The impact of economic complexity on energy demand in OECD countries

Environmental Science and Pollution Research - This paper investigates the role of economic complexity on energy demand using the panel dataset of 25 Organization for Economic Co-operation and...     

Comparison of multi-criteria analysis methodologies for the prioritization of arsenic-contaminated sites in the southwest of China

The issue of contaminated sites has been highlighted as an immediate priority in the 13th Five-Year Plan of China. Identification and prioritization of contaminated sites are of key importance for proposing effective strategies for the regional management of contaminated sites. In this study, three advanced multi-attribute methodologies, the risk-based priority methodology, the regional risk assessment methodology, and the dominance-based rough set approach (DRSA), were comparatively employed to screen contaminated sites in, Guangxi, Southwest of China. The results of the three prioritizations show that the highest ranking site identified by the three methods had great agreement. In regard to the screening attributers, while the risk-based prioritization methodology and regional risk assessment methodology allowed a high discrimination in the screening of contaminated sites associated with different attributes, such as farmland, residential areas, contaminant level, number of people, area, storage quality, site service life, and surrounding communities, the DRSA allowed the identification of contamination strength (CS) and contamination potential (CP).

     

Mechanism of Hg oxidation in the presence of HCl over a commercial V2O5–WO3/TiO2 SCR catalyst

Experiments were conducted in a fixed-bed reactor containing a commercial V₂O₅/WO₃/TiO₂ catalyst to investigate mercury oxidation in the presence of HCl and O₂. Mercury oxidation was improved significantly in the presence of HCl and O₂, and the Hg⁰ oxidation efficiencies decreased slowly as the temperature increased from 200 to 400°C. Upon pretreatment with HCl and O₂ at 350°C, the catalyst demonstrated higher catalytic activity for Hg⁰ oxidation. Notably, the effect of pretreatment with HCl alone was not obvious. For the catalyst treated with HCl and O₂, better performance was observed with lower reaction temperatures. The results showed that both HCl and Hg⁰ were first adsorbed onto the catalyst and then reacted with O₂ following its adsorption, which indicates that the oxidation of Hg⁰ over the commercial catalyst followed the Langmuir–Hinshelwood mechanism. Several characterization techniques, including Hg⁰ temperature-programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS), were employed in this work. Hg-TPD profiles showed that weakly adsorbed mercury species were converted to strongly bound species in the presence of HCl and O₂. XPS patterns indicated that new chemisorbed oxygen species were formed by the adsorption of HCl, which consequently facilitated the oxidation of mercury.     

Effect of Al2O3 doping on the structure and performance of an Al2O3/Fe2O3 catalyst for mercury oxidation

In this study,the thermal stability of a Fe_2 O_3 catalyst for mercury oxidation was significantly improved by doping with Al_2 O_3.After 1 hr,the catalyst doped with 10 wt.% Al_2 O_3 still exhibited a mercury conversion efficiency of 70.9%,while the undoped sample even lost its catalytic activity.Doping with Al_2 O_3 retarded the collapse of the catalyst mesoporous structure during high-temperature calcination,and the doped samples maintained a higher specific surface area,smaller pore size,and narrower pore size distribution.Transmission electron microscope images revealed that after calcination at 350℃,the average size of the catalyst grains in Fe_2 O_3 was 23.4 nm;however,the corresponding values for 1%Al_2 O_3/Fe_2 O_3,3%Al_2 O_3/Fe_2 O_3,and 10%Al_2 O_3/Fe_2 O_3 were only 13.3,7.1,and 4.7 nm,respectively.Results obtained from X-ray diffraction and thermogravimetry coupled with differential scanning calorimetry confirmed that doping with Al_2 O_3 also retards the crystallization of the catalysts at high temperature,constraining catalyst grains to a smaller size.     

Pilot study of intense dewatering of urban sewage sludge

Urban sewage sludge treatment has become a severe problem due to its large quantities and enrichment with heavy metals, refractory organic contaminants and pathogenic bacteria. Accordingly, it is essential to develop an effective and low-cost intense dewatering technique to decrease sludge water content so that it can be easily treated by subsequent incineration, landfilling or composting. In this study, a new intense sludge dewatering technique using conditioner of coagulant and flocculant (polyacrylamide) mixture and the diaphragm filter press was developed and investigated systematically by measuring the water content, calorific value and coliform bacteria in the sludge and investigating the dewatering efficiency under different conditions. The results showed that the water content of the sludge was effectively reduced from 80 % to the minimum of 43.6 % by adding conditioners and subsequent dewatering using the diaphragm press. Moreover, the low calorific value of dewatered sludge increased significantly from that of the original sludge, and was conducive to subsequent incineration. The water content of the dewatered sludge cake decreased to less than 25 % after being kept in the open air for 9 days. Therefore, it is proposed that this technique be applied to large-scale engineering applications.     

石油化工废水处理技术研究进展

石油化工废水组成复杂、浓度高、毒性强和难降解,对环境危害大.概括介绍了国内外石油化工废水的主要处理方法如物化法、化学法和生化法,并评述了各种处理方法的适用条件和处理效果,总结了各种处理方法的优缺点.最后,提出推行清洁生产,开展废水资源化,并用高效的末端治理方法处理废水,是石油化工行业水污染控制的出路.     

Role of NO in Hg oxidation over a commercial selective catalytic reduction catalyst V2O5–WO3/TiO2

Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst, V₂O₅–WO₃/TiO₂, to investigate mercury oxidation in the presence of NO and O₂. Mercury oxidation was improved by NO, and the efficiency was increased by simultaneously adding NO and O₂. With NO and O₂ pretreatment at 350°C, the catalyst exhibited higher catalytic activity for Hg⁰ oxidation, whereas NO pretreatment did not exert a noticeable effect. Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O₂. Although NO promoted Hg⁰ oxidation at the very beginning, excessive NO counteracted this effect. The results show that NO plays different roles in Hg⁰ oxidation; NO in the gaseous phase may directly react with the adsorbed Hg⁰, but excessive NO hinders Hg⁰ adsorption. The adsorbed NO was converted into active nitrogen species (e.g., NO₂) with oxygen, which facilitated the adsorption and oxidation of Hg⁰. Hg⁰ was oxidized by NO mainly by the Eley–Rideal mechanism. The Hg⁰ temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O₂.     

设立国家高新区能否驱动城市绿色发展——基于双重差分法的经验数据

国家高新区是新时代中国落实创新驱动发展战略、实现经济高质量发展和绿色发展的重要制度安排。本研究以2008年之后设立了国家高新区的城市为实验组，以一直未设立国家高新区的城市为对照组，形成2003—2019年的231个城市的面板数据，采用多期双重差分法实证检验国家高新区的设立对城市绿色发展水平的驱动作用及其机制。研究发现，设立国家高新区能显著提升城市绿色发展水平，但提升效应有待进一步加强。其机制主要是国家高新区通过提高经济增长质量和资源节约利用水平，提升环境治理和生态保护水平，改善居民绿色行为和居住环境，进而提升城市的绿色生产指数、绿色生态指数和绿色生活指数。以上结论表明国家高新区可通过推动产业结构提档升级和节能减排来进一步增强绿色先行示范作用，引领城市绿色发展。