漂白废水中的氯代芳香化合物的生物降解技术

本文简单地概括了含氯漂白废液的特性及处理现状，对氯代芳香化合物的生物降解机理作了简单介绍，并提出今后的研究方向。     

芳香化合物降解的研究进展

芳香化合物的毒性严重影响人类健康和生态环境,随着工业化社会的不断发展,芳香化合物正在以每年数百万t的速度增长。开发高效、环境友好的降解芳香化合物的方法已成为国际上的研究热点之一。生物降解和高级氧化技术是目前最重要的两种降解芳香化合物的技术,二者在作用的机理上互为补充。文章综述了近年来生物降解和高级氧化法降解芳香化合物技术的研究进展和发展趋势。     

氯代有机污染物的电化学还原脱氯降解技术研究进展

氯代有机污染物的电化学还原脱氯降解技术在环境处理等领域有重要作用。从氯代有机物的电还原脱氯机理、有机物结构性质、阴极材料、反应容器等多个方面,介绍了目前国内外在电化学还原脱氯领域的最新进展,并提出了今后值得关注的几个方向。     

氯代烷烃在Fe/Cu二相金属体系中的催化还原脱氯研究

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。     

零价金属对氯代有机物还原脱氯的研究进展

对零价金属及双金属体系在还原氯代有机物中的应用做了综述,展望了零价金属还原脱氯降解氯代有机物研究领域的发展前景.     

Fe/Cu催化还原法处理氯代有机物的机理分析

研究了多种氯代有机物在铁、铜二金属体系中的还原脱氯处理效果,着重分析了氯代有机物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、出水中Fe2 浓度的变化以及有机物结构性质对还原脱氯反应的影响。     

零价铁处理有机氯农药的实验研究

本文结合氯代烃和多氯联苯等氯代芳香烃的零价铁还原脱氯技术的研究进展,对零价铁在还原降解六六六、滴滴涕和六氯苯等有机氯农药中的应用进行了评述,讨论了零价铁降解有机氯农药的反应机理、动力学、铁表面活性作用,指出了该研究技术中存在的某些问题及不足并提出了建议,为之后进一步开展有机氯农药的零价铁脱氯降解实验研究确定了方向.     

Raney Ni高效催化氯酚类污染物还原脱氯降解

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。     

Ni-Fe双金属对氯代苯酚催化还原脱氯的试验

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。     

纳米Co3O4催化降解1,2,4-三氯苯

选取1,2,4-三氯苯作为氯代有机物的模型化合物,利用气相色谱、气相色谱-质谱联用仪等实验手段,研究了纳米Co3O4催化降解1,2,4-三氯苯的影响因素及效果。获得的主要研究结果有：纳米Co3O4对1,2,4-三氯苯具有较高的催化降解活性,200 mg纳米Co3O4与1.5μL 1,2,4-三氯苯在300℃下反应60 min,对1,2,4-三氯苯的降解效率可接近100%。1,2,4-三氯苯在纳米Co3O4表面上的降解主要是逐级加氢脱氯,其中,1,2,4-三氯苯经过一级脱氯得到对二氯苯,然后对二氯苯再经过二级脱氯得到一氯苯是加氢脱氯的主要途径。     

Treatment of chlorinated organic contaminants with nanoscale bimetallic particles

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.     

负载型纳米零价铁及含铁双金属颗粒降解氯代有机物的研究进展

零价铁及含铁双金属颗粒因对氯代有机物降解效率高,而受到国内外的广泛关注.目前该领域的研究热点是纳米铁的改性研究.主要对零价铁及含铁双金属颗粒的负载改性、降解氯代有机物过程中主要的影响因素作了介绍.对颗粒负载改性技术存在的问题作了简要的探讨,并且展望了该技术的应用前景和发展趋势.     

Kinetic correlation between degradation and dechlorination of perchloroethylene in the Fenton reaction

In the Fenton reaction, degradation and dechlorination are directly affected by the concentrations of hydrogen peroxide and Fe³⁺. Although there is considerable research on the biodegradation of chlorinated compounds combined with the Fenton reaction, the kinetics of degradation and dechlorination of the reaction, with various concentrations of hydrogen peroxide and Fe³⁺, have been rarely investigated. Therefore, we investigated the degradation and dechlorination of PCE with various concentrations of hydrogen peroxide and Fe³⁺. The initial concentration of PCE (10 μM) decreased from a value of 8.9 μM (with 0.1 mM of hydrogen peroxide and 5 mM of Fe³⁺) to 1.1 μM (with 10 mM of hydrogen peroxide and 5 mM of Fe³⁺); the respective values for chloride ions produced were 0.9 and 21.6 μM. Also, the initial 10 μM of PCE decreased from 8.9 (with 0.1 mM of Fe³⁺ and 5 mM of hydrogen peroxide) to 2.2 μM (with 10mM of Fe³⁺ and 5 mM of hydrogen peroxide); the respective chloride ions produced were 0.7 and 14.5 μM. The logarithmic correlations between the degradation and dechlorination coefficients were 0.7682 and 0.7834 for concentrations of hydrogen peroxide and Fe³⁺, respectively. Both coefficients were used, from all possible cases, to derive six models which displayed both the ratio of degradation and dechlorination and the hydrogen peroxide and Fe³⁺ concentrations. The dechlorination of PCE could then be predicted with the model obtained by the coefficient with the concentration of hydrogen peroxide and Fe³⁺. The models could be applied to various Fenton reactions for optimization of degradation or dechlorination, such as biodegradation of PCE which is scarcely degraded by aerobic bacteria.     

Combination of Advanced Oxidation and/or Reductive Dehalogenation and Biodegradation for the Decontamination of Waters Contaminated with Chlorinated Organic Compounds

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.     

催化还原技术处理水溶液中氯代有机物的实验研究

以四氯化碳和四氯乙烷为代表物,研究了水溶液中氯代烷烃的催化还原脱氯技术,使用的还原剂为废铁刨花并添加催化剂和极化材料．结果表明该方法能使氯代有机物在零价铁体系中有效地发生还原反应,能迅速脱氯为氯离子,降低氯代有机物的毒性。探讨了有机物浓度对反应速率的影响,并分析了还原脱氯速率和反应中间产物,四氯化碳的反应产物主要是二氯甲烷,而1,1,2,2-四氯乙烷的主要反应产物是二氯乙烯。氯代有机物直接得到电子而发生还原脱氯是其主要反应机理。     

Studies on the dechlorination and detoxification of organochlorine compounds II. Chlorinated cyclodiene insecticides and the polychlorinated insecticide ‘mirex’

In the first paper on the dechlorination of organochlorine compounds, results were reported for polychlorinated biphenyls and polychlorinated naphthalenes, using the Ni₂B in-situ catalytic dechlorination technique. In the present study, the work has been extended to the dechlorination and detoxification of some chlorinated polycyclic hydrocarbons belonging to a cyclodiene insecticide group (dieldrin, aldrin and endrin). In addition, a cage-structured polychlorinated insecticide, ‘mirex’, has also been investigated. During the dechlorination process, intermediates were detected by GC/MS and identified by their characteristic mass fragments and retention in mass.     

选择性催化加氢合成氯代苯胺最新进展

如何抑制脱氯氢解副反应是实现高效绿色合成氯代芳胺的核心问题。依据氯代硝基苯催化加氢合成氯代苯胺反应的抑制脱氯方法,选择性加氢催化剂设计思路可分为调变催化剂金属组分与载体的相互作用,制备双/多金属催化剂、非晶态合金催化剂、聚合物稳定的贵金属催化剂和杂原子修饰的贵金属催化剂等。本文分别综述了近年来各类抑制脱氯方法的研究进展及抑制脱氯机理,并进一步分析比较了不同反应介质对催化反应性能的影响。现有研究表明,杂原子修饰的贵金属催化剂表现出更好的催化性能,无溶剂条件下合成氯代苯胺彰显了绿色友好化工理念。两者有望成为今后的研究热点。     

超声波/纳米铁粉协同脱氯降解四氯化碳

采用超声波／纳米铁粉协同脱氯降解四氯化碳,探讨了纳米Fe粉用量、反应液的初始pH值、CCl4初始浓度对脱氯降解效果的影响。结果表明：纳米铁粉用量为0．5g／100mL时,脱氯率最高;反应液的初始pH值为2．0时,可获得较高的脱氯率;CCl4的初始浓度越高,其脱氯率越低。     

氯代有机物污染场地的监控自然衰减修复初探

氯代有机物因其高毒性、高富集性、高环境残留的特点及其“致癌、致畸、致突变”效应被美国环保局(EPA)列为优先控制污染物。氯代有机物污染场地的传统物理、化学、生物修复方式修复费用相对较高,对污染场地周边环境影响较大。监控自然衰减(MNA)是一种国际上应用较广的污染场地修复和管理技术,近年来在我国逐渐得到关注,其利用污染物自身的自然衰减作用达到修复目标,从而降低修复成本,规避工程风险。本文重点介绍监控自然衰减技术,并结合氯代有机物自然衰减过程中的生物降解作用、降解途径与机理、主要降解菌和酶等要素对氯代有机物污染场地实施监控自然衰减修复的可行性进行初步探究。