Ozone catalytic oxidation of toluene over triple perovskite-type catalysts modified with KMnO4.

A unique triple perovskite-type catalyst was successfully synthesized using the simple sol-gel approach, and surface acid modification was added to improve the ozone catalytic oxidation (OZCO) process ability to remove toluene more effectively. Our study indicates that La3MnCuNiO9 catalyst treated with KMnO4 shows the best toluene oxidation activity. At 250 °C, the rates of conversion and mineralization were 100% and 83%, respectively, under thermal catalytic system when C7H8 concentration = 500 ppm. During the OZCO system ([C7H8] = 20 ppm, O3/C7H8=8; room temperature), for 6 h, the conversion rate remained at 100%. The high ratios of Mn4+/(Mn4++Mn3+), Cu2+, and abundant surface oxygen species, high specific surface area, and pore volume lead to remarkable catalytic performance of this catalyst. Meanwhile, the catalyst contributes to superior stability and water resistance. The catalytic mechanism of La3MnCuNiO9 after KMnO4 treatment in the context of OZCO was further discussed. Overall, after KMnO4 treatment, the La3MnCuNiO9 catalyst reveals extraordinary catalytic activity and excellent stability combination of this catalyst with ozone exhibits high toluene removal efficiency in the OZCO system and has a good potential for industrial applications.

Ozone catalytic oxidation of low-concentration formaldehyde over ternary Mn-Ce-Ni oxide catalysts modified with FeOx.

Manganese oxide-based catalysts have attracted extensive attention due to their relatively low cost and remarkable performance for removing VOCs. In this research, we used the Pechini method to synthesize manganese-cerium-nickel ternary oxide catalysts (MCN) and evaluated the effectiveness of catalytic destruction of formaldehyde (HCHO) and ozone at room temperature. FeOx prepared by the impregnation method was applied to modify the catalyst. After FeOx treatment, the catalyst represented the best performance on both HCHO destruction and ozone decomposition under dry conditions and exhibited excellent water vapor resistance. The as-prepared catalysts were next characterized via H2-temperature programmed reduction (H2-TPR), temperature programmed desorption of O2 (O2-TPD), and X-ray photoelectron spectroscopy (XPS), and the results demonstrated that addition of FeOx increased Mn3+ and Ce3+ concentrations, oxygen vacancies and surface lattice oxygen species, facilitated adsorption, and redox properties. Based on the results of in situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS), possible mechanisms of ozone catalytic oxidation of HCHO were proposed. Overall, the ternary mixed-oxide catalyst developed in this study holds great promise for HCHO and ozone decomposition in the indoor environment.

[Performances Analysis of an Upflow Anaerobic Filter for Domestic Sewage Treatment].

Upflow anaerobic filter (UAF) with actual domestic wastewater were examined in this study. The Impacts of hydraulic retention time (HRT) on the performance of a UAF and a primary methanogen group were investigated at mesophilic conditions. The chemical oxygen demand (COD) removal rate was more than 75% after 28 days acclimation at 35℃ and HRT of 24 h. With a gradual decrease in the HRT, the COD removal rate first increased and then decreased. When the HRT was 5 h, the COD removal rate was the highest, with an average 81.71% and a maximum of 87.18%. When the HRT decreased to 2.5 h, the average COD removal rate decreased to 75.12%. The methane produced per unit mass of substrate consumed (CH4/CODre) and volume fraction increased with a decrease in HRT. When the HRT was 2.5 h, it reached 0.30 L·g-1, and the volume fraction of methane was maintained at about 73%. The energy generated by the system met the energy demands of the peristaltic pump. Quantitative analysis of the primary methanogen group in the system indicates that Methanosarcinales is the dominant in the system. With a decrease in HRT, the abundances of acetoclastic and hydrogenotrophic methanogens increased significantly.