共查询到18条相似文献,搜索用时 171 毫秒
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氯代烷烃在Fe/Cu二相金属体系中的催化还原脱氯研究 总被引:1,自引:1,他引:0
以氯代甲烷系列为例研究了多种氯代烷烃在Fe/Cu二相金属体系中的还原脱氯反应.分析了氯代有机物结构性质对还原脱氯反应的影响和规律性,以及反应过程中pH的变化.并探讨了氯代烷烃在金属还原作用下的还原脱氯机理。 相似文献
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Ni-Fe双金属对氯代苯酚催化还原脱氯的试验 总被引:3,自引:0,他引:3
分别采用Ni-Fe双金属体系和单一零价铁对氯代有机物2,4-二氯苯酚、2-氯苯酚和4-氯苯酚进行了催化还原脱氯的研究。结果表明:单一零价铁能够对氯代苯酚还原脱氯,但效率不高,通常在10%~25%。在镍的催化作用下,零价铁对氯代苯酚的还原脱氯效率大大提高。当零价铁加入量为60 g/L,硫酸镍为0.6 g/L,初始氯代苯酚的质量浓度在25 mg/L左右,反应初始pH值控制在偏酸性的条件下,还原脱氯效率可达到70%以上。氯代苯酚降解的准一级速率常数和降解率满足以下规律:4-氯苯酚大于2-氯苯酚大于2,4-二氯苯酚。 相似文献
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采用化学还原法制备了纳米级Co/Fe双金属催化剂,对其催化水溶液中四氯化碳还原脱氯性能进行了考察,并与废铁屑催化性能进行了对比。同时,考察了反应条件对脱氯性能的影响。结果表明,采用化学还原法制备的纳米级Co/Fe双金属催化剂具有较高的比表面积和表面反应活性,对四氯化碳的脱氯效果优于废铁屑。搅拌转速、反应温度和脱氯时间对脱氯效率有促进作用。 相似文献
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研究了Zn/Ag二元金属体系对五氯吡啶的催化还原脱氯性能。实验考察了初始pH值、催化剂的投加量、反应温度等参数对反应的影响,在此基础上探讨了其脱氯机理。实验结果表明:反应温度为60℃时,单一锌粉能够对五氯吡啶进行还原脱氯生成四氯吡啶,但是收率不高,只有20%左右,在银的催化作用下,四氯吡啶收率得到了很大提高。当反应初始pH控制在弱酸条件下(5左右),硝酸银浓度为10 g·L-1时,反应3h后四氯吡啶收率可达到60%以上。在Zn/Ag双金属表面,五氯吡啶的脱氯反应符合一级反应,速率常数为0.0097 min-1。 相似文献
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本文研究了多种氯代有机物在铁、铜双金属体系中的还原脱氯处理效果,着重分析了氯代有机物在还原脱氯处理中的机理问题,探讨了还原脱氯反应的基本原理、还原脱氯反应中pH值的变化以及有机物结构性质对还原脱氯反应的影响。 相似文献
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A new uniform process for the solution chlorination of PVC, PE, and natural rubber has been developed with initiation by γ-irradiation or radical initiators (azocompounds). The solvent used is dichloromethane instead of the industrially used tetrachloroethane or tetrachloromethane. The reaction is carried out in an autoclave with stirrer at temperatures between 70 and 100°C and pressures from 4 to 7 bar. As a result of the simultaneous chlorination of the solvent, trichloromethane is formed and only less than 1 wt.-% tetrachloromethane. Characterization of the chlorinated polymers by DSC and NMR measurements showed no differences to conventionally chlorinated products. 相似文献
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采用Raney Ni催化剂,选择50%乙醇-水(50/50,体积比)作为溶剂体系,考察了不同类型碱及其添加量对Raney Ni催化4-氯苯酚(4-CP)还原脱氯反应的影响。结果表明,强碱(NaOH和KOH)和Et3N更有利于Raney Ni催化下还原脱氯反应的进行,而且当n(NaOH/Et3N)∶n(4-CP)=1.1~2.2时,Raney Ni能够保持较高的催化活性,可以在30min内实现4-CP的彻底还原脱氯,并建立了Raney Ni-50%乙醇-水(50/50,体积比)-NaOH催化体系。将该体系应用于研究取代基对Raney Ni催化芳香氯代物还原脱氯的影响,研究表明,Raney Ni催化剂对4-CP和4-氯苯胺(4-CA)的还原脱氯具有较高的选择性。进一步将Raney Ni-50%乙醇-水(50/50,体积比)-1.5NaOH催化体系应用于高浓度氯酚工业危废的还原脱氯处理,发现在该催化体系中氯酚工业危废中的氯代有机污染物可以彻底还原脱氯,且催化剂可以至少重复使用5次。该催化体系可以有效、彻底地还原脱氯降解氯酚工业危废,对高浓度氯酚工业危废的还原脱氯降解具有良好的应用前景。 相似文献
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《分离科学与技术》2012,47(7):1613-1625
Abstract The method of decomposition of chlorinated organic substances in contaminated water based upon successive steps of chemical pretreatment of organic compound with a) active radicals (Fenton reaction) and/or with b) reductive dehalogenation on metallic Pd in the presence of zero‐valent iron, followed by aerobic biodegradation using bacteria strain Pandoraea sp. was studied. 4‐chlorophenol was chosen as a model compound. Generally, chlorophenols show limited biodegradability. The average efficiency of biodegradability of 4‐chlorophenol with both free and immobilized cells does not exceed 70% after 42 days of biodegradation, but their intermediates obtained by partial oxidation (products of hydrolytic‐hydroxylation) and/or a product of their partial reductive dechlorination (phenol) show increased biodegradability. To test the efficiency of the method, water exposed to this contaminant was treated in the laboratory in batch conditions. Because the products of partial oxidation and partial reductive dehalogenation of 4‐chlorophenol essentially differ, the main factor studied was the efficiency of biodegradation of 4‐chlorophenol after oxidative or reductive pre‐treatment steps. In comparison with the rate of biodegradation using free cells without application of the pre‐treatment step, the rate of degradation of 4‐chlorophenol by the application of consecutive combination of Fenton reagent and biotreatment was two‐fold. As for the combination of reductive dechlorination pre‐treatment step with consecutive biodegradation, the rate of decontamination of the 4‐chlorophenol was a little bit higher here in comparison with the rate of biotreatment after the pre‐oxidizing step: the remaining concentration of 4‐chlorophenol corresponding to the sampling in 7, 28, and 56 days after the inoculation were 70 mg/L, 12 mg/L, and 1.1 mg/L, respectively, in samples containing the average initial concentration of 126 mg/L of 4‐chlorophenol. Positive results may probably be due to the co‐substrate effect of phenol presented in the samples after the pre‐traetment reductive step. We have shown that both procedures followed with aerobic biodegradation can be considered suitable for removing hazardous chlorinated compounds from contaminated waters. The rate of biodegradation after the application of pre‐treatment procedures was slightly enhanced in comparison with the rate of biodegradation without the application of the pre‐treatment steps. It is evident that the choice of the decontamination pre‐treatment procedure cannot be generalized and will essentially depend upon the type and concentration of target contaminants and on process costs. 相似文献
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《Carbon》2014
The main objective of this study was to test the capability of CNMs to mediate the reductive dechlorination of chlorinated aliphatic hydrocarbons. We herein investigated the mediation effects of graphene oxide (GO) and multi-walled carbon nanotubes (CNT) on the reductive dechlorination of hexachloroethane by sodium sulfide in aqueous solutions (pH buffered). The presence of 10 mg/L CNT or GO enhanced the observed pseudo-first-order rate constant (kobs) of the reaction by a factor of 2 and 4, respectively; the enhancement effects were significantly greater than that of a soil humic acid (20 mg C/L). The strong enhancement effects of the test CNMs were attributable to the facilitated electron transfer by the graphitic surfaces and particularly to the activation of C–Cl bonds of hexachloroethane by the zigzag carbon atoms at the edges and defects of the carbon nanomaterials. Additionally, changes of pH and the presence of dissolved humic acid could significantly affect the CNT- and GO-mediated reactions. The reaction rate was markedly accelerated by the increase of pH, but was suppressed by the coexisting dissolved humic acid. The findings imply that CNMs have the potential to enhance reductive dechlorination of relatively recalcitrant contaminants, such as chlorinated aliphatic hydrocarbons, in natural aquatic environments. 相似文献
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Nanoscale bimetallic particles (Pd/Fe, Pd/Zn, Pt/Fe, Ni/Fe) have been synthesized in the laboratory for treatment of chlorinated organic pollutants. Specific surface areas of the nanoscale particles are tens of times larger than those of commercially available microscale metal particles. Rapid and complete dechlorination of several chlorinated organic solvents and chlorinated aromatic compounds was achieved by using the nanoscale bimetallic particles. Evidence observed suggests that within the bimetallic complex, one metal (Fe, Zn) serves primarily as electron donor while the other as catalyst (Pd, Pt). Surface-area-normalized reactivity constants are about 100 times higher than those of microscale iron particles. Production of chlorinated byproducts, frequently reported in studies with iron particles, is notably reduced due to the presence of catalyst. The nano-particle technology offers great opportunities for both fundamental research and technological applications in environmental engineering and science. 相似文献
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High density polyethylene has been chlorinated by three different methods: in suspension and in solutions of two different solvents. Carbon-13 NMR and infrared analysis show that chlorination in chlorobenzene solution leads to statistically random distribution while chlorination in suspension gives highly blocky substitution. An intermediate distribution was obtained by chlorination in tetrachloroethane solution. 相似文献