Co负载量对Co/TiZrO4催化CO2氧化乙烷脱氢制乙烯反应性能的影响

Co基催化剂在低碳烷烃直接脱氢及氧化脱氢制烯烃方面表现出良好的应用潜力.为了探究Co物种的价态对CO₂氧化乙烷脱氢制乙烯的影响,以共沉淀法制备的TiZrO₄固溶体为载体,采用浸渍法制备了一系列X%Co/TiZrO₄(X=0.5、1、3、5和7.5)催化剂.结果表明,0.5%Co/TiZrO₄和1%Co/TiZrO₄催化剂的催化活性较差,但保持了相当高的C₂H₄选择性(>90%)和碳平衡(≈100%);3%Co/TiZrO₄催化剂在反应过程中表现出良好的C₂H₆和CO₂活化能力,在650℃、质量空速WHSV=9000 mL?g^-1?h^-1的反应条件下获得了约25%的乙烯收率;而5%Co/TiZrO₄和7.5%Co/TiZrO₄催化剂则在600℃及以上温度反应...     

粉煤灰对烟气中CO2的吸收特性及矿物相演变机理研究

粉煤灰矿化CO₂是一种极具前景的减少燃煤电厂CO₂排放的技术.然而,目前还缺乏从矿物学角度对碳酸化反应机理的详细认识.本研究选取了3种粉煤灰开展碳酸化实验和矿物学研究,考察碳酸化过程中温度对碳酸化能力及粉煤灰矿物学变化的影响.结果表明,在任一温度下,BJ粉煤灰的碳酸化率均高于YA和LY粉煤灰,这是由于BJ粉煤灰中硬石膏、钙铁石和无定形相等活性矿物相含量较高,LY粉煤灰缺少高活性的钙、镁结晶相.对YA粉煤灰而言,升高温度可显著提高透辉石、尖晶石、黑钙铁矿和方镁石的转化率.在碳酸化YA粉煤灰中同时检测出碳酸钙和碳酸镁/铁,说明除含钙相其他活性元素(Mg和Fe)也参与了碳酸化过程.因此,需要对每个粉煤灰原始材料的矿物学和操作温度进行具体的个案优化,以最大限度地提高固定CO₂能力和碳酸化率.结果还表明温度对不同晶型碳酸钙的形成具有重要作用.方解石在低温(40和80℃)下形成,而文石在高温(180和220℃)下形成.     

Review on recent progress in on-line monitoring technology for atmospheric pollution source emissions in China

Emissions from mobile sources and stationary sources contribute to atmospheric pollution in China, and its components, which include ultrafine particles (UFPs), volatile organic compounds (VOCs), and other reactive gases, such as NH₃ and NO_x, are the most harmful to human health. China has released various regulations and standards to address pollution from mobile and stationary sources. Thus, it is urgent to develop online monitoring technology for atmospheric pollution source emissions. This study provides an overview of the main progress in mobile and stationary source monitoring technology in China and describes the comprehensive application of some typical instruments in vital areas in recent years. These instruments have been applied to monitor emissions from motor vehicles, ships, airports, the chemical industry, and electric power generation. Not only has the level of atmospheric environment monitoring technology and equipment been improving, but relevant regulations and standards have also been constantly updated. Meanwhile, the developed instruments can provide scientific assistance for the successful implementation of regulations. According to the potential problem areas in atmospheric pollution in China, some research hotspots and future trends of atmospheric online monitoring technology are summarized. Furthermore, more advanced atmospheric online monitoring technology will contribute to a comprehensive understanding of atmospheric pollution and improve environmental monitoring capacity.     

Measurement of atmospheric nanoparticles: Bridging the gap between gas-phase molecules and larger particles

Atmospheric nanoparticles are crucial components contributing to fine particulate matter(PM2.5), and therefore have significant effects on visibility, climate, and human health. Due to the unique role of atmospheric nanoparticles during the evolution process from gas-phase molecules to larger particles, a number of sophisticated experimental techniques have been developed and employed for online monitoring and characterization of the physical and chemical properties of atmospheric nanoparticles,...     

双酚类化合物的毒理学效应及微生物降解机制的研究进展

双酚类化合物作为重要的有机化工原料,广泛应用于各行各业。然而双酚类化合物是一类内分泌干扰物,毒性评价结果表明其与许多疾病发病率的升高密切相关。伴随双酚类化合物的大量使用,诸多环境样品中都检测出双酚类化合物。由于双酚类化合物的结构稳定,很难在自然界中被完全降解,会不断累积,对生态安全和人体健康产生危害,亟待有效修复。有机污染物的物理化学修复方法易对环境造成二次污染,微生物降解因其获取容易、无二次污染等特点成为双酚类化合物修复的有效途径。本文总结概述了几种典型双酚类化合物的毒性评价及微生物降解机制。     

Research on ammonia emissions characteristics from light-duty gasoline vehicles

In this study, ammonia emissions characteristics of typical light-duty gasoline vehicles were obtained through laboratory vehicle bench test and combined with New European Driving Cycle (NEDC) condition and Worldwide Harmonized Light Vehicles Test Cycle (WLTC) condition. The influence of ambient temperature on ammonia emissions is mainly concentrated in the cold start stage. The influence of ambient temperature on ammonia emission is shown that the ammonia emissions of light-duty gasoline vehicles under ambient temperature conditions (14 and 23°C) are lower than those under low ambient temperature conditions (?7°C) and high ambient temperature conditions (35 and 40°C). The influence of TWC on ammonia emission is shown that ammonia is a by-product of the catalytic reduction reaction of conventional gas pollutants in the exhaust gas in the TWC. Under NEDC operating conditions and WLTC operating conditions, ammonia emissions after the catalyst are 45 times and 72 times that before the catalyst, respectively. In terms of ammonia emissions control strategy research, Pd/Rh combination can reduce NH₃ formation more effectively than catalyst with a single Pd formula. Precise control of the engine's air-fuel ratio and combination with the optimized matched precious metal ratio TWC can effectively reduce ammonia emissions.     

自吸式文丘里洗涤器雾化液滴尺寸影响因素的实验研究

为研究雾化液滴尺寸对自吸式文丘里洗涤效率的影响,从喉部气速、液面高度差以及文丘里扩散段结构等方面,研究了自吸式文丘里洗涤器雾化液滴平均直径(D_(32))的变化规律,并与Boll模型对D_(32)的预测值进行了对比。研究表明,随着喉部气速的增加,D_(32)的实验值和预测值均呈逐渐减小的趋势,且预测值略小于实验值。另外,液面高度差的增加会导致D_(32)的减小,当气相速度增大时,D_(32)加速减小。研究发现,当喉部气速大于54.6 m/s时,A_1挡板对液相流体具有更好的雾化效果,当喉部气速小于54.6 m/s时,在环形挡板内径为46～54 mm之间存在一个最佳内径,使得雾化液滴平均直径最小,文丘里洗涤器达到最佳雾化效果。     

流态变化对污水管网沉积污染物分布及转化的影响

为探明城市污水汇流管网流速变化对沉积层污染物及生物菌群演替的影响,通过控制污水管道中试系统中干管、支管流速,模拟了不同汇流条件下城市污水管网系统运行状态,探究了不同汇流条件下沉积层碳、氮、硫类污染物的分布特征以及微生物种群结构的分布规律.结果表明,在不同汇流条件下,COD、TN、NH₃-N、NO₃-N、硫酸盐含量沿沉积层深度方向均逐渐减小,而硫化物含量逐渐升高.当干管、支管流速均增加时,促进了汇流区域不同深度污染物的沉积富集,但由于DO、ORP环境因子的改变,以及流速的增大,将沉积层中原有的碳源基质剥离到污水中,减少了微生物可利用的营养物质,同时造成沉积层内部溶解氧含量的上升,沉积层中产甲烷菌（MA）中优势菌属Methanosaeta、硫酸盐还原菌（SRB）中优势菌属Desulfomicrobium、水解发酵菌（FB）中优势菌属Caldisericum的相对丰度逐渐降低,硫氧化细菌（SOB）中优势菌属Thiobacillus相对丰度增加,显著影响了沉积污染物的转化特性.污水管网汇流区域流态是改变污水水质及管道微生物系统的重要因素.     

东北黑土区典型地域耕地生态退化时空分异——以富锦市为例

耕地生态退化严重威胁黑土区耕地的可持续利用,明确其时空分异规律是提高黑土耕地产能实现农业可持续发展的重要科学命题。以东北黑土区典型地域富锦市为研究区,立足于耕地外部扰动变化所引发的环境胁迫与生态恢复,利用遥感驱动的多源环境胁迫监测模型、改进的CRITIC模型、优化的InVEST模型,明确二者间的作用结果,揭示研究区2000—2020年耕地生态退化的时空分异规律。研究结果表明：（1）研究区耕地外源环境胁迫强度整体偏低,呈现出以东部、西部、北部高,中部、南部低为主基调的时空分异格局;（2）研究区耕地內源生态恢复强度高于胁迫强度,表现出以西部—东部—中部梯度衰减的时空分异格局;（3）研究区共有968.12 km²耕地发生生态退化,展现出以团块状集中分布在研究区东部和中部,零星分布在其他区域的空间分异格局。研究明晰了多源环境胁迫/多源生态恢复之间的交互效应,实现了各耕地图斑对多种环境胁迫力和生态恢复力的动态敏感度测算,进一步刻画出了生态退化过程,测度结果与现实耕地利用强度吻合,为准确诊断黑土区耕地生态退化提供了理论参考和技术支撑。     

Mechanisms of Pb(II) coprecipitation with natrojarosite and its behavior during acid dissolution

Lead (Pb) coprecipitation with jarosite is common in natural and engineered environments, such as acid mine drainage (AMD) sites and hydrometallurgical industry. Despite the high relevance for environmental impact, few studies have examined the exact interaction of Pb with jarosite and the dissolution behavior of each phase. In the present work, we demonstrate that Pb mainly interacts with jarosite in four modes, namely incorporation, occlusion, physically mixing, and chemically mixing. For comparison, the four modes of Pb-bearing natrojarosite were synthesized and characterized separately. Batch dissolution experiments were undertaken on these synthetic Pb-bearing natrojarosites under pH 2 to simulate the AMD environments. The introduction of Pb decreases the final Fe releasing efficiency of jarosite-type compounds from 18.18% to 3.45%-5.01%, showing a remarkable inhibition of their dissolution. For Pb releasing behavior, PbSO₄ dissolves in preference to Pb-substituted natrojarosite, i.e., (Na, Pb)-jarosite, which primarily results in the sharp increase of Pb releasing concentration (> 40 mg/L). PbSO₄ occlusion by jarosite-type compounds can significantly reduce the release of Pb. The results of this study could provide useful information regarding Fe and Pb cycling in acidic natural and engineered environments.