Ppm Formaldehyde Research Articles

Highly selective detection of ppb-level formaldehyde realized by regulating the surface chemisorbed oxygen of Ga-doped In2O3 microspheres

Formaldehyde is a ubiquitous indoor pollutant. Developing metal oxide semiconductors gas sensors for selective ppb-level formaldehyde detection is challenging. Therefore, developing gas sensors that can selectively detect indoor formaldehyde at ppb levels is important. In this study, outer-walled thin sheet-like microspheres of Ga-doped In2O3 (GaxIn2-xO3, x = 0, 0.1, 0.2, 0.3, and 0.4) were fabricated using a facile two-step synthetic method. The Ga0.3In1.7O3 based sensor shows the response (556 ± 25) to 100 ppm formaldehyde at 80 °C, which is around 6.5 times that of the pure In2O3 based sensor at 90 °C. Furthermore, it has fast response time (< 3 s), excellent selectivity (SFormaldehyde/SEthanol = 160, SFormaldehyde/SAcetone = 267), good stability (at least 60 days), and ultra-low limit of detection (10 ppb) for formaldehyde at 80 °C. The improved formaldehyde sensing performance of Ga0.3In1.7O3 microspheres is attributed to the optimization of surface chemisorbed oxygen, which is caused by Ga doping regulating the Fermi level of In2O3 as well as an increase in the specific surface area.

Adsorption dynamics of gaseous toluene with and without formaldehyde and water vapors on composites of UiO-66-NH2 and microporous carbon

To improve the adsorption capacity/selectivity of activated carbon (AC) against diverse volatile organic compounds (VOCs), a series of AC-based composites have been prepared with UiO-66-NH2 (U6N) and coded as AC-U6Nx (x = 1–20 wt/wt%). The adsorption potential of AC-U6Nx is evaluated against toluene in relation to the effects of composite compositions and the presence of competing feed gases/vapors (e.g., formaldehyde (FA) and water vapor). Although AC-U6N(1%) adsorbs toluene preferentially over FA, the selectivity factor of the former decreases from 6.4 to 2.63 as the x value increases from 1 to 20 wt%. This indicates the crucial role of U6N-NH2 groups in active capturing of FA over toluene through Schiff-base adsorption mechanism. Interestingly, the partition coefficient (PC100%: 0.045 ± 0.004 mol kg−1 Pa−1) of AC-U6N(1%) for 100 ppm FA remains nearly constant across varying toluene levels (1–100 ppm), suggesting the preferential occupation of active sites by FA (pore-filling). The contrasting role of relative humidity (RH) is also evidenced, as AC-U6N(1%), exhibits the highest capacity for toluene and FA under dry (0 % RH) and humid (20 % RH) conditions, respectively. The adsorption behavior of VOC on AC-U6N(1%) surface active sites (e.g., graphitic basal planes, NH2, COO–, and Zr sites) is predictable with a good fit of experimental data to the Freundlich isotherm and pseudo-second-order (PSOM) kinetic models. A density functional theory (DFT) simulation supports the enhancement of toluene adsorption on the interface of AC and U6N-based systems. Overall, this work offers practical guidelines for the construction of advanced functional adsorbents against diverse VOCs under both competitive and non-competitive conditions.

Magnetic Field Assisted Enhanced Sensitivity of Nonferromagnetic Materials Boosting the Carrier Transfer: Mechanistic Studies.

The performance of semiconductor sensors is determined by reaction kinetics, conductivity, and electron mobility, which are undoubtedly closely related to the electron motion behavior. Therefore, the effective regulation of electronic states is crucial for improving gas sensing properties. Previous methods of enhancing the gas-sensing performance have induced complex material modifications, and the extent of performance improvement is usually very limited. Further optimization of the gas sensing performance requires continuous efforts to advance new technologies. Toward this issue, a novel magnetic field-induced strategy is adopted to boost the carrier transfer efficiency of nonferromagnetic semiconductors. The gas sensing investigation results manifest that the applied magnetic field can effectively enhance the sensitivity and reduce the baseline resistance. The In2O3 NC-2 (In2O3 nanocubes) with an applied magnetic field have a greatly enhanced response of 161.4 toward 100 ppm formaldehyde, which is 2.5 times higher than that without magnetic field. The enhanced gas sensing properties can be mainly attributed to magnetization of reactive materials, which makes the orientation of electronic magnetic moments consistent, thus greatly contributing to reactivity. This work introduces a practical approach to effectively improve gas sensing performance without further morphology optimization, noble metal catalysis, structural modification, and material cladding. The results of this study provide new insights for designing novel gas sensors to improve the gas sensing performance.

Emerging 2D nanoscale metal oxide sensor: semiconducting CeO2nano-sheets for enhanced formaldehyde vapor sensing.

Herein, we fabricated nanoscale 2D CeO2sheet structure to develop a stable resistive gas sensor for detection of low concentration (ppm) level formaldehyde vapors. The fabricated CeO2nanosheets (NSs) showed an optical band gap of 3.53 eV and cubic fluorite crystal structure with enriched defect states. The formation of 2D NSs with well crystalline phases is clearly observed from high-resolution transmission electron microscope (HRTEM) images. The NSs have been shown tremendous blue-green emission related to large oxygen defects. A VOC sensing device based on fabricated two-dimensional NSs has been developed for the sensing of different VOCs. The device showed better sensing for formaldehyde compared with other VOCs (2-propanol, methanol, ethanol, and toluene). The response was found to be 4.35, with the response and recovery time of 71 s and 310 s, respectively. The device showed an increment of the recovery time (71 s to 100 s) with the decrement of the formaldehyde ppm (100 ppm to 20 ppm). Theoretical fittings provided the detection limit of formaldehyde ≈8.86 ± 0.45 ppm with sensitivity of 0.56 ± 0.05 ppm-1. The sensor device showed good reproducibility with excellent stability over the study period of 135 d, with a deviation of 1.8% for 100 ppm formaldehyde. The average size of the NSs (≈24 nm) calculated from HRTEM observation showed lower value than the calculated Debye length (≈44 nm) of the charge accumulation during VOCs sensing. Different defect states, interstitial and surface states in the CeO2NSs as observed from the Raman spectrum and emission spectrum are responsible for the formaldehyde sensing. This work offers an insight into 2D semiconductor-based oxide material for highly sensitive and stable formaldehyde sensors.

Effects of Betanin Isolate Administration on the Lung Histopathological Image of Wistar Rats (Rattus norvegicus) Exposed to 40 ppm Formaldehyde

Purpose: This research investigates the effects of betanin isolate derived from beetroot on the lung histopathological image of Wistar rats exposed to 40 ppm formaldehyde, which is a known carcinogen. This research aims to evaluate the potential of betanin isolate to prevent lung cancer caused by formaldehyde exposure. Patients and methods: This research uses Wistar rats (Rattus norvegicus) as sample, which are divided into six groups, control group, positive control group, negative control group, and three treatment groups with different doses of betanin isolate. The research adopts a true experiment with post-test only design. The rats were exposed to 40 ppm formaldehyde for 12 weeks, except for the control group. The lung histopathological image of the rats was examined and graded for dysplasia. The data were analyzed using Mann-Whitney U test to compare the degree of dysplasia among different groups. Results: The control group is significantly different from all other groups, except treatment group 3. The negative control and control group has significant difference, which means the treatment of formaldehyde in this research is successful in inducing dysplasia. There is also seen a significant difference between treatment group 1 and treatment group 3 which indicates that the protective effect of betanin is dose dependent. There are some tissues with no dysplasia in treatment group 3 that shows the protective effect of betanin in higher dose. Conclusion: This research shows that betanin isolate has a dose-dependent protective effect, with higher dose being more effective. However, the highest dose tested is not enough to prevent dysplasia completely.

Room temperature thermocatalytic removal of formaldehyde in air using a copper manganite spinel-supported palladium catalyst with ultralow noble metal content

The room temperature (RT)-catalytic oxidation of gaseous formaldehyde (FA) in the dark is regarded as one of the most viable technical options for its removal from indoor air. Herein, the copper manganite spinel (CuMn2O4) supported palladium (Pd) catalysts are firstly synthesized for the thermocatalytic oxidation of FA in air. In particular, 0.05% Pd-CuMn2O4-R (‘R’ denotes high-temperature reduction pre-treatment using hydrogen) achieves 100% conversion (XFA) of 50 ppm FA at RT (gas hourly space velocity of 4342 h−1). The performance of 0.05% Pd-CuMn2O4-R against FA, if assessed in terms of the reaction kinetic rate (r at 10% XFA), is estimated as 3.01E−02 mmol g−1h−1. The lowering of XFA with the increases in FA concentration, flow rate, and relative humidity indicates the detrimental effects of such variables on the catalytic activity. FA oxidation kinetics predominantly follows the Mars van Krevelen mechanism. In-situ diffuse reflectance infrared Fourier transform spectroscopy shows that FA oxidation proceeds through multiple reaction intermediates (e.g., dioxymethylene and formate). The density functional theory simulations indicate that the catalytic oxidation efficacy of FA over CuMn2O4 increases by the synergy between Pd loading and surface reduction. The present study represents the first report on the synthesis of CuMn2O4-supported Pd catalysts and their application for the RT oxidative removal of FA in air under dark conditions. The findings of the present work offer valuable insights into the construction of efficient and cost-effective catalysts with ultra-low noble metal content for the RT oxidative removal of VOCs in indoor environment.

The practical utility of nitrogen doped TiO2 as a photocatalyst for the oxidative removal of gaseous formaldehyde

This study reports the development of nitrogen-doped TiO2 (N–TiO2: N/Ti molar ratio = 1) photocatalyst with the enhanced photoelectronic properties for the phtocatalytic oxidation (PCO) of formaldehyde (FA). The N–TiO2 photocatalyst is coated with ceramic beads and placed in a packed-bed tube reactor to examine the PCO-based mineralization of FA vapor (100 - 500 ppm) under ultraviolet (UV)-A illumination (32 W light source) with the control of flow rate (100–500 mL min−1), O2 (0–21%), and relative humidity (RH: 0–100%). Accordingly, the N-TiO2 in dry conditions showcases 100% degradation of 100 ppm FA with high stability over 5 reuse cycles (compared to the P25 (75.9%) and bare TiO2 (69.2%)) at a flow rate of 100 mL min−1 and a 21 % O2 level (quantum yield = 1.72.E−02 molecules photon−1 and space-time yield = 3.44.E−03 molecules photon−1 mg−1). The superior performance of N–TiO2 may reflect the combination of N/O atoms in the crystal structure to enhance the photo-redox reactivities with the heightened valence band enegry and prolonged lifespan of charge carrier (1.34 ns) relative to 1.04 ns of P25 and 1 ns of pure (anatase) TiO2. The PCO efficiency of N–TiO2 increases by around 1.6 times in slightly humid conditions (74.6%: RH 20%) compared to dry conditions (47%: RH 0%) while the absence of oxygen (at 0% O2) reduces it significantly down to 13.6%. In situ diffuse reflectance infrared Fourier transform spectroscopy and electron paramagnetic resonance studies confirm the critical role of O2 and H2O vapor on the enhanced FA mineralization rate (CO2 yield = 91 %) through the generation of •O2-/•OH oxidative radicals. This study offers deep insights into the practical utility of N–TiO2 for the photocatalytic mineralization of aldehyde VOCs.

Highly-improved formaldehyde gas sensitivity, selectivity and stability of Ce-doped In2O3 sensors at low temperature

Formaldehyde, a prevalent indoor toxic gas, can quickly harm individuals when the concentration reaches 20 ppm. Therefore, the development of gas sensors with high selectivity and sensitivity to ppm formaldehyde is highly promising. Ce-doped In2O3 microtubes are prepared through environmentally friendly one-step hydrothermal method. After the characterization of microstructure, morphology and composition of Ce-doped In2O3 microtubes, the gas-sensing performance is investigated in detail. All results indicate that Ce-doping results in lattice defects and grain refinement, leading to the higher specific surface area and more oxygen vacancies. Ce-doping greatly improves the formaldehyde gas-sensing performance of Ce-doped In2O3 sensors. 5Ce–In2O3 sensor the highest response value (563.07) to 10 ppm formaldehyde at the lower operating temperature of 210 °C, which is 4.59 times of In2O3 sensor at 230 °C. Moreover, Ce-doped In2O3 sensors exhibit the excellent selectivity, long-term stability and humidity stability. The overall-improved formaldehyde gas-sensing behavior of Ce-doped In2O3 sensors is attributed to more oxygen vacancies, larger specific surface area, reduced bandgap, Ce3+→Ce4+ transition and Ce4+ donor doping due to Ce-doping.

UV activated formaldehyde gas sensing based on gold decorated ZnO@ In2O3 hollow nanospheres at room temperature

Using uniform carbon nanospheres as sacrificial templates, gold nanoparticle-modified ZnO@ In2O3 hollow nanospheres with controlled dimensions and porous architectures were successfully synthesized through water bath, hydrothermal and chemical reduction methods. Gas sensing evaluation revealed that the Au-decorated ZnO@ In2O3 hollow nanostructures exhibited a dramatically amplified response up to 14.8 when exposed to 10 ppm formaldehyde analyte at room temperature. Furthermore, multifaceted performance benefits of Au-decorated ZnO@ In2O3 over single-phase ZnO, Au-ZnO, ZnO@ In2O3 heterojunction-based composites were observed, including excellent selectivity towards formaldehyde even in complex gas mixtures; tremendous sensitivity enhancement stemming from synergies between efficient gas diffusion through hollow heterojunction nanospheres and accelerated surface reactions at catalytically-active Au sites; and rapid, fully-reversible response/recovery time of 32 s and 42 s, respectively. In-depth investigations were conducted into the fundamental sensing mechanisms enabling formaldehyde detection using AC impedance spectroscopy, in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and density functional theory (DFT) computational modeling analyses.

Thermocatalytic oxidation potential of cobalt(II,III) oxide against gaseous formaldehyde in relation to hydrothermal synthesis temperature

The catalytic activity of various transition metal oxides has been reported to be tuned by controlling their synthesis conditions. In this perspective, the thermocatalytic oxidation performance of cobalt(II,III) oxides (Co3O4) against formaldehyde (FA) is studied in relation to the temperature selected for their hydrothermal synthesis (e.g., 30 (as room temperature (RT)), 60, 120, and 250℃) with the corresponding sample codes as Co3O4-RT, Co3O4-60, Co3O4-120, and Co3O4-250, respectively. The best performing Co3O4-RT records the lowest T90 (temperature required to obtain 90 % conversion) for 50 ppm FA at 72 °C when operated at 0 % relative humidity (RH), 30 mg (catalyst mass: mcat), and 100,000 mL g-1h−1 (weight hourly space velocity). The performance of Co3O4-RT, if assessed in terms of reaction kinetic rate (r) at XFA = 10 %, is 2.02E-02 mmol g-1h−1. According to X-ray photoelectron spectroscopy and temperature programmed characterization analysis, the catalytic activities of Co3O4-RT improve greatly through the synergistic combination of diverse factors (e.g., high Co3+ content, abundant oxygen vacancies (OVs) and surface adsorbed oxygen (Oβ) species, and good surface lattice oxygen (Oα) mobility). The analysis of in-situ diffuse reflectance infrared Fourier transform spectroscopy indicates that the FA should be oxidized into water (H2O) and carbon dioxide (CO2) via dioxymethylene (DOM) and formate (HCOO–) as reaction intermediates. The density functional theory simulations suggest the (111) surface of Co3O4 to be catalytically active against FA. The output of this research is expected to help establish effective strategies for designing high-performance transition metal oxide catalysts for the catalytic oxidation of FA.

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.

Rapid YFeO3 gas sensor for detecting formaldehyde working at room temperature

The YFeO3 (12 h, 24 h, 48 h and 72 h) microcrystals were prepared by hydrothermal process. Structural characterization using X-ray diffraction confirms the orthorhombic perovskite of the synthesized materials. YFeO3 based gas sensor has good selectivity to formaldehyde. The response value of YFeO3 (72 h) sensor is up to 318 for 100 ppm formaldehyde at room temperature. Furthermore, YFeO3 has an ultra-fast response-recovery time of about 6.3 s/0.9 s and exhibits excellent cycle repeatability and stability. This trait can play significant practical role in kind of sensors with real-time detectability. Further SEM and XPS analysis suggest that enhanced sensing property can be related to the uniform hierarchical structure and high oxygen vacancies. Our research indicates that adjusting the experimental approach can alter the structural and sensing properties of the sample.

An all-in-one self-supporting Na-Bi2WO6 photocatalyst for portable air purifier: Laminar splitting boosts high efficacy in mineralizing toluene and disinfection

An air purifier that provides clean air will be popular if it is portable and capable of removing volatile organic chemicals and reducing exposure to bacteria. Herein, ultra-thin and dense Bi2WO6 nanoflakes grown on W meshes specialize in offering abundant oxygen vacancies due to Na+ driving laminar splitting. Under visible lights, the photogenerated carriers streaming along the ultrathin Bi2WO6 surface produce bountiful reactive oxygen species for mineralizing VOCs and sweeping bacteria. Enriched with •O2- and •OH, a 15 cm*5 cm Na-Bi2WO6 mesh can completely degrade 30 ppm toluene in 0.45 dm3 reactor in 1 hour without producing any toxic intermediates like benzene, and its efficacy only decayed by 4% after a continuous 14-hour run. A cup-shaped air purifier was assembled with the Na-Bi2WO6 mesh, enabling the rapid elimination of 1 ppm toluene, 2 ppm formaldehyde, and bacteria within a 120 dm3 test space.

Indoor Air Remediation Using Biochar from Bark: Impact of Particle Size and Pollutant Concentration

The growing emphasis on indoor air quality and public health is fuelling the need for efficient yet affordable air purification techniques. In this study, the influence of biochar particle size on its adsorption efficiency toward airborne pollutants was examined. Bark-derived biochar particles were treated by grinding or ball milling, and then, seven samples with different particle size groups were separated. Biochar particles were characterized by particle size, proximate, SEM, XRD, and physisorption analyses. For adsorption efficiency, two different pollutants were tested at variable initial concentrations. The physical composition and XRD patterns of the biochar with different particle sizes were comparable. The ball-milled sample was an exception in that it had higher ash content and additional XRD peaks signifying contamination of the sample. The porosity of biochar was greater in smaller particles. Ball milling increased the specific surface area and total pore volume by 102% and 48%, respectively. Biochar with finer particle size exhibited the highest adsorption potential towards formaldehyde and methanol among other samples. It should be emphasized that simple mechanical grinding is preferred for reducing biochar size to avoid the risk of eventual contamination, greater energy consumption, and slower processing related to ball milling. When a low concentration of pollutant was tested (1 ppm formaldehyde), the effect of particle size on the adsorption efficiency was more noticeable. However, the effect of particle size was less dominant when higher concentrations of pollutants were tested. Smaller biochar particles (&lt;100 μm) are more favourable for indoor air remediation given their superior adsorption efficiency of volatile organic compounds occurring at low concentrations in the buildings.

Formaldehyde Exposure of Aquaculture Workers in Korea

ABSTRACT Objectives Korea’s aquaculture sector primarily cultivates aquatic life, with fish seed production as a focus. Formalin, a parasiticide, consists of 37% formaldehyde mixed with yellow No. 4 dye. Formaldehyde vaporization poses cancer risks, classified as a carcinogen. Korea regulates formaldehyde as a hazardous substance, requiring workplace environment measurements. Few aquaculture farms have conducted these checks in recent years. In this study, we investigated actual formaldehyde exposure levels among Korean aquaculture workers, highlighting a critical safety concern. Methods A field survey was conducted to measure formaldehyde exposure at 10 aquaculture farms in areas where Korean aquaculture is concentrated. Short-term and long-term personal samples, local samples, and direct-reading measurements were conducted. Formaldehyde exposure levels were detected in short-term personal samples from six farms and in long-term personal samples from two farms, and formaldehyde was detected in all local samples. In direct-reading measurements, a high concentration of formaldehyde was sustained for short periods. Results Long-term (8-hour) personal samples were mostly non-detectable, except for farms A and D, which had levels of 0.0009 ppm and 0.0017 ppm, respectively. Short-term (15-minute) samples were non-detectable in four farms, with an average of 0.0158 (±0.0130) ppm in the remaining six farms. Local samples from all farms had an average of 0.0384 (±0.0957) ppm of formaldehyde. For farms A and D, where long-term sampling detected formaldehyde, real-time measurements showed a sustained high concentration in farm A for about 48 minutes before decreasing. Farm D had no detectable formaldehyde throughout the monitoring period. Conclusion According to the formaldehyde exposure level assessment, short term exposure to formaldehyde during and immediately after application of formalin nearly exceeded the ACGIH TLV STEL in one farm. However, concentration of long term samples appeared at 10% of ACGIH TLV TWA. Additional study is recommended to determine whether exposure to formaldehyde poses a health risk for aquaculture workers during application of formalin.

The practical utility of ternary nickel-cobalt-manganese oxide-supported platinum catalysts for room-temperature oxidative removal of formaldehyde from the air

Formaldehyde (FA), a carcinogenic oxygenated volatile organic compound, is present ubiquitously in indoor air. As such, it is generally regarded as a critical target for air quality management. The oxidative removal of FA under dark and room-temperature (RT) conditions is of practical significance. A series of ternary nickel–cobalt-manganese oxide–supported platinum catalysts (Pt/NiCoMnO4) have been synthesized for FA oxidative removal at RT in the dark. Their RT conversion values for 50 ppm FA (XFA) at 5,964 h−1 gas hourly space velocity (GHSV) decrease in the following order: 1 wt% Pt/NiCoMnO4 (100 %) > 0.5 wt% Pt/NiCoMnO4 (25 %) > 0.05 wt% Pt/NiCoMnO4 (14 %) > NiCoMnO4 (6 %). The catalytic performance of 1 wt% Pt/NiCoMnO4 has been examined further under the control of various process variables (e.g., catalyst mass, flow rate, relative humidity, FA concentration, time on stream, and molecular oxygen content). The catalytic oxidation of FA at low temperatures (e.g., RT and 60 °C) is accounted for by Langmuir–Hinshelwood mechanism (single-site competitive-adsorption), while Mars van Krevelen kinetics is prevalent at higher temperatures. In situ diffuse-reflectance infrared Fourier-transform spectroscopy reveals that FA oxidation proceeds through a series of reaction intermediates such as DOM, HCOO–, and CO32–. Based on the density functional theory simulations, the unique electronic structures of the nearest surface atoms (platinum and nickel) are suggested to be responsible for the superior catalytic activity of Pt/NiCoMnO4.

Anti-competitive adsorption of gaseous benzene on hydrophilic microporous carbon in humid conditions

The adsorption capture of ambient volatile organic compounds (VOCs) is of practical importance for air quality management. Herein, unique anti-competitive adsorption behavior of benzene on a hydrophilic activated carbon (Procarb-900 (P900)) is evidenced in the presence of competing components (e.g., formaldehyde (FA) and/or moisture). Contrary to general expectations, the adsorption capacity of 10 Pa benzene (QB) onto P900 (30 mg) at the 99 % breakthrough level improves from 144.8 to 187 mg g−1 as the relative humidity (RH) increases from 0 to 25 %. Such pattern is maintained at 183.9 mg g−1 even at the relatively high RH of 50 %. Furthermore, QB exhibits a remarkable increase of 56.1 % (to 226.0 mg g−1) in the binary phase (100 ppm benzene plus 50 ppm FA) relative to its single phase (144.8 mg g−1). The kinetic studies confirm the occurrence of anti-competitive adsorption of benzene under humid conditions with the unusual decrease in rate constants at the elevated RHs (i.e., 25 and 50 %). The thermodynamic studies suggest the exothermic nature of benzene adsorption onto P900. The hydrophilicity of P900's outer surface promotes the preferential adsorption of polar FA and water vapor over non-polar benzene, which deforms the activated carbon texture and lowers the pore size distribution (PSD). The narrow PSD enhances benzene uptake in the complex systems due to the confinement effect. Overall, this study offers insights into the unique anti-competitive adsorption of non-polar VOCs (e.g., benzene) on hydrophilic microporous adsorbents in the presence of potential interferences such as polar water vapor and FA. These findings offer a guideline for the practical implementation of adsorption techniques for gaseous VOCs in humid conditions.

A formaldehyde gas sensor based on Ag-decorated ZnCo2O4/FF composite

Cobalt-containing spinel oxides are highly active materials for gas sensing and have shown promise in various applications. In this study, we prepared a series of gas-sensitive composites by doping Ag into ZnCo2O4/Phenylalanine dipeptide (ZCO/FF) and investigated their gas sensitivity to formaldehyde. The experiments showed that the response of ZCO/FF-3 wt%Ag to 20 ppm formaldehyde was 23 at an optimum operating temperature of 175 °C. Further experimental data show that the sensor has excellent selectivity and stability. These results provide basic knowledge for the practical use of spinel oxide gas sensors.

Hepatic Alteration due to Formaldehyde Exposure on Wistar Rats (Rattus norvegicus)

Formaldehyde is a hazardous chemical substance that can be found commonly in the environment which has various effects on cellular functions and could induce the cellular oxidative stress. Oxidative stress has a direct impact on the hepatic condition and could induce the activation of inflammatory mediators, lipid peroxidation, proteosomal degradation, and mitochondrial dysfunction resulting in hepatocyte injury that could be marked by hepatic enzyme elevation and hepatic weight alterations. This research was conducted using 16 Wistar rats (Rattus norvegicus), divided into 4 groups each containing 4 Wistar rats. The first group was the control group, while the other groups were exposed to formaldehyde 10% by inhalation at doses of 20, 30, and 40 ppm formaldehyde persistently for 6 hours daily for about 16 weeks. The result of this study reveals that formaldehyde induction has a significant impact on hepatic weight elevations (p=0.007) and ALT enzyme elevations (p=0.000) in the treatment groups compared with the control group. Collectively, our results provide valuable information on the hazardous effects of formaldehyde inhalation, especially on the liver.

Nanocube-shaped In2O3@TiO2 core-shell based chemiresistive-type sensors for formaldehyde detection at room temperature

In2O3@TiO2 core-shell nanocubes were successfully prepared via hydrothermal method and subsequent water bath method. The characterization results show that the size of the In2O3@TiO2 nanocomposites is 250–350 nm. The In2O3@TiO2 nanocomposites based sensor presents excellent sensing response to formaldehyde at ppb level. The response of In2O3@TiO2 nanocomposites based sensor to 1 ppm formaldehyde is about 5.3 at room temperature under UV activation, which is three times higher than that of the pure In2O3 based sensor. The response/recovery time of In2O3@TiO2 nanocomposites based sensor are 24 s and 52 s, respectively. The involved chemical reactions activated by UV had been investigated by in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). This work proves that core-shell nanocubes combined with UV activation could significantly enhance the sensing properties of the sensors.