Formaldehyde Removal Performance Research Articles

Cement-based composites with ZIF-8@TiO2-coated activated carbon fiber for efficient removal of formaldehyde

Abstract Formaldehyde is one of the most common indoor air pollutants that seriously damage human health. It is of significant importance to effectively remove indoor formaldehyde. In this work, a novel cement-based composite with ZIF-8@TiO2-coated activated carbon fibers (TiO2-ACFs) was prepared and shown to remove the indoor formaldehyde effectively. TiO2 was coated on ACFs via atomic layer deposition, and then ZIF-8 was grown on the surface of TiO2-ACFs. The ZIF-8@TiO2-ACFs were then mixed with cement slurry and thus formed a cement-based composite, which exhibited excellent formaldehyde removal performance. In particular, if assisted with UV light, the removal efficiency for formaldehyde by the cement-based composite showed an obvious increase.

Experiment on the formaldehyde removal performance of TiO2 coating agent for finishing materials

As the frequency of indoor habitation escalates and advancements in building technology optimize airtightness, the importance of maintaining high-quality indoor air has grown increasingly critical. This urgency is further amplified by the proliferation of chemical building materials, necessitating more effective strategies for air pollutant abatement. To address this need, the current study explored the utility of titanium dioxide photocatalysts, which possess chemical decomposition capabilities, as a means of improving air quality within indoor environments. To verify the effectiveness of this approach, the research focused on the removal of formaldehyde—a quintessential indoor air pollutant—by incorporating a titanium dioxide photocatalyst into a coating agent commonly employed in construction materials. Notably, ultraviolet (UV) light, essential for activating the photocatalytic process, is generally absent in indoor settings. To mitigate this limitation, a consistent source of UV radiation was provided through the use of an UV lamp. Adhering to protocols outlined by the International Organization for Standardization, we employed a photoreactor to evaluate the photocatalytic efficiency of the composite material under varying intensities of UV radiation and reactor volumes. The results unequivocally confirmed that variations in UV radiation intensity and reactor volume significantly influenced the photocatalytic effectiveness of the material, resulting in a demonstrable reduction in pollutant concentrations. These findings suggest the feasibility of utilizing titanium dioxide photocatalysts for mitigating outdoor air pollutants, where natural UV radiation is more readily available. However, for indoor applications, the absence of naturally occurring UV radiation presents a considerable challenge. Overcoming this constraint could facilitate the indoor application of photocatalytic coatings, as informed by the optimal conditions of low pollutant reactivity and robust UV radiation revealed in this study, thereby substantially enhancing indoor air quality.

Preparation and Properties of Papers Added to Formaldehyde Removal Pulp

By means of scanning electron microscope, specific surface area analysis and formaldehyde removal performance comparison, calcium carbide powder and activated carbon powder were selected from five different functional powders. The calcium carbide powder and activated carbon powder were added to the pulp to prepare the base paper added to the formaldehyde removal pulp. The amount of active carbon powder and calcium carbide powder added to the pulp, the amount of retention aid used and the ratio of the two functional powders were investigated, and the microscopic morphology, pore size and porosity of the base paper added to the formaldehyde removal pulp were analyzed. The experimental results show that the best mass ratio of kraft hardwood fiber to powder is 1:1, the best amount of retention aid (based on the fiber quality) is 0.6%, the best mass ratio of activated carbon powder to calcium carbide powder is 1:1, and the formaldehyde removal rate of the prepared formaldehyde removal pulp added with base paper is 79.53% and 82.24% in 1 and 5 hours, and the average pore size and porosity are 331.50 nm and 69.25% respectively.

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.

Performance and characterization of bamboo-based activated carbon prepared by boric acid activation

Exposure to formaldehyde (HCHO) may have serious harm to human health because of its existence in indoor air. It is a simple and effective solution to remove formaldehyde from the environment by adsorption. Activated carbon is the primary adsorbent for the formaldehyde pollution control strategy. In this study, bamboo-based activated carbon (BAC) was prepared from bamboo charcoal (BC) by boric acid activation method and applied to remove formaldehyde in the air at room temperature. The structure and physicochemical properties of BAC were investigated by N2 adsorption-desorption, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, thermogravimetric and X-ray photoelectron spectroscopy. The results showed that the oxygen-containing functional group, amorphous degree and specific surface area of BAC were improved compared with BC, which improved its formaldehyde removal performance. The specific surface area and formaldehyde removal rate of BAC were 289.21 m2/g and 93.25% respectively, which were 288.37 m2/g and 49.95% higher than those of BC. This study provides a new idea for a better understanding of BC adsorbent that controls HCHO pollutant.

Effect of heat treatment temperature of the glaze lager on the structure and the formaldehyde removal performance of an interior wall tile

Effect of heat treatment temperature of the glaze lager on the structure and the formaldehyde removal performance of an interior wall tile

Effect of calcination temperature on the structure and formaldehyde removal performance at room temperature of Cr/MnO2 catalysts

Effect of calcination temperature on the structure and formaldehyde removal performance at room temperature of Cr/MnO2 catalysts

Harnessing Adsorption–Catalysis Synergy: Efficient Oxidative Removal of Gaseous Formaldehyde by a Manganese Dioxide/Metal–Organic Framework Nanocomposite at Room Temperature

AbstractThe potential utility of a transition metal oxide/metal–organic framework (MOF) nanocomposite has been explored using manganese dioxide (MnO2)/Universitetet i Oslo (UiO)‐66‐amine (NH2 (prototypical zirconium (Zr) MOF)) to develop an efficient adsorption–catalysis system for the removal of formaldehyde (FA) from the air. The room‐temperature FA (100 ppm) conversion (XFA (%)), when tested using five different MnO2 (wt%) loadings in the nanocomposite, is estimated as: 1% MnO2 (88%) > 2% MnO2 (86%) > 4% MnO2 (84%) > 6% MnO2 (75%) > 20% MnO2 (47%). The FA removal performance is lowered as the active catalytic sites are covered with the increases in the MnO2 loading (e.g., >1 wt%). The FA and molecular oxygen species preferably adsorb (and activate) onto the Zr atoms attached to the NH2 groups. The oxidation of FA into carbon dioxide proceeds subsequently through the formation of intermediates (e.g., dioxymethylene and formate). The MnO2 nanoclusters act as secondary reactive adsorption sites to boost the capture, activation, and oxidation of the FA molecules at the Zr active centers. Accordingly, the MnO2/UiO‐66‐NH2 nanocomposite is demonstrated to effectively harness the adsorption–catalysis synergy for highly efficient removal of FA relative to other well‐known catalysts (e.g., platinum and metal oxide‐based nanomaterials).

Performance assessment of a liquid desiccant system for formaldehyde removal based on a novel criterion

In the era of requirements in indoor air quality, liquid desiccant (LD) dehumidification is regarded as an energy-saving method removing indoor air contaminants during the dehumidification process, which has made considerable progress in recent years. Many previous studies have confirmed that the heat and mass transfer characteristics associated with absorption characteristics and thermophysical properties in LDs play a vital role in contaminants removal performance. The main purpose of this research is to numerically assess the indoor formaldehyde removal performance of a LD dehumidification system with different LDs. In order to make a fair assessment, a novel criterion based on the same temperature and the same vapor pressure which is the same desiccant condition is proposed. A numerical model integrated with heat, moisture, and formaldehyde transfer is used to predict the system performance. This model can rationally simulate the formaldehyde removal performance of the LD dehumidification system by inputting various operating parameters, including indoor air status parameters and outdoor air status parameters. The simulation results show that the number of mass transfer units of formaldehyde (NTUmf) plays a key role in the formaldehyde removal performance. The formaldehyde removal performances decrease with the increase of temperature and humidity ratio of return air, while they increase with the increase of temperature and humidity ratio of fresh air. With the aforementioned results, the study is expected to be beneficial to further improve the removal ability and potential of LD systems for indoor formaldehyde.

Passive Control of Indoor Formaldehyde by Mixed-Metal Oxide Latex Paints.

This work reports the incorporation of mixed-metal oxides (MMOs) such as Si/Ti and Si/Zr into latex paints in the form of thin coatings for permanent trapping of indoor formaldehyde. The formaldehyde removal performance of the surface coatings was evaluated in a lab-scale indoor air chamber, and the results were compared with those of powder analogues. Due to the pore blockage by the latex, the incorporation led to 6-30% reduction in adsorption capacity and 50-70% drop in the adsorption rate for MMO-latex paints relative to their powder MMO analogues. Under the operating conditions of concentration, temperature, and relative humidity, the Si/Zr-latex paints outperformed the Si/Ti counterparts. It was also observed that performance could decrease over excessive loading, for example, Si/Zr-latex paint with 15/1 Si/Zr weight ratio showed a 20% lower adsorption capacity than that of the Si/Zr-latex paint with 25/1 Si/Zr ratio at 5 ppmv, 25 °C, and 70% RH. While high temperature greatly reduced the adsorption rate of the MMO-latex paints, high humidity slightly promoted the rate of formaldehyde capture. In 10 L, flow-through chamber tests, 25Si/Zr-latex paint reduced 5 ppmv formaldehyde by up to 60% at 25 °C and 70% RH with an adsorption rate of 0.34 ppmv/h. Overall, this study highlights the potential of MMO-latex paints with optimized formation for the efficient abatement of indoor aldehydes.

Amine-Containing Resin for Coating with Excellent Formaldehyde Removal Performance

Formaldehyde (HCHO) is known to be a strong carcinogen, widely present in construction substances. To remove HCHO in the environment, we propose to graft organic amines to the chains of resins used in coatings, and when the indoor walls are coated by the materials containing such resins, HCHO can diffuse from the environment into the coatings to react with amines through irreversible nucleophilic addition. Specifically, we have introduced diallylamine (DA; as a comonomer) in poly(methyl methacrylate–butyl acrylate–methacrylic acid) (PMA) to form the DA–PMA resins through emulsion polymerization. It is found that the films formed from the DA–PMA resins with the mass fraction of DA from 1 to 5% can effectively remove HCHO. The largest average rate in HCHO removal has reached 0.198 mol h–1 kg–1 in the case of DA–PMA with 5% DA. In addition, the introduction of DA is able to improve the colloidal stability of DA–PMA particles, and the smoothness of the DA–PMA films is rather similar to that of pure PMA. Because of the cross-linking role of DA, the thermal stability of the DA–PMA polymers has been significantly improved with respect to pure PMA. It should be noted that a similar amine-containing resin was prepared using N,N′-methylenebis(2-propenamide) as the comonomer, but it did not perform as well as that made with DA. Proper theoretical (density functional theory) calculations provided an explanation and might enable one to predict in advance whether other related calculations might, or might not, work.

Light‐Induced Dynamic Stability of Oxygen Vacancies in BiSbO4 for Efficient Photocatalytic Formaldehyde Degradation

Defect engineering has been regarded as a versatile strategy to maneuver the photocatalytic activity. However, there are a few studies concerning how to maintain the stability of defects, which is important to ensure sustainable photocatalytic performance. Here, a novel strategy to modulate the structural properties of BiSbO4 using light‐induced dynamic oxygen vacancies is reported by us for efficient and stable photocatalytic oxidation of formaldehyde. Interestingly, the continuous consumption and replenishment of vacancies (namely dynamic vacancies) ensure the dynamic stability of oxygen vacancies, thus guaranteeing the excellent photocatalytic stability. The oxygen vacancies could also accelerate the electron migration, inhibit the photogenerated electron/hole recombination, widen the light absorption spectra, and thus improve the photocatalytic formaldehyde removal performance. Combined with the results of in situ DRIFTS, the reaction mechanism for each step of formaldehyde oxidation is revealed. As supported by DFT calculation of Gibbs free energy, the introduction of oxygen vacancies into BiSbO4 can promote spontaneous process of formaldehyde oxidation. Our work highlights a promising approach for stabilizing the defects and proposes the photocatalytic reaction mechanism in combination with the thermodynamic functions.

Cement-based composite with humidity adsorption and formaldehyde removal functions as an indoor wall material

Indoor air environment is of great significance for the comfort and health of residents while humidity adjustment and air purification are essential to provide favorable air environment. This paper aims to prepare multifunctional cement-based composite with both humidity adsorption and formaldehyde removal properties for indoor walls. Bamboo charcoal loading silver doped titanium dioxide (Ag/TiO2-BC) was synthesized and used in cement-based paste. Properties of the prepared paste including flowability, bonding strength, humidity adsorption and formaldehyde removal ratio, were investigated. Results show that Ag/TiO2-BC increases superplasticizer demand to keep the mini slump spread at a desirable level due to the higher specific surface area and porous structure of Ag/TiO2-BC. Besides, sample with higher content of Ag/TiO2-BC has lower bonding strength whereas the limit value of 0.5 MPa can be met if cement content is not lower than 30%. Humidity adsorption result indicates that Ag/TiO2-BC significantly improves the humidity content of mixture, which shows an approximately linear trend with Ag/TiO2-BC content. Cement paste with Ag/TiO2-BC has 226.5% higher humidity adsorption capacity compared to that with diatomite, which is the result of combined effects of specific surface area and effective pore volume. Formaldehyde removal result shows that formaldehyde removal ratio increases as Ag/TiO2-BC content rises and equilibrium removal ratio can be reached at 24 h. The removal of formaldehyde by cement with diatomite is due to the adsorption of diatomite while cement with Ag/TiO2-BC has both adsorption and photocatalytic decomposition effects. These findings demonstrate that cement-based composite with favorable humidity adsorption and formaldehyde removal performance as well as traditional properties can be prepared by incorporating Ag/TiO2-BC, showing a high potential to be used as wall materials to enhance indoor air environment.

Facile synthesis of highly efficient mpg-C3N4/TiO2 visible-light-induced photocatalyst and its formaldehyde removal performance in coating application

A facile method was developed to prepare mesoporous graphic C3N4 (MGCN)/TiO2 composites by synthesizing MGCN through a chemical template method and combining it with TiO2 by a solvothermal route. The as-prepared nanocomposites were respectively characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and diffuse reflectance UV-vis spectroscopy (DR-UV-Vis). The specific surface areas and pore sizes of the samples were obtained by the Brunauer-Emmett-Teller (BET) method, and the photocatalytic performance of MGCN/TiO2 was evaluated by photocatalytic degradation of methyl blue (MB) aqueous solution under visible-light irradiation, with the result that the composite prepared at the MGCN/TiO2 mass ratio of 1:1 displayed a higher photodegradation, 1.85 folds and 6.72 folds of that of pure MGCN and commercial TiO2. As-prepared MGCN/TiO2 composites were utilized as coatings on the carpet tile for removing indoor HCHO and the purification efficiency of formaldehyde can reach 39.69% (24 h˙0.25 m2)−1, which was higher than that of the blank carpet with − 16.20% (24 h˙0.25 m2)−1 for self-releasing, indicating their potential application prospect in functional coatings.

Degradation of formaldehyde from plywood with an iron electrode in alkaline solution

Formaldehyde emitted from formaldehyde-based adhesive profoundly affects human health. Accordingly, increasing attention has been paid to developing effective source-control measures to reduce the amount of formaldehyde released from plywood. In this study, the formaldehyde removal performance of a combined ammonia and electric field plywood treatment method was investigated. By performing orthogonal experiments, the respective influences of the concentration of ammonium hydroxide solution, intensity of the electric field, heating temperature, and heating time were analyzed. It was found that the concentration of formaldehyde released from the plywood was reduced by 48% using the ammonia and electric-field method. In addition, the treatment method was applied to high-emitting plywood. Here, it was found that a higher formaldehyde concentration within the untreated samples corresponded to a higher removal rate. The intensity of the electric field was the most influential factor affecting the performance of the method. The optimal operating conditions for the orthogonal experiment corresponded to a 12.5% concentration of ammonium hydroxide solution, an electric field intensity of 25 V, a heating temperature of 343 K and a heating time of 150 min. The ammonia and electric field treatment method can effectively reduce the concentration of formaldehyde emitted from plywood. Therefore, it can be applied as a promising method for pollution source control.

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

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

Analysis of Formaldehyde Removal Performance of Gingko Leaf for Indoor air Quality Improvement

Analysis of Formaldehyde Removal Performance of Gingko Leaf for Indoor air Quality Improvement

A predictive model for the formaldehyde removal performance of sorption-based portable air cleaners with pleated composite filter

Sorption-based portable air cleaners (PACs) are widely-used to remove gaseous contaminants. However, their capacity decline as a result of saturation cannot be well predicted through tests alone. Therefore, a predictive model to characterize the performance of a sorption-based PAC installed with a pleated composite filter is proposed in this paper. A salient merit of this proposed model is that once verified, it merely requires information regarding the adsorbent to simulate the assembled PAC. The model verification was conducted at three levels: 1) Dynamic adsorption test on the single-layer filter segment; 2) Contaminant removal test on the assembled PAC in the laboratory, which validated the extrapolation from the filter to the actual PAC unit; and 3) Field test in the research building. The third part estimated the robustness of the model in real situations. Formaldehyde was chosen as the target contaminant. Resultsshow that the model can handle changes in significant factors including temperature, relative humidity, flow rate, and inlet concentration. It was successfully extrapolated to an assembled PAC and was able to capture the point of decline of the clean air delivery rate (CADR) in the laboratory. Besides, the average relative errors between the tested and simulated results in the field test were under 20%, which is considered suitable for engineering applications.

Assessment of Adsorptive Filter for Removal of Formaldehyde from Indoor Air

We varied face velocities and initial formaldehyde concentrations to investigate the formaldehyde removal performance of coconut shell activated carbon (AC) adsorptive filter media. AC surface were rather uneven, with coarse and small pores, and with amorphously formed irregular layer structures. C, O, Mg, P etc. were detected, which showed the existence of MgO in AC. The AC surface area was 1333.3304 m2 g–1, and ketone -C=O bonds were successfully grafted onto the carbon. At any given face velocity, the experimental results indicate that the adsorption capacity increased and the breakthrough time decreased as the initial concentration increased. The breakthrough behavior of the AC adsorptive filter could henceforth be evaluated with confidence using the breakthrough curves predicted by the Yoon-Nelson model. Of the three kinetic models that were assessed, the experimental and calculated results show that the correlation coefficient and mean absolute performance error (MAPE) of the pseudo-second-order model generated the best approximation of the kinetic dynamics of the adsorption process—better than those of the pseudo-first-order model and intraparticle diffusion model. Both the intraparticle diffusion model and the membrane diffusion affected the overall rate of the adsorption process by more than one step. The equilibrium data of the AC adsorptive filter media was found to best fit the Langmuir model. The D-R equation predicted the equilibrium capacity of AC at a relative pressure of 0.151.

Formaldehyde removal performance analysis of a liquid desiccant dehumidification system

Liquid desiccant (LD) systems are an efficient method for humidity control. Moreover, LD systems also function to purify the air and remove volatile organic compounds such as formaldehyde. This study aims to analyze the performance of a LD system for formaldehyde removal from indoor air while simultaneously considering air dehumidification requirements. A theoretical model is proposed to predict the formaldehyde removal efficiency (εformaldehyde) of the LD system with various flow mediums, such as an air-LiBr solution, air-LiCl solution, and air-CaCl2 solution. Prior to assessing the LD system performance with the model, Henry's law constants (HLCs) of formaldehyde in the three solutions are tested at the salt concentration range of 30–50 wt% and at the temperature range of 10–50 °C. Based on the results, the correlation equation of the HLC's temperature dependence are given, and then adopted for the simulation model. The effects of the number of mass transfer units of formaldehyde (NTUmf), formaldehyde concentration in the return air, solution flow rate, and airflow rate on system performance are investigated and compared with various flow mediums. The results indicate that NTUmf is a key factor influencing the εformaldehyde. However, the NTUmf do not influence the dehumidification performance of the LD system. Both the εformaldehyde and dehumidification performance remain unchanged with the increase of formaldehyde concentration in the return air. Both the εformaldehyde and dehumidification performances decreased when the solution flow rate increased, and they likewise decreased with increased airflow rates.