Photocatalytic Degradation Of Formaldehyde Research Articles

Smart manufacturing of ZIF-8 photonic crystals: Catalytic formaldehyde degradation and colorful eco-friendly coatings

Formaldehyde and other harmful gases cause environmental pollution and threaten human health. Environment-friendly coatings is an effective strategy to address these environmental and health concerns. In this study, a large-scale amorphous photonic crystals (APC) based on modified ZIF-8 (Hxh-ZIF-8) with photocatalytic degradation of formaldehyde and tunable structural color were designed for eco-friendly coatings by programmable smart manufacturing. As APC unit, Hxh-ZIF-8 nanoparticles with controllable diameters were synthesized utilizing solvothermal method and the −N = C = O group was introduced with thermal oxidation. The results of photocatalytic degradation revealed that H5h-ZIF-8, through thermal oxidation, exhibited a formaldehyde degradation rate 9.8 times than that of ZIF-8. The main reactive components in photocatalysis were holes (h+) and superoxide radicals (·O2–), showcasing both stability and reproducibility. The color and brightness of the APC were adjusted by tuning the Hxh-ZIF-8 diameter. The angle-independent APC ranging from red to purple were fabricated with 177, 165 and 235 nm Hxh-ZIF-8 nanoparticles in various proportions with programmable smart manufacturing. In this study, a large-scale ZIF-8-based APC was designed with programmable smart manufacturing for environment-friendly coating, which combined environmental protection technology with structural color, and paved a new strategy for the development of multifunctional materials in air quality management.

Synthesis of BiOX-Red Mud/Granulated Blast Furnace Slag Geopolymer Microspheres for Photocatalytic Degradation of Formaldehyde.

Release of formaldehyde gas indoors is a serious threat to human health. The traditional adsorption method is not stable enough for formaldehyde removal. Photocatalytic degradation of formaldehyde is effective and rapid, but photocatalysts are generally expensive and not easy to recycle. In this paper, geopolymer microspheres were applied as matrix materials for photocatalysts loading to degrade formaldehyde. Geopolymer microspheres were prepared from red mud and granulated blast furnace slag as raw materials by alkali activation. When the red mud doping was 50%, the concentration of NaOH solution was 6 mol/L, and the additive amount was 30 mL, the prepared geopolymer microspheres possessed good morphological characteristics and a large specific surface area of 38.80 m2/g. With the loading of BiOX (X = Cl, Br, I) photocatalysts on the surface of geopolymer microspheres, 85.71% of formaldehyde gas were adsorbed within 60 min. The formaldehyde degradation rate of the geopolymer microspheres loaded with BiOI reached 87.46% within 180 min, which was 23.07% higher than that of the microspheres loaded with BiOBr, and 50.50% higher than that of the microspheres loaded with BiOCl. While ensuring the efficient degradation of formaldehyde, the BiOX (X = Cl, Br, I)-loaded geopolymer microspheres are easy to recycle and can save space. This work not only promotes the resource utilization of red mud and granulated blast furnace slag, but also provides a new idea on the formation of catalysts in the process of photocatalytic degradation of formaldehyde.

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.

G-C3N4/TiO2 for gas-phase formaldehyde photodegradation under visible light in the humidity control coatings

BackgroundsThe control of relative humidity and degradation of volatile organic compounds are regarded as major considerations in the enhancement of living quality in the indoor environment. From the viewpoints of circular economy, the valorization of inorganic wastes to prepare green building materials is crucial. MethodsFor the practical applications, the multifunctional coatings, applied in the indoor humidity control and photocatalytic degradation of formaldehyde, are prepared by recovering inorganic wastes (i.e., white carbon (WC) and spent fluid catalytic cracking catalysts (sFCCC)) and photocatalysts (graphitic carbon nitride/TiO2, denoted as GCN/TiO2) via a simple sol-gel method. Various physicochemical and analytic tools are used to characterize the coating properties and performance. Significant findingsCompared to commercial coatings, the prepared multifunctional coatings (i.e., W/B/S-47/47/6, where W, B and S represent the weight percentage (%) of white carbon, bassanite and sFCCC, respectively) have superior textural properties which can improve the buffering ability of indoor humidity. Moreover, the W/B/S-47/47/6 coatings exhibit the surpassing photodegradation of formaldehyde over commercial coatings by ca. 3 times. The higher charge transfer kinetics and greater thermodynamic driving force toward superoxide radical formation are responsible for the improved photocatalytic activity of W/B/S-47/47/6 coatings. According to the toxicity characteristic leaching procedure tests, no evident leaching heavy metals are observed, which provides an environmental-friendly and economical route for valorization of inorganic wastes.

Activated metal Bi and La modified SAPO-34 molecular sieve and its photocatalytic degradation of formaldehyde in aqueous solution

Activated metal Bi and La modified SAPO-34 molecular sieve and its photocatalytic degradation of formaldehyde in aqueous solution

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.

Effect of Transition Metal (Fe, Co) Ion Doping on TiO2 Nano Particles.

Keywords: Growth from solution, Nanomaterials, Oxides, Photocatalytic, Sol-Gel method, DMS. . we report the growth of [Fe, Co]xTiO2 (x=0.01, 0.02 & 0.04) Nano quantum dots prepared by Sol-Gel technique, followed by freeze-drying treatment at -30°C temperature for 12hrs. The obtained Gel was thermally treated at different temperature like 200,400,600, 800°C. The crystalline size of 4 to 40 nm is achieved. X-ray diffraction pattern of samples show anatase phases of TiO2, up to 600°C. At 800°C, the phase is Rutile. Figure 1 shows the XRD patterns acquired from different samples heated at different temperatures. The diffraction peak at 25.22°, 25.49°and 25.6° observed from the XRD pattern of the Fe, Co doped TiO2 shows that the main crystal phase is anatase, and the peak at 27.47° indicates the presence of the rutile phase. All the peaks in the XRD patterns of the sample calcined at 200°C, 400°C and 600°C of TM doped TiO2 can be designated to the anatase phase (most active phase) without any indication of other crystalline phases such as rutile or brookite . As a variant valence metal cation, Fe, Co ions can react with Ti4+ on the surface of TiO2, and Ti4+ is reduced to Ti3+ which inhibits the transformation of anatase to rutile [1]. It leads to the reduction in the oxygen vacancies on the TiO2 surface and suppresses the crystallization of other phases by adsorbing onto the surface of the TiO2 particles [2]. The photocatalytic degradation of formaldehyde has been successfully demonstrated using a 250 V UV lamp with TM doped TiO2 nano powder in a specific experimental setup. The degradation rate increases linearly with dopant content increases. This indicates that the photocatalytic reaction in this experiment was effected by dopant concentration. The results obtained in this research contribute to the understanding of binary doped transition metal ions in TiO2 nanoparticles can lead the efforts of enhancing their environmental application. Study of Magnatic proprty has been carried out by using VSM. The magnetic susceptibility of the Fe, Co doped TiO2 nanopowder increases with increase in doping concentration. Fe, Co doped TiO2 exhibits ferromagnetism at room temperature. Figure 1

Z-scheme K-C3N4/Ag/Ag3PMo12O40 heterojunction with improved visible light photodegradation of formaldehyde

Photocatalytic degradation of formaldehyde is an ideal way to solve indoor air pollution. The development of Z-scheme heterojunction photocatalysts is economic and effective way in eliminating formaldehyde pollution. Herein, a ternary heterojunction photocatalyst K-C3N4/Ag/Ag3PMo12O40 (abbreviated as K-C3N4/Ag/APM) was synthesized by self-assembly of PMo12O403- with Ag+ and K-C3N4 followed by in-situ photoreduction. The Ag/Ag3PMo12O40 (APM) hetero-nanoparticles obtained by photoreduction are uniformly loaded on K-C3N4 nanosheets. The structure, morphology, optical and photoelectrochemical properties etc. of K-C3N4/Ag/APM were characterized and explored. The photocatalytic activity of K-C3N4/Ag/APM was assessed on the degradation of HCHO. K-C3N4/Ag/APM showed remarkably improved photocatalytic activity than the g-C3N4, K-C3N4 and K-C3N4/Ag in the degradation of HCHO under visible light irradiation. The K-C3N4/Ag/APM heterojunction can degrade 60% gaseous HCHO (0.16 mg L-1) in 60 min (λ > 400 nm). The optimum experimental parameters were temperature 20 ℃, RH 70%, catalyst amount 20 mg and initial HCHO concentration 0.16 mg L-1. The enhanced photocatalytic efficiency of K-C3N4/Ag/APM is attributed to the synergistic effect of improved light harvesting, excellent interface contact and accelerated transmission and separation of photogenerated carriers in the Z-scheme structure with Ag as efficient electron transfer mediators. Free radical trapping and electron spin resonance (ESR) experiments confirmed the Z-scheme charge transfer mechanism, and proved that •O2– and h+ were the main active species in HCHO oxidation reaction. The intermediate species in the HCHO photocatalytic degradation process were tested by in situ DRIFTS technology. The construction of g-C3N4 based Z-scheme photocatalyst may provide an insight for the design of new and efficient photocatalysts for environmental applications.

Preparation of Novel Ag–Si–TiO2 Composite and Research on Its Photocatalytic Degradation of Formaldehyde

A novel Ag–Si–TiO2 composite was prepared via sol–gel method for removing residual formaldehyde in shiitake mushroom. The structure of Ag–Si–TiO2 composite was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. Ultraviolet-visible absorption spectroscopy (UV-Vis) and N2 adsorption-desorption tests showed that Ag and Si co-doped decreased the band gap, the Brunauer-Emmett-Teller (BET) specific surface area of the samples increased and the recombination probability of electron-hole pairs (e--h+) reduced. Effect on removal rate of formaldehyde with different Ag-Si co-doped content, formaldehyde concentration and solution pH were investigated, and the results showed that 6.0 wt%Ag-3.0 wt%Si-TiO2 samples had an optimum catalytic performance, and the degradation efficiency reached 96.6% after 40 W 365 nm UV lamp irradiation for 360 min. The kinetics of formaldehyde degradation by Ag–Si–TiO2 composite photocatalyst could be described by Langmuir-Hinshelwood first-order kinetic model.

Comparison of Ga2O3 and TiO2 Nanostructures for Photocatalytic Degradation of Volatile Organic Compounds

The photocatalytic degradation of formaldehyde, acetaldehyde, toluene, and styrene are compared using monoclinic Ga2O3 and anatase TiO2 nanostructures under ultraviolet-C irradiation. These Ga2O3 and TiO2 photocatalysts are characterized using a field emission scanning electron microscope, a powder X-ray diffraction system, the Brunauer–Emmett–Teller method, and a Fourier transform infrared spectrometer. The Ga2O3 shows a higher reaction rate constant (k, min−1) than TiO2 by a factor of 7.1 for toluene, 8.1 for styrene, 3.1 for formaldehyde, and 2.0 for acetaldehyde. The results demonstrate that the photocatalytic activity ratio of the Ga2O3 over the TiO2 becomes more prominent toward the aromatic compounds compared with the nonaromatic compounds. Highly energetic photo-generated carriers on the conduction/valence band-edge of the Ga2O3, in comparison with that of the TiO2, result in superior photocatalytic activity, in particular on aromatic volatile organic compounds (VOCs) with a high bond dissociation energy.

In situ synthesis of TiO2@NH2-MIL-125 composites for use in combined adsorption and photocatalytic degradation of formaldehyde

TiO2@NH2-MIL-125, composite photocatalysts with close interfacial contact between NH2-MIL-125 and TiO2, were successfully synthesized via an in-situ solvothermal method for formaldehyde (HCHO) removal under UV irradiation. Samples were characterized by using a variety of analytical techniques. The results showed that TiO2 particles were highly dispersed on the surface of NH2-MIL-125, and there was a strong electronic interaction (Ti-N-C) between elements of the composite. TiO2@NH2-MIL-125 exhibited significantly enhanced photocatalytic performance for HCHO removal compared to pure TiO2 and NH2-MIL-125 that was ascribed to the synergistic combination of high adsorption capacity of NH2-MIL-125, high dispersion of TiO2 and efficient interfacial charge transfer between TiO2 and NH2-MIL-125. Furthermore, the HCHO removal rate over the composite remained at 90% after 122 h of continuous photocatalytic reaction, indicating the high stability of the catalyst. This work provides new insights that will be helpful in the further development of photocatalysts for indoor air purification.

Colored TiO2 composites embedded on fabrics as photocatalysts: Decontamination of formaldehyde and deactivation of bacteria in water and air

This paper presents the fabrication of colored photocatalytic fibers by individually combining white TiO2 with red α-Fe2O3, green copper perchlorophthalocyanine (CuPcCl16), and blue copper phthalocyanine (CuPc), followed by immobilization of three as-prepared nanocomposites (i.e., Fe2O3/TiO2, CuPcCl16/TiO2, and CuPc/TiO2) onto the low melting point sheath-core composite polyester fibers (LMPET). The spectroscopic and surface measurements of colored fabrics show uniform distribution of the composites on LMPET fibers. Compared with TiO2-based white fabric, the prepared colored catalytic fabrics have better performance in photocatalytic degradation of formaldehyde (HCHO), a pollutant in water and indoor air. In addition, the prepared fibers could be recycled or reused without any appreciable decrease in their effectiveness. The investigation of antibacterial activity of colored fabrics shows 6-log inactivation of both Escherichia coli and Staphylococcus aureus. The enhancement in the photocatalytic activity of colored fabric is attributed to a broadening photo-absorption region and also a decrease in the recombination of electron-hole pairs. In the photocatalytic process, an increase in photocurrent response suggests the increase in charge separation. Additionally, hydroxyl radicals (OH) as the major reactive species in photocatalytic activity of colored fabrics are confirmed by the electron paramagnetic resonance technique. This study suggests that the developed colored photocatalysts can be applied in textiles to clean water and air.

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.

Honeycomb-like micro-mesoporous structure TiO2/sepiolite composite for combined chemisorption and photocatalytic elimination of formaldehyde

Structured hybrid materials based on the combination adsorbent-photocatalyst have large surface area, an average pore diameter, good dispersion and strong adsorptivity, showing promising performance for environmental applications. In this study, honeycomb-like micro-mesoporous structure TiO2/sepiolite composites were fabricated using TiCl4 and modified sepiolite (MS) nanofibers as the precursors by a hydrolysis-precipitation method. The effect of the textural, morphological and structural properties of TiO2/sepiolite composites on the adsorption and photocatalytic degradation of formaldehyde (HCHO) in gas phase was analyzed. The results indicate that thermal treatment at 550 °C and TiO2/MS weight ratios of 1/2 ensure an optimum combination of textural, optical and HCHO adsorption and photocatalytic properties. At ambient temperature, the optimal catalyst (relative humidity of 45%, and HCHO initial concentration of 6.56 mg/m3) could efficiently decompose HCHO into CO2 and H2O, and still showed a good performance even after 4 cycles under UV irradiation. The excellent performance of the TiO2/sepiolite is primarily ascribed to the synergistic effect between the adsorbability of sepiolite nanofibers and the catalytic ability of TiO2 nanoparticles.

Photocatalytic degradation of formaldehyde by PAN nonwoven supported Fe(iii) catalysts under visible light irradiation

Amidoximated PAN nonwoven fabrics coordinated with Fe(iii) as a photocatalyst for formaldehyde degradation by activating O2 under visible irradiation.

Natural silicate-TiO2 hybrids for photocatalytic oxidation of formaldehyde in gas phase

Structured hybrid materials based on the combination adsorbent-photocatalyst with optimal mechanical resistance and reduced cost, are prepared by extrusion using four different natural silicates with similar mesoporous distribution: sepiolite (S), bentonite (B), mordenite (M) and kaolinite (K). The effect of the textural, morphological and structural properties of plate shaped composites calcined at different temperatures on the adsorption and photocatalytic degradation of formaldehyde in gas phase is analyzed. Silicates allows TiO2 extrusion into flat plates with a content of 50wt% of titania. All shaped materials present adequate mechanical resistance to be scaled-up for use in continuous-flow gas-phase catalytic reactors. Thermal treatment at 500°C ensures an optimum combination of mechanical, textural and HCHO adsorption properties. The silicates cover part of the TiO2 particles thus reducing the fraction of TiO2 actually exposed on the surface of the composites, essential to carried out the photocatalytic process, but they also allow controlling TiO2 dispersion and the amount of HCHO adsorbed. The HCHO degradation rate is enhanced with all the silicate-TiO2 composites with respect to that of the benchmark TiO2. The incorporation of titania into the silicate matrix favors the gas phase removal of HCHO in the following sequence: MTi>KTi>STi>BTi>TiO2. The exposed fraction of titania particles and the size of the TiO2-anatase crystalline domains determine the efficiency of the hybrid material, which is optimized in high-aluminum kaolinite and mordenite based hybrids.

Study of photocatalytic activity and magnetic properties of Co, Mn metal ions doped nanocrystalline TiO2 prepared by Sol–Gel method

We report the growth of [Mn, Co]xTiO2 (x=0.01, 0.02 and 0.04) nanocrystals prepared by Sol–Gel technique, followed by freeze-drying treatment at −30°C temperature for 12h. The obtained Gel was thermally treated at different temperatures like 200, 400, 600 and 800°C. The average crystalline size of 6–60nm is achieved. The diffraction peak at 25.22°, 25.49° and 25.6° shows that the main crystal phase is anatase without any indication of other phases. Transition metal doping leads to the reduction in the oxygen vacancies on the TiO2 surface and suppresses the crystallization of other phases by adsorbing onto the surface of the TiO2 particles. The peak at 27.47° indicates the presence of the rutile phase at 800°C. Valence metal cation, Mn, Co ions can react with Ti4+ on the surface of TiO2, and Ti4+ is reduced to Ti3+ which inhibits the transformation of anatase to rutile. The photocatalytic degradation of formaldehyde has been successfully demonstrated using a 250W UV. The binary doped transition metal ions in TiO2 nanoparticles can lead the efforts of enhancing their environmental application as photocatalyst. Magnetic measurement was carried using VSM. The magnetic susceptibility of the Mn, Co doped TiO2 nanopowder increases with increase in doping concentration and exhibits room temperature ferromagnetism.

A Short Review on Photocatalytic Degradation of Formaldehyde.

Nowadays, it is a great challenge to eliminate toxic and harmful organic pollutants from air and water. This paper reviews the role of TiO2 as a photocatalyst, light source and photoreactor in the particular case of removal of formaldehyde using the photocatalytic reaction by titanium dioxide (TiO2) in aqueous and gaseous systems. The reaction mechanisms of the photocatalytic oxidation of gaseous formaldehyde are given. We also present a detailed review of published articles on photocatalytic degradation of formaldehyde by modified titanium dioxide doped with foreign species such as metal and non-metal components. We point out the most prospective developments of the photocatalyst compositions for the future potential commercial applications.

Photocatalytic degradation of formaldehyde by nanostructured TiO2 composite films

Interest in the photocatalytic oxidation of formaldehyde from contaminated wastewater is growing rapidly. The photocatalytic activity of the nanocrystalline Fe3+/F− co-doped TiO2–SiO2 composite film for the degradation of formaldehyde solution under visible light was discussed in this study. The films were characterised by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy, X-ray diffraction (XRD), BET surface area, UV–Vis absorption spectroscopy, and photoluminescence spectroscopy. The FE-SEM results revealed that the Fe3+/F− co-doped TiO2–SiO2 film was composed of uniform round-like nanoparticles or aggregates with the size range of 5–10 nm. The XRD results indicated that only the anatase phase was observed in the film. Compared with a pure TiO2 film and a singly modified TiO2 film, the Fe3+/F− co-doped TiO2–SiO2 composite film showed the best photocatalytic properties due to its strong visible light adsorption and diminished electrons-holes recombination.

Photodegradation of formaldehyde by activated carbon loading TiO2 synthesized via microwave irradiation

A microwave-assisted synthetic method to form a series of AC/TiO2 for application as photocatalytic degradation of formaldehyde (HCHO) is presented. The influence of prepared conditions such as microwave power, microwave time, and the ratio of activated carbon and titanium dioxide sol (AC/TiO2-sel) on the degradation of HCHO was investigated. HCHO conversion of 58.68% was achieved by AC/TiO2 at microwave power of 700W for 15 min with AC/TiO2-sel ratio of 1: 2, which maintained multiple properties including high content of anatase and TiO2 largely distributed on AC without reunion, and possessed abundant functional groups for degradation. The influence of operation parameters on the degradation was also investigated: increasing dosage of catalyst and decreasing the initial concentration of HCHO could increase the conversion of HCHO. Acidic conditions can promote degradation effect. Stronger intensity of UV irradiating could improve efficiency of photocatalytic conversion of HCHO.