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This study focused on measuring the pollution characteristics, the monthly and seasonal variation rule of formaldehyde in the teaching machine room of Guangxi Normal University from March 2016 to February 2018, and the correlation between formaldehyde concentration and temperature or humidity were also analyzed. The results indicated that seasonal and monthly variation rule of formaldehyde changed with temperature and humidity in the teaching machine room. The concentration of formaldehyde was higher in summer and autumn, while was lower in winter and spring. Further analysis indicated that there was a strongly positive correlation (R2>0.87, R2>0.85, R2>0.81, p

Formaldehyde (HCHO) is one of the major air pollutants, and its effective removal at room temperature has proven to be a great challenge. In this study, an Ag/Mn/CeO2 catalyst for the catalytic oxidation of low-concentration HCHO at room temperature was prepared by a hydrothermal-calcination method. The removal performance of the Ag/Mn/CeO2 catalyst for HCHO was systematically studied, and its surface chemical properties and microstructure were analyzed. The incorporation of Ag did not change the mesoporous structure of the Mn/CeO2 catalyst but reduced the pore size and specific surface area. The Ag species included metallic Ag as the main component and part of Ag+. The well-dispersed Ag species on the catalyst provided sufficient active sites for the catalytic oxidation of HCHO. The more the Ag active sites, the more the lattice defects and oxygen vacancies generated from the interaction of Ag with Mn/CeO2. Precisely because of this, the Ag/Mn/CeO2 catalyst exhibited high catalytic activity for HCHO at room temperature with a removal efficiency of 96.76% within 22 h, which is 22.91% higher than that of the Mn/CeO2 catalyst. Moreover, the Ag/Mn/CeO2 catalyst showed good cycling stability and the removal efficiency reached 85.77% after five cycles. Therefore, the as-prepared catalyst is an effective and sustainable material that can be used to remove HCHO from actual indoor polluted air. This paper provides ideas for the research and development of efficient catalysts. [ABSTRACT FROM AUTHOR]

As one of the significant pollutants in indoor air, formaldehyde (HCHO) has attracted increasing attention due to its negative effects on human health. Thus, to reduce formaldehyde pollution, herein, an Ag-promoted Cr/MnO2 catalyst (Ag/Cr/MnO2) was obtained via a hydrothermal–calcination method, which was employed for the catalytic oxidation of low-concentration indoor HCHO (∼1 ppm) at room temperature. The Ag/Cr/MnO2 catalyst eliminated approximately 98.62% HCHO within 14 h and maintained a high removal efficiency continuously under the dynamic test conditions. Furthermore, the catalyst exhibited good recycling stability and outstanding activity in a humid environment. Different characterization techniques were utilized to determine the physicochemical properties that contribute to improving the catalytic performance. The Ag substance contained metallic Ag (Ag0) as the main component and some Ag2O, and the Ag0 particles provided ample active sites for the catalytic oxidation of HCHO. Besides, the incorporation of Ag increased the reducibility of the catalyst and the content of Mn4+, Cr6+ and oxygen vacancies. The abundant active sites, high reducibility, rich Mn4+, Cr6+, oxygen vacancies, and surface lattice oxygen species, and the powerful interaction between Cr/MnO2 and Ag were the reasons for the splendid catalytic capability for HCHO by the Ag/Cr/MnO2 catalyst. In conclusion, the Ag/Cr/MnO2 catalyst can be a promising catalyst to degrade HCHO with practical application significance. [ABSTRACT FROM AUTHOR]

The Co3O4/CN-x%CeO2 (x = 0, 3, 6) composites for enhanced photocatalytic degradation of formaldehyde (HCHO) performance were prepared by hydrothermal-calcination method. The structure, microstructure and surface functional groups of samples were investigated by using the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectrometer, and the degradation mechanism of Co3O4/CN-3%CeO2 was also discussed this paper. The results showed that the Co3O4/CN-3%CeO2 sample could degrade 91.5% of HCHO within 9 h which was 190% higher than that of the CN, and maintained excellent performance for 24 h. The sample was in the form of irregular block-based flakes and particles, the specific surface area was 111.92 m2/g which was 2.5 times than that of the CN sample. The sample was composed of CN and Co3O4 phases, existed O–H, N–H, C=O, C–N, Co–O, Ce–O functional group and mesoporous structure with pore size distribution of 2 to 20 nm. [ABSTRACT FROM AUTHOR]

In this paper, Cr/MnO2 catalysts were prepared by hydrothermal–calcination method and applied to the catalytic oxidation of formaldehyde (HCHO) at room temperature. The effects of calcination temperature on the physicochemical properties of Cr/MnO2 catalysts were investigated by means of N2 adsorption–desorption, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Based on this, the formaldehyde removal mechanism of Cr/MnO2 catalysts was proposed. The results showed that the specific surface area, OII/OI, Mn4+/Mn3+ and Cr6+/Cr3+ ratios of the Cr/MnO2 catalysts varied with the calcination temperature. The Cr/MnO2 catalyst calcined at 400 °C (CM400) has higher specific surface area (64.6 m2/g) and oxygen vacancy content, so it exhibits better formaldehyde removal performance, which could reach 92.1% within 22 h. It is concluded that the high specific surface area, abundant oxygen vacancy content, rich Mn4+ and Cr6+ species are primary reasons for the excellent formaldehyde removal performance of CM400 sample. The Cr/MnO2 catalysts reveal great application potential in indoor formaldehyde degradation, and will be promising industrial formaldehyde degradation catalyst. [ABSTRACT FROM AUTHOR]

CuxO/Bi2O3 oxides grown on nickel foam were synthesized via an electrodeposition method to degrade indoor HCHO under visible light irradiation and fully characterized by XRD, SEM, FT-IR, and UV-Vis technologies. The characterization results showed that the CuxO/Bi2O3 oxides were successfully loaded on nickel foam and the visible light response spectrum was expanded to 740 nm. Plackett–Burman design combined with central composite design has been used to optimize factors that affect HCHO removal performance. The results demonstrated that bismuth nitrate content, polyethylene glycol 600 content, sintering time, and lactic acid concentration were the four most important factors affecting the HCHO removal performance over CuxO/Bi2O3 sample. The optimum CuxO/Bi2O3 sample could degrade 88.796% of HCHO in 300 min at the conditions of 4.28 mol/L lactic acid, 4.86% polyethylene glycol 600, 194.03 min sintering time, and 45.83 g bismuth nitrate, and the HCHO removal rate remained 82.3% after five cycles. A plausible mechanism for the degradation of HCHO under visible light irradiation was proposed. This work provides a feasible solution for removing indoor formaldehyde in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

In this work, the Mn-doped Fe2O3 catalyst (Mn/Fe2O3) was prepared by hydrothermal and calcination methods to remove formaldehyde. The effect of calcination temperature on the structure and performance of Mn/Fe2O3 catalyst was elucidated by X-ray diffraction, Raman spectroscopy, scanning electron microscope, transmission electron microscopy, energy dispersive spectroscopy, selected area electron diffraction, N2 adsorption–desorption, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The result showed that the Mn/Fe2O3 catalyst calcined at 200 ℃ (MFC200) possessed the best specific surface area (176.04 m2/g, 4.96 times that of pure Fe2O3). The active oxygen content on the catalyst surface varies with the calcination temperature, and that of MFC200 sample is the highest compared with the samples calcined at other calcination temperatures. In addition, the content of Mn4+ species also varies with the calcination temperature, which plays a key role in Mn/Fe2O3 catalysts for HCHO removal. It is concluded that the high specific surface area, the abundant active oxygen species and rich Mn4+ were contributed to the excellent formaldehyde removal performance of MFC200 sample. The Mn/Fe2O3 catalyst will be a promising catalyst to degrade formaldehyde in industrial applications. [ABSTRACT FROM AUTHOR]

The metal-modified Co3O4 sample (metal: Zn or Cr, Zn and Cr) was prepared through hydrothermal approach, and applied in low concentration of HCHO removal under room temperature. The Cr/Zn/Co3O4 exhibited the best formaldehyde removal activity and stability. The effect of dopants on the physicochemical properties of the Co3O4 samples was characterized by X-ray diffraction, Raman, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric (TG-DTG) and X-ray photoelectron spectroscopy, resulting that the Cr/Zn/Co3O4 sample possessed the optimal specific surface area (177.53 m2/g, 3.4 times that of pure Co3O4). Meanwhile, Cr and Zn incorporated into Co3O4 lattice simultaneously and promoted the formation of defects, which is the prerequisite for increasing the reactive oxygen species of Cr/Zn/Co3O4. In addition, Cr6+/Cr3+ ion pairs in the sample could be an important role in the removal of formaldehyde. It is concluded that the ideal HCHO removal performance and stability of Cr/Zn/Co3O4 were associated with its high vacancy oxygen content, excellent specific surface area and the promotion of Cr6+/Cr3+ ion pairs. [ABSTRACT FROM AUTHOR]

In this paper, removal of formaldehyde on Zn-modified Co3O4 catalyst under room temperature was investigated. The performance tests on different zinc nitrate molar concentration doped catalysts which were prepared by the hydrothermal method demonstrated that the catalyst shows excellent HCHO removal performance when the zinc nitrate molar concentration was 0.6 (Zn0.6CoO). The effects of Zn addition on the structure and activity of the Co3O4 catalyst was studied by X-ray diffraction, Fourier transform infrared spectroscopy, N2-absorption/desorption, Raman, scanning electron microscopy, a transmission electron microscope and X-ray photoelectron spectroscopy. The results showed that Zn is doped into the lattice of Co3O4 and caused lattice distortion, which should be the key to increase the oxygen vacancy concentration. In addition, doping Zn improves the specific surface area of the Co3O4 catalyst, which indirectly provides more active sites for HCHO, and the activity of Zn0.6CoO catalyst with high oxygen vacancy concentration is higher than Co3O4 nanobelts, which indicates that doping Zn enhances the HCHO removal performance by increasing the oxygen vacancy content. [ABSTRACT FROM AUTHOR]

The Ce‐CdS‐TiO2 photocatalysts were successfully synthesized by a simple sol‐gel way and loaded on the nickel foam. The specific surface area, crystalline phase, microstructure and surface functional groups of prepared photocatalysts were characterized by Brunauer‐Emmett‐Teller (BET) surface area, X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT‐IR). The photocatalytic tests of Ce‐CdS‐TiO2 samples demonstrated that Ce as the active component plays an irreplaceable role in degradation of gaseous formaldehyde. The results showed that high Ce doping levels restrained the photocatalytic activity due to lower specific surface area, whereas moderate doping levels showed the highest photocatalytic performance due to higher specific surface area and evenly dispersion of the active component. The rate of formaldehyde degradation on 0.9 wt % Ce‐CdS‐TiO2, 1.5 wt % Ce‐CdS‐TiO2, and 2.1 wt % Ce‐CdS‐TiO2 photocatalysts can reach to 59, 84, and 49 %, respectively, which are higher than pure TiO2 (20 %). Ce‐doping into CdS‐TiO2 photocatalyst produce the Ce‐O‐Ti bonds, which enhanced the interaction between Ce and TiO2. The introduction of Ce increased the UV/Vis absorption of Ce‐CdS‐TiO2 photocatalyst. Furthermore, Ce‐CdS‐TiO2 possesses high photocatalytic performance, since Ce may reduce the recombination of photoexcited electrons and holes. [ABSTRACT FROM AUTHOR]

The removal efficiency, adsorption kinetics, and thermodynamics of Auramine-O (AO) onto sugarcane leaf-based activated carbon prepared by ammonium dihydrogen phosphate were investigated systematically. The optimal AO removal conditions were found to infuse 1.2 g/L sugarcane leaf-based activated carbon in 200 mg/L AO solution which the initial pH (pH0) was 9.0 for 180 minutes. The adsorption kinetics of AO was described well by the pseudo-second-order and intra-particle diffusion model. The intra-particle diffusion was not the exclusive rate controlling step in the adsorption process. The isotherm obeyed the Langmuir isotherm with a high correlation coefficient (R2 > 0.99), and the thermodynamic analysis suggested that ΔG < 0, ΔH > 0, and ΔS > 0, which indicated that the adsorption of AO onto sugarcane leaf-based activated carbon was a spontaneous chemical and endothermic adsorption process. [ABSTRACT FROM PUBLISHER]