Initial Formaldehyde Concentration Research Articles

Novel resource utilization of fly ash and blast furnace slag for formaldehyde-degrading alkali-activated cementitious composite

Herein, alkali-activated cementitious materials (AACM) were fabricated using fly ash and blast furnace slag as raw materials, while foamed alkali-activated cementitious materials (FAACM) were prepared by a physical foaming method. They were regarded as suitable supporting carriers to load nano-TiO2 by a three-layered method and blending-foaming method to synthesize TiO2-AACM and TiO2-FAACM, respectively. The relationship between the microstructure of the alkali-activated cementitious composites with the photocatalytic activity and stability of formaldehyde degradation was revealed. The nano-TiO2 blended with AACM and FAACM exhibited good mechanical properties. Moreover, a systematic mechanism study revealed that the incorporation of nano-TiO2 did not change the hydration products of composites. There were similar forbidden bandwidths in TiO2-AACM and TiO2-FAACM compared with nano-TiO2, as nano-TiO2 was not involved in geopolymerization. The degradation efficiency of formaldehyde by TiO2-AACM and TiO2-FAACM attained 52.21 % and 55.02 %, respectively, at an initial formaldehyde concentration of 20 ppm after illumination (300 W Xe lamp) of 2 h. It was found that the excellent porous structure of FAACM promoted the adsorption efficiency of formaldehyde in the composites, which contributed to the higher photocatalytic degradation efficiency of formaldehyde. Compared with Portland cement, the CO2 emission of alkali-activated cementitious materials made from fly ash and blast furnace slag was decreased by 61.28 %. This research promotes the comprehensive utilization of solid wastes for developing the functionalized application of green materials.

Performance extrapolation of an ultraviolet-based photocatalytic air purifier against near-ambient-level formaldehyde

The practical utility of an air purifier (AP) with built-in adsorbent/catalyst-based filtration systems is assessed for the treatment of indoor volatile organic compounds (VOCs) through extrapolation of its performance based on a lab-scale chamber study. The feasibility of a commercial prototype AP unit with TiO2-based filters is tested in this work against 0.5–5 ppm formaldehyde (FA) in a 17 L chamber with an air recirculation rate of 565 h−1 under the control of key process variables (e.g., initial FA concentration, flow rate, and dark/light conditions). The performance of the AP unit is evaluated by the clean air delivery rate (CADR), quantum yield, and space time yield in diverse operation settings (e.g., photocatalysis only or along with adsorption). The effects of ultraviolet (UV) irradiation are evident as the CADR value of 5 ppm FA sharply increases from 5.67 (UV-off) to 15 L/min (UV-on): however, the CADR values increase only slightly (12 to 15 L/min) as the recirculation flow rate changes from 100 to 160 L/min, respectively. Further, FA concentration vs. time relationship exhibit an apparent bimodal exponential decay, with the fastest and near 100 % removal at [FA] < 0.5 ppm. The performance of the proposed AP platform in relatively large real-world volume (e.g., 4 m3, 2.4 h−1 air recirculation rate) is further estimated through extrapolation to offer valuable guidelines for the construction of AP systems in real-world applications.

Experimental Study on Ultra-Low Concentration Methane Regenerative Thermal Oxidation

As a major coal country, China faces the issue of significant gas emissions during the coal mining process. This study aims to improve the utilization efficiency of mine gas, reduce greenhouse gas emissions, and promote the low-carbon and green transformation of the coal industry. A 10 kW gas regenerative thermal oxidizer (RTO) experimental system was constructed. The effects of initial methane concentration, low-temperature flue gas proportion, and operating load on combustion temperature, methane oxidation rate, high-temperature flue gas energy, and system thermal efficiency were studied. The results show that when the combustion temperature is below 600 °C, the CH4 combustion reaction cannot proceed effectively, and the system temperature continuously decreases and cannot be maintained stably. The experiment determines the stable operating methane concentration range of the RTO. In this experimental system, the lower limit of the initial methane concentration is 0.28%, corresponding to an 86% methane oxidation rate. As the initial methane concentration decreases, the combustion temperature also decreases, and the methane oxidation rate follows suit. The higher the low-temperature flue gas proportion, the higher the combustion temperature, and the system’s thermal efficiency and output heat decrease with the increase in the low-temperature flue gas proportion. This experiment explores multiple factors affecting regenerative thermal oxidation, providing a basis for ensuring the safe and stable operation of the system and its optimization. Improving the thermal insulation and heat exchange performance of the storage body can expand the lower limit of the initial methane concentration, thereby increasing the stability and thermal efficiency of the system.

Study on the effect of humidity on formaldehyde emission parameters of wood-based panels

Wood-based panels are a significant source of indoor volatile organic compounds (VOCs), crucial for managing indoor pollution. The emissions from wood-based panels are influenced by both intrinsic factors, including their composition and manufacturing process, and extrinsic environmental conditions, such as temperature and humidity. In this paper, the emission of formaldehyde in plywood was studied under different temperature conditions (15°C, 23°C, 32°C and 37°C) and different humidity conditions (40%, 60% and 80%) by environmental chamber method. To understand the influence of relative humidity on the key parameters of panels from a mechanism perspective, this paper investigates the influence of relative humidity on the initial emittable concentration of formaldehyde, based on the hydrolysis reaction of urea-formaldehyde resin. Concurrently, the molecular dynamics and porous panels model were amalgamated to assess the influence of relative humidity on both the partition and diffusion coefficient. To simulate the emission process in a real environment, a control equation that allows for variations in both temperature and humidity is needed. This paper employs the method of variable separation to derive a simplified control equation. Subsequently, experimental data was utilized to validate the derived equation’s effectiveness within the practical indoor environmental range.

Obtainment and Inoculation of Acinetobacter pittii Strain JJ-2, and Combined Action with Plants for Formaldehyde and CO2 Removal: A Research Study.

A formaldehyde-degrading bacterium JJ-2 was isolated from the rhizosphere of Chlorophytum and identified as Acinetobacter pittii by colony morphology and 16S rDNA sequence analysis. Further studies showed that under optimal conditions, JJ-2 could maintain activity for six cycles at an initial formaldehyde concentration of 450mgL-1. At the same time, the complete degradation time was shortened from 12 to 6h. When the JJ-2 strain was inoculated into sterile soil, the surface spray method had the best effect, and the removal efficiency of 5ppm formaldehyde increased by 22.63%. In an actual potted plants system colonized with strain JJ-2, the first and second fumigations (without re-inoculation) increased removal by 1.36 times and 0.92 times during the day and 1.27 times and 2.07 times at night. In addition, in the second fumigation, the plant-bacteria combined system was 693.63ppm and the plant system was 715.34ppm, effectively reducing the CO2 concentration. This study provides an economical, ecological, and efficient approach to improve the combined system of plants and bacteria to remove gaseous formaldehyde from indoor air, with a positive impact on carbon neutrality.

Formaldehyde Removal by Expanded Clay Pellets and Biofilm in Hydroponics of a Green Wall System

Air pollution with formaldehyde (FA) has been an emerging concern over recent years. This study was aimed at evaluating the contribution of green wall system-derived expanded clay pellets (ECP) and biofilms to FA removal in liquid phase. The effects of four plant species on this process were compared. An inhibition of the fluorescein diacetate hydrolysis activity of biofilm-derived microorganisms was detected during the exposure to FA in both air and liquid phases, and this effect was plant-species-specific. Liquid chromatography with a UV detector was applied for the quantification of FA. The FA removal activity of ECP in the liquid phase was 76.5 mg ECP−1 after a 24 h incubation in the presence of 100 mg/L FA, while the removal activity of the biofilm differed depending on the plant species used, with the highest values detected in the set with Mentha aquatica, i.e., 59.2 mg ECP−1. The overall FA removal from the liquid phase during 24 h varied in the range from 63% to 82% with the initial FA concentration of 100 mg/L. Differences in biofilm formation upon ECP enrichment were detected by using confocal laser scanning microscopy. These results contribute to the understanding of air biofiltration mechanisms in hydroponic systems.

The impact of operational factors on degradation of formaldehyde as a human carcinogen using Ag3 PO4 /TiO2 photocatalyst.

Background: The International Agency for Research on Cancer (IARC) identified formaldehyde as a carcinogen in 2004, yet formaldehyde is widely used in health care settings and various industries. In recent years, photocatalytic oxidation has been developed as a potential technique for removing pollutants arising from organic chemical agents and consequently promoting the health indices. This study investigated the effect of operational factors in optimizing formaldehyde removal from the air using Ag3 PO4 /TiO2 photocatalyst. Methods: An experimental study was designed to investigate the effect of operational factors on the efficiency of formaldehyde degradation. The variables investigated in this study include pollutant retention time, initial pollutant concentration and relative humidity. Sol-gel method was used to synthesize the nano-composite photocatalyst. An ideal experimental design was carried out based on Box-Behnken design (BBD) with response surface methodology (RSM). The sample size in this study includes all the glasses coated with Ag3 PO4 /TiO2 photocatalyst. Results: The maximum formaldehyde degradation of 32% was obtained at the initial concentration of 2 ppm, 20% relative humidity, and 90 minutes of retention time. Based on the statistical results, the correlation coefficient of the present study for the impact of operational factors on formaldehyde degradation was 0.9635, which means that there is only 3.65% probability of error in the model. Conclusion: The operational factors examined in this study (retention time, relative humidity, and initial formaldehyde concentration) were significantly influential in the degradation efficiency of formaldehyde by the photocatalyst. Due to the high exposure of employees and clients of health and treatment centers to formaldehyde as a carcinogenic substance, the results of this study can be used in ventilation systems to remove environmental pollutants in health care centers and other occupational settings.

Simultaneous influence of light and CO2 on phytoremediation performance and physiological response of plants to formaldehyde

Phytoremediation technology is an effective method to remove formaldehyde indoors, but the purification capacity and physiological response of plants to formaldehyde under the simultaneous influence of light and CO2 have not been examined in previous studies. In this study, formaldehyde fumigation experiments were conducted on the C3 plants Epipremnum aureum A. and Chlorophytum comosum L., and the crassulacean acid metabolism (CAM) plant Dieffenbachia maculate A. The phytoremediation performance and physiological response of plants were studied. The initial concentration of formaldehyde was established at 11.950 ± 1.442 [Formula: see text]; the light intensities were 448 ± 7 [Formula: see text], 1628 ± 22 [Formula: see text], and 3259 ± 22 [Formula: see text], respectively; and the concentrations of CO2 were 455 ± 29 [Formula: see text], 978 ± 50 [Formula: see text], 2020 ± 66 [Formula: see text], and 3006 ± 95 [Formula: see text], respectively. The results indicated that the highest purification rates of formaldehyde by E. aureum, D. maculata, and C. comosum were 55.8%, 43.7%, and 53.2%, respectively. The light intensity had a positive effect on the formaldehyde purification rates of all three plants and positively stimulated peroxidase (POD) activity, while the CO2 concentration had no significant impact on the formaldehyde purification capacity and plants' physiological characteristics. Exposure to formaldehyde inhibited formaldehyde dehydrogenase (FADH) activity and positively stimulated catalase (CAT) activity. The superoxide dismutase (SOD) activity positively correlated with the formaldehyde purification capacity of plants.

Experimental study and kinetic model analysis on photothermal catalysis of formaldehyde by manganese and cerium based catalytic materials

ABSTRACT Modern people spend more and more time in cars in their daily lives, and the pollution of formaldehyde in the car may directly affect people’s health. Thermal catalytic oxidation technology by solar light is a potential way to purify formaldehyde in cars. MnOx-CeO2 was prepared by the modified co-precipitation method as the main catalyst, and the basic characteristic (SEM, N2 adsorption, H2-TPR, UV-visible absorbance) were also analyzed in detail. The experimental study was set up to simulate the solar photothermal catalysis of formaldehyde in-car environment. The results showed that the higher the temperature in the experimental box (56.7 ± 0.2°C, 62.6 ± 0.2°C, 68.2 ± 0.2°C), the better the formaldehyde degradation by catalytic effect (formaldehyde degradation percentage: 76.2, 78.3, 82.1). With increase of the initial formaldehyde concentration (200 , 500 , 1000 ), the catalytic effect first increased and then decreased (formaldehyde degradation percentage: 63, 78.3, 70.6). The catalytic effect risen gradually with the increase of load ratio (10, 20, and 40), and the formaldehyde degradation percentages were 62.8, 78.3, and 81.1, respectively. According to the expressions of the Eley-Rideal (ER) model, the Langmuir-Hinshelwood (LH) model, and the Mars-Van Krevelen (MVK) model, the experimental results were fitted and verified, and it was found that the ER model had a high degree of fit. It is more suitable to explain the catalytic mechanism of formaldehyde by MnOx-CeO2 catalyst in the experimental cabin, where formaldehyde is in the adsorption state and oxygen is in the gas phase. Implications: Judging from the current research status, vehicles have become an indispensable mode of travel for people, and the air quality in the vehicle is not optimistic. Most vehicles generally have the phenomenon of excessive formaldehyde. The characteristic of formaldehyde in the car is the continuous release, especially in the hot summer, the temperature inside the car rises sharply under the sun radiation. At this time, the formaldehyde concentration exceeds the standard by 4 to 5 times, which can cause great damage to the health of the passengers. In order to improve the air quality in the car, it is necessary to adopt the correct purification technology to degrade formaldehyde. The problem brought by this situation is how to effectively use solar radiation and high temperature in the car to degrade formaldehyde in the car. Therefore, this study uses the thermal catalytic oxidation technology to catalyze the degradation of formaldehyde in the high temperature environment of the car in summer. The selected catalyst is MnOx-CeO2, mainly because manganese oxide (MnOx) itself is the most effective catalyst for volatile organic compounds (TCO) among transition metal oxides, and CeO2 has excellent oxygen storage and release capacity and Oxidation activity, which helps to improve the activity of MnOx. Finally, the effects of temperature, initial concentration of formaldehyde and catalyst loading on the experiment were explored, and the kinetic model of thermal catalytic oxidation of formaldehyde with MnOx-CeO2 catalyst was analyzed to provide technical support for the future application of this research in practice.

Peroxymonosulfate activation based on Co9S8@N−C: A new strategy for highly efficient hydrogen production and synchronous formaldehyde removal in wastewater

Formaldehyde (FA), as an important chemical raw material, has been widely used in many fields. However, the discharge of a large amount of FA-containing wastewater poses a serious threat to the environment and human health. Recently, the in-situ hydrogen energy release technology of hydrogen-containing stable liquid has been extensively explored due to its safe storage. Exploring a robust method to achieve FA removal and synchronous in-situ hydrogen release from FA containing wastewater is of great significant for environmental protection and energy crisis alleviation. Here, we have innovatively introduced peroxymonosulfate (PMS) activation technology into FA removal and hydrogen production simultaneously. The composite of nitrogen doped carbon coating Co9S8 nanotubes (Co9S8@N−C) is employed as a proof of concept for FA decomposition and simultaneously hydrogen production based on PMS activation system. As expected, the Co9S8@N−C/PMS system presents much superior hydrogen production efficiency and satisfactory FA removal rate towards FA wastewater than those of common catalysis, photocatalysis and Fenton reaction in the basic condition in a wide range of FA concentration. The hydrogen yield reaches a value as high as 471 μmol within 60 min, corresponding to a FA degradation rate of 30% with an initial FA concentration of 0.722 mol L−1. Characterizations and density functional theory (DFT) calculations suggest that the free radical process dominated by superoxide radical (O2⋅−) and nonradical process dominated by singlet oxygen (1O2), which are induced by Co9S8@N−C/PMS system, are responsible for highly efficient hydrogen production via FA degradation. These generated O2⋅−and 1O2 can extract ⋅H from FA to form ⋅OOH intermediate, which can further combine with the ⋅H from water to produce hydrogen. This study provides an applicable technique for environmental purification and new energy development based on FA containing wastewater.

Experimental study of the dissociation of a double gas hydrate with a change in the initial height of the layer

In this work, experimental studies of the dissociation of methane-ethane hydrate with and without combustion are carried out with a change in the initial height of the layer. Gas hydrate powder with an initial height of 3 and 15 mm was used. In the samples, the initial concentration of methane is 64% and ethane is 36%. An increase in the initial height of the powder layer led to a 1.3-fold increase in the flame front velocity. Due to the increase in the initial height of the layer, the dissociation rate decreases by 7.2 times before combustion and by 4.1 times during combustion.

Kinetics of Liquid-Phase Condensation of Propylene with Formaldehyde over H–MFI and H–BEA Zeolites

This study investigated the kinetic patterns of the liquid-phase Prins condensation of propylene with formaldehyde in the range of 120–180°C over H–MFI and H–BEA zeolites. The apparent reaction order with respect to formaldehyde was found to vary between 0.1 and 0.2 for H–BEA and to be close to zero for H–MFI. The apparent activation energy for H–MFI and H–BEA was 26.1±0.6 kJ/mol and 20.0±4.0 kJ/mol, respectively. Based on these results, the reaction was demonstrated to occur in the intradiffusion or transition region; the calculated Thiele modulus and effectiveness factor further confirmed this fact. The diffusion limitations were partially removed by raising the initial formaldehyde concentration, as indicated by an increase in the apparent order of formaldehyde conversion to 1.0 for H–BEA and to 0.4 in the H–MFI case. To describe the substrate transformations observed, a modernized reaction mechanism was proposed.

Enhanced Methane Oxidation Potential of Landfill Cover Soil Modified with Aged Refuse

Aged refuse with a landfill age of 1.5 years was collected from a municipal solid waste landfill with high kitchen waste content and mixed with soil as biocover material for landfill. A series of laboratory batch tests was performed to determine the methane oxidation potential and optimal mixing ratio of landfill cover soil modified with aged refuse, and the effects of water content, temperature, CO2/CH4, and O2/CH4 ratios on its methane oxidation capacity were analyzed. The microbial community analysis of aged refuse showed that the proportions of type I and type II methane-oxidizing bacteria were 56.27% and 43.73%, respectively. Aged refuse could significantly enhance the methane oxidation potential of cover soil, and the optimal mixing ratio was approximately 1:1. The optimal temperature and water content were about 25 °C and 30%, respectively. Under the conditions of an initial methane concentration of 15% and an O2/CH4 ratio of 0.8–1.2, the measured methane oxidation rate was negatively correlated with the O2/CH4 ratio. The maximum methane oxidation capacity measured in the test reached 308.5 (μg CH4/g)/h, indicating that the low-age refuse in the landfill with high kitchen waste content is a biocover material with great application potential.

Study of manganese–cerium composite oxide catalysed oxidation for low concentration formaldehyde at room temperature

Catalytic oxidation at room temperature is a promising alternative approach for indoor formaldehyde elimination. However, the development of non-precious metal room temperature catalysts is still highly challenging. In this study, manganese-cerium composite oxides (MC) were developed and optimized. The removal performance of low concentrations of formaldehyde at room temperature was comprehensively evaluated. Formaldehyde removal was achieved with MC under dark at a level comparable to that of the commercial P25 catalyst. The removal efficiency of 90.9% in 24 h at room temperature was obtained for the initial formaldehyde concentration of 1.2 ± 0.1 ppm. Using electron paramagnetic resonance spectroscopy, free radicals were confirmed to play a key role in formaldehyde degradation on MC. Formate was detected as the main intermediate product by in situ DRIFTs, and the mechanism of MC catalytic oxidation at room temperature was deduced.

Effect of methane flow rate on gas-jet MPCVD diamond synthesis

The paper describes synthesis of diamonds by the method of gas-jet deposition with microwave activation of precursor gases. This method involves the use of a supersonic jet for delivering the components activated in the discharge chamber to the substrate located in the deposition chamber. A series of experiments was carried out with different amounts of methane supplied at a hydrogen flow rate of 8000 sccm. The obtained samples of diamond coatings were studied by scanning electron microscopy and Raman spectroscopy. The temperature of the mixture and the intensities of H, CH, and C2 lines in the plasma of the discharge chamber were measured by optical emission spectroscopy. The values of pressure and temperature in the discharge chamber were used to estimate the composition of the mixture. Thus, the numerical dependences of the molar concentrations of CH3, CH, C2 and C2H2 on the initial concentration of methane have been obtained. These dependences are in qualitative agreement with the dependences of the intensities of H, CH, and С2 lines. The numerical-experimental study performed allows us to conclude that the optimal value of methane concentration in the supplied mixture for the gas-jet deposition method in the considered range of parameters is about 1%.

Hamiltonian chemical kinetics for studying roaming in formaldehyde dissociation: Linear and nonlinear models

A recently developed theory for formulating chemical kinetics with a Hamiltonian theory similar to classical mechanics is applied to study linear and nonlinear kinetic models for the photodissociation of formaldehyde ( H 2 CO ) via roaming pathways. Chemical kinetic equations are proposed by mapping time invariant phase space structures, such as stationary points of the potential energy surface and periodic orbits, to relevant intermediate chemical species. Solving kinetic equations in the Hamiltonian framework, we calculate reaction paths to asymptotically stable equilibria for closed reactions and varying the initial concentration of H2CO at constant temperature and pressure. The reaction paths may be classified by defining a thermodynamic distance between initial and equilibrium states, as well as the entropy production. A brusselator-type nonlinear model is proposed as the phenomenological equivalent to the periodic orbit description of roaming mechanism given before. Treating the photodissociation of formaldehyde as an open system and properly selecting the rate coefficients of the reactions and the initial concentration of formaldehyde, a periodic orbit emanates as the result of a Hamiltonian Hopf bifurcation. This yields an oscillatory reaction between the two long-range metastable intermediates, { H…CHO } and { H…HCO }, which lead to radical and molecular products.

Improving Formaldehyde Removal from Water and Wastewater by Fenton, Photo-Fenton and Ozonation/Fenton Processes through Optimization and Modeling

This study aimed to assess, optimize and model the efficiencies of Fenton, photo-Fenton and ozonation/Fenton processes in formaldehyde elimination from water and wastewater using the response surface methodology (RSM) and artificial neural network (ANN). A sensitivity analysis was used to determine the importance of the independent variables. The influences of different variables, including H2O2 concentration, initial formaldehyde concentration, Fe dosage, pH, contact time, UV and ozonation, on formaldehyde removal efficiency were studied. The optimized Fenton process demonstrated 75% formaldehyde removal from water. The best performance with 80% formaldehyde removal from wastewater was achieved using the combined ozonation/Fenton process. The developed ANN model demonstrated better adequacy and goodness of fit with a R2 of 0.9454 than the RSM model with a R2 of 0. 9186. The sensitivity analysis showed pH as the most important factor (31%) affecting the Fenton process, followed by the H2O2 concentration (23%), Fe dosage (21%), contact time (14%) and formaldehyde concentration (12%). The findings demonstrated that these treatment processes and models are important tools for formaldehyde elimination from wastewater.

Long-term indoor formaldehyde variations and health risk assessment in Chinese urban residences following renovation

Formaldehyde is a ubiquitous indoor gaseous pollutant classified as a human carcinogen. Indoor formaldehyde concentrations tend to change over time in newly renovated buildings. However, this variation is not typically considered in inhalation cancer risk assessments. In this study, long-term indoor formaldehyde concentrations in newly renovated residences in China were collected from related literature. A total of 66 data sets collected from 42 different studies in 38 cities were analyzed. An exponential model was used to describe the variation patterns of indoor concentrations. The distribution of initial indoor formaldehyde concentrations immediately after renovation (Ca0) and the decay constant (k) were then obtained. The mean values of Ca0 and k were 0.376 mg/m3 and 1.98 × 10−4 h−1, respectively. Exposure model was revised by considering the long-term variation characteristics. The inhalation health risks related to formaldehyde exposure were then estimated. The median cancer risk was 3.41 × 10−5, and the probability of exceeding the acceptable risk was 99%. The median cancer risk decreased by 40% and 60% if the start time of room occupancy was increased to 0.5 y and 1 y after renovation, respectively. k (>1 y) contributed the most to the variation in cancer risk, followed by Ca0 (>1 y). Ignoring the decay of indoor formaldehyde concentrations overestimates the health risks related to exposure to formaldehyde in newly renovated residences. Our results present a more accurate method for determining human health risks related to indoor formaldehyde that can also be applied to other volatile organic compounds.

Platinum-supported aluminum oxide on activated carbon filter media for removal of formaldehyde in the indoor condition

Formaldehyde is one of the hazardous indoor air pollutants which have harmful effects on humans, domestic animals, and environmental health. The goal of this study was to synthesize a Pt/Al2O3 coated on granular activated carbon (GAC), which is easily recoverable and can be used as an absorbent for formaldehyde removal from polluted indoor air. Moreover, the Pt/Al2O3 catalyst could achieve complete and stable HCHO oxidation at ambient temperature. The characteristic properties of the Pt/Al2O3/GAC sample were analyzed using scanning electron microscopy, energy-dispersive spectrometer, Fourier-transform infrared spectroscopy, and Brunauer–Emmett–Teller techniques. The Pt/Al2O3/GAC catalyst was investigated to determine the catalytic performance with regard to formaldehyde (HCHO) oxidation under different face velocity and initial formaldehyde concentration applicable to a building environment. It was revealed that the removal capacity of Pt/Al2O3 catalyst reached a maximum of 2.23 mg g−1 during 0.1 m s−1 face velocity and 0.75 ppm HCHO inlet concentration. Among zero-, first- and second-order reaction kinetic model, the correlation coefficient of the first-order reaction kinetic model (0.7948 < R2 < 0.9249) and second-order reaction kinetic model (0.6056 < R2 < 0.8146) is lower than zero-order reaction kinetic model (0.9352 < R2 < 0.9921) of Pt/Al2O3 catalyst. The oxidation kinetic of HCHO was well fitted with the zero-order reaction for Pt/Al2O3 catalyst. This study provides some instructions for the design and manufacture of environmentally harmless and cost-effective catalysts with excellent catalytic oxidation properties to remove HCHO at room temperature.

Isolation, Identification, and Degrading Characteristics of an Oil Resistant Formaldehyde-Degrading Bacterium

In recent years, the health risks of cooking oil fumes have been widely concerning. Since formaldehyde is one of the major pollutants emitted from cooking oil fumes, the degradation of formaldehyde should be investigated. Due to the advances and innovations in the degradation of pollutants, biodegradation was evaluated in this research. In this study, we screened out the strain of XF-1, which can degrade formaldehyde from cooking oil fume condensates. The strain of XF-1 was identified as Bacillus amyloliquefaciens sp. by a sequence analysis combing morphology, physiological, and biochemical experiments. The degrading characteristics of the strain were further studied. In the medium with a formaldehyde concentration of 100 mg·L-1, the efficiency of XF-1 for degrading formaldehyde was 95.80% within 34 h. When the initial concentration of formaldehyde was <300 mg·L-1, the XF-1 strain could completely degrade the formaldehyde within 120 h. When the formaldehyde concentration was 800 mg·L-1, the degradation rate of the XF-1 strain reached 73.01% at 96 h. The maximum tolerated concentration of formaldehyde was 1500 mg·L-1. According to a single factor experiment (pH, inoculation amount, formaldehyde concentration, and temperature), the influence of each factor on the degradation of formaldehyde was studied. The optimal growth condition of the strain was 30℃ at pH 6 with an inoculum amount of 10%. The degradation specificity of formaldehyde was studied by comparing it with that of other bacillus species. The results showed that XF-1 strain was specific with regard to the function of degrading formaldehyde and was able to withstand a high oil environment. The maximum tolerable oil concentration of XF-1 was 900 g·L-1. By analyzing the extracellular metabolites, it was determined that the metabolic pathway of formaldehyde degradation was the RuMP assimilation pathway. In this paper, a strain of formaldehyde degrading bacteria that was also resistant to oil was screened out and its metabolic mechanism was studied. The results indicated that the bacteria had broad application prospects in the treatment of formaldehyde emitted from cooking oil fumes.