零价金属脱氯降解有机氯化污染物研究进展

综述了国内外在零价金属还原脱氯降解有机氯化物领域的研究情况,讨论了零价铁还原脱氯作用机理,展望了零价金属还原脱氯降解有机氯化物研究领域的发展前景。     

Electrocatalytic dechlorination of 2,4,5-trichlorobiphenyl using an aligned carbon nanotubes electrode deposited with palladium nanoparticles

Palladium loaded carbon nanotubes cathode with well-aligned nanotubes array was successfully fabricated on a titanium foil (Pd/CNTs/Ti) using a chemical vapor deposition technique and subsequent electrochemical deposition method. Pd particles were well dispersed on CNTs wall surfaces with average sizes no more than 20 nm, in most cases around 10 nm. Experiments for dechlorination of 2,4,5-trichlorobiphenyl (PCB 29) in methanol/water solution were carried out for the first time using Pd/CNTs/Ti cathode for investigation of its performance in electrocatalytic dechlorination of PCBs. Results show that Pd/CNTs/Ti presented better dechlorination efficiency (up to 90% in 6 h) than Pd/Ti and Pd/graphite cathodes owing to unique properties owned by CNTs, which benefited enhanced dechlorination of PCB 29. Complete dechlorination for PCB 29 was observed and biphenyl was identified to be final dechlorination product. The amount of Pd loading, cathode potential, and electrolytes were found to be key factors influencing dechlorination performance.     

基于网络的计算机语言类学习框架系统的开发

根据计算机语言类课程教学内容的共性，提出了一个独立于具体语言的框架式结构．基于该结构开发的系统支持交互式个别化教学模式．它具有教师用户位置透明的特点     

Interactively interfacial reaction of iron-reducing bacterium and goethite for reductive dechlorination of chlorinated organic compounds

The interactively interfacial reactions between the iron-reducing bacterium （Shewanella decolorationis, S12） and iron oxide （α-FeOOH） were investigated to determine reductive dechlorination transformation of chlorinated organic compounds （chloroform and pentachlorophenol）. The results showed that the interactive system of S12＋ α-FeOOH exhibited relatively high dechlorination rate. By comparison, the S12 biotic system alone had no obvious dechlorination, and the α-FeOOH abiotic system showed low dechlorination rate. The enhanced dechlorination of chloroform and pentachlorophenol in the interactive system of S12＋α-FeOOH was derived from the promoted generation of adsorbed Fe（Ⅱ） by S12. A decrease in redox potential of the Fe （Ⅲ）/Fe （Ⅱ） couple in the interactive reaction system was determined by cyclic voltammetry. Our results will give new insight into interactively interfacial reaction between iron-reducing bacterium and iron oxides for degradation of chlorinated organic compounds under anaerobic condition.     

氯代芳烃脱氯速率常数的QSPR研究

测定钯／铁催化还原水中８种氯代烃的反应速率常数,以ＰＭ３算法计算了表征氯代芳烃分子结构的量子化学参数,并用一元回归分析对氯代芳烃的分子结构与与其催化还原脱氯速率进行了定理结构－性能相关研究。     

1，1-二氯乙烷微生物降解菌群的生理学鉴定

从纽约哈得逊河河底淤泥样品中富集分离得到的微生物菌群,在厌氧条件下,可将1,1-二氯乙烷通过还原脱氯的呼吸代谢方式降解生成一氯乙烷.这个微生物菌群可以利用氢气、甲酸、乙酸、苯甲酸和延胡索酸作为电子供体进行还原脱氯生长,并能以丙酮酸发酵的呼吸方式生长,但丙酮酸不能用来作为电子供体进行还原脱氯.通过对其他氯代化合物是否能作为电子受体的实验,发现只有1,1-二氯乙烷能被脱氯.在培养基中加入亚硫酸盐可完全抑制二氯乙烷的还原脱氯,但硫酸盐、硝酸盐和延胡索酸盐的加入却不影响还原脱氯.在以氢气作为电子供体进行还原脱氯时,每摩尔氯原子的还原相应地使细胞干重增加(4.402±1.241)g.同时对富集分离的菌群进行16S rRNA基因序列分析发现,在脱氯生长方式下,该微生物菌群中Dehalobacter细菌占主导地位.     

Frequency Effects on 2-Chlorobiphenyl Sonication

In order to better understand sonication, this paper studies the effect of sound frequency on the 2-chlorobiphenyl (2-CB) sonication and analyzes two prevailing hypotheses. Four frequencies 205, 358, 618 and 1071 kHz were tested. The 2-CB degradation kinetics, dechlorination, and inhibition by a free radical scavenger were examined. The results show that sonication effectively degrades 2-CB, and the first order rate constants using 0.4 W/cm^3 sonication are 0.214, 0.508, 0.454, and 0.248 min6-1 at 205, 358, 618, and 1071 kHz, respectively. Good dechlorination was also achieved. 358 kHz frequency provided the most efficient 2-CB degradation, but the worst dechlorination, and was most sensitive to the free radical scavenger. Detailed analyses show that thermolysis is relatively stable at these frequencies while the free radical reaction depends strongly on the sound frequency.     

地下水高浓度三氯乙烯厌氧生物降解的进展

 三氯乙烯是工业中普遍使用的有机溶剂,是土壤和地下水中普遍存在的污染物,而高浓度三氯乙烯污染更具有持久性。本文从高浓度三氯乙烯脱氯降解的可行性入手,分析其厌氧还原脱氯的降解途径和降解机制的重要要素：电子供体和微生物。同时,讨论了pH值及各种抑制因素对脱氯程度和速率的影响,着重综合比较了常用的还原降解动力学模型,并对今后的研究发展趋势进行了展望。在试验方面,耐高浓度氯代乙烯的脱氯菌株的筛选和培养,以及电子供体基质的效果需要进一步研究;在数值模拟方面,生物反应、水文地球化学反应和地下水物理流动、多组分溶质运移相耦合的模型仍较缺乏,此外模型中的诸多反应类参数仍缺少系统的实验验证,这些都需要进一步研究。     

Pd修饰Ti电极上2-氯酚的电催化还原

采用循环伏安法和交流阻抗法研究了碱性水溶液中Pd修饰Ti电极对2-氯酚（2-CP）的电催化还原特性,考察了Pd的沉积时间和甲酸钠对2-CP脱氯效率的影响。研究表明：2-CP在还原过程中属准可逆反应,且由电荷传质与扩散过程混合控制,Pd沉积300s时的催化性能最好,甲酸钠能够促进2-CP的脱氯反应。     

无尘与含尘条件下煤气成分对HCl脱除的影响

实验利用固定床反应法,通过改变气体成分单一变量的方法,研究了无尘条件下与含尘条件下高炉炉顶煤气的气体成分变化对低温钙基脱氯剂脱除HCl的影响.结果表明:高炉炉顶煤气中,CO2含量增加,含尘条件下与无尘条件下脱氯剂的脱氯效果均明显变差;CO含量和N2含量增加,含尘与无尘条件下的脱氯环境都有着明显的改善;H2含量变化,含尘与无尘条件下脱氯剂的脱氯效果均没有明显的变化;含尘条件下脱氯剂的穿透时间比无尘条件下高出40~60 min左右,穿透氯容量百分比高出6%左右.     

混凝-水解-接触氧化处理造纸漂白废水的研究

本文研究了混凝,厌氧酸化,生物接触氧化一体化反应器处理造纸制浆含氯漂白废水,在水力停留时间为15h时,整个系数CODcr总去除率达88．1％,BOD5去除率达81％,AOX去除率达98．4％,毒性值去除了92％,絮凝单元去除的主要是大分子氯代有机物,厌氧单元通过还原脱氯及酸性水解,氯代有机物得到了基本的去除;好氧单元对COD有较高的去除率,红外光谱的分析结果表明：废水中既有木素又有纤维素和半纤维素,虽然漂白废水厌氧处理效果不如好氧处理,但厌氧,好氧联合处理可有效地提高其处理效果。     

间二氟苯的合成研究

提出了一种以间二氯苯为原料,经硝化,氟代,氯化和脱氯反应合成间二氟苯的新工艺路线,探索了各步反应的工艺条件,对其中的关键步骤氟化反应,使用相转移催化剂取得较好的效果,反应收率可达68％左右,用离子交换法制备Pd/C催化剂,脱氯活性更高,实验表明,该合成路线具有原料成本低,反应条件缓和,操作方便等优点。     

聚乙二醇存在下钯催化氯代芳烃氢转移脱氯的研究

研究了以甲酸钠为氢源，聚乙烯吡咯烷酮锚定的ＰｄＣｌ２（ＰＶＰ－ＰｄＣｌ２）催化氯代芳烃脱氯．结果表明：ＰＶＰ－ＰｄＣｌ２是使氯代芳烃有效脱氯的催化剂，加入聚乙二醇可明显提高脱氯效果．该方法催化剂用量少，反应条件温和，操作简便     

Studies on treatment of chlorophenol-containing wastewater by microbial fuel cell

A microbial fuel cell with 4-CP as oxidant was established to investigate the feasibility of 4-CP dechlorination in the cathodic chamber of MFC. It demonstrated good performance on electricity generation with Pmax 12.4 mW/m2 and CE 22.7%. Besides, 60 mg/L 4-CP could be completely dechlorinated in 45 h in the MFC, and 4-CP dechlorination process and electricity generation process had obvious synergistic effect.     

PVP-PdCl2/Al-PRT-PEG催化对氯甲苯水相脱卤

聚乙烯吡咯烷酮（PVP）络合Pd^2＋后,负载于聚乙二醇（PEG）功能化的Al2O3柱支撑后的膨润土（Al-PRT）上,制备了催化剂PVP-PdCl2／Al-PRT-PEG,并用于催化不溶于水的对氯甲苯水相脱氯．实验表明该催化剂呈现出较高的脱氯活性和重复使用功能．用IR,XRD等手段表征了Al-PRT,并探讨了催化剂各组分在催化脱氯反应中的作用．     

Reductive dehalogenation of chlorinated dioxins by an anaerobic bacterium

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs and PCDFs) are among the most notorious environmental pollutants. Some congeners, particularly those with lateral chlorine substitutions at positions 2, 3, 7 and 8, are extremely toxic and carcinogenic to humans. One particularly promising mechanism for the detoxification of PCDDs and PCDFs is microbial reductive dechlorination. So far only a limited number of phylogenetically diverse anaerobic bacteria have been found that couple the reductive dehalogenation of chlorinated compounds--the substitution of a chlorine for a hydrogen atom--to energy conservation and growth in a process called dehalorespiration. Microbial dechlorination of PCDDs occurs in sediments and anaerobic mixed cultures from sediments, but the responsible organisms have not yet been identified or isolated. Here we show the presence of a Dehalococcoides species in four dioxin-dechlorinating enrichment cultures from a freshwater sediment highly contaminated with PCDDs and PCDFs. We also show that the previously described chlorobenzene-dehalorespiring bacterium Dehalococcoides sp. strain CBDB1 (ref. 3) is able to reductively dechlorinate selected dioxin congeners. Reductive dechlorination of 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD) demonstrates that environmentally significant dioxins are attacked by this bacterium.     

硫化纳米零价铁对五氯苯酚的脱氯及其增强反应

硫化作用可以提高纳米零价铁(nZVI)的催化活性.利用硼氢化物还原法合成了硫化钠米零价铁(S-nZVI),采用比表面积(BET)、X射线衍射(XRD)、扫描电镜(TEM)、傅立叶变换-红外光谱(FT-IR)和X射线光电子能谱(XPS)等方法对材料进行了物理化学性质的表征,应用高效液相色谱仪和离子色谱仪研究了S-nZVI对五氯苯酚(PCP)的脱氯性能.结果表明:与nZVI相比,S-nZVI在聚集体形态和孔隙率上发生明显改变;不同n(Fe2+)/n(S2-)、溶液pH、S-nZVI的老化以及S-nZVI的重新硫化活化对S-nZVI催化PCP的脱氯均有重要的影响;PCP脱氯效率在n(Fe2+)/n(S2-)=60时达到最大;S-nZVI对PCP的还原转化率随溶液pH(5~8)的升高而显著增加;老化的S-nZVI对PCP的降解性能降低,归因于该老化材料的结构发生了变化;而重新硫化活化产生的FeS层可以减小S-nZVI表面的钝化,从而延长S-nZVI的寿命.文中研究对拓展纳米零价铁的应用和环境污染物治理方面具有一定的参考价值.     

Characterization of nanoscale iron and its degradation of 2,4-dichlorophenol

Nanoscale iron was detected by TEM, X-ray diffraction and X-ray photoelectron spectroscopy. It was found that the size of the nanoscale iron particles is in the range of 30–40 nm according to TEM image, and it contains abundant Fe₃O₄ as passivating layers on the surface of the core-shell structure. To improve its performance, dilute HCl was used for the removal of the passivating layers, and the degradation of 2,4-dichlorophenol (2,4-DCP) was measured for the nanoscale iron samples treated and untreated. Experimental results demonstrated that the removal of 2,4-DCP by untreated nanoscale iron is mainly due to the adsorption of 2, 4-DCP by nanoscale iron, and there are no degradation products detected by HPLC in the process. However, excellent dechlorination of 2,4-DCP was gained by HCl-treated nanoscale iron, and 2-chlorophenol, 4-chlorophenol and phenol were detected during the process. It was concluded that dechlorination is the key reaction pathway for the degradation of 2,4-DCP by activated nanoscale iron, and phenol is found to be the main product.     

基于量子化学理论研究氯代阻燃剂得克隆的降解路径

以零价金属Al和石英砂（SiO₂）为添加剂, 采用机械化学法及基于密度泛函理论的量子化学方法, 计算阻燃剂得克隆结构中所有的C-Cl键的键级和解离能, 推测其可能脱Cl的位置, 并将其降解, 得到了得克隆降解的主要路径.     

Bacterial dehalorespiration with chlorinated benzenes

Chlorobenzenes are toxic, highly persistent and ubiquitously distributed environmental contaminants that accumulate in the food chain. The only known microbial transformation of 1,2,3,5-tetrachlorobenzene (TeCB) and higher chlorinated benzenes is the reductive dechlorination to lower chlorinated benzenes under anaerobic conditions observed with mixed bacterial cultures. The lower chlorinated benzenes can subsequently be mineralized by aerobic bacteria. Here we describe the isolation of the oxygen-sensitive strain CBDB1, a pure culture capable of reductive dechlorination of chlorobenzenes. Strain CBDB1 is a highly specialized bacterium that stoichiometrically dechlorinates 1,2,3-trichlorobenzene (TCB), 1,2,4-TCB, 1,2,3,4-TeCB, 1,2,3,5-TeCB and 1,2,4,5-TeCB to dichlorobenzenes or 1,3,5-TCB. The presence of chlorobenzene as an electron acceptor and hydrogen as an electron donor is essential for growth, and indicates that strain CBDB1 meets its energy needs by a dehalorespiratory process. According to their 16S rRNA gene sequences, strain CBDB1, Dehalococcoides ethenogenes and several uncultivated bacteria form a new bacterial cluster, of which strain CBDB1 is the first, so far, to thrive on a purely synthetic medium.