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11.
实验采用共沉淀法制得CeO_2负载型双金属Pd/Fe催化剂,并对催化剂的结构特征进行了X射线衍射(XRD)和扫描电子显微镜(SEM)分析.使用负载型双金属催化剂对四氯化碳进行还原脱氯研究,探究了温度、溶液初始pH值、催化剂投加量及不同钯载率对四氯化碳脱氯的影响;对比了不同催化剂包括纳米零价铁、纳米钯铁双金属和CeO_2负载型双金属Pd/Fe对四氯化碳的脱氯效果.实验结果表明负载型双金属催化剂在温度为40℃,溶液初始pH为6.5,催化剂投加量为0.4 g·L-1,钯载率为0.5%的条件下,对初始浓度为5 mg·L-1的四氯化碳的去除率高达99.88%.在相同的反应条件下,纳米零价铁和纳米钯铁双金属对四氯化碳的脱氯率分别为58.25%、87.94%.此外,对四氯化碳的脱氯机制进行了探讨.  相似文献   
12.
采用车载GC-MS技术,建立了顶空-GC-MS方法对CFCs产品组分及排污废水中三氯一氟甲烷、二氯二氟甲烷、四氯化碳等成分进行监测分析,实现了快速鉴定企业是否违规生产CFCs相关产品,对于判定企业是否违规提供技术依据。同时,采用顶空-GC/ECD方法对废水中的四氯化碳进行定量分析,以排查企业是否超标排污。  相似文献   
13.
Sorption of organic contaminants to soils has been shown to limit bioavailability and biodegradation in some systems. Use of surfactants has been proposed to reverse this effect. In this study, the effects of a high organic carbon content soil and a nonionic surfactant (Triton X-100) on the reductive dechlorination of carbon tetrachloride (CCl4) were examined in anaerobic systems containing Shewanella putrefaciens. Although more than 70% of the added CCl4 was sorbed to the soil phase in these systems, the reductive dechlorination of CCl4 was not diminished. Rather, rates of CCl4 dechlorination in systems containing soil were enhanced relative to systems containing non-sorptive sand slurries. This enhancement was also observed in sterile soil slurries to which a chemical reductant, dithiothreitol was added. It appears that the organic soil used in these experiments contains some catalytic factor capable of transforming CCl4 in the presence of an appropriate chemical or microbial reductant. The addition of Triton X-100 to sand and soil slurries containing S. putrefaciens resulted in increased CCl4 degradation in both systems. The effect of Triton could not be explained by: (i) surfactant induced changes in the distribution of CCl4, (i.e. decreased sorption) or the rate of CCl4 desorption; (ii) a direct reaction between Triton and CCl4; or (iii) increased cell numbers resulting from use of the surfactant as a substrate. Rather, it appears that Triton X-100 addition resulted in lysis of bacterial cells, a release of biochemical reductant, and enhanced reductive transformation of CCl4. These results provide insights to guide the development of more effective direct or indirect bioremediation strategies.  相似文献   
14.
Hydraulic conductivity and sorption coefficients for chlorinated hydrocarbons (chloroform, carbon tetrachloride and tetrachloroethylene) were evaluated for 216 sediment samples collected across a 15 m transect and a 21 m depth interval in a contaminated aquifer near Schoolcraft, Michigan. Relationships between hydraulic conductivity, linear sorption partition coefficients, grain size classes, and spatial location were investigated using linear regression analysis and geostatistical techniques. Clear evidence of layering was found in sorption properties, hydraulic conductivity and grain sizes. Conductivity correlated well with grain size, as expected, but sorption varied inversely with grain size, contrary to some previous reports. No significant correlation was found between sorption properties and hydraulic conductivity. This is likely due to the unexpected presence of small amounts of highly sorptive coal-like solids, which dominate the sorption behavior but have little effect on conductivity. The results demonstrate that recent findings regarding the high sorption capacity of coal materials found in soils can exert a controlling influence on contaminant transport. Designers of in situ remediation systems should be cautioned that 1) it is not reasonable to assume that sorption capacity and hydraulic conductivity are related, 2) sorption capacity and hydraulic conductivity are critical measurements for contaminant site characterization and subsequent transport modeling, 3) estimating sorption capacity from organic carbon measurement may lead to greater errors than performing sorption isotherms, and 4) it is more important to characterize vertical heterogeneity rather than horizontal heterogeneity because both sorption and hydraulic conductivity are correlated across longer distances in the horizontal plane.  相似文献   
15.
四氯化碳的生产与应用及其淘汰策略   总被引:2,自引:0,他引:2  
四氯化碳是一种消耗臭氧层物质,其生产和消费都面临着严峻的淘汰形势。简要叙述了四氯化碳的生产技术,以四氯化碳为原料生产大宗化学品和精细化学品的转化技术,四氯化碳作为化工助剂在我国的应用情况以及相应的淘汰方法和技术进展。  相似文献   
16.
国标方法中环境空气中二氧化硫的测定方法主要有甲醛吸收-副玫瑰苯胺分光光度法和四氯汞盐吸收-副玫瑰苯胺分光光度法.对国标方法中两种副玫瑰苯胺分光光度法测定环境空气中二氧化硫所用的两种吸收液(四氯汞钾、甲醛)的吸收效果及方法的准确性、精密度等条件作了比较试验.结果表明,采用甲醛溶液作吸收液与四氯汞钾溶液作吸收液相比,吸收效果、精密度和准确度更好,测定的检出限低.用甲醛溶液做吸收液,除了上述优点外,还可避免使用大量的汞盐,有利于环境保护.  相似文献   
17.
Dechlorination of carbon tetrachloride by the catalyzed Fe-Cu process   总被引:2,自引:0,他引:2  
The electrochemical reduction characteristics of carbon tetrachloride (CT) were investigated using cyclic voltammetry in this study. In addition, the difference in reduction mechanisms of CT between Master Builders' iron and the catalyzed Fe-Cu process was discussed. The results showed that CT was reduced directly on the surface of copper rather than by atomic hydrogen produced at the cathode in the catalyzed Fe-Cu process. The reduction was realized largely by atomic hydrogen in Master Builders' iron. The entire CT in 350 ml aqueous solution with 320 mgL was reduced to trichloromethane and dichloromethane in 2.25 h when 100 g of scrap iron with FeCu ratio of 10:1 (ww) were used. Moreover, the reduction rate slowed with time. CT could be reduced at acidic, neutral and alkaline pH from solution by Fe-Cu bimetallic media, but the mechanisms were di?erent. The degradation rate was not significantly in?uenced by pH in the catalyzed Fe-Cu process; in Master Builders' iron it clearly increased with decreasing pH. The kinetics of the reductions followed pseudo-first order in both cases. Furthermore, the reductions under acidic conditions proceeded faster than that under the neutral and alkaline conditions. The catalyzed Fe-Cu process was superior to Master Builders' iron in treating CT-containing water and this advantage was particularly noticeable under alkaline conditions. The reduction was investigated in the cathode (Cu) and anode (Fe) compartments respectively, the results showed that the direct reduction pathway played an important role in the reduction by the catalyzed Fe-Cu process. The catalyzed Fe-Cu process is of practical value.  相似文献   
18.
某市南郊水源地土壤四氯化碳污染特征   总被引:1,自引:0,他引:1  
含四氯化碳废水在排放的过程中沿排污渠侧壁和底部的渗漏对土壤造成污染.在对某市南郊受四氯化碳污染的水源地进行钻孔检测的过程中发现,土壤四氯化碳污染的特征:靠近排污沟的钻孔均检测出四氯化碳,而远离排污沟的钻孔则未检出;四氯化碳的垂向分布存在不连续性,且受降雨影响较大;大部分钻孔浅层土壤中基本未检测到四氯化碳,而在3 m以下的土层和基岩中检测到四氯化碳;抽水井的抽水行为导致抽水井附近土壤中四氯化碳明显高于其他钻孔点位检测结果.  相似文献   
19.
四氯乙烯代替四氯化碳测定水中油类物质初探   总被引:1,自引:0,他引:1  
通过使用四氯乙烯代替四氯化碳测定水中油类物质的对比实验,得到如下结论:四氯乙烯作萃取剂时,标准曲线线性相关系数为0.9999,检出限为0.336mg/L,精密度和准确度符合质控要求。但标准曲线方程的斜率较差,在分析浓度较低的样品时,准确度相对误差较大,萃取回收率不高。由此可以看出,使用四氯乙烯分析油类物质的局限性较大,分析方法还需进一步研究。  相似文献   
20.
Fe~0催化还原转化水中CCl_4的实验研究   总被引:2,自引:0,他引:2  
通过在Fe0表面化学沉积Cu、Ag、Pd、Ni构建了Cu/Fe、Ag/Fe、Pd,Fe、Ni/Fe多种双金属催化还原体系.通过序批实验研究了水体中毒性污染物CCl在Fe0以及上述双金属催化Fe0体系中的还原脱氯.结果表明,CCl4在上述5种Fe0还原体系中都能发生快速还原脱氯反应,Cu、Ag、Pd等催化剂的加入能明显提高反应速率.还原脱氯反应服从准一级反应动力学方程,CCl4水溶液在Fe0、Cu/Fe、Ag/Fe、Pd/Fe、Ni/Fe 5种还原体系中的反应速率常数分别为0.039 3、0.092 5、0.158、0.049 6和0.053 3 min-1.使用GC/MS分析了CCl4在各种还原体系中的还原脱氯产物,探讨了水体中CCl4还原脱氯降解的反应途径和可能中间产物.CCL4在不同反应体系中不但反应速率不同而且降解产物也不相同,在Cu/Fe、Ag/Fe体系产物以三氯甲烷、二氯甲烷为主,而在Pd/Fe体系主要为甲烷.逐步氢解是CCl4在Fe0还原体系中发生还原脱氯反应的最主要途径.  相似文献   
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