孔径分布和溶液浓度对碳气凝胶电极电吸附除盐性能的影响分析

在不同进水浓度下,采用两种比表面积相似但是孔径分布不同的碳气凝胶作为电极进行了一系列电吸附除盐平衡试验.结果表明,随着溶液浓度的变化,不同的孔径分布对碳气凝胶除盐效果影响不一样.其机理为双电层的存在,使得碳气凝胶空隙内的双电层扩散层相互叠加;同时,根据德拜定律,碳气凝胶空隙内的双电层扩散层在不同浓度溶液中厚度不同,从而使得双电层扩散层相互叠加的情况也随浓度变化而变化.这两种作用共同导致了实验结果.当溶液浓度为 0.01 mol·L-1时,选择主要孔径不小于20hm的碳气凝胶电极;当溶液浓度为 0.1 mol·L-1时,应选用主要孔径不小于 10nm 的材料;当溶液浓度为几 mol·L-1时.则分散层几乎消失,孔径大小对电吸附性能影响几乎不考虑.     

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi (AMF) have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony (Sb). The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis (PCA) indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis (RDA) showed that Sb contaminationwas the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Glomus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.     

利用大型土柱自然淋溶条件下研究土壤重金属的迁移及形态转化

为研究不同重金属在土壤中的迁移和形态转化,通过分层填装土柱,在土柱0~5 cm深度范围内添加Pb、Ag、Bi、In、Sb和Sn等重金属污染土壤,并在自然条件下淋溶4 a,分析各重金属在红壤、潮土、黑土和砂土中的迁移速率及其形态组成. 结果表明:①在>30 cm深度范围内,红壤、潮土和黑土中各重金属质量分数与其相应本底值相比变化不大;与试验前土壤相比,砂土整个剖面中6种重金属质量分数均较高. ②6种重金属在4种土壤中的残留率表现为砂土<潮土<黑土<红壤;对于0～10 cm土壤中Pb的残留率,在潮土中大于Ag和Sb,在黑土中大于Ag,在红壤中大于In,在砂土中则大于Sn. ③模拟试验后残留在土柱中的重金属主要分布在土壤表层(0～30 cm),而深层(>30 cm)较少;6种重金属在红壤、潮土、黑土和砂土中的残留率平均值分别为98.0%、65.1%、65.9%和56.5%. ④与添加污染土壤之前相比,试验后土壤中残渣态等稳定形态重金属质量分数较低,其中Pb、In和Sb均以碳酸盐结合态和有机金属络合态为主,Ag和Sn分别以有机金属络合态、双氧水可提取有机结合态和有机金属络合态、无定形铁锰氧化物结合态为主,而Bi则以碳酸盐结合态和双氧水可提取有机结合态为主. 结果显示,红壤中Pb的迁移风险较低,潮土和黑土中Ag、Sb的迁移风险较高,而砂土中Sn和Sb的迁移风险需要格外关注.      

膜分离技术用于非电解质除杂

介绍电渗析装置工艺及基本原理，提出使用离子选择性透过膜的依据及极限电流的确定方法．论述了不同方法对冷冻液与ＮａＳＣＮ分离效果影响，指出采用电渗析法分离冷冻液中的ＮａＳＣＮ，使除杂率可达９５％以上。本工艺为腈纶冷冻液除杂及防治污染提供了新途径。     

乡镇企业环境保护工作初探

近年来，乡镇企业蓬勃发展的趋势要求我们必须重视其环境保护工作．笔者通过联系当地的实际情况力图阐明自己对于如何搞好乡镇企业环境保护工作的一些观点。     

转pBinMoBc基因棉花的培育与应用

采用农杆菌介导法将含有复合OM启动子和增强子Ω因子的外源基因pBinMoBc导入冀棉20中.转化再生株经分子检测表明,外源基因已整合到转基因植株基因组内,并得到了表达,转化外源基因插入拷贝数是1~2个.转化后代材料经6~7代选育为纯合品系2001pb-3.2001pb-3抗虫性较好,每公顷产皮棉1534.5kg,比对照增产18.68%.图5表3参4     

不同环境条件下聚羟基烷酸(PHAs)薄膜生物降解性研究

采用不同形态的PHAs薄膜（聚β－羟基丁酸（PHB）及β－羟基丁酸与β－羟基戊酸的共聚物（PHBV）膜）,在各种环境（如土壤和水体）的不同条件下,对膜的生物降解性进行了研究,并对其降解机制作了初步探讨。结果表明：PHAs膜具有生物降解性,在无菌条件下不能被降解;在不同的环境中,如不同土壤和水体,PHAs膜的降解情况不同;不同的条件,如pH、温度,对环境中PHAs膜的降解率有着不同的影响;PHB膜的生物降解速度比PHBV膜快;PHAs膜的厚度对其降解能力有很大影响。     

德国汉诺威高铁出轨事故的机理分析

本文阐述了进行突发事故机理研究的意义和重要性,强调了对事故酝酿、发生、发展的全过程进行机理分析的模式,并设计了一个类似射击瞄准过程来追踪突发事故的形成与最终结果的定性分析模型,通过将该原理与模型应用于对德国汉诺威高铁出轨事故的研究,说明了其分析过程与实际意义。     

A comparative study of the effect of clay binders on iron oxide sorbent in the high-temperature removal of hydrogen sulfide

The purpose of this study is to investigate the effect of clay binder, an important additive, on the performance of iron oxide sorbent in high temperature coal gas desulfurization. The four clay binders chosen for the study were kaolinite, diatomite, bentonite and brick clay. The sulfidation–regeneration cycles were conducted in a fixed-bed reactor. XRD, DTA and FTIR, together with texture characterizing techniques, such as mercury porosimetry and nitrogen adsorption, were adopted to characterize the sorbents and raw materials. The results obtained show that sorbents prepared from various clay binders exhibit different breakthrough behaviors. In addition, a correlation between pore volume and sulfur capacity reveals that sorbents with a greater number of pores larger than 200 nm (diameter), exhibit higher sulfur capacity. The reason for this is that a greater number of large pores can improve diffusion and provide a larger space for relieving heat impact. However, too many large pores may result in weak strength and very low bulk density, thus a balance between large pores and the density must be achieved. This study also reveals that clay binder can contribute to the modification of a sorbent's texture as gas is released when the mineral structure changes during calcination. In addition, a clay mineral with an active interlayer has been shown to be beneficial in improving the dispersion of active components in the sorbent, because of the existence of an interaction between the mineral and red mud.     

Performance and mechanism study for low-temperature SCR of NO with propylene in excess oxygen over Pt/TiO2 catalyst

A 0.5 wt.% Pt/TiO2 catalyst was prepared and used for the low-temperature selective catalytic reduction(SCR) of NO with C3 H6 in the presence of excess oxygen.The effects of Pt loading and O2 concentration on Pt/TiO2 catalytic performance for low-temperature SCR were investigated.It was found that optimal Pt loading was 0.5 wt.% and excess O2 favored low-temperature SCR of NOx.The mechanism of low-temperature SCR of NO with C3 H6 was investigated with respect to the behavior of adsorbed species over Pt/TiO2 at 150°C using in situ DRIFTS.The results indicated that surface nitrosyl species(Pt δ+-NO and Ti 3+-NO) and Pt 2+-CO are main reaction intermediates during the interactions of NO,C3 H6 and O2.A simplified NO decomposition mechanism for the low-temperature SCR of NO with C3 H6 was proposed.