Indoor Formaldehyde Research Articles

Assessment of Formaldehyde’s Impact on Indoor Environments and Human Health via the Integration of Satellite Tropospheric Total Columns and Outdoor Ground Sensors

Formaldehyde (HCHO) is harmful to human health and an adequate assessment of its concentrations, both in outdoor and indoor environments, is necessary in the context of sustainable policies designed to mitigate health risks. In this research, ground indoor and outdoor HCHO measurements are integrated with the analysis of tropospheric total columns obtained by satellite surveys to assess the concentrations of HCHO in a number of environments, exploiting the proximity of a World Meteorological Organization—Global Atmosphere Watch (WMO/GAW) observation site in Calabria, Southern Italy to a National Institute for Insurance against Accidents at Work (INAIL) department in the municipality of Lamezia Terme. The meteorological parameters used by the WMO station are also used to provide additional data and test new correlations. Using statistical significance tests, this study demonstrates the presence of a correlation between indoor and outdoor HCHO concentrations, thus showing that an exchange between indoor and outdoor formaldehyde does occur. Rooms located in the local INAIL building where indoor measurements took place also demonstrate degrees of susceptibility to HCHO exposure, which are correlated with the orientation of prevailing wind corridors in the area. The new findings constitute an unprecedented characterization of HCHO hazards in Calabria and provide regulators with new tools with which to mitigate formaldehyde-related risks.

Removal of formaldehyde from indoor air by potted Sansevieria trifasciata plants: dynamic influence of physiological traits on the process

AbstractPlant-based removal of indoor formaldehyde is a widely studied method, yet little is known about the dynamic changes in this process. In this study, potted Sansevieria trifasciata Prain plants were exposed to 5-ppm formaldehyde gas concentration for 7 days. The results showed that formaldehyde exposure led to plant stress, affected photosynthesis, and damaged membrane lipids, as evidenced by a decrease in chlorophyll content, an increase in Chl a/b ratio and malondialdehyde content. However, the formaldehyde removal ability of the plants increased over the first 5 days, peaking at 18.02 mg h−1 kg−1 dry weight on the 5th day. This trend was correlated with changes in various indicators in the plant roots, including phytohormone and antioxidant enzymes. Notably, catalase activity in the roots behaved differently from other indicators. The indicators in the leaves showed turning points around the 3rd day due to the direct exposure of the leaves to formaldehyde. The relative abundance of endophytes indicated an increase in plant growth-promoting bacteria, which helped the plant cope with formaldehyde stress. The study suggests that under formaldehyde stress, plants manage active oxygen content by increasing phytohormones and regulating redox reactions. This enhances their tolerances to formaldehyde, thereby improving their ability to remove formaldehyde and aiding recovery after formaldehyde exposure. Graphical abstract

Insight into physiological and biochemical markers against formaldehyde stress in spider plant (Chlorophytum comosum L.).

Formaldehyde is a prominent volatile organic compound and also considered as an indoor air pollutant. Chlorophytum comosum, an indoor plant, has been reported to metabolize indoor formaldehyde. But the phytotoxic effects of formaldehyde, being a pollutant, on C. comosum are not well explored. Furthermore, C. comosum responses that can be considered as markers at the physiological and biochemical level against formaldehyde stress are not yet investigated. Therefore, the current research study was aimed to evaluate such potential markers against formaldehyde in C. comosum. Briefly, C. comosum was exposed to 5-, 10-, and 20-ppm formaldehyde doses in an airtight glass chamber. Plant samples were then taken to analyze morpho-anatomical, physiological, and biochemical responses after short (2, 4, and 6h), medium (12 and 24h), and extended durations (48 and 96h) for each tested dose. Application of 10 and 20ppm formaldehyde doses leads to a significant incline in enzymatic antioxidants. Formaldehyde concentration of 10ppm leads to a maximum increase in catalase (30.30 U/mg of protein), guaiacol peroxidase (135.64 U/mg of protein), and superoxide dismutase (44.76 U/mg of protein) compared to their respective controls. A significant change is also observed in non-enzymatic parameters, including total phenolic content, which ranged from 3.62mg GAE/g (control) to 10.51mg GAE/g, total antioxidants vary from 27.37% (control) to 85.05% in 20ppm formaldehyde, respectively. However, formaldehyde application negatively affected the physiological responses of C. comosum by reducing its photosynthetic rate, transpiration rate, and stomatal conductance. Additionally, extended exposure of C. comosum to 10- and 20-ppm formaldehyde doses leads to visible leaf damage. Principal component analysis indicated that enzymatic parameters including SOD, CAT, and GPX and non-enzymatic parameters including MDA, TPC, TFC, TAOs, carotenoids, TSS, and intercellular CO2 contributed the most to the total variance. Thus, these parameters have potential to serve as physiological and biochemical markers in C. comosum against formaldehyde stress.

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

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

Efficient visible-light-driven photocatalytic degradation of indoor formaldehyde using an indium-based MOF/graphene oxide composite

Formaldehyde (HCHO) severely degrades indoor air quality, and conventional remediation methods are often inadequate for addressing low concentrations of HCHO indoors. In this study, we synthesized a MIL-68(In)-NH2/graphene oxide (GO) composite using a solvothermal method, aimed specifically at enhancing the photocatalytic degradation of HCHO under visible light. Our results show that the integration of GO enhances visible light absorption and facilitates efficient electron transport, significantly improving photocatalytic performance. The MIL-68(In)-NH2/GO composite achieves a 77 % degradation rate of HCHO, significantly outperforming MIL-68(In)-NH2 (51 %) and GO (22 %) alone. This enhanced activity is attributed to the effective separation of electron-hole pairs and synergistic interactions within the composite. We proposed an enhanced photocatalytic mechanism for the MIL-68(In)-NH2/GO system, identifying h+ and •O2– as the principal active species. Moreover, the MIL-68(In)-NH2/GO composite shows excellent reusability and stability, making it a promising candidate for eco-friendly and efficient indoor air purification using metal–organic frameworks.

Generation of oxygen vacancies in CuO/TiO2 heterojunction induced by diatomite for highly efficient UV–Vis-IR driven photothermal catalytic oxidation of HCHO

Photothermal catalytic oxidation is a promising and sustainable method for the degradation of indoor formaldehyde (HCHO). However, the excessively high surface temperature of existing photothermal catalysts during catalysis hinders the effective adsorption and degradation of formaldehyde under static conditions. Catalyst loading and oxygen vacancies (OVs) modulation are commonly employed strategies to reduce the photothermal catalytic temperature and enhance the efficiency of photothermal catalytic oxidation. In this work, a p-n type CuO/TiO2 heterojunction is successfully loaded onto diatomite using a wet precipitation method. Under the irradiation of a 300W xenon lamp, the prepared composite material achieved a 100% removal rate of HCHO within 2 h, with a 98% conversion rate to CO2, surpassing the performance of both individual photocatalysts and thermocatalysts. Additionally, by adjusting conditions such as light irradiation and temperature, we have demonstrated that this material exhibits synergistic photothermal catalytic properties. Based on HRTEM, XPS, Raman, and EPR analyses, the introduction of diatomite as a catalyst support was shown to effectively increase the number of OVs. Experimental results, along with O2-TPD, photoelectrochemical characterization, and radical detection, demonstrate that the presence of OVs enhances the oxidative efficiency of both photocatalysis and thermocatalysis, as well as the UV–Vis-IR photothermal catalytic performance. The ternary composite material generates weak hydroxyl (•OH) and superoxide (•O2−) radical under high-temperature with dark conditions, indicating its catalytic oxidation activity under this condition. The increase in temperature and the expansion of the spectral range both enhance the generation of these radicals. In summary, this work demonstrates that the use of diatomite as a support increases the material's specific surface area and OVs content, thereby enhancing adsorption and photothermal catalysis. It elucidates the enhanced catalytic degradation mechanism of this mineral-based photothermal catalyst.

Highly sensitive formaldehyde detection using biomass hydrogel with core-shell structure

The indoor formaldehyde concentration is in trace quantities; however, it considerably deteriorates indoor air quality and poses a serious threat to human health and ecosystems. Since current formaldehyde analyzers are only suitable for high-concentration detection or are expensive, there is a pressing need for an easy-to-use, storable, and highly sensitive formaldehyde detector. In this study, we developed a colorimetric sensing sphere using affordable and eco-friendly sodium alginate as a porous matrix. Polyethyleneimine, a molecule rich in amino groups, and an indicator are embedded in the matrix to create a core-shell structured, responsive porous hydrogel colorimetric sensor for indoor formaldehyde detection. The sensing sphere exhibits high sensitivity and excellent detection limits at a polyethyleneimine to pH agent mass ratio of 23:1, reaching a sensitivity of 0.02 mg/m3 and a detection limit of 0.06 mg/m3. The sensing sphere demonstrates superior selectivity among common indoor pollutants and remains unaffected by temperature (up to 70 ℃) or humidity (20–80 %) changes. Moreover, the core-shell structure of the colorimetric sensor ball addresses the poor stability and storage issues. The core-shell structure resists interference from external environmental changes, offering remarkable stability for 6 months and longer, hence, facilitating easy transportation and storage. The colorimetric sensing sphere is simple, cost-effective, and reliable for ordinary households, thus maintaining the indoor air quality and health of residents.

Protonated amine and pyrene co-functionalized sodium alginate templated on reduced graphene oxide for highly efficient removal of formaldehyde and acid pollutants

Indoor formaldehyde pollution can cause inestimable harm to human health and even cancers, thus studies on the removal of formaldehyde attract extensive attentions. In this paper, an environmentally friendly and low-cost biomass material, sodium alginate (SA) was utilized to prepare pyrene functionalized amido-amine-alginic acid (AmAA-Py) by acidification and two-step amidation, which is subsequently self-assembled on reduced graphene oxide (rGO) by π-π stacking interaction, and the final composites were acidified to afford a highly porous composite material for chemical removal of formaldehyde. The formaldehyde chemical removal performance of composite is evaluated at different conditions and find that 1.0 g of acidified alginate derivatives and graphene composites (HCl·AmAA-Py-rGO) can adsorb 69.2 mg of HCHO. Simultaneously, amino groups in amido-amine derivative of acidified sodium alginate (AmAA) can react with acidic pollutants such as H2S and HCl via forming ionic bonding without generating any other by-products, which enables efficient and environment-friendly removal of acidic pollutants. The subtle design of the highly porous composite material utilizing low-cost SA and rGO with large specific surface area opens up a new methodology for fabricating highly porous materials for efficient removal of formaldehyde and other indoor hazardous pollutants.

Nanoarchitectonics of bamboo-based heterojunction photocatalyst for effective removal of organic pollutants

A high-performance photocatalyst with both efficient and reusable performance is essentially demanded for the purification of organic wastewater and the removal of indoor formaldehyde. However, recovery of photocatalyst particles from the reaction system remains a challenge. Herein, based on the abundant pore structure of natural bamboo and the outstanding photocatalytic activity of ZnO/WO3, we fabricated an efficient bamboo-based photocatalyst (ZnO/WO3@bamboo) for the efficient photocatalytic degradation of formaldehyde and organic dyes. The pretreatment of bamboo substrates with NaOH solution resulted in the formation of nucleation sites for ZnO/WO3 growth within bamboo cellulose channels. Subsequently, the as-prepared ZnO and WO3 were mixed in different mass ratios, and loaded on the pretreated bamboo substrates using the hydrothermal method. The results showed that the ZnO/WO3@bamboo had the effective function of photocatalytic degradation of formaldehyde gas and organic dyes. Moreover, the as-prepared ZnO/WO3@bamboo photocatalyst demonstrated superior recycling ability toward organic pollutants, which was described by photocatalytic degradation efficiency of formaldehyde gas more than 89% after 10 cycles, and organic dyes over 93% after 20 cycles. The coupling of ZnO and WO3 leads to electron delocalization, which caused the electron holes generated in the valence band (VB) of ZnO to delocalize to the VB of WO3, and reduced the recombination of electron-hole. Therefore, the photocatalytic degradation performance of the ZnO/WO3@bamboo was enhanced. The proposed ZnO/WO3@bamboo photocatalyst holds great promise in the field of air pollution and wastewater remediation.

A bladeless wind-tunnel generator based on a flutter-driven triboelectric nanogenerator with on-demand micro-structuring

With the unremitting demand for renewable energy sources, triboelectric nanogenerators as efficient micro-energy, particularly wind-energy harvesting devices, have garnered increased attention. This study introduces an innovative wind flutter-driven triboelectric nanogenerator (WF-TENG). It employs an on-demand integrated design of a "mortise and tenon" microstructure and is assembled in a "negative-positive-negative" configuration mimicking a "corrugated paper" macrostructure, effectively converting wind energy into electrical energy. The porous crosslinked ethyl cellulose/polyethyleneimine positive friction layer and the bionic rose-petal-like fluorinated ethylene propylene negative friction layer are assembled to form a miniaturized "mortise and tenon" structure, which greatly improves the charge transfer efficiency. Surprisingly, due to the collaborative structural design on micro-/macro-scale, WF-TENG elevates the breakthrough power density of WF-TENG to 455.932 mW cm−2. Further, the integrated-equipped bladeless wind tunnel generator, assembled with the WF-TENG array, utilizes airflow disturbances to produce high-frequency flutter-driven frictional motions. This system outputs up to 7.5 kV at a startup wind speed of 7.9 m s−1 and maintains stable performance for 60 days. Application experiment substantiates the ample electrical energy collected by the bladeless wind tunnel generator for powering an indoor formaldehyde purifier demonstrates a high formaldehyde purification rate of 94 %, providing new insights for the design and applications of novel micro-energy harvesting devices.

Properties of multi-solid waste cementitious materials for highly efficient indoor formaldehyde degradation via response surface method

The environment-friendly cementitious materials with efficient indoor formaldehyde degradation properties (PRCS) were prepared by using slag to supplement the percentage of silica and aluminium in the phosphogypsum (PG)-red mud (RM) system, cement as an activator, and activation through the sulphate component in PG. PG-MnO2, a component of PRCS, was obtained by redox of potassium permanganate with PG as the carrier. The mechanism of formaldehyde degradation on PG-MnO2 was analyzed by catalytic model fitting, the multi-objective optimization of PRCS was achieved using response surface methodology (RSM), and the hydration products and microstructure of PRCS were characterized. The results show that the maximum compressive strength of PRCS can reach 26.02 MPa (7 days) and 35.13 MPa (28 days), respectively. The response surface model can be effectively used to simulate the compressive strength of PRCS since the experimental results of the best fitting ratio are close to the predicted results. PRCS achieves an initial 84 % degradation of formaldehyde through adsorption and surface active sites, and maintains 63 % efficiency after five degradation cycles. Also, there is no risk of heavy metal ion leaching.

Three-dimensional Ni foam supported Pt/NiFe LDH catalyst with enhanced oxygen activation for room-temperature formaldehyde oxidation

Room-temperature catalytic oxidation of formaldehyde (HCHO) has been extensively investigated due to its high efficiency, convenience, and environmental friendliness. Herein, nickel-iron layered double hydroxide (NiFe LDH) nanosheets were synthesized in-situ on a nickel foil (NF) using a facile one-step hydrothermal method, followed by the deposition of ultra-low content (0.069 wt%) of Pt nanoparticles through NaBH4 reduction. The resulting three-dimensional (3D) hierarchical Pt/NiFe-NF catalyst exhibited exceptional activity for the complete decomposition of formaldehyde to carbon dioxide (CO2) at room temperature (∼95 % conversion within 1 h), as well as remarkable cycling stability. The 3D porous structure of Pt/NiFe-NF provides fast transport channels for the diffusion of gas molecules, making the active catalyst surfaces more accessible. Moreover, abundant hydroxyl groups in NiFe LDH serve as adsorption centers for HCHO molecules to form dioxymethylene (DOM) and formate intermediates. Furthermore, electronic interactions between NiFe LDH and Pt enhance the adsorption and activation of O2 on Pt surfaces, leading to the complete decomposition of intermediates into non-toxic products. This work presents new insights into the design and preparation of Pt-based 3D hierarchical catalysts with surface-rich hydroxyl groups for the efficient removal of indoor HCHO.

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.

Comprehensive performance investigation of a novel thermal catalytic semi-transparent PV double-skin ventilated window integrated with CdTe cells

Human health is adversely impacted by indoor formaldehyde. Given that buildings with conventional PV-DSVs fail to improve indoor air quality in the indoor or outdoor air circulation mode without any air handling devices. To remove indoor formaldehyde, a thermal-catalytic CdTe PV double-skin ventilated window is proposed. A corresponding mathematical model was established and validated against experiment data. Based on the validated model, the thermal, electrical, daylighting, and formaldehyde degradation performances were investigated and compared with a conventional PV-DSV (PV-CDSV). Additionally, parametric analysis was conducted to analyse impacts of four factors, including the area of catalytic coating, the window-to-wall ratio, outdoor solar radiation, and ambient temperature, on the energy performance of the proposed window. Main results are: (1) The proposed window had a higher power output but a bit lower thermal efficiency than PV-CDSV, and it had a higher ηtotal in winter, which reached 35.35 % and was 31.45 % higher than that of the PV-CDSV. (2) The net energy consumption of PV-TCDSV increased by 6.59 % and 6.26 % compared with PV-CDSV in winter and summer, respectively. (3) Among the four influencing factors, the solar radiation and ambient temperature had strong impacts on the effectiveness of formaldehyde degradation.

Density functional theory-based screening of Ti4C3O2-loaded single atoms for efficient selective catalytic oxidation of formaldehyde

Indoor formaldehyde (HCHO) pollution poses a major risk to human health. Low-temperature catalytic oxidation is an effective method for HCHO removal. The high activity and selectivity of single atomic catalysts provide a possibility for the development of efficient non-precious metal catalysts. In this study, the most stable single-atom catalyst Ti–Ti4C3O2 was screened by density functional theory among many single atomic catalysts with two-dimensional (2D) monolayer Ti4C3O2 as the support. The computational results show that Ti–Ti4C3O2 is highly selective to HCHO and O2 in complex environments. The HCHO oxidation reaction pathways are proposed based on the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. According to the reaction energy and energy span models, the E-R mechanism has a lower maximum energy barrier and higher catalytic efficiency than the L-H mechanism. In addition, the stability of the Ti–Ti4C3O2 structure and active center was verified by diffusion energy barrier and ab initio molecular dynamics simulations. The above results indicate that Ti–Ti4C3O2 is a promising non-precious metal catalyst. The present study provides detailed theoretical insights into the catalytic oxidation of HCHO by Ti–Ti4C3O2, as well as an idea for the development of efficient non-precious metal catalysts based on 2D materials.

Catalytic oxidation of formaldehyde by MnOx-decorated anatase TiO2{001}: Investigation of the effect of calcination temperature on catalytic activity and reaction mechanism

The removal of indoor formaldehyde (HCHO) is crucial for human health. The design of highly catalytically active nonprecious metal catalysts has major challenges, and the use of transition metal element modification to improve the catalytic performance is an effective strategy. In this study, the active component Mn was loaded on highly active crystalline anatase TiO2{001}, and the effect of the calcination temperature on the catalytic activity was investigated. The important influence of temperature on the catalyst valence distribution, surface active oxygen species, and content was thoroughly determined by characterization techniques, such as XPS, H2-TPR, and O2-TPD. The catalytic reaction process was further analyzed by in situ infrared technology to determine the reaction intermediates and to clarify the catalyst reaction poisoning mechanism; additionally, a reasonable HCHO catalytic reaction pathway was proposed with the combination of density function theory calculations. In addition, oxygen defects on the catalyst surface were determined by EPR, and based on theoretical calculations, the oxygen defects could further reduce the reaction energy barrier through the Langmuir-Hinshelwood mechanism. By exposing specific crystal surfaces and increasing the number of oxygen defects, the catalytic activity could be effectively improved; based on these results, our study provides a concept for the subsequent development of nonprecious metal catalysts.

Long-lasting removal of indoor formaldehyde in continuous airflow by B–TiO2@AC composites

Formaldehyde can cause unacceptable indoor air quality. Traditional adsorption-based materials for indoor formaldehyde removal have the problem of short lifespan and potential secondary pollution. The black TiO2 was synthesized to engineer a material for long-lasting removal in this study, which has a disordered surface layer and defects, resulting in higher light absorption and a narrower band gap under UV and visible light. The novel TiO2 catalyst was composited with different mass fraction of activated carbon to increase active adsorption sites and improve electron transport efficiency. Besides, the formaldehyde decomposition mechanism and kinetics were investigated by material characterization. The performance of the developed material in removing formaldehyde was evaluated using a high-precision, variable-condition continuous flow system designed to simulate actual application environment. B–TiO2@15AC exhibited 1.5 times higher cumulative removal capacity than traditional KMnO4@Al2O3 material after 16h, while maintaining constant efficiency over 40h. Formaldehyde concentration, activated carbon ratio, relative humidity, irradiation wavelength and air flow were chosen as variables and their effect on the removal efficiency was analyzed using Response Surface Methodology. This study presents a promising new material which is low-cost, easy-to-prepare and applicable in indoor formaldehyde removal.

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.

Comprehensive environmental management research for indoor sports and fitness facilities in community sports center

Formaldehyde, as one of the main indoor air pollutants, poses a significant threat to human health. Therefore, to effectively reduce indoor formaldehyde pollution, we prepare a novel silver carbonate (Ag2CO3)/amorphous silver silicates (a-AgSiO)/g-C3N4 nanosheets (CNNS) composite catalyst using in-situ precipitation and ion exchange methods. The Ag2CO3/a-AgSiO/CNNS composite was characterized by various methods, including XRD, FT-IR, and XPS. Compared to the a-AgSiO/CNNS composite, the formaldehyde degradation efficiency of the Ag2CO3/a-AgSiO/CNNS composite is significantly enhanced, reaching up to 81.9% under the same conditions. Cycling stability tests also demonstrated the excellent chemical stability of the Ag2CO3/a-AgSiO/CNNS composite, with a formaldehyde degradation efficiency of 72.6% after five cycles. By investigating the mechanism of Ag2CO3/a-AgSiO/CNNS composite, we found that the formation of double Z-type heterogeneous structure in the Ag2CO3/a-AgSiO/CNNS composite enhanced the separation efficiency of photoinduced charge carriers and improved the photocatalytic activity. In conclusion, the prepared Ag2CO3/a-AgSiO/CNNS composite catalyst with excellent photocatalytic performance can be used for the efficient degradation of indoor formaldehyde.

Solvent-free preparation of high synthetic yield carbon dots from sodium ligninsulfonate for on-site detection of formaldehyde in the environment

Formaldehyde (FA), as a widespread toxic pollutant in cars, furniture and construction materials, has been implicated in hazardous health effects on the human body. This paper presents a green and large-scale preparation of carbon dots (CDs) using sodium ligninsulfonate and o-phenylenediamine through a solvent-free reaction method. The prepared CDs exhibit a synthetic yield of 43 % and show green fluorescence. In addition, the CDs can be employed as an ideal fluorescent FA probe, exhibiting excellent linearity within the range of 0–50 μM (R2 = 0.998, limit of detection (LOD) = 79 nM). By taking advantage of the obvious color changes in detection, the droplet detection system is investigated for on-site visual detection of indoor FA gas. This work not only contributes to the efficient utilization of agricultural waste but also represents a significant process in the development of FA on-site detection.