Formaldehyde Removal Research Articles

Removal of Formaldehyde and Its Analogues Using a Hybrid Assembly of Pyrene-Modified Hydrazide and rGO: A Negative Carbon Emission and Green Chemical Decomposition Method.

Indoor gaseous formaldehyde is the main environmental pollutant that can cause fatal threats to human health. A number of physical and chemical methods have been developed to tackle this issue. However, the existing methods are still unsatisfactory to meet the requirement of sustainable development owing to the flaws of low efficiency and reversible or second pollution. Herein, a chemical method based on a nucleophilic reaction between hydrazine and aldehyde that generates the only by-product of H2O is designed for the removal of formaldehyde. 1-Pyrenebutyric hydrazide was synthesized by a simple esterification reaction and then self-assembled on reduced graphene oxide (rGO) with a large surface area by forming π-π stacking to obtain a composite for chemical removal of gaseous formaldehyde under ambient conditions. In a practical test, the formaldehyde removal rate could reach 91% of the theoretical value, which meets the requirement for commercial formaldehyde removal applications. After 10 times recycling, the formaldehyde removal rate still remains as high as 85%. Moreover, the composite could be regenerated in weak acidic media, which greatly reduce the manufacturing cost in practical applications.

Preparation of a Novel Formaldehyde-Free Impregnated Decorative Paper Containing MnO2 Nanoparticles for Highly Efficient Formaldehyde Removal.

The loading of catalytic manganese dioxide (MnO2) nanoparticles onto an impregnated decorative paper has been an effective method for the removal of indoor formaldehyde (HCHO) pollutants. However, its preparation can present numerous challenges, including instability in dipping emulsions and leaching. In this investigation, a novel and stable formaldehyde-free polyacrylate dipping emulsion containing MnO2 particles was prepared and then back-coated on a decorative paper. To improve the dispersion and fixation, the MnO2 was modified with silane. HCHO can undergo physical adsorption on the cellulosic fibers present in the paper, while it can also undergo chemical degradation into CO2 within the MnO2 groups. The silane not only enhanced the interfacial adhesion to a polyacrylate resin but also increased the interlayer distance, thereby creating a larger space for HCHO absorption. The impregnated decorative paper back-coated with 10 wt % of silane-modified MnO2 exhibited a removal efficiency of approximately 90% for HCHO at 20 °C. The removal rate further improved to approximately 100% when the temperature was increased to 60 °C. Moreover, it is worth noting that the release of volatile organic compounds was exceptionally minimal. Additionally, the particleboard bonded with this impregnated decorative paper exhibited an extremely low emission of HCHO, with a value that approached 0 mg·L-1. Furthermore, the bonding strength of the surface remained unaffected. Therefore, this study provides a simple and eco-friendly method for effectively removing HCHO, which can enhance indoor air quality.

Formulating the Li sites of Li-CoOx composites for achieving high-efficiency oxidation removal of formaldehyde over the Ag/Li-CoOx catalyst under ambient conditions

Oxide supported noble metals are extensively investigated for ambient formaldehyde oxidation, and the Ag-CoOx complex is one promising combination in terms of cost and activity. Further, we previously observed that cooperating Ag with Li + greatly boosted formaldehyde degradation on CoOx. Yet, there is still room for improvement in removal efficiency, mineralization capacity and resistance to severe conditions. These objectives could be realized via strategically formulating the Li+ sites of Li-CoOx composite in this sister study. Three samples with Li + ---Co3+—O2- connections (L-CO), spinel Li+ (LCO-S) and layered Li+ (LCO-L) were obtained at low (300 °C), moderate (500 °C) and high (700 °C) temperatures, respectively. The specific Li+ positions and componential interaction were demonstrated by Hyperspectral imaging (HSI), XRD, SEM, TEM, HAADF mapping, UV–vis DRS and XPS. Moreover, the effect of reactive oxygen exposure on catalytic oxidation of formaldehyde (330–350 mg/m3) was disclosed through CO-TPR and O2-TPD. Compared with the LCO-S and LCO-L, L-CO exhibited dominant formaldehyde degradation due to the larger content of surface oxygen. After Ag decoration, the Li+---Co3+—O2- connections uniquely caused a strong binding of Ag species with catalyst host, which boosted the amount of reactive oxygen and finally resulted in an even higher elimination of ∼73% (CO2 yield = ∼21%), 47% higher than that of the L-CO (CO2 yield = ∼6%). But in contrast, the Ag@LCO-S only achieved ∼53% removal (CO2 yield = ∼9%) and Ag modification was powerless in altering the inertness of LCO-L, demonstrating that the chemical environment of alkali metal is crucial to effectively tuning the catalyst activity. The advantage of Ag@L-CO in formaldehyde depollution was further reflected from its much better resistance to moisture and aromatic compound omnipresent in indoor air. For the first time, this study extended the understanding of the alkali-metal-promoted formaldehyde oxidation reaction to an in-depth level.

Formaldehyde Oxidation of Ce0.8Zr0.2O2 Nanocatalysts for Room Temperature: Kinetics and Effect of pH Value.

Ce0.8Zr0.2O2 catalysts were prepared via the co-precipitation method under different pH conditions. The catalysts were characterized via TEM, XRD, XPS, BET, Raman, and FTIR. The oxidation performance of formaldehyde was tested. Precipitation pH affects the physicochemical properties and performance of the Ce0.8Zr0.2O2 catalyst. By controlling the precipitation pH at 10.5, the Ce0.8Zr0.2O2 catalyst with the largest specific surface area, the smallest grain size with the best formaldehyde removal rate (98.85%), abundant oxygen vacancies, and the best oxidation performance were obtained. Meanwhile, the kinetic parameters of the catalyst were experimentally investigated and the calculated activation energy was 12.6 kJ/mol and the number of reaction steps was 1.4 and 1.2.

High Efficiency of Formaldehyde Removal and Anti-bacterial Capability Realized by a Multi-Scale Micro-Nano Channel Structure in Hybrid Hydrogel Coating Cross-Linked on Microfiber-Based Polyurethane.

Inspired by the transpiration in the tree stem having a vertical and porous channel structure, high efficiency of formaldehyde removal is realized by the multi-scale micro-nano channel structure in a hybrid P(AAm/DA)-Ag/MgO hydrogel coating cross-linked on microfiber-based polyurethane. The present multi-scale channel structure is formed by a joint effect of directional freezing and redox polymerization as well as nanoparticles-induced porosity. Due to the large number of vertically aligned channels of micrometer size and an embedded porous structure of nanometer size, the specific surface area is significantly increased. Therefore, formaldehyde from solution can be rapidly adsorbed by the amine group in the hydrogels and efficiently degraded by the Ag/MgO nanoparticles. By only immersing in formaldehyde solution (0.2 mg mL-1) for 12 h, 83.8% formaldehyde is removed by the hybrid hydrogels with a multi-scale channel structure, which is 60.8% faster than that observed in hydrogels without any channel structure. After cross-linking the hybrid hydrogels with a multi-scale channel structure to microfiber-based polyurethane and exposing to the formaldehyde vapor atmosphere, 79.2% formaldehyde is removed in 12 h, which is again 11.2% higher than that observed in hydrogels without any channel structure. Unlike the traditional approaches to remove formaldehyde by the light catalyst, no external conditions are required in our present hybrid hydrogel coating, which is very suitable for indoor use. In addition, due to the formation of free radicals by the Ag/MgO nanoparticles, the cross-linked hybrid hydrogel coating on polyurethane synthetic leather also shows good anti-bacterial capability. 99.99% of Staphylococcus aureus can be killed on the surface. Based on the good ability to remove formaldehyde and to kill bacteria, the obtained microfiber-based polyurethane cross-linked with a hybrid hydrogel coating containing a multi-scale channel structure can be used in a broad field of applications, such as furniture and car interior parts, to simultaneously solve the indoor air pollution and hygiene problems.

Synergistic effects of multitype carbon doping and oxygen vacancies in TiO2/CNTs composite fabricated via nonthermal plasma for formaldehyde removal

Formaldehyde as one of the typical indoor pollutants has long been concerned as it can pose a threat to human health. TiO2/CNTs composite with oxygen vacancies and multitype carbon doping (C–TiO2/CNTs) was fabricated using nonthermal plasma for the photocatalytic degradation of formaldehyde. The maximum degradation rate of formaldehyde was 93% and 83% via the new catalyst (with 5% CNTs content) under solar and visible light, respectively. The characterization of the catalyst confirmed the in-situ multitype carbon doping and oxygen vacancies: interstitial carbon doping and oxygen vacancies could dramatically reduce the bandgap and contribute to the improved absorption capability of formaldehyde and electrons. Interfacial carbon doping in the form of C–O–Ti bonds provided a migration channel, whereby photogenerated electrons could efficiently transfer from CNTs to TiO2 and then quench the holes left in the VB of TiO2. Therefore, the multitype carbon doping and oxygen vacancies can expand the light response as well as promote the separation of photo-generated electron/hole pairs. EPR results and experiment section indicated that O2·− plays the most significant role in formaldehyde removal due to the reverse transfer of the electrons. This work advances the understanding of photo-degradation of TiO2/CNTs composite and provides a new route for the abatement of formaldehyde.

Development of PVA/GO Nanocomposites Membranes for Air-Filtration and Purification

Climate change due to the air pollution is actually one of the largest environmental challenges worldwide. Preparation and development of stable and highly efficient nanocomposite membranes remain a significant goal because of its enormous importance of controlling the environment. This study investigated a simple synthesis of poly (vinyl alcohol)/graphene oxide (PVA/GO) nanocomposite membrane for air pollutant remediation. The chemical and physical structures, morphologies, and conductivities were investigated as a function of the GO loading. The objective of the present study was to evaluate the efficiency of novel PVA/GO membranes in the removal of both formaldehyde (FA) as a pollutant VOCs model and SO2 as a model of greenhouse gases. Furthermore, the purpose of this study is to identify good predictors for selecting the appropriate optimal GO content in GO/PVA nanocomposites that exhibit higher air pollutant removal performance as well as design an economical GO/PVA nanocomposite air purification system for removal of the air pollutants in the field. To our knowledge, field application of GO/PVA nanocomposite volatile organic compound (VOCS) filters and control of SO2 gas pollutants from indoor air has not yet been realized. The nanocomposite membranes with an optimum GO content exhibited higher removal performance for the FA gas pollutant, this enhancement reached 90% in the laboratory scale. However, during the application in the field, it showed 75% FA removed from the indoor air. These new nano-membranes reveal also wide efficiencies of SO2 removal (80%) when applied in the field. Therefore, this filter system proved an excellent efficacy in the removal of air pollutants and could be more promising in various industrial applications.

Spiral grass inspired eco-friendly zein fibrous membrane for multi-efficient air purification

Air pollution, one of the severest threats to public health, may lead to cardiovascular and respiratory illnesses. In order to cope with the deteriorating air pollutant, there is an increasing demand for filters with high purification efficiency, but it's tough to strike a balance between efficiency and resistance. Fabricating an eco-friendly fibrous filter which can capture both PM2.5 and gaseous chemical hazards with high efficiency but under ultra-low resistance is a long-term challenge. Herein, inspired by the interesting ribbon shape of spiral grass, a green and robust 3D nonwoven membrane with controllable hierarchical structure made of self-curved zein nanofibers modified by zeolitic imidazolate framework-8 (ZIF-8) via bi-solvent electrospinning and fumigation welding method was fabricated. The obtained ZIF-8 modified zein membranes showed extraordinary overall performance with high PM2.5 removal efficiency (99.04 %) at a low stress drop (54.87 Pa), first-rate formaldehyde removal efficiency (98.8 %) and excellent photocatalytic antibacterial. In addition, the relatively weak mechanical properties of zein fibrous membranes have been improved via solvent fumigation welding of the joint zein fibers. This study provides a green and convenient insight to the manufacturing of environmentally-friendly zein fibrous membranes with high filtration efficiency, low air resistance and high formaldehyde removal for sustainable air remediation.

Improving the Efficiency of the Indoor Air Purification from Formaldehyde by Plants Colonized by Endophytic Bacteria Ochrobactrum sp.

The endophytic bacteria can be in symbiosis with host plants, owing to the natural stability advantages in degrading pollutants. To explore the technological feasibility of this method for indoor formaldehyde removal, a system combining endophytic bacteria and plants was established. In the present study, highly efficient formaldehyde-degrading bacteria Ochrobactrumintermedium, named strain ZH-1, was successfully induced with antibiotics (rifampicin) to an antibiotic-labeled strain ZH-1R without microbial variation. The strain ZH-1R was then used for colonization in the Epipremnum aureum and Chlorophytum comosumf. variegate plants by three inoculation methods: root irrigation (RI), acupuncture injury to stem (AS), and acupuncture injury to leaves (AL). The results demonstrated that the acupuncture injury to stem (AS) method was the most effective for inoculating ZH-1R strain in Epipremnum aureum plants. Conversely, acupuncture injury to stem (RI) method yielded the best results for the Chlorophytum comosumf. variegate plants, highlighting the importance of usage of optimal plant specific inoculation method ensuring the highest possible performance characteristics of the biological system. The results of 8-day formaldehyde dynamic fumigation experiment demonstrated that the removal efficiency of the formaldehyde by Chlorophytum comosum f. variegata inoculated with ZH-1R was significantly higher than the one demonstrated by non-inoculated plants. The average increase of 20.17% was observed during daytime, while much more significant improvement by 62.88% was achieved at night. This implied that endophytic bacteria could not only effectively improve the removal efficiency of formaldehyde, but also increased the resistance of not-native host plants to formaldehyde toxicity, suggesting its potential in an integrated system which provides a new path of an efficient and economical approach to radically improve indoor air quality, especially at nighttime.

Performance validation of a non-photocatalytic air purifier built by reactive adsorbent against a commercial UV-based air purifier

A portable non-photocatalytic air purifier (AP) was built by modifying a honeycomb-type ceramic (HC) filter through immobilization of a reactive adsorbent (i.e., manganese dioxide (MnO2 (1 wt%))-Universitetet i Oslo (UiO)-66-amine (NH2): namely, M-U6N). This non-photocatalytic AP system was examined for the removal of gaseous formaldehyde (FA) at room temperature (RT) in a 17 L airtight chamber. The kinetic reaction rates (RW, μmol h−1 g−1) of AP (M-U6N), when measured at 10%, 50%, 90%, and 100% of its removal, were 631, 433, 191, and 114, respectively. This non-photocatalytic AP system fully mineralized FA to CO2 and H2O through the Mars–van Krevelen (MvK) mechanism with a significantly higher (i.e., 1.6–3.3 times) kinetic reaction rate (RF, μmol h−1 filter−1) than that of its UV-based AP counterpart. As such, based on our experimental performance validation, the non-photocatalytic AP system developed in this work was demonstrated to be superior to the commercial photocatalytic AP system in the treatment of gaseous FA. The findings of this study offer practical guidelines for the fabrication of cost-effective non-photocatalytic AP systems.

The performance investigation on a multifunctional wall with photo-thermal catalytic blinds for heating, shading and formaldehyde removal

A novel multifunctional wall with photo-thermal catalytic blinds (PTC-Blind/TW) for heating, shading and formaldehyde removal was proposed. The system can realize indoor air purification all year by using solar energy, space heating in winter and cooling in summer simultaneously. The hybrid wall system was built and thermal and formaldehyde degradation performance was tested experimentally. The coupled heat, mass and reaction dynamic model was established and experimentally verified. Based on the model, the optimal blind angle control strategy was studied when the system runs in different cities all year. Main results were: (1) Under the solar radiation of 300–900 W/m2, the thermal efficiency, formaldehyde single-through convention and CADR of system were in the range of 20–40%, 30–60% and 20–80 m3/h respectively. (2) For the thermal and purification performance of the system, the fitted degree R2 between the simulation results and the experimental results reaches 80–90%. (3) The optimal blind turning angle operation strategy in Nanjing, Beijing, Xining and Guangzhou was obtained. (4) When applied optimal operation strategy in four cities, the total generated clean air annually, reduced heating loads in winter seasons and reduced cooling loads in summer and transition seasons were in range of 0.8–1.7*104 m3/m2, 86.3–739.5 MJ/m2 and 261.2–388.5 MJ/m2 respectively.

The impact of water co-adsorption on the removal of formaldehyde from the indoor air by oxygen-rich activated carbons: A theoretical and experimental study

Surface oxygen modification of activated carbon has been considered an effective sorbent to remove formaldehyde from indoor air, while the role of co-existing moisture on formaldehyde adsorption by oxygen-rich carbons is unclear. This study investigates the dynamic impact of water on formaldehyde adsorption from simulated indoor air was studied experimentally and theoretically. Among them, the improvement of formaldehyde adsorption on oxygen-rich activated carbon originated from forming stronger hydrogen bonds between oxygen functional groups and formaldehyde compared to conventional van der Waals force. However, the more vital interaction forces between water and oxygen functional groups by forming more hydrogen bonds and the pore blockage by accumulated water molecules around adsorption sites with the increasing adsorption time became the significant barriers of formaldehyde adsorption on carbon surface in a wet environment. Oxygen functional groups with pre-adsorbed water/formaldehyde can accommodate at least one more water while it can hardly adsorb another formaldehyde due to the weak interaction force that can easily be replaced by water molecules. Formaldehyde cannot form hydrogen bonds with the double bond O atom of the carboxyl group, but water can. The sustained adsorption capacity of water is much stronger than that of formaldehyde.

Removal of gaseous formaldehyde by portable photocatalytic air purifier equipped with bimetallic Pt@Cu-TiO2 filter

In this research, a mini-scale air purifier (AP) system was built with a series of honeycomb (HC) ceramic filters coated with 1 wt% Pt@Cu/TiO2 (AP (PCT-x), where x = 1, 2, and 3 for Pt:Cu weight ratios). The designed AP (PCT-x) photocatalytic systems were investigated for the removal of formaldehyde (FA) vapor under varying operational conditions (e.g., FA concentration (0.5–5 ppm), AP-flow rate (100–160 L/min), and UV light intensity (0.004–0.982 W)). The enhanced photocatalytic activities of AP (PCT-x) system (e.g., compared to the monometallic analogues) are suspected to reflect the synergistic role of Pt metal sites (in terms of high work function (5.93 eV) for the 111 crystal plane) in the Pt@Cu bimetallic structures and the high electronic transitions between Pt and Cu sites on the TiO2 surface. Nonetheless, their photocatalytic activities tend to decrease at higher Pt content (e.g., PCT-3 relative to PCT-2) due possibly to the formation of Pt clusters and associated shielding effect. Overall, AP (PCT-2) exhibited the highest efficacy (over five reuse cycles) to attain 100% removal of FA (0.5 ppm) within 5 min at an AP-flow rate of 160 L/min and UV light intensity of 0.982 W (quantum yield (QY) of 1.94E-04 molecules/photon and figure of merit (FOM) of 1.21E-06 L∙mol/ (mg∙ J∙h)). According to the in-situ DRIFTS analysis, Pt2@Cu metal sites were favorable to promote the transfer of photo-induced charge carriers by TiO2 so as to accelerate the oxidation reaction of FA vapor (e.g., through the generation of OH• and O2•- radicals). This study offers practical insights into the potential of controlled tuning of redox dynamics (i.e., between Pt and Cu metal sites on TiO2) in the enhancement of the photocatalytic performance for air purification system.

Zn-doped MnCe catalyst designed and applied for indoor low concentration formaldehyde removal and simultaneous antibacterial

As typical indoor air pollutants, the simultaneous removal of formaldehyde and microorganisms at room temperature was significant to purify indoor environment satisfactorily. Based on the practical problems of room temperature catalytic oxidation, Zn-doped MnCe (MC-Zn) aerogel catalysts were designed with dual functions of catalytic oxidation and bacterial inhibition in this study. It was found that MC aerogel exhibited excellent formaldehyde removal performance, which obtained 97.6% formaldehyde removal efficiency at 24 h. Besides, a small amount of Zn doping had little effect on the Lewis acidic sites and Mn3+/Mn on the MC aerogel catalyst surface, and the equivalent formaldehyde removal efficiency was achieved with the increasing specific surface area.The antibacterial tests demonstrated that the Zn-doped catalysts inhibited the growth of Staphylococcus aureus(S. aureus), Bacillus subtilis(B. subtilis) and Escherichia coli(E. coli). When the molar ratio of Mn:Zn:Ce was 5:1:4, the catalyst exhibited the optimal room temperature catalytic oxidation activity and appropriate bacterial inhibition performance. This paper provides a technical reference for the effective treatment of indoor co-contaminated environment.

Formaldehyde Reduction in an Operating Room Setting: Comparison of a Catalytic Surgical Vacuum Device With a Traditional Smoke Evacuator.

Introduction Electrosurgery exposes healthcare workers to volatile organic compounds (VOCs) including formaldehyde. Adopting electrosurgical devices that catalytically transform formaldehyde to benign substances has the potential to improve safety in surgical settings. Materials and methods We compared the efficiency of formaldehyde removal of two medical devices.The first was a novel surgical vacuum (SV) device containing ultra-low particulate air (ULPA) filtration, activated carbon and catalytic transition metal oxide.The second was a commonly utilized handpiece evacuator (HE) that contained only mechanical filtration and activated carbon granules. Both devices were exposed to formalin vapor. Results The time weighted average (TWA), median and peak concentrations of detected formaldehyde at the outflow of the SV unit were 90% lower than the corresponding values detected at the outflow of the HE device (p = 0.0034). When catalytic material was added to the HE device, the detected formaldehyde concentration at the outflow was reduced by 55%(p = 2.9 x 10-15). Conclusions The catalytic SV device has the potential to considerably reduce formaldehyde levels in operating room (OR) environments.

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.

Synthesis of δ-MnO2 via ozonation routine for low temperature formaldehyde removal

Nowadays, it is still a challenge to prepared high efficiency and low cost formaldehyde (HCHO) removal catalysts in order to tackle the long-living indoor air pollution. Herein, δ-MnO2 is successfully synthesized by a facile ozonation strategy, where Mn2+ is oxidized by ozone (O3) bubble in an alkaline solution. It presents one of the best catalytic properties with a low 100% conversion temperature of 85°C for 50 ppm of HCHO under a GHSV of 48,000 mL/(g·hr). As a comparison, more than 6 times far longer oxidation time is needed if O3 is replaced by O2. Characterizations show that ozonation process generates a different intermediate of tetragonal β-HMnO2, which would favor the quick transformation into the final product δ-MnO2, as compared with the relatively more thermodynamically stable monoclinic γ-HMnO2 in the O2 process. Finally, HCHO is found to be decomposed into CO2 via formate, dioxymethylene and carbonate species as identified by room temperature in-situ diffuse reflectance infrared fourier transform spectroscopy. All these results show great potency of this facile ozonation routine for the highly active δ-MnO2 synthesis in order to remove the HCHO contamination.

Self-Luminous Wood Coatings with Carbon Dots/TiO2 Grafted Afterglow SrAl2O4: Eu, Dy Core-Shell Phosphors for Long-Lasting Formaldehyde Removal.

Long-term relief of indoor volatile pollution has become a competitive issue worldwide in both visible and dark environments. A novel self-luminous wood coating with carbon dots (CDs)/titanium dioxide (TiO2) nanomaterial coated SrAl2O4: Eu2+, Dy3+ (CDs/TiO2@SAO) composite was prepared for the long-term degradation of formaldehyde through a simple sol-gel method. The microstructure, chemical composition, ultraviolet-visible (UV-vis) spectra, and long-lasting fluorescence of the CDs/TiO2@SAO photocatalyst were analyzed to illustrate the mechanism for degrading formaldehyde. The obtained CDs with a particle size of ~2-7 nm have a good graphite structure and presented good absorption in visible light. In addition, owing to the synergistic effect of the CDs/TiO2 nanomaterial coating layer and the long-afterglow luminescence of the SAO phosphor, the CDs/TiO2@SAO composite can absorb a part of the visible light for photocatalytic degradation and store luminous energy efficiently at daytime so as to give out visible luminescence continuously for a few hours in the darkness. Furthermore, the functional wood coatings with CDs/TiO2@SAO composite presented continuous and efficient photocatalytic activity in the presence and absence of light exposure. The current research could provide a new strategy for designing an efficient photocatalyst for degrading formaldehyde pollution in the daytime with a visible light supply and in an indoor dark environment without an external light source.

Study of preparation and properties of environmentally friendly phenolic resin for mining

AbstractIn order to solve the problem of formaldehyde release from the traditional phenolic foam (PF) in the process of coal mine filling and plugging. In this paper, the effect of different factors on the efficiency of formaldehyde trapping agents were studied by adding formaldehyde trapping agents containing amino compounds after PF synthesis. The effect of formaldehyde trapping agents on the performance of resin was investigated. The results showed that the addition of formaldehyde trapping agents could greatly reduce the residual formaldehyde content in phenolic resin. Fourier‐transform infrared spectroscopy (FTIR) data showed that the addition of formaldehyde trapping agent not only successfully prepared PF, but also produced a stable formaldehyde trapping agent product. Compared with the unmodified PF, the pore size and foaming rate of the modified PF decreased in varying degrees, and the foaming temperature also decreased in varying degrees. Among them, urea modified phenolic resin (PUF) had the highest formaldehyde removal efficiency. It had the t lowest heat release during combustion and the foam pore size was large and uniform. In addition, through the application of urea‐modified PF in the goaf return air corner fissure sealing application, it was found that the CO concentration in the goaf maintained at the lowest state of 0.002%. It has reached the national industry standard of polymer gas plugging materials and conforms to the green development concept in the field of coal mine fire prevention.

Self-Assembled Construction of Robust and Super Elastic Graphene Aerogel for High-Efficient Formaldehyde Removal and Multifunctional Application.

Simultaneously achieving exceptional mechanical strength and resilience of graphene aerogel (GA) remains a challenge, while GA is an ideal candidate for formaldehyde removal. Herein, flexible polyethyleneimine (PEI) is grafted chemically onto carbon nanotube (CNT) surface, and CNT-PEI@reduced GA (rGA) is fabricated via hydrothermal self-assembly, pre-frozen, and hydrazine reduction process. Introducing CNT-PEI contributes to well-interconnected/robust 3D network construction by connecting reduced graphene oxide (rGO) nanosheets through enhancing cross-linking, while entangled CNT-PEI is intercalated into rGO layers to avoid serious restacking of sheets, producing larger surface area and more formaldehyde adsorption sites. Ultralight CNT-PEI@rGA exhibits extreme high strength (276.37 kPa), reversible compressibility at 90% strain, and structural stability, while FA adsorption capacity reached 568.41 mg g-1 , ≈3.28 times of rGA, derivable from synergistic chemical-physical adsorption effect. Furthermore, CNT-PEI@rGA is ground into powder for first preparing polyoxymethylene (POM)/CNT-PEI@rGA composite, while formaldehyde emission amount is 69.63%/73.96% lower than that of POM at 60/230 °C. Moreover, CNT-PEI@rGA presents outstanding piezoresistive-sensing and thermal insulation properties, exhibiting high strain sensitivity, wide strain detection range, and long-term durability.