days did not significantly increase the amount of acid. It was also found that heating of the paraformaldehyde is not necessary, since depolymerization may take place at room temperature. We conclude that formaldehyde prepared from paraformaldehyde remains stable for considerable periods of time, and it is therefore unnecessary to prepare it immediately prior to fixation. Also, in many cases, buffering of the fixative may be omitted, since only minor changes in the pH occur during fixation.