Formaldehyde Removal Efficiency Research Articles

Enhanced formaldehyde oxidation of plywood using MnO2 nanoflowers supported on porous hydrothermal carbon at ambient temperature

MnO2 nanoflowers were supported on porous hydrothermal carbon via in situ loading and used for the catalytic oxidation of formaldehyde from plywood manufactured with UF adhesive. The prepared MnO2 had a δ-type structure. The use of hydrothermal carbon (Hcs) improved the dispersion of active components in the materials and provided space for the catalytic reactions. Hcs/MnO2 exhibited catalytic activity and stability during formaldehyde oxidation at room temperature. The formaldehyde removal efficiency reached 90.43 % in 30 min. The Hcs/MnO2 had more oxygen vacancies than the MnO2 catalyst, providing more abundant active substances such as -OH, O2-, O- and other active substances to promote the catalytic reaction. The effects of Hcs/MnO2 on the formaldehyde emission and the mechanical properties of plywood were investigated. The MOR, MOE and bonding strength of the Hcs/MnO2-loaded plywood with 9 % Hcs were 51.1 MPa, 2994 MPa, and 0.8 MPa, respectively. After 28 d of exposure, the formaldehyde emitted from the plywood treated with Hcs/MnO2 decreased to 0.023 mg/m3, which fulfilled the requirement for ENF grading. The controlled release of free formaldehyde from plywood by Hcs/MnO2 was reflected by changes in mass transfer and catalytic oxidation. The manganese oxides in the micropores of the wood reduced the diffusion coefficient of free formaldehyde and hindered migration through the substrate. Once the concentration of formaldehyde decreased to a certain level, it was degraded by Hcs/MnO2, thus removing formaldehyde from the source.

A novel nCP-PVA@ACA composite with core–shell structure for efficient formaldehyde removal from air

Removing formaldehyde from indoor environments is crucial for the health of residents. However, developing a highly efficient and cost-effective material that is safe and stable and capable of continuously removing formaldehyde from ambient air is challenging. In this study, an environmentally friendly plant composite active calcium alginate gel (nCP-PVA@ACA) was prepared by fixing slow-release nanosized calcium peroxide (nCP-PVA) and active components from cactus stems into a three-dimensional network structure of a calcium alginate gel. The microscopic morphology, chemical composition, and structure of nCP-PVA@ACA were characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller. In the purification column, nCP-PVA@ACA was used as a filler, which effectively removed formaldehyde from the airflow. The results indicate that nCP-PVA was well dispersed and encapsulated by the calcium alginate gel. The formaldehyde removal efficiency of nCP-PVA@ACA ranged from 90.56 % to 98.51 % when the formaldehyde concentration in the air was in the range of 0.146–0.984 mg·m−3, with a maximum removal capacity of 89.31 mg·kg−1 (based on the dry weight of Na alginate). After 3.0 h of continuous purification, the formaldehyde concentration in the treated airflow was reduced to 0.020–0.053 mg·m−3, which was significantly lower than the recommended limit of 0.08 mg·m−3 of formaldehyde in ambient air. The synergistic effects of plant active components and slow-release nCP are key to effective formaldehyde removal. This study highlights the potential of calcium peroxide for air pollution control, providing new insights and theoretical support for their applications.

Optimization Strategy for Formaldehyde Removal by Carbon Cathode Electro-Fenton: Enhancement of Formaldehyde and Oxygen Co-adsorption by Rational Nitrogen Doping Types.

This study investigates the effect of N-doped coal-based activated carbon cathode on formaldehyde-oxygen coadsorption. Further investigation investigates the effect of formaldehyde-oxygen coadsorption on H2O2 generation and formaldehyde removal in an electro-Fenton system. Nitrogen doping enhances formaldehyde and oxygen coadsorption by modulating competitive adsorption. Density Functional Theory (DFT) calculations confirm pyrrole nitrogen favors formaldehyde, and graphite nitrogen favors oxygen adsorption. N-doped activated carbon adsorbs 0.36 mg of formaldehyde and 0.1 mg of oxygen in 120 min and removes 82.43% of formaldehyde after electro-Fenton treatment. N-doped activated carbon enhances the synergistic adsorption of formaldehyde and oxygen. In the synergistic adsorption process, the amount of formaldehyde adsorbed is greater than the amount of oxygen adsorbed. This improves the removal efficiency of formaldehyde by electro-Fenton technology. It provides a new method for electro-Fenton removal of organic pollutants.

Conditional Optimization on the Photocatalytic Degradation Removal Efficiency of Formaldehyde using TiO2 – Nylon 6 Electrospun Composite Membrane

Conditional Optimization on the Photocatalytic Degradation Removal Efficiency of Formaldehyde using TiO2 – Nylon 6 Electrospun Composite Membrane

High‐Performance Ceramic Catalyst Filters with Textured Waveguides for Efficient Removal of Volatile Organic Compounds

AbstractThe cordierite‐based ceramic catalyst filter (CCF) has attracted considerable attention as a promising future air purification system due to its ability to filtrate particulate matter (PM), as well as decompose volatile organic compounds (VOCs) through ultraviolet (UV)‐activated photocatalytic reactions. Its performance, however, is strictly limited because majority of UV photons are absorbed near the entrance of the high‐aspect‐ratio air‐flow channels, thus, only a limited portion of photocatalysts is activated during the flow of polluted air. In this study, a high‐performance CCF is presented featuring textured waveguides (TWs) aligned with an array of UV light‐emitting diodes (LEDs) emitting at a peak wavelength of 365 nm, which are inserted into an array of high‐aspect‐ratio channels. TWs ensure the delivery of UV photons deep inside channels via total internal reflection and scattering, enabling the activation of majority of photocatalysts, resulting in remarkable improvement in VOCs removal efficiency. The proposed CCF system exhibits much higher formaldehyde (HCHO) removal efficiency by 70% compared to conventional CCF systems even subjected to much lower UV light power densities. It is strongly believed that it is possible to further improve the removal efficiency, while maintaining effective PM filtering and ultralow electrical power consumption, by optimization of the geometry of the CCF system with TWs.

Functional biocarbon-based coatings for wood protection and indoor air depollution

Growing concerns about indoor air pollution heighten the need to develop depolluting materials to achieve a healthy built environment. This study developed functional coatings for wooden surfaces using 20 wt% photocatalytic biocarbon particles doped with manganese oxide (BC–MnO2) and two different coating materials (linseed oil and waterborne acrylic). The samples' surface hydrophobicity and color properties were tested before and after accelerated aging. The depolluting potential of the samples was evaluated by formaldehyde removal efficiency test in indoor conditions. Results showed that adding BC-MnO2 particles increased the hydrophobicity regardless of the coating material's type. After accelerated aging, the hydrophobicity of all samples increased, which was attributed to the curing of the oil and acrylic polymers and the increase in surface roughness eventually caused by surface damage. The color change (ΔE) was more intense in the case of uncoated wood and samples without BC-MnO2. However, the BC-MnO2-containing coatings were effective in color preservation (ΔE < 2), which was attributed to the anti-UV property of biocarbon. The BC-MnO2-containing coatings exhibited a promising formaldehyde removal efficiency of up to 24 % and 46 % for oil and acrylic samples, respectively. The combination of BC-MnO2 and acrylic material was more favourable to attracting the formaldehyde molecules, likely due to the similar polarity. The developed functional coatings exhibited an acceptable ability for wood protection and formaldehyde remediation and can be potentially used to enhance indoor air quality.

Mechanisms of efficient indoor formaldehyde removal via electro-Fenton: Synergy in ·OH generation and utilization through a modified carbon cathode

Indoor formaldehyde poses a significant carcinogenic risk to human health, making its removal imperative. Electro-Fenton degradation has emerged as a promising technology for addressing this concern. In the electro-Fenton system, ·OH is identified as the primary active species responsible for formaldehyde removal. Hence, its generation and utilization are pivotal for the system's effectiveness and economy. Experimental and quantum chemical methods were employed to investigate the effects and mechanisms of nitrogen doping on various aspects influencing ·OH generation and utilization. Results indicate that nitrogen doping synergistically enhances the generation and utilization of ·OH, leading to an improved formaldehyde removal efficiency in nitrogen-doped cathodic systems. The dominant nitrogen type influencing ·OH generation and utilization varies across different stages. Pyridinic nitrogen facilitates H2O2 adsorption through hydrogen bonding, while pyrrolic and graphitic nitrogen contribute to formaldehyde adsorption and catalyze the conversion of H2O2 to ·OH. Both pyridinic nitrogen and pyrrolic nitrogen boost the degradation of formaldehyde by ·OH. In comparison to the unmodified system, the modified system with NAC-GF/700C as cathode exhibits remarkable improvements. The formaldehyde removal efficiency has increased twofold, and energy consumption reduced by 73.45%. Furthermore, the system demonstrates excellent cyclic stability. These advancements can be attributed to the activation temperature, which leads to the appropriate types and high content of nitrogen elements in NAC-GF/700C. The research represents an important step towards more economical and efficient electro-Fenton technology for indoor formaldehyde removal.

Manganese dioxide-coated biocarbon for integrated adsorption-photocatalytic degradation of formaldehyde in indoor conditions

Formaldehyde is a common indoor air pollutant with hazardous effects on human health. This study investigated the efficiency of biocarbon (BC) functionalized with variable contents of MnO2 for formaldehyde removal in ambient conditions via integrated adsorption-photocatalytic degradation technology. The sample with the highest formaldehyde removal potential was used to prepare a functional coating made of acrylic binder mixed with 20 wt% of the particles and applied on beech (Fagus sylvatica L) substrate. SEM images showed that MnO2 was deposited around and inside the pores of the BC. EDX spectra indicated the presence of Mn peaks and increased content of oxygen in the doped BC compared to pure BC, which indicated the successful formation of MnO2. Raman spectra revealed that the disorder in the BC's structure increased with increasing MnO2 loadings. FTIR spectra of BC–MnO2 samples displayed additional peaks compared to the BC spectrum, which were attributed to MnO vibrations. Moreover, the deposition of increased MnO2 loadings decreased the porosity of the BC due to pores blockage. The BC sample containing 8 % Mn exhibited the highest formaldehyde removal efficiency in 8 h, which was 91 %. A synergetic effect between BC and MnO2 was observed. The formaldehyde removal efficiency and capacity of the coating reached 43 % and 6.1 mg/m2, respectively, suggesting that the developed coating can be potentially used to improve air quality in the built environment.

The effects of metal-oxide content in MnO2-activated carbon composites on reactive adsorption and catalytic oxidation of formaldehyde and toluene in air

The deterioration in air quality caused by volatile organic compounds (VOCs) has become an important environmental issue. Here, activated carbon (AC) composites with manganese oxide (MnO2: 1 % to 50 %) are synthesized as MAC for the removal of formaldehyde (FA) and toluene in air through a combination of reactive adsorption and catalytic oxidation (RACO) at room temperature (RT). The best-performing composite (MAC-20: 20 % of MnO2) exhibits a 10 % breakthrough volume (BTV10%) of FA and toluene at 41.2 and 377 L g−1, respectively while realizing complete oxidation of FA and toluene into carbon dioxide (CO2) at 100 °C and 275 °C, respectively. The reaction kinetic rates (r) for 10 % removal efficiency of FA and toluene (XFA or T) at RT are estimated as 9.82E-02 and 3.20E-02 mmol g−1 h−1, respectively. The high performance of MAC-20 can be attributed to its enriched adsorption capacity of oxygen vacancy (OV) and the presence of adsorbed oxygen (OA), as shown by an Mn3+/Mn4+ ratio of 0.729 and an OA/lattice‑oxygen (OL) ratio of 1.50. The results of this study highlight the interactive roles of oxygen abundance and temperature in the generation of distinctive oxidation patterns for FA in reference to toluene. This study is expected to offer practical guidance for the implementation of RACO against diverse VOCs for efficient management of air quality.

Rare Earth Dopants Enhance Thermocatalytic Activity of Manganese Oxides on Corrugated Silica Carriers for Formaldehyde Degradation

AbstractThe development of high efficiency thermocatalysts remains a great challenge for gaseous formaldehyde elimination. Herein, rare earth‐doped manganese dioxide (RE‐MnO2) particles with sizes of approximately 200 nm were deposited on corrugated silica carrier (CSC) by using cerium or samarium as dopants. One part of rare earth ions in RE‐MnO2/CSC were substituted for the manganese ions in α‐MnO2, and the other part existed in the form of cerium oxide or samarium oxide. RE‐MnO2/CSC exhibited better thermocatalytic activity than MnO2/CSC. The formaldehyde removal efficiency over RE‐MnO2/CSC reached nearly 100 % even after cycle tests of 5 times. Both the cerium and samarium doping accelerated HCHO oxidation via increasing lattice oxygen and Mn4+ amounts, improving low‐temperature redox properties, and reducing apparent activation energy. Notably, the RE oxides in the catalysts played different roles in HCHO degradation. Samarium oxide did not possess thermocatalytic activity, while cerium oxide in RE‐MnO2/CSC participated directly in the formaldehyde degradation via the CeO2↔Ce2O3 redox reaction and facilitated the oxidation of Mn2O3 into MnO2. This work revealed the effect mechanisms of RE doping and RE oxide on the enhanced thermocatalytic activity, and provided a novel viewpoint to develop RE‐doped catalysts for formaldehyde removal.

Photocatalytic efficacy of air purifiers equipped with self-cleaning titanium dioxide xerogel coatings against gaseous formaldehyde: A study using DRIFTS and DFT analysis

In this research, the practical efficacy of a portable air purifier (AP) loaded with a self-cleaning titanium dioxide xerogel (TX) has been investigated for the photocatalytic degradation of formaldehyde (FA) from the air. The photocatalytic performance of the AP system is optimized through control on the synthesis variables (e.g., annealing temperatures (150–750°C), colloidal volume of photocatalysts in filter fabrication (1–10 mL), and process variables (e.g., air-circulation speeds (100-160 L/min), type of light sources (UVA vs. UVC), and FA concentrations (0.5–5 ppm)). The self-cleaning potential of the AP-TX system is validated with FA removal efficiencies of ≥96 % across diverse settings and over 10 repeated cycles. The optimum kinetic rate constant for FA (e.g., 0.0195 s−1) is attained by a TX-coated honeycomb filter annealed at 450°C based on a Langmuir–Hinshelwood first-order kinetic model. The high photocatalytic efficacy of the AP-TX system is supported further in terms of a clean air–delivery rate (CADR) of 19.57 L/min, a quantum yield (QY) of 1.93×10−3 molecules/photon, and a space–time yield (STY) of 2.57×10−2 molecules/photon/g. The formation of dioxymethylene and formate as intermediates of FA degradation is confirmed by diffuse reflectance infrared Fourier transform spectroscopy analysis (DRIFTS). The results derived from density functional theory (DFT) simulations also suggest that the photocatalytic degradation of FA should proceed endothermically. The overall findings of this research are expected to help establish advanced strategies for the fabrication of self-cleaning photocatalysts for air purification applications.

Performance study of organic photovoltaic/thermal system with synergistic effect of photocatalytic and thermal catalytic technology

Organic photovoltaic cells are considered to be an effective solution for maintaining excellent electrical energy output in high temperature environment. However, the application of OPV alone has a low utilization rate of the solar spectrum. The combined application of OPV and other technologies is explored to improve the utilization efficiency of the solar spectrum. Based on the above gaps, this study proposes an organic photovoltaic/thermal system with synergistic effect of photocatalytic and thermal catalytic (PC/TC-OPV/T). By integrating organic photovoltaic cells, photocatalytic technology, thermal catalysis technology and photothermal components, the utilization efficiency of the solar spectrum is improved, and the triple functions of formaldehyde removal, electrical energy and hot water are realized. Therefore, this study proposes a new air purification-thermal-electrical model, establishes the heat transfer balance equation inside the system and the air purification and mass transfer balance equation in the air duct, proposes the performance evaluation index of the system, and uses Ansys Fluent software to predict the working characteristics of the system under different operating conditions, and draw the following conclusions: (1) Under the synergistic action of photocatalytic and thermal catalytic technologies, the formaldehyde removal efficiency is 84.4%, which is 30% higher than that of photocatalytic alone. (2) The electrical efficiency of the new system benefits from high solar irradiance and environment temperature, enabling it to achieve the efficiency of 17.84% within the research scope. (3) Under the research conditions, the instantaneous water flow heating efficiency of the system is up to 69.6%.

Determining Formaldehyde Phytoremediation Efficacy of Selected Ornamental Plants

In the recent past, deterioration of indoor air quality has become a serious concern due to the increased energy efficiency and reduced air exchange rate inside urban buildings. Volatile organic compounds (VOCs) are a major category of indoor air pollutants that can lead to adverse health outcomes such as headaches, allergies and asthma in those exposed for prolonged periods. Formaldehyde, the VOC used in the present study is a common contaminant of indoor air which originates from particle board, plywood, paper products, certain adhesives, tobacco smoke and other sources. The use of plants for the mitigation of indoor air pollution is viewed as a cost effective and eco-friendly method with untapped potential. The main objective of the present study was to determine the formaldehyde removal efficacy of selected plant species while investigating the mechanisms used by these plants in the removal process. The selected plant species were Zamioculcas zamiifolia, Hedera helix, Dracaena sanderiana and Ficus sp. Plants of the same age were used with three replicates from each species. Phytoremediation potential was assessed by exposing the plants for 24 hours to gaseous formaldehyde (2.0 μL L-1) in air tight chambers made of Plexiglass (an inert material for VOCs) with dimensions of 0.9 m height×0.58 m length×0.55 m width. Formaldehyde removal was measured using GC-MS and the result was expressed as removal percentages. Several leaf anatomical characters (cuticle thickness, epidermal thickness and mesophyll layer thickness), stomatal characters (stomatal density, stomatal index, guard cell length and potential conductance index) and physiological characters (stomatal conductance and photosynthetic rate) were measured to study the possible mechanisms involved in the formaldehyde removal process. The data were subjected to ANOVA and Pearson correlation test. According to the results obtained, Ficus sp. had the highest formaldehyde removal percentage (92.80%) while Hedera helix had the lowest (56.86%). The study further showed that stomatal density and stomatal conductance play a major role in formaldehyde removal by these plants while cuticle and epidermal thickness act as hindrances to this process. This conclusion was further confirmed by Pearson‘s correlation values in correlation analysis. The current study was carried out for 24 hours of exposure and it would be of interest to explore, the long term behavior of the plants through further studies. Overall, the results justify future studies on a cross-section of diverse plant species for formaldehyde removal efficiency to determine species with superior removal efficiencies for a better phytoremediation process. &#x0D; Keywords: Phytoremediation, VOCs, Formaldehyde, GC-MS technology

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

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

Optimized methane combustion behavior by engineering dual oxygen defect structures between Co3O4 and MOF-derived Ce1-xLaxO2-δ solid solution

Herein, Co3O4/Ce1-xLaxO2-δ nanocatalysts were established for methane combustion, integrating the sacrificial MOF-template method and deposition-precipitation technique. A favored La-insertion into CeO2 matrix created smaller-sized Ce1-xLaxO2-δ sosoloid with more defective structure due to the enhanced transformation of Ce4+ to Ce3+, helping in the intimate contact with Co3O4. This lessened the particle sizes of Co3O4 and alleviated the hybridization strength of Co3+ 3d and O 2p orbitals, which optimized the mobility of surface lattice oxygen and reducibility of Co3O4, and enriched Co3+ species to attack C–H bonds. Moreover, the transmission of gaseous oxygen and/or activated oxygen of Ce1-xLaxO2-δ to Co3O4 was expedited, availing the compensation of oxygen vacancies on reduced Co3O4 to regain dissociation centers for methane. Expectedly, the combined function of Co3+/Co2+, Ce4+/Ce3+ and O/OV redox couples allowed Co3O4/Ce0.6La0.4O2-δ with preferable methane removal efficiency to its counterparts, accompanied with desirable recyclability and long-term stability.

Evaluation of properties and formaldehyde removal efficiency of biocarbon prepared at variable pyrolytic temperatures

Biocarbon (BC) represents a potential material for application in air remediation. This study investigated the efficiency of BC particles in the removal of formaldehyde. BC samples were prepared from Arundo donax (AD) and olive stone (OS) feedstocks at variable pyrolysis temperatures (from 300°C to 800°C). The BC particles were characterized using proximate, Fourier transform infrared, water contact angle, particle size, and physisorption analyses. The formaldehyde removal capacity was tested using an electrochemical formaldehyde sensor in a batch experiment. The physicochemical and structural properties depended on the pyrolysis temperature at which the BC was produced. The increase in pyrolysis temperature increased the BC’s pH, hydrophobicity, and porosity. All the samples achieved a formaldehyde removal capacity ranging between 26% and 64% for BC pyrolyzed at 300°C and 800°C, respectively. In BC pyrolyzed at temperatures under 500°C, the formaldehyde capture was governed by a partitioning mechanism through diffusion in the noncarbonized organic fraction. In comparison, formaldehyde capture was controlled by a physical adsorption mechanism through pore filling for BC pyrolyzed at 500°C or above. BC pyrolyzed at 800°C was more efficient for formaldehyde adsorption due to the well-developed microporous structure for both AD and OS. AD-derived BC prepared at 800 °C (AD-BC800) was selected for the re-usability test, using thermal regeneration to remove the adsorbed components. The regenerated sample maintained a comparable formaldehyde removal capacity up to four re-use cycles. Moreover, the comparison between non-activated and activated AD-BC800 revealed that physical activation significantly enhanced BC’s adsorptive ability.

High-Efficiency Degradation of Formaldehyde and Bioelectricity Generation by Microbial Fuel Cell

Formaldehyde is a common organic pollutant in water with teratogenic and carcinogenic effects. This study reports that 200 mg l−1 formaldehyde in water can be effectively degraded with generating electricity by using microbial fuel cell (MFC) technology. A novel composite anode M-Co3O4-PEDOT-GF was prepared by modifying Co3O4 nanoparticles (M-Co3O4) derived from ZIF-67 and poly (3,4-ethylenedioxythiophene) (PEDOT) on the surface of Graphite felt (GF). The results showed that the MFC loading M-Co3O4-PEDOT-GF anode exhibited excellent electricity generation performance and formaldehyde degradation. The maximum voltage of the MFC was 549 mV, 46.0% increase than that of GF anode (376 mV), and higher than N-Co3O4-PEDOT-GF anode (488 mV) modified with commercial Co3O4 (N-Co3O4). The maximum power density of the MFC loading composite anode was 4177 mW m−2, while that of MFC loading bare GF anode was 1562 mW m−2. The dominant microorganisms were Pseudomonadales and Rhizobiales at the order level. The removal efficiency of formaldehyde by MFC loading M-Co3O4-PEDOT-GF anode was 89.2% in 152 h. The high efficiency of formaldehyde degradation was still maintained after 10 cycles. The results could be attributed to the composite anode with loose porous three-dimensional structure and good biological compatibility of PEDOT.

Impact of temperature on the performance of compost-based landfill biocovers

Methane (CH4) emissions from landfills are a major contributor to global greenhouse gas emissions. Compost-based biocovers offer a viable approach to reduce CH4 emissions from landfills; however, the effectiveness in climates with varying temperatures is not well understood. The methane removal performances of two compost-based biocover materials (food and yard waste compost) were examined under different temperature conditions using laboratory column experiments. A reactive transport model was used to simulate the experimental results to develop a better quantitative understanding of the effect of temperature on overall methane removal efficiency. As expected, experimental results indicated that the oxidation rate was influenced by temperature, as it was reduced when the temperature decreased from 22 °C to 8 °C. However, some oxidation was observed at a lower temperature, which was confirmed by CO2 concentrations above the initial level and the observed temperatures above the exposure temperature along the height of biocover column. Furthermore, results showed that when the compost-based materials were subjected to 8 °C and then increased to 22 °C, methane oxidation within the material recovered quickly and returned to similar oxidation rates as observed before the temperature was reduced, suggesting that compost-based biocovers may not be affected by cyclic temperature variations when used in colder climates. Methane oxidation capacity was limited by the maximum oxidation rate, the biocover porosity, and the gas saturation profile that affects residence time and overall methane oxidation in the columns. The model results show that the CH4 oxidation rate was reduced by one order of magnitude when the temperature decreased from 22 °C to 8 °C. Therefore, the calculated Q10 values were 4.19 and 5.18 for the food and yard waste compost, respectively. Overall, compost-based landfill biocovers, such as food and yard waste compost, are capable of mitigate CH4 emissions from old and small landfills under different temperature conditions.

TiO2@g-C3N4/SiO2 with superior visible-light degradation of formaldehyde for indoor humidity control coatings

Indoor air quality is a critical concern in people's daily life due to the adverse effects of formaldehyde and humidity on human health. The development of multifunctional indoor coatings which can photodegrade formaldehyde and regulate humidity is desirable. In this study, we use a simple route to synthesize a heterostructure photocatalyst (denoted as TiO2@g-C3N4/SiO2-x%) via combining TiO2, graphitic carbon nitride (g-C3N4), and enhancement silica fume (SiO2). The results indicate that the prepared TiO2@g-C3N4/SiO2-12% photocatalyst is capable of degrading formaldehyde with a removal efficiency of 83.5%, which is higher than those of pure TiO2 (10.8%) and g-C3N4 (67.8%) after 3 h of visible-light irradiation. The above findings may be attributed to the enhanced visible light absorption and the fast transfer of photogenerated electrons. Electron paramagnetic resonance spectra and Mott-Schottky plots show that the generation of ･O2− and ･OH active species via Z-scheme route on TiO2@g-C3N4/SiO2-12% are responsible for the decomposition of formaldehyde under visible light. For practical applications, the TiO2@g-C3N4/SiO2-12% photocatalyst is further employed to fabricate the sustainable coating (denoted as TGS coating), which exhibits a formaldehyde removal efficiency of 85.0% with outstanding humidity control performance over ten times higher than commercial coatings. The remarkable improvement of humidity control performance on TGS coatings is due to the effect of better textural properties. More importantly, this study demonstrates the valorization of waste silicas to fabricate sustainable TGS coatings with great stability, which may provide the practical applications in the indoor environment.

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.