Science Letters:Dechlorination mechanism of 2,4-dichlorophenol by Ni/Fe nanoparticles in the presence of humic acid

To understand the feasibility of its application to the in situ remediation of contaminated groundwater, the dechlori-nation of 2,4-dichlorophenol (2,4-DCP) by Ni/Fe nanoparticles in the presence of humic acid (HA) was investigated. We found that, as high performance liquid chromatography (HPLC) was used, the 2,4-DCP was first quickly reduced to o-chlorophenol (o-CP) andp-chlorophenol (p-CP), and then reduced to phenol as the final product. Our experimental results indicated that HA had an adverse effect on the dechlorination of 2,4-DCP by Ni/Fe nanoparticles, as the HA concentration increased, the removal rate decreased evidently. It also demonstrated that 2,4-DCP was reduced more easily to o-CP than to p-CP, and that the sequence of the tendency in dechlorination of intermediates was p-CP>o-CP. Transmission electron microscope (TEM) showed that HA could act as an adsorbate to compete reactive sites on the surface of Ni/Fe nanoparticles to decrease the dechlorination rate. Also we con-cluded that the dechlorination reaction of 2,4-DCP over Ni/Fe nanoparticles progressed through catalytic reductive dechlorination.     

Dechlorination mechanism of 2,4-dichlorophenol by Ni/Fe nanoparticles in the presence of humic acid

To understand the feasibility of its application to the in situ remediation of contaminated groundwater, the dechlorination of 2,4-dichlorophenol （2,4-DCP） by Ni/Fe nanoparticles in the presence of humic acid （HA） was investigated. We found that, as high performance liquid chromatography （HPLC） was used, the 2,4-DCP was first quickly reduced to o-chlorophenol （o-CP） andp-chlorophenol （p-CP）, and then reduced to phenol as the final product. Our experimental results indicated that HA had an adverse effect on the dechlorination of 2,4-DCP by Ni/Fe nanoparticles, as the HA concentration increased, the removal rate decreased evidently. It also demonstrated that 2,4-DCP was reduced more easily to o-CP than to p-CP, and that the sequence of the tendency in dechlorination of intermediates was p-CP〉o-CP. Transmission electron microscope （TEM） showed that HA could act as an adsorbate to compete reactive sites on the surface of Ni/Fe nanoparticles to decrease the dechlorination rate. Also we concluded that the dechlorination reaction of 2,4-DCP over Ni/Fe nanoparticles progressed through catalytic reductive dechlorination.     

Simulation of reductive dechlorination processes in a lab-scale anaerobic biobarrier with enriched TCP dechlorinating consortium

In order to design and predict the dechlorination processes for remediating the halogenated aromatic compounds in the biobarrier system applied in situ,an anaerobic continuous-flow column was set up with the introduction of an enriched 2,4,6-trichlorophenol(TCP) reductive dechlorinating consortium.The fates of TCP and its metabolites were simulated according to the first-order sequential dechlorination kinetic model.The enriched TCP anaerobic dechlorinating consortium dechlorinated 100 μmol/L TCP to 4-chlorophenol(4-CP) via 2,4-dichlorophenol(DCP) in 10 d.The consortium was predominated with the phylum of Firmicutes and Bacteroidetes,based on the PCRdenaturing gradient gel electrophoresis(DGGE) analysis.After the consortium was applied to the column,the experimental data in the steady state were fitted by the least square method,and the first-order dechlorination kinetic constants from TCP to 2,4-DCP,from 2,4-DCP to 4-CP and from 4-CP to phenol,were 1.58 d-1,2.23 d-1 and 0.206 d-1,respectively.According to the fitting results,the required biobarrier width for the complete remediation of TCP,2,4DCP and 4-CP were 126 cm,130 cm and 689 cm,respectively.The dechlorination/degradation of 4-CP must be increased when the technology is applied to the real site.     

2,4-二氯酚表面磁性分子印迹聚合微球合成及其吸附特性研究

采用表面印迹技术制备了磁性分子印迹聚合物（Fe3O4@SiO2@MIPs）,使用扫描电镜（SEM）、透射电镜（TEM）和红外光谱（FT-IR）对产物的结构进行了表征。通过吸附性能实验研究证实了制备的Fe3O4@SiO2@MIPs对目标分子2,4-二氯酚（2,4-DCP）具有快速的吸附动力学特征和较高的吸附容量;与非印迹聚合物（Fe3O4@SiO2@NIPs）比较,Fe3O4@SiO2@MIPs对2,4-DCP表现出显著的亲和性;吸附选择性实验表明,Fe3O4@SiO2@MIPs对2,4-DCP具有较强的特异结合性能。此外,5次的重复使用后,制备材料的吸附效率仍可达80%以上,说明该材料具有可重复使用性。     

水中2,4-二氯苯酚和五氯苯酚电子束辐射降解的研究

用电子束辐射降解水中的2, 4-二氯苯酚(2, 4-DCP)和五氯苯酚(PCP), 研究辐照剂量对溶液初始质量浓度各为50 mg/L的2种氯代苯酚辐射降解和去除有机氯的影响. 同时研究了溶液不同的初始质量浓度、pH值和去氧状态等条件对辐射降解的影响. HPLC的测试结果表明: 随着辐照剂量的增加,氯代苯酚的降解率增加, 溶液中的氯离子增加, 但辐照后溶液中仍有2, 4-DCP和PCP的残余物. 试验结果表明: 有机氯辐射降解的速度要比无机氯生成的速度快得多; 溶液的去氧也能加快氯代苯酚的降解; 在酸性到中性条件下比碱性条件下更利于有机氯裂解.     

Removal of hexavalent chromium from aqueous solution by iron nanoparticles

Groundwater remediation by nanoparticles has收稿日期increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe0) nanoparticles. Cr(Ⅵ) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(Ⅵ), is an option in the remediation of contaminated sites, transforming Cr(Ⅵ) to essentially nontoxic Cr(Ⅲ). At a dose of 0.4 g/L, 100% of Cr(Ⅵ) (20 mg/L) was degraded. The Cr(Ⅵ) removal efficiency decreased significantly with increasing initial pH. Different Fe0 type was compared in the same conditions. The reactivity was in the order starch-stabilized Fe0 nanoparticles＞Fe0 nanoparticles＞Fe0 powder＞Fe0 filings. Electrochemical analysis of the reaction process led to the conclusion that Cr(OH)3 should be the final product of Cr(Ⅵ). Iron nanoparticles are good choice for the remediation of heavy metals in groundwater.     

Adsorption of 2,4-Dichlorophenol from Aqueous Solution onto Microwave Modified Activated Carbon： Kinetics and Equilibrium

Batch experiments were conducted to investigate the adsorption of 2,4-dichlorophenol (2,4-DCP) onto microwave modified activated carbon (AC) at three different temperatures (303 K, 313 K and 323 K). Adsorption isotherms, kinetics, and thermodynamics of the adsorption process were explored. Equilibrium data were fitted into Langmuir and Freundlich equations, and the result reveals that the Freundlich isotherm model fits better than the Langmuir model. Three simplified kinetic models: pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations were adopted to examine the mechanism of the adsorption process, and the pseudo-second-order kinetic model proved to be the best in describing the adsorption data. The thermodynamic parameters of the adsorption process were estimated, showing that the adsorption of 2,4-DCP was exothermic and spontaneous, and the adsorption studied in this paper can be assigned to a physisorption mechanism.     

六氯苯的水相催化脱氯研究

一种新型双负载双金属催化剂PVP-PdCl2-MnXm/MontK10-PEG400的制备,是把起相转移作用的聚乙二醇(PEG),键合到蒙脱土上,将聚乙烯吡咯烷酮(PVP)络合双金属后再负载其上。以甲酸钠为氢转移试剂,用此催化剂在水相中对六氯苯进行催化脱氯。当反应温度为90℃,反应时间为36小时,且Pd和金属M的摩尔比为4∶1时,其转化率为100%。该催化剂不但易于制备,而且便于分离。     

Rapid dechlorination of chlorinated organic compounds by nickel/iron bimetallic system in water

Detoxification of chlorinated organic compounds via reaction with nickel/iron powder was implemented in aqueous solution. Compared to iron, nickel/iron bimetallic powder had higher hydrodechlorination activities for both atrazine (ATR) and p-chlorophenol (pCP); nickel/iron (2.96%, w/w) was shown to have the largest specific surface area and the optimum proportion for the dechlorination of both ATR and pCP. Electrochemical measurements showed that the adsorbed hydrogen atom on the nickel must have been the dominant reductive agent for the dechlorination of both ATR andpCP in this system.     

Catalytic dechlorination and detoxification of 1-（2-chlorophenyl） ethanol by Pd/Fe

1-（2-chlorophenyl） ethanol （CPE） is of health and environmental concern due to its toxicity and its use as an intermediate in pharmaceutical manufacturing. The current work deals with the catalytic reductive dechlorination and detoxification of CPE by Pd/Fe bimetal. CPE was effectively dechlorinated to l-phenyl ethanol （PE） accompanied by the equivalent release of chloride. The extent of CPE dechlorination increased with temperature, Fe dosage and Pd loading. A decrease in solution pH increased CPE dechlorination, resulting presumably from an increase in hydrogen production. Under the specific conditions of 20 g/L Pd/Fe, 0.10% Pd （w/w） and initial pH 5-6, the CPE dechlorination was completed within 145 rain. The dechlorination followed a pseudo-first-order kinetics with an activation energy of 56.7 kJ/mol. The results of toxicity testing showed that CPE was very toxic to Chlorella, whereas PE showed little toxicity. The toxicity of the reaction solution declined gradually and the promoting effects on Chlorella intensified consequently with the dechlorination process. Thus, the reductive dechlorination of CPE to PE by Pd/Fe was a detoxification process. It may be used to effectively reduce the toxicological effects of CPE-contaminated wastewater, thereby enhancing the performance of subsequent biological processes in wastewater treatment.     

一种新型脱卤催化剂的制备及红外光谱分析

一种新型双负载双金属催化剂PVP－PdCl2-SnCl4/MontK10-PECG400,用于催化难溶于水的芳香卤化物水相脱卤，在无须加入任何有机溶剂情况下，对芳香氯化物呈现出高的脱卤活性和选择性，并具有良好的重复使用性能，通过IR测定探讨了催化剂各组分在催化脱卤中的作用。     

N,N-二(2,6-二异丙基苯基)-2,4-戊二亚胺和N,N-二(2,6-二甲基苯基)-2,4-戊二亚胺的合成与表征

以乙酰丙酮、2,6-二异丙基苯胺(或2,6-二甲基苯胺)和对甲苯磺酸为原料通过两步反应高产率的合成了N,N'-二(2,6-二异丙基苯基)-2,4-戊二亚胺(1)和N,N'-二(2,6-二甲基苯基)-2,4-戊二亚胺(2),产率分别为78%和72%,并用元素分析和1HNMR对产物进行了结构表征.     

2,4-D和6-BA对点地梅愈伤组织诱导的影响

以点地梅(A.umbellate(Lour.)Merr.)无菌苗的嫩叶为外植体,研究了不同质量浓度的2,4-D和6-BA对愈伤组织诱导的影响。结果表明:较高浓度的2,4-D(1.0～2.0 mg/L)单独使用能促进愈伤组织形成,随着2,4-D质量浓度的增加,愈伤组织的形成逐渐变弱;在培养基、2,4-D和6-BA诱导愈伤组织的正交试验中,发现诱导愈伤组织的较优培养基组合为MS+2,4-D 1 mg/L+6-BA 0.4 mg/L,且产生的愈伤组织多为淡绿色、质地疏松、生长快、褐化时间长,适合于点地梅愈伤组织的诱导。     

间戊二酮合钛(Ⅳ)配合物的应用研究

对二氯二(间戊二酮)合钛(Ⅳ)、间戊二酮合钛(Ⅳ)配合物的的结构、种类及应用进行介绍,并在初步分析其新特征后,指出了进一步研究的方向.     

高效液相色谱法分析卷烟烟气中的丙烯醛

建立了高效液相色谱测定卷烟烟气中丙烯醛的新方法.改进了卷烟烟气的捕集方法,使用吸附有2,4-二硝基苯肼(DNPH)的剑桥滤片捕集丙烯醛;考察了在剑桥滤片上丙烯醛与DNPH衍生化反应的条件,实验了新的流动相体系对卷烟烟气中丙烯醛分离效果的影响.实现了卷烟烟气中丙烯醛的简便快速测定.结果表明,本法可消除复杂基体的干扰,测定结果准确.方法的相对标准偏差为2.35%,回收率在99.8%～101.2%范围,检测限为2.5 ng/mL.     

Synthesis of 3-Alkyl-5-Benzylidene-2,4-Thiazolidinedione Under Microwave Irradiation

5 Benzylidene 2 ,4 thiazolidinedionederivativesarere portedtohavediversebiologicalactivities[1] suchasantidia betic[2 ] ,antibacterial[3] andanticonvulsant[4 ] activities .Forexample,pioglitazoneandrosiglitazonehavebeenlaunchedrecentlyfortypeⅡdiabetesmellitus[2 ] .Theyalsocanbeusedforthetreatmentofpsoriasis[5] andobesity[6 ] .　　Thegeneralmethodsforthesynthesisof 5 benzylidene 2 ,4 thiazolidinedionewasKnoevenagelcondensationof 2 ,4 thiazolidinedionewitharomaticaldehyde .　　Inrecentyear…     

2，4-二硝基苯苄醚合成的改进

采用2,4-二硝基苯酚与苄基氯为主要反应原料,在碘化钾存在下,用相转移催化剂在水相中催化合成了2,4-二硝基苯苄醚。研究了反应中催化剂、活化剂及碱的用量、反应温度以及时间等因素对产品产率的影响。最终优化了反应条件,最佳条件为：催化剂：活化剂：碳酸钾（摩尔比）=0．14：0．15：0.3;2,4-二硝基苯酚：苄基氯（摩尔比）=1．5：3．0;在70～75℃反应3．5h产品收率达到90．65％。     

2,4-二甲氧基苯甲醛的合成

目的研究2,4-二甲氧基苯甲醛的合成.方法以间苯二酚为原料,用Gatternann-Adams法合成2,4-二羟基苯甲醛,再经硫酸二甲酯甲基化.结果总收率65.6%.结论在2,4-二羟基苯甲醛的甲基化的反应中,我们改变了传统的以氢氧化钠为碱,以水为溶剂的方法,收率有较大提高.     

土工离心机地下水曝气试验装置研制与试验

针对地下水的修复问题,在50 gt土工离心机上,研制了一套地下水曝气试验装置,该装置包括曝气模型箱、控制与试验量测系统.该装置可满足0.1～5 mm的玻璃微珠材料进行地下水的土工离心曝气模型试验.从2 mm的玻璃微珠的初步试验表明,该系统结构简单,使用方便,可靠性及稳定性好.有效曝气压力与气体质量流量有较好的线性关系,曝气影响区域随着有效曝气压力的增大而增大,最终趋于稳定.     

Designing Pd-based supported bimetallic catalysts for environmental applications

Supported bimetallic nanoparticulate catalysts are an important class of heterogeneous catalysts for many reactions including selective oxidation, hydrogenation/hydrogenolysis, reforming, biomass conversion reactions, and many more. The activity, selectivity, and stability of these catalysts depend on their structural features including particle size, composition, and morphology. In this review, we present important structural features relevant to supported bimetallic catalysts focusing on Pd-based bimetallic systems and recently reported strategies to control them through different synthesis methodologies. Further, we focus on a few reactions that are relevant to environmental catalysis, i.e. CO oxidation, hydrocarbon oxidation, hydrodechlorination, and NO _x decomposition, where Pd-based catalysts are often used successfully. In spite of much progress in these areas, still there is a need for more advanced catalytic technologies to address the grand challenges like environmental remediation. Some of the recent advances in the design of bimetallic catalysts were made because of the combined efforts of material scientists, spectroscopists, microscopists, catalysis chemists, and engineers through state-of-the-art characterization methodologies, mechanistic investigations, and structure-activity correlations. This review is aimed at inspiring scientists to rationally design catalysts for a green and sustainable future.