碘化阶层孔氧化硅纳米球对水中典型有机氯污染物的吸附性能研究

采用共缩聚法,成功地原位合成了碘改性的阶层多孔氧化硅纳米球（SiO₂-I）,研究了其基于卤键作用对典型有机氯污染物六六六的吸附性能,并考察了改性剂I-硅烷含量和pH值对吸附效果的影响.实验结果表明,该纳米材料对六六六表现出优异的吸附富集性能,吸附速率快,60 min内对六六六的去除率为71.6%,240 min内达到吸附平衡,去除率可达98.3%,最大吸附量为178.6 mg·g^-1;吸附动力学符合拟二级动力学模型;碘物种的加入提高了阶层多孔氧化硅的吸附速率和吸附效率.另外,为了便于纳米吸附材料的分离,本研究对SiO₂-I纳米球进行了磁性化.研究发现,磁性化修饰后,SiO₂-I纳米材料仍然保留对六六六优异的吸附富集性能,240 min时的吸附去除率达90.3%.     

Research on the effects of diesel engine exhaust transport distance on particulate microstructure

This study aims to reveal the evolutionary process of particles during the diesel exhaust transport process and to further understand the effects of diesel exhaust transport distance (D_ET) on a particulate microstructure. Specifically, the micromorphological, particle size distribution, and aggregate characteristics of particles as well as the variation of the structural characteristics of elementary carbon particles (ECPs) as D_ET changed were examined using an engine exhaust particle size spectrometer, a high-resolution transmission electron microscopy system, and a small-angle X-ray scattering system. The results show the following: As D_ET increased, the chains gradually lengthened, the extent of accumulation and stacking increased, and a number of clusters gradually rose. The average particle diameter increased from 23.1 nm at 0 m to 92.7 nm at 3 m. In addition, as D_ET increased, the number of accumulation-mode particles, the number of folded, curved carbon layers in the inner core of carbon particles, and the disorderliness of carbon layers in the outer shell of carbon particles all increased. Moreover, the boundary between the inner core and the outer shell became increasingly obscure. As D_ET increased, there was a gradual decrease in the difference in electron density between particles, and the fractal dimensionality of the distribution, average cross-sectional size, radius of gyration, and axial length of pores were, respectively, 33.3%, 40%, 38.2%, and 50.3% less at 3 m than at 0 m. Besides that, the number of small (< 3 nm) pores gradually increased, and the number of large (> 10 nm) pores gradually decreased. Overall, as D_ET increased, pore size and number decreased. There was a gradual increase in the number of folded and curved carbon layers in the inner core of ECPs and an increase in the disorderliness of carbon layers in their outer shell as D_ET increased. Furthermore, the boundary between the inner core and the outer shell became increasingly obscure as D_ET increased. The crystallite size of ECPs decreased from 1.365 nm at 0 m to 1.098 nm at 3 m. This suggests that the number of continuously arranged carbon atoms decreased, the arrangement of carbon atoms was more disorderly, and the degree of graphitization decreased. As D_ET increased, there was a gradual increase in the interlayer spacing and curvature of ECPs. This suggests that increasing D_ET led to a more disorderly distribution of electron orbitals inside the carbon layers, less electron resonance stability in the carbon layers, greater oxidative activity of ECPs, and greater inherent oxidative capacity of particles.

     

Study on microstructure and extinction characteristics of particulate matter in diesel engine fueled with different biodiesels

Environmental Science and Pollution Research - Biodiesel combustion particulate matter (PM) is different from diesel combustion PM in terms of microscopic morphology, which directly affects the...     

V2O5/TiO2与MoO3/TiO2催化剂表面结构形貌及其对催化氧化碳烟活性的影响

为研究纳米级V₂O₅与MoO₃催化剂表面结构对其催化氧化碳烟活性的影响,以TiO₂为载体,采用等体积浸渍法制备了不同负载率(5%、10%、20%、40%)的V₂O₅/TiO₂与MoO₃/TiO₂催化剂,通过扫描电镜(SEM)、X射线衍射仪(XRD)对比研究了2种催化剂在TiO₂载体上的分散状态及物相结构.以Printex-U碳黑为试验用碳烟,采用热重分析仪对V₂O₅与MoO₃催化剂催化碳烟氧化的活性进行了比较.结果表明:V₂O₅与MoO₃在TiO₂载体上均存在一个单层分散饱和阈值,分别为V20(负载率为20%,下同)、Mo10,在该阈值前后活性组分在载体上分别以单层分散状态和明显的晶态存在.对于V₂O₅催化剂,其最佳催化活性出现在负载率接近单层分散饱和阈值时,与无催化状态相比,T_i(起燃温度)、T_p(最大失重率温度)以及T_f(燃尽温度)分别下降了69.1、46.0、23.0 ℃,有明显的阈值效应.而对于MoO₃催化剂,因其自身低熔点性而表现出良好的表面迁移能力,再加上α-MoO₃晶体特有的层状结构,使其可释放出更多的晶格氧,随着负载率的增加,该催化剂催化氧化碳烟活性持续增加,并且未观察到明显的阈值效应.研究显示,在相同负载率下,MoO₃催化剂催化氧化碳烟活性均高于V₂O₅催化剂.