Abatement of dichloromethane with high selectivity over defect-rich MOF-derived Ru/TiO2 catalysts.

The regulation of oxygen vacancies and Ru species using metal-organic frameworks was synergically adopted in a rational design to upgrade Ru/TiO2 catalysts, which are highly active for the catalytic oxidation of dichloromethane (DCM) with less undesired byproducts. In this work, Ru/M-TiO2 and Ru/N-TiO2 catalysts were synthesized by the pyrolysis of MIL-125 and NH2-MIL-125 incorporated with Ru, the existence of Ru nanoclusters and nanoparticles was detected by XAFS, respectively, and the catalytic performance was analyzed comprehensively. Complete oxidation of DCM was obtained at ∼290 °C over Ru/M-TiO2 and Ru/N-TiO2 catalysts, while Ru/N-TiO2 showed quite less monochloromethane (MCM) and higher CO2 yields, and better dechlorination capacity in oxidation. The distinction comes down to that the easier desorption of chlorine could be achieved over Ru4+ which act as the main activated adsorption sites for DCM in Ru/N-TiO2, compared to oxygen vacancies that serve as the main dissociation sites in Ru/M-TiO2. Additionally, Ru/N-TiO2 exhibited superior stability and excellent resilience in moisture. An in situ DRIFTS experiment further indicated the different DCM catalytic degradation process as well as the reaction mechanism over the as-prepared catalysts.

Synergetic effect over flame-made manganese doped CuO-CeO2 nanocatalyst for enhanced CO oxidation performance.

CuO-CeO2 nanocatalysts with different amounts of Mn dopping (Mn/Cu molar ratios of 0.5 : 5, 1 : 5 and 1.5 : 5) were synthesized by flame spray pyrolysis (FSP) method and tested in the catalytic oxidation of CO. The physicochemical properties of the synthesised samples were characterized systematically, including using X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), oxygen-temperature programmed desorption (O2-TPD), hydrogen-temperature programmed reduction (H2-TPR) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The results showed that the 1Mn-Cu-Ce sample (Mn/Cu molar ratio of 1 : 5) exhibited superior catalytic activity for CO oxidation, with the temperature of 90% CO oxidation at 131 °C at a high space velocity (SV = 60 000 mL g-1 h-1), which was 56 °C lower than that of the Cu-Ce sample. In addition, the 1Mn-Cu-Ce sample displays excellent stability with prolonged time on CO stream and the resistance to water vapor. The significantly enhanced activity was correlated with strong synergetic effect, leading to fine textual properties, abundant chemically adsorbed oxygen and high lattice oxygen mobility, which further induced more Cu+ species and less formation of carbon intermediates during the CO oxidation process detected by in situ DRIFTS analysis. This work will provide in-depth understanding of the synergetic effect on CO oxidation performances over Mn doped CuO-CeO2 composite catalysts through FSP method.

Removal of hydrophobic volatile organic compounds with sodium hypochlorite and surfactant in a co-current rotating packed bed.

A co-current flow rotating packed bed was applied to remove volatile organic compounds (VOCs) by sodium hypochlorite (NaClO) and surfactant (sodium dodecyl benzene sulfonate, SDBS) from air stream. Xylene was used as a model VOC herein. The effect of pH, concentration of NaClO and SDBS solution, liquid flow rate, gas flow rate and rotational speed on xylene removal efficiency and overall mass transfer coefficient (KGa) were discussed. Then, a correlation for KGa of the co-current rotating packed bed was proposed by fitting the experimental data of KGa and independent variables of liquid/gas ratio, rotational speed, pH, NaClO concentration and treatment time, which was in good agreement with the experimental data (the deviation≤±30%).

Removal of low concentration CH3SH with regenerable Cu-doped mesoporous silica.

Mercaptans are highly volatile compounds responsible for disagreeable odors and very low olfactory threshold, especially for CH3SH (0.4 ppvb). To the best knowledge of us, approach for controlling low-concentrated odors (i.e. 1-10 ppm) is scarcely reported. In this research, Cu-doped mesoporous silica was synthesized for removal of low-concentrated CH3SH. The as-prepared samples show considerably thermal and mechanical stability and could be thermal-regenerated. Copper loading ratio and humidity have significant impacts on eliminating odors. According to XRD, TEM, BET, NMR and EPR, we deduce that surface groups on CuO nanoparticles and the SiOCu group are highly possibly transformed into a hydrated complex which is much more effective in capturing CH3SH with its empty Cu-3d orbit. Although CH3SH has to compete with water for absorption sites, it is always the "winner" owing to the strong chelating ability between SH group and Cu (Ⅱ).

Distinct biokinetic behavior of ZnO nanoparticles in Daphnia magna quantified by synthesizing 65Zn tracer.

ZnO nanoparticles (nZnO) are widely used in different fields and there are increasingly concerns for their hazards in the environment. The biokinetic behavior of nZnO in aquatic organisms however remains essentially unknown. The aim of this study was to separate the uptake and depuration behavior of nZnO and Zn ions in a freshwater cladoceran Daphnia magna. We for the first time radio-synthesized the nZnO and followed its uptake and depuration in D. magna. Two concentrations (0.5 mg/L and 2 mg/L) of nZnO were employed in this study, and the releases of nZnO into soluble Zn were 20-30% during the experiments. We found that the uptake of nZnO by D. magna was related to nZnO concentration. The uptake of ionic Zn released from nZnO by D. magna followed a linear increase during the exposure period (40 min or 8 h). The nanoparticles could enter the body of daphnids and reached a peak within a short time, followed by a rapid release. Uptake of nanoparticles was mainly by direct ingestion, with negligible nZnO absorption onto the carapace. The depuration of nZnO was also rapid and controlled by nZnO dissolution in the body of D. magna. Our study showed a distinctive uptake mode of nZnO and suggested that both dissolved Zn and nanoparticles should be considered in studying the toxicology of nZnO.