Simultaneous catalytic elimination of formaldehyde and ozone over one‐dimensional rod‐like manganese dioxide at ambient temperature

Abstract

BACKGROUND: Formaldehyde (HCHO) and ozone (O 3 ) are seriously hazardous materials to human health, especially in the indoor environment, and need to be inhibited. Manganese dioxide (MnO 2 ) catalysts have been extensively studied in the field of environmental pollution owing to their various morphologies and crystal structures. In this study, one-dimensional rod-like MnO 2 catalysts were prepared by a hydrothermal method. The crystal form and other factors affecting the activity were explored through an activity test and various characterization methods. The decomposition process of HCHO and O 3 on the most active catalyst was analyzed by in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). RESULTS: -MnO 2 displayed the best catalytic performance and achieved 90% HCHO conversion, 100% carbon dioxide (CO 2 ) yield and 100% O 3 decomposition under different experimental conditions. The characterization results illustrated that the crystal phase of -MnO 2 has a suitable tunnel structure for HCHO adsorption, also leading to greater mobility of adsorbed oxygen species, abundant oxygen vacancies and active surface oxygen species, which could be the reason for the superior catalytic performance of -MnO 2 . Formate and dioxymethylene (DOM) species were identified as the dominant intermediates by in situ DRIFTS. The surface hydroxyl (OH) group was confirmed to play an essential role in the complete oxidation of carbonaceous intermediates into harmless CO 2 and water (H 2 O). CONCLUSION: -MnO 2 exhibited the best catalytic performance among the as-prepared samples and can efficiently eliminate HCHO and O 3 in the environment. Activity testAs mentioned, O 3 decomposition is the rate-determining step for promoting the catalytic oxidation of volatile organic compounds (VOCs). Previous studies 49,50 indicate a typical three-step reaction process for O 3 decomposition, as follows:

Effective low‐temperature catalytic abatement of benzene over porous Mn‐Ni composite oxides synthesized via the oxalate route

“…As seen in Fig. (a), both adsorbed oxygen species and lattice oxygen species of Ni‐containing catalysts showed lower desorption temperatures than those of MnO x , implying looser bonding of oxygen species to the Mn‐Ni composite oxides . The adsorbed oxygen species of Mn4Ni1 can be desorbed at 241 °C, which is lower than the other three samples; thus, Mn4Ni1 exhibits stronger oxygen mobility.…”

Ozone catalytic oxidation capacity of Ti‐Co@Al2O3 for the treatment of biochemical tailwater from the coal chemical industry

“…Zhang et al used a sol-gel method to prepare a cellulose-based mesoporous CeO 2 catalyst for the treatment of phenol-simulated wastewater. The removal rates of phenol and COD by ozone-catalyzed oxidation reaction in their study were 91.7% and 69.2%, corresponding to increases by 40.1% and 48.2% in comparison with those ozone oxidation alone, respectively (Zhang, Shi, et al, 2019).…”

“…Ozone catalytic oxidation can be divided into homogeneous and heterogeneous (Zhang, Shi, et al, 2019). Heterogeneous catalytic ozonation involving the addition of a solid catalyst overcomes the problem wherein the homogeneous catalytic ozonation catalyst is difficult to recover and may cause pollution; it also reduces treatment costs and demonstrates strong adaptability to various factors, such as water quality and wastewater quantity (Xiao, Xie, & Cao, 2015).…”

“…This damage weakened the catalyst activity (Chen, Xu, & Sun, 2019). The characterization of the Ti-Co@γ-Al 2 O 3 catalyst prepared at different calcination temperatures indicated that calcination temperature directly affected the crystal morphology and size of the catalyst surface and the pore structure of the support, thus influencing the catalytic activity greatly (Zhang, Shi, et al, 2019). A large amount of the surfaceactive component of the Ti-Co@γ-Al 2 O 3 catalyst led to a small crystal particle size and good catalytic activity (Tan et al, 2017).…”

Coadsorption of gaseous xylene, ethyl acetate and water onto porous biomass carbon foam pellets derived from liquefied Vallisneria natans waste

“…Various technologies, such as advanced oxidation processes, biotechnology, bioelectrochemical systems and adsorption, are used to purify waste gas containing VOCs. Among these technologies, the adsorption method is favored owing to its wide range of applications, low operating costs, easy operation, low‐cost and readily available raw materials and absence of secondary contaminants with substantial toxicity.…”