Degradation Efficiency Of Formaldehyde Research Articles

Selective Heterogeneous Fenton Degradation of Formaldehyde Using the Fe-ZSM-5 Catalyst.

As a toxic Volatile Organic Pollutant (TVOC), formaldehyde has a toxic effect on microorganisms, consequently inhibiting the biochemical process of formaldehyde wastewater treatment. Therefore, the selective degradation of formaldehyde is of great significance in achieving high-efficiency and low-cost formaldehyde wastewater treatment. This study constructed a heterogeneous Fe-ZSM-5/H2O2 Fenton system f or the selective degradation of target compounds. By immobilizing Fe3+ onto the surface of a ZSM-5 molecular sieve, Fe-ZSM-5 was prepared successfully. XRD, BET and FT-IR spectral studies showed that Fe-ZSM-5 was mainly composed of micropores. The influences of different variables on formaldehyde-selective heterogeneous Fenton degradation performance were studied. The 93.7% formaldehyde degradation and 98.2% selectivity of formaldehyde compared with glucose were demonstrated in the optimized Fenton system after 360 min. Notably, the resultant selective Fenton oxidation system had a wide range of pH suitability, from 3.0 to 10.0. Also, the Fe-ZSM-5 was used in five consecutive cycles without a significant drop in formaldehyde degradation efficiency. The use of reactive oxygen species scavengers indicated that the hydroxyl radical was the primary active species responsible for degrading formaldehyde. Furthermore, great degradation performance was acquired with high concentrations of formaldehyde for this system, and the degradation efficiency was more than 95.0%.

Silica wastes derived multifunctional coatings for formaldehyde photodegradation and autonomous indoor humidity buffering

To maintain a comfortable and healthy indoor environment without large amounts of energy consumption is of great importance. The progress of multifunctional indoor coatings with formaldehyde photodegradation and humidity buffering capability is necessary. From the viewpoints of circular economy, the preparation of effective photocatalysts (denoted as sFCC/GCN-x and ESF/GCN-y) via the decoration of recycling industrial wastes (i.e., spent fluid catalytic cracking catalysts (sFCC) and enhancement silica fume (ESF)) onto graphitic carbon nitride (GCN) by using a simple route is reported. The obtained results show that the prepared sFCC/GCN-0.15 and ESF/GCN-0.15 photocatalysts have the rate constants of formaldehyde degradation of 0.0075 and 0.0082 min−1, respectively, which are superior to that of pristine GCN (0.0044 min−1) under visible-light irradiation. The enhanced transfer kinetics of photogenerated electrons and declined recombination of electron-hole pairs may account for the surpassing photocatalytic performance. Results obtained from electron paramagnetic resonance spectra and Mott-Schottky plots indicate that the formation of ･O2− via the reaction of O2 with electrons generated on the conduction band is the major reaction pathway to photodegrade formaldehyde under visible light. To further assess the real applications of prepared photocatalysts, the sFCC/GCN-0.15 and ESF/GCN-0.15 are used to fabricate the multifunctional coatings (denoted as s- and E-coatings) with sFCC and ESF as the main compositions. Experimentally, the E-coatings could reach the formaldehyde degradation efficiency of ca. 84.5% after 3 h of visible light irradiation and excellent humidity buffering ability (293.8 g m−2) which is at least 10-folds higher than commercial coatings (28.9 g m−2). This notable progress of humidity buffering capacity on E-coatings can be attributed to their surface textural properties. Most importantly, this study exemplifies the valorization of inorganic silica wastes to produce sustainable and multifunctional coatings which may offer the practical and cost-effective applications in the indoor living space.

Improving Photocatalytic Activity for Formaldehyde Degradation by Encapsulating C60 Fullerenes into Graphite-like C3N4 through the Enhancement of Built-in Electric Fields.

The photocatalytic degradation of formaldehyde by graphite-like C3N4 is one of the most attractive and environmentally friendly strategies to address the significant threat to human health posed by indoor air pollutants. Despite its potential, this degradation process still faces issues with suboptimal efficiency, which may be attributed to the rapid recombination of photogenerated excitons and the broad band gap. As a proof of concept, a series of graphite-like C3N4@C60 composites combining graphite-like C3N4 and C60 was developed via an in situ generation strategy. The obtained graphite-like C3N4@C60 composites exhibited a remarkable increase in the photocatalytic degradation efficiency of formaldehyde, of up to 99%, under visible light irradiation, outperforming pure graphite-like C3N4 and C60. This may be due to the composites' enhanced built-in electric field. Additionally, the proposed composites maintained a formaldehyde removal efficiency of 84% even after six cycles, highlighting their potential for indoor air purification and paving the way for the development of efficient photocatalysts.

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 Cu-Doped TiO2 on Wood Substrate with Highly Efficient Photocatalytic Performance and Outstanding Recyclability for Formaldehyde Degradation.

Photocatalytic oxidation is considered one of the most effective ways to remove formaldehyde from indoor air. However, the use of powder photocatalysts is limited by their low adsorption capacity and strong aggregation tendency. Hence, there is a need for a composite material with good cycling stability and high degradation efficiency. In the present study, a unique wood-based composite is produced by arranging Cu-TiO2 nanoparticles on porous structured wood. The porous structure of wood can adsorb formaldehyde, and the abundant functional groups on the surface can act as a reaction platform for anchoring the Cu-TiO2 nanoparticles. Cu doping facilitates electron interaction between TiO2 and Cu, promotes the transfer of charge carriers, lowers the electron-hole recombination rate, and improves the photocatalytic degradation efficiency of formaldehyde. The photocatalytic efficiency of the wood-based composites was highest (85.59%) when the n(Cu)/n(Ti) ratio was 7%. After nine cycles, the wood composites still had a high degradation rate, indicating good recyclability. Overall, this wood composite is an eco-friendly and promising material for indoor air filtration.

Ceramic tiles coated with Zr‐Ag co‐doped TiO2 thin film for indoor air purifying and antimicrobial applications

AbstractIn this study, Zr‐Ag co‐doped TiO2 (ZAT) photocatalyst films having varied numbers of layers (1, 2, 3, and 4) have been developed to coat on ceramic tile substrates by sol‐gel spin coating technique. The specimens were tested to determine antibacterial activity against Escherichia coli and the capability to degrade gaseous formaldehyde under visible light. X‐ray diffraction, ultraviolet and visible absorption spectroscopy, water contact angle, and scanning electron microscopy were applied to characterize the structural and morphological properties of the samples. The photocatalytic reactivity of the nanocomposite films was investigated by the decolorization of methylene blue (MB) dye under visible light irradiation. The results showed that the two‐layer ZAT photocatalyst film on ceramic tile exhibited the highest photocatalytic decolorization of MB, with 60.36% efficiency. The ZAT tile had formaldehyde degradation efficiency up to 32.74% within only 6 h under visible light irradiation, higher than that of the bare ceramic tile (4.90%). Additionally, the ZAT thin films could enhance anti‐E. coli activity and could be capable of degrading air pollution.

Enhanced photocatalytic degradation efficiency of formaldehyde by in-situ fabricated TiO2/C/CaCO3 heterojunction photocatalyst from mussel shell extract

The marine waste shells with inherent advantages are applied to synthesize high value-added products instead of environmental issues. In this work, a ternary TiO2/C/CaCO3 composite photocatalyst (TCC) was precisely designed in the presence of mussel shell extract (MST). The characterization results revealed that the TCC photocatalyst with the optimal ratio of MST could be synthesized by doping multi-elements naturally presented in the MST. The composite photocatalyst exhibits a small diameter, abundant oxygen defects, and efficient interfacial charge transfer capability. The photocatalytic investigation demonstrated that HCHO could be effectively and thoroughly degraded within 80 ​min over TCC-0.4 under visible-light. Furthermore, the HCHO removal rate remained up to 95% after five cycles, revealing the high stability of the photocatalyst. The enhanced photocatalytic property is attributed to synergistic effect of in situ synthesized TiO2/C/CaCO3 composite photocatalyst. This work provides new insights into the efficient, economical and sustainable photocatalyst for indoor air purification.

The Application of Bi‐Doped TiO2 for the Photocatalytic Oxidation of Formaldehyde

AbstractThe photocatalytic oxidation technology has a great potential for the removal of volatile organic compounds (VOCs). In this research, a novel TiO2/Bi2O3 catalyst is developed to degrade indoor formaldehyde by the photocatalytic oxidation technology. The TiO2/Bi2O3 catalysts with different mass fractions of Bismuth(Bi) are prepared by impregnation method. The characterizations of the TiO2/Bi2O3 catalysts by X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectrophotometry, and Brunauer–Emmett–Teller analyses suggest that the doping of TiO2 with Bi neither changes the crystal structure nor the crystal phase of the TiO2, but increases the number of mesopores on the TiO2/Bi2O3 surface and the specific surface area of the TiO2/Bi2O3. By optimizing such parameters as the flow rate; the concentration; and the relative humidity of formaldehyde, the mass fraction of Bi, and the loading amount of the catalyst, a formaldehyde degradation efficiency as high as 96% is obtained.

A Simple Preparation Method of Graphene and TiO2 Loaded Activated Carbon Fiber and Its Application for Indoor Formaldehyde Degradation

Formaldehyde has a significant impact on human health. This study used a simple dipping method to load graphene-titanium dioxide (GR-TiO2) on activated carbon fibers (ACFs). The microstructure of GR-TiO2/ACF hybrid material was observed by SEM, combined with XRD and BET analysis. The result showed that the GR-TiO2/ACF hybrid material had a specific surface area of 893.08 m2/g and average pore size of 2.35 nm. The formaldehyde degradation efficiency of the prepared material was tested under different conditions, such as ultraviolet (UV) radiation, air supply volume, relative humidity, initial mass concentration. The results showed that the UV radiation intensity, airflow and the initial mass concentration were positively correlated with the formaldehyde removal rate, and the relative humidity was negatively correlated with the formaldehyde removal rate. The GR-TiO2/ACF hybrid material had a maximum formaldehyde removal rate of 85.54% within 120 min.

Insight into the defective sites of TiO2/sepiolite composite on formaldehyde removal and H2 evolution

TiO2/sepiolite composites (T–S–R) with different contents of Ti3+ and oxygen vacancy were successfully prepared through 0D/1D structural assembly and thermal treatment under various atmospheres (R = Air, O2, N2, Ar and H2). The content of Ti3+ and oxygen vacancy was confirmed through electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), which exhibited significant effect on the photocatalytic formaldehyde (HCHO) removal and H2 evolution. The T–S–Ar composite exhibited much higher formaldehyde degradation efficiency (91.8% within 90 min) and H2 production performance (1974.8 μmol/h/g) than other samples under simulated solar light. According to the material characterizations and DFT calculations, the improved photocatalytic activity could be ascribed to the synergistic effect between natural sepiolite and TiO2. Besides, the generation of mid-gap levels induced by the appropriate content of Ti3+ and oxygen vacancy led to the larger specific surface area, smaller nano-sized TiO2 and higher photogenerated carriers’ separation efficiency. Furthermore, it was found that higher content of oxygen vacancies would act as the recombination centers for electron–hole pairs, thereby greatly reducing the photocatalytic performance. Notably, our study provides a promising candidate for effectively addressing the air pollution (e.g. HCHO removal) and energy issues (e.g. H2 production) based on the defect engineering and mineral support technology.

Solar-thermal energy conversion prediction of building envelope using thermochemical sorbent based on established reaction kinetics

In this paper, the dehydration (heat charge) and hydration (discharge) reaction kinetics of thermochemical sorbents synthesised in previous work by the author is established by using the isothermal method, with the aim of understanding their thermochemical conversion behaviour and developing reaction models for numerical simulations. The effects of temperature, reaction advancement, and vapour pressure are fully considered and employed in a thermochemical energy storage model. The derived dehydration reaction activation energies of the LiOH/LiCl@ expanded graphite (LiO2C1@EG and LiO3C1@EG) sorbents are 54.7 and 52.2 kJ/mol, respectively, which are lower than that of pure LiOH·H2O. To achieve the dual-function of space heating and air purification in an efficient manner, a novel solar building envelope combining thermochemical energy storage and photocatalysis is proposed and studied numerically based on the established reaction kinetics. Fresh air can be produced during solar harvesting. The porous wall, which is made of a composite sorbent, absorbs thermal energy to heat air near the wall and thus creates a chimney effect in the channel for continuous space heating. During discharge, the desorbed heat storage wall adsorbs the moist air and the hydration reaction enthalpy can be used again for air heating. The total efficiency including the equivalent formaldehyde degradation efficiency and the thermal efficiency is around 81% when the solar radiation is 600 W/m2. Results indicate that this passive building envelope can achieve a higher heat harvesting and utilisation efficiency in a more compact space compared to previous studies. Moreover, the influence of radiation intensity on air purification and thermal performance is investigated. The present work provides new insights and promotes the integration of passive solar building envelopes and thermochemical energy storage.

Microencapsulation of formaldehyde scavenger agent and its application to veneered panels

Formaldehyde scavenger agent can effectively control formaldehyde emissions from wood-based panels, but the existing formaldehyde scavenger agent can only work in the short term. For the purpose of long-term control of formaldehyde emissions from wood-based panels, microencapsulation of formaldehyde scavenger agent was synthesized in this paper. The effect of the emulsifying agent and the core to shell ratio on the microcapsules' morphology and formaldehyde degradation efficiency was investigated. The results showed that microcapsules of optimum morphology with high degradation efficiency can be obtained under the condition of 1% of the sodium dodecyl sulfate emulsifier, 3% of the shell solution, and a core to shell ratio of 1:3 with 1000 r/min stirring speed. The loading ratio and efficiency of the microcapsules achieved 36.25% and 8.05% respectively. Compared with control panels, the formaldehyde released from veneered panels treated with microcapsules was 39.7% and 41.4% lower in short-term and long-term emissions.

Enhanced Photocatalytic Degradation Efficiency of Formaldehyde by <i>In-Situ</i> Fabricated TiO <sub>2</sub>/C/CaCO <sub>3</sub> Heterojunction Photocatalyst from Mussel Shell Extract

Enhanced Photocatalytic Degradation Efficiency of Formaldehyde by <i>In-Situ</i> Fabricated TiO <sub>2</sub>/C/CaCO <sub>3</sub> Heterojunction Photocatalyst from Mussel Shell Extract

Thermal, electrical and purification performance of a novel thermal-catalytic CdTe double-layer breathing window in winter

CdTe PV cell is one perfect candidate for window application because of its good daylighting performance, low-temperature coefficient and excellent electrical performance under weak light. In addition, thermal catalytic oxidation is an thermal driven air purification technology and the thermal energy can be easily obtained from PV window systems. Therefore, a novel thermal-catalytic CdTe double-layer breathing window was proposed. Firstly, the electrical, thermal and daylighting performances of proposed window were investigated experimentally. Secondly, the removal of formaldehyde was investigated using the verified coupled formaldehyde mass transfer and thermal-catalytic reaction kinetic model. Finally, the evolution of indoor formaldehyde concentration considering formaldehyde release source was calculated. Main results were: (1) The thermal and electrical efficiencies were respectively 0.297 and 0.0715, which were closed to the reported results. Also, the proposed window had better daylighting uniformity compared with conventional window. (2) The total generated clean air was 25.7 m3/(m2•day), with the equivalent formaldehyde degradation efficiency of 0.010 based on purification performances of various air purifiers in market. (3) The comprehensive thermal efficiency was 0.518, with increase of 9.28% considering the contribution from formaldehyde removal. (4) The proposed window could make the indoor concentration approach to standard concentration under most working conditions.

Novel Nanoarchitechtonics Olive-Like Pd/BiVO₄ for the Degradation of Gaseous Formaldehyde Under Visible Light Irradiation.

In this research, olive-like Pd/BiVO₄ was successfully prepared through a facile hydrothermal coreduction method for the photocatalytic degradation of formaldehyde under visible light irradiation. The structure, composition, and optical properties of the as-prepared Pd/BiVO₄ were characterized through X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectrophotometry, X-ray photoelectron spectroscopy, and photoluminescence. In addition, the photocatalytic activities of Pd/BiVO₄ were evaluated through the photodegradation of formaldehyde. The experimental results demonstrated that the degradation efficiency of formaldehyde increased with increasing irradiation time. Moreover, 1.0 wt% Pd/BiVO₄ exhibited the highest photocatalytic performance for formaldehyde degradation in 180 min, with the formaldehyde degradation rate as high as 87.5%.

Synthesis of immobilised Ni-doped TiO2 nanoparticles through hydrothermal route and their efficiency evaluation in photodegradation of formaldehyde

ABSTRACTThe aim of the present study was to synthesis Ni-doped TiO2 nanoparticles (NPs) in order to evaluate their effectiveness in photocatalytic degradation of formaldehyde in the aqueous phase. The Ni-doped TiO2 NPs were synthesised using a mild hydrothermal method. They were then immobilized on glass plates by the calcination method. Characterisation of Ni-doped TiO2 NPs was also carried out using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The SEM images showed the uniform distribution of as-synthesised NPs on the surface of glass plates, with multidimensional crystalline structures. The results indicated that increasing the dopant weight ratio to 0.7% enhanced the photocatalytic degradation efficiency of formaldehyde; however, a further increase in the dopant weight ratio reduced the process efficacy. According to the results, increasing the initial pH from acidic and neutral to alkaline conditions decreased the efficacy of the process. Furthermore, the results showed that increasing the amount of nanocatalyst and decreasing the initial concentration of formaldehyde favoured the photocatalytic degradation of formaldehyde.

Fabrication of Bi2MoO6 Photocatalytic Fibers via Wet Spinning and Enhanced Photocatalytic Activity

In this paper, Bi2MoO6 photocatalytic fibers were fabricated by wet spinning method and the photocatalytic activity was found to be enhanced significantly. The Bi2MoO6 powders were prepared by hydrothermal process at different pH (0.4, 6, 8, 10), which is recorded as BMO-0.4, BMO-6, BMO-8, BMO-10. The powders were then mixed with sodium alginate colloid, and fabricated into photocatalytic fibers by wet spinning. The samples were recorded as FB-0.4, FB-6, FB-8, FB-10, respectively. The crystal phase, morphology and photophysical properties of the fiber samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and laser particle size analysis (LPSA). In order to investigate the photocatalytic performance of the synthesized photocatalysts, RhB and formaldehyde were used as simulated water pollutant and air pollutant, respectively. It showed that the efficiency of the degradation of RhB over BMO-10 was 75%, while that enhanced to 85% over FB-10. It should be noted that the content of photocatalyst in the fiber FB-10 was only 1%. The degradation efficiency of formaldehyde in FB-10 sample reaches 92%.

Advanced oxidation of formaldehyde in the aqueous solutions using UVC/S2 O8 2- process: Degradation and mineralization

Background: As a human carcinogen, formaldehyde is a toxic chemical imposing adverse effects on public health and environment. Due to its high reactivity, colorless nature, sustainability, purity in commercial forms, and low prices, the production and consumption of this compound has expanded vastly in industries. Methods: In this study, a UVC photoreactor with a total volume of 120 mL was used and operated in a rotary mode. To determine the residual concentration, high-performance liquid chromatography (HPLC) device was applied whose detector was set at a wavelength of 355 nm and equipped with C18 column (with dimensions of 25 × 4.6 mm i.d, and particle size of 5 µm). Total organic carbon (TOC) was determined using a TOC analyzer. Results: The optimal condition in this study was obtained at pH=3 and formaldehyde concentration of 350 mg, so that the removal of formaldehyde and TOC was 98.2% and 95.1%, respectively, after 35 minutes reaction time. The formaldehyde removal efficiency was assessed in the presence of methanol (MeOH), tert-butyl alcohol (TBA), and salicylic acid (SA) scavengers, and it was indicated that SO4 •- radicals were the most effective factors in formaldehyde destruction. By increasing the concentrations of MeOH, TBA, and SA to 2.5 g/L, the degradation efficiency of formaldehyde dropped from 98.02% to 69.78%, 64.68%, and 45.14%, respectively, at 35 minutes reaction time. The removal of formaldehyde in the presence of nitrate was significantly reduced and it had a significant effect on the removal of formaldehyde. Conclusion: In this study, the removal of formaldehyde was investigated in the presence of various anions including bicarbonate, carbonate, chloride, sulfate, and nitrate. According to the results, the UVC/S2 O8 2- process is a convenient and cost-effective method for the removal of formaldehyde.

Powder Quartz/Nano-TiO2 Composite: Mechanochemical Preparation and Photocatalytic Degradation of Formaldehyde

Powder quartz (PQ)/nano-TiO2 composite was prepared by a mechanochemical method. Based on as-prepared PQ/nano-TiO2 composite, we prepared interior paints and investigated the degradation efficiency of formaldehyde (DEF). Scanning electron microscopy showed that nano-TiO2 got well dispersed by the adding of PQ. Thermogravimetric analysis indicated that the mass ratio of 4:1 was a relatively good proportion for the most production of PQ/nano-TiO2 composite. Fourier transform-infrared spectrometry showed that the peak position of Ti-O-Si bond varied with the milling time. At the early stage, no characteristic peak of Ti-O-Si bond was observed, while at the later stage, new peaks at 902 cm-1 and 937 cm-1 appeared. Meanwhile, PQ/nano-TiO2 composite-based interior paint exhibited significant DEF of 96.3% compared to that consisting of sole nano- TiO2 of 92.0% under visible light illumination. As an abundant mineral resource, PQ would make interior paints with HCHO purifying effect much more efficient and cheaper.

Degradation of Formaldehyde From Synthetic Wastewater Using Fe2+/H2 O2 /O3 Process

Formaldehyde is used in many industries for its different chemical characteristics. The wastewater in these industries contains large amounts of formaldehyde which is dangerous and toxic for human and environment. The purpose of this study was to investigate the efficiency of Fe2+/H2 O2 /O3 process in degradation of formaldehyde from synthetic wastewater. This experimental bench-scale study in batch system was conducted on the synthetic wastewater in primary concentration of formaldehyde (500 mg/L). The maximum percentage of formaldehyde removal was 72.5% that was observed in molar ratio of 2.4 [H2 O2 ]/[Fe2+]. After determining optimum [H2O2]/[Fe2+], the effects of pH variables, function time, and ozone concentration were studied in formaldehyde removal. In this process, the maximum degradation efficiency of formaldehyde in 0.7 mg/L ozone concentration and in 2.4 of molar ratio for [H2 O2 ]/[Fe2+] was 85.84% after 20 minutes. Moreover, the effect of pH and ozone concentration was significant in degradation efficiency (P<0.05). Generally, the Fe2+/ H2 O2 /O3 process seems to be a practical and reliable method in treating the industrial wastewater contaminated with high concentrations of formaldehyde.