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Zongcheng Zhan Xiaojun Liu Dongzhu Ma Liyun Song Jinzhou Li Hong He Hongxing Dai 《Frontiers of Environmental Science & Engineering》2014,8(4):483-495
A novel Ultrasonic Assisted Membrane Reduction (UAMR)-hydrothermal method was used to prepare flower-like Pt/CeO2 catalysts. The texture, physical/chemical properties, and reducibility of the flower-like Pt/CeO2 catalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), N2 adsorption, and hydrogen temperature programmed reduction (HE-TPR) techniques. The catalytic performance of the catalysts for treating automobile emission was studied relative to samples prepared by the conventional wetness impregnation method. The Pt/CeO2 catalysts fabricated by this novel method showed high specific surface area and metal dispersion, excellent three-way catalytic activity, and good thermal stability. The strong interaction between the Pt nanoparticles and CeO2 improved the thermal stability. The Ce4+ ions were incorporated into the surfactant chains and the Pt nanoparticles were stabilized through an exchange reaction of the surface hydroxyl groups. The SEM results demonstrated that the Pt/CeO2 catalysts had a typical three-dimensional (3D) hierarchical porous struc- ture, which was favorable for surface reaction and enhanced the exposure degree of the Pt nanoparticles. In brief, the flower-like Pt/CeO2 catalysts prepared by UAMR-hydrothermal method exhibited a higher Pt metal dispersion, smaller particle size, better three-way catalytic activity, and improved thermal stability versus conven- tional materials. 相似文献
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With large quantity of flux (Na2CO3), lead can be recovered from the funnel glass of waste cathode-ray tubes via reduction–melting at 1000 °C. To reduce flux cost, a technique to recover added flux from the generated oxide phase is also important in order to recycle the flux recovered from the reduction–melting process. In this study, the phase separation of sodium and the crystallization of water-soluble sodium silicates were induced after the reduction–melting process to enhance the leachability of sodium in the oxide phase and to extract the sodium from the phase for the recovery of Na2CO3 as flux. A reductive atmosphere promoted the phase separation and crystallization, and the leachability of sodium from the oxide phase was enhanced. The optimum temperature and treatment time for increasing the leachability were 700 °C and 2 h, respectively. After treatment, more than 90% of the sodium in the oxide phase was extracted in water. NaHCO3 can be recovered by carbonization of the solution containing sodium ions using carbon dioxide gas, decomposed to Na2CO3 at 50 °C and recycled for use in the reduction–melting process. 相似文献
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Brian P. Leaderer Jan A. J. Stolwijk Rebecca T. Zagraniski 《Environmental management》1977,1(2):131-137
A method is presented by which an upper limit of the adverse health effect of existing ambient CO concentrations on the U. S. population can be estimated. The method is based upon estimating the primary human physiological response to CO concentrations (COHb%) for the population in terms of person-hour-COHb>1.5% resulting from the time exposure of the population to CO concentrations in excess of the federally designated ambient air quality standard. The estimates of person-hour-COHb>1.5% are for exposures only to ambient CO concentrations and do not take into account the additional CO exposure for people who smoke or have occupational exposures.We estimate that there were up to 30.9×109 person-hour-COHb>1.5% in 1973 due to ambient concentrations in excess of the ambient 8-hour CO standard, with approximately 5×109 person-hour-COHb>1.5% occurring West of the Continental Divide and 25.9>109 person-hour-COHb>1.5% occuring East of the Continental Divide; of these 21.3×109 personhour-COHb>1.5% occurred in New York City. It was also estimated that a 60% reduction in 1973 ambient concentrations of CO (corresponding to an automotive emmision standard of less than 15 g/mile) would be needed to reduce to zero the person-hour-COHb>1.5%. The maximum estimated effects on the U.S. population of increases in ambient CO concentration above 1973 levels are also presented. 相似文献
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调整能源结构,减少大气污染物排放 总被引:3,自引:1,他引:3
上海在“十五”期间能源结构调整的重点为严格控制煤炭消费总量,加强煤炭洁净利用;加快电网建设和改造,优化电源结构;扩大天然气利用,建设天然气管网系统;建立能源安全供应体系,加强能源储备,到2005年,经过能源结构调整,煤炭在能源消费中的比重将下降到55%以下, 天然气和外来电能将上升到10%左右,与2005年的基础情景比较,实施能源结构调整后,上海将分别减少SO2和PM10排放量18万t和2.8万t,全市SO2和PM10排放总量可控制在45.7万t和12.4万t,与2000年基本持平。 相似文献
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Cr(VI) is a common heavy metal ion, which will seriously harm human body and environment. Therefore, the removal of Cr(VI) has become an attractive topic. In this work, cinder was used as a raw material to synthesize a nanoneedle material: γ-([email protected]) (γ[email protected]). The physicochemical properties of γ[email protected] were thoroughly characterized, and its effectiveness as a catalyst for photocatalytic reduction of Cr(VI) was evaluated. The results showed that Cr(VI) could be efficiently reduced by γ[email protected] in the presence of tartaric acid (TA) under visible light. The variable factors on the reaction were investigated in detail, and the results showed that under optimal conditions (γ[email protected] 0.4 g/L, TA 0.6 g/L, pH 2), Cr(VI) was completely reduced within 7 min. Besides, scavenger experiments and EPR proved that O2? — and CO2? — played a significant role in the photocatalytic reduction of Cr(VI). TA acts as a sacrificial agent to trap the holes and generate strong reducing free radicals: CO2? —. Dissolving O2 could react with electrons to generate O2? —. This work discussed the performance and mechanism of photocatalytic reduction of Cr(VI) in detail, which provided a new idea for the resource utilization of solid waste and the treatment of heavy metal sewage. 相似文献