几种典型有毒有机污染物的光催化降解研究

本文研究了氯代苯酚和苯胺类化合物的光催化降解,探讨了这些有机污染物分子的氯取代和化合物毒性与光催化降解之间的关系.研究表明,氯代苯酚和苯胺类化合物的光催化降解均符合表观一级反应动力学模型.有机物分子中氯取代基的引入加快了化合物的光催化降解,且反应速率随氯取代基个数的增多而增大.光催化降解的表观速率常数与正辛醇-水分配系数之间存在有较好的线性关系:logk=alogKow+b,该模型可以用于有机污染物的光催化降解性预测.     

纳米级Pd/Fe双金属体系对水中2,4-二氯苯酚脱氯的催化作用

 利用化学沉淀法制备了纳米级Fe和纳米级Pd/Fe双金属催化剂,研究了它们对2,4-二氯苯酚(2,4-DCP)还原脱氯的催化性能. 结果表明,纳米级颗粒具有较高的比表面积和表面反应活性,其BET比表面积可达12.4 m2/g,当Pd/Fe用量为6 g/L时,2,4-DCP脱氯率达到90%以上. 脱氯效率与pH值、温度、钯含量和Pd/Fe投加量等因素有关. 2,4-DCP在脱氯过程中先生成2-氯苯酚和4-氯苯酚,最终生成苯酚,而少量的2,4-DCP可直接降解成苯酚.     

正己烷溶液中4一氯联苯的紫外光降解研究

研究了正己烷溶液中4一氯联苯的紫外光降解反应。首次讨论了正己烷溶液中多氯联苯的特征紫外吸收和光反应中氯的形成的研究，光降解的主要反应途径为一级反应的脱氯。分子中C-Cl键断裂形成联苯自由基，该自由基从溶剂分子上脱去氢形成联苯，在光照下联苯继续降解最终生成脂肪烃。联苯的紫外光降解实验进一步证明了这种机理。     

环戊烯开环聚合中的高效活化剂——多卤代苯酚

本文研究了苯酚、卤代苯酚和多卤代苯酚对 WCl_6-i-Bu_3Al 催化体系在环戊烯开环聚合中的活化效果。实验结果表明:(1)在苯环上至少有两个取代的氯原子的苯酚在芳烃中才能具有高活化作用;在烷烃中至少要有三个取代的氯原子的苯酚,如2,4,6-三氯苯酚、2,3,4,6-四氯苯酚和五氯苯酚,其活化效果才更显著。(2)在无活化剂或活化效果较差的苯酚和一溴苯酚存在下,溶剂效应次序:氯苯>甲苯(苯)>加氢汽油(庚烷、环已烷);在活化效果高的多卤代苯酚存在下,溶剂效应不显现。(3)比较了三种卤代烷基铝的助催化效果,其助催化活性次序:Et_2AlI>Et_2AlCl>Et_2AlBr。(4)双烯烃对环戊烯开环聚合有一定的调聚作用。在实验条件下聚合物反式链节含量没有明显改变。     

苯酚在含氯体系中的电化学氧化

以Ru-Ir/Ti三元电极作阳极电解处理苯酚废水,研究废水中Cl-初始浓度对处理效果的影响.结果表明,在一定的电解时间内,苯酚的电化学氧化符合一级动力学方程;废水中Cl-的初始浓度越大,苯酚完全被氧化所需的时间也越短,即其表观速率常数越大.苯酚在Cl-体系中降解的中间产物主要有4-氯苯酚,1-氯苯酚,2,4-二氯苯酚,2,6二氯苯酚,2,4,6-三氯苯酚及各种短链脂肪酸和氯代醇等;最终产物是CO2、CHCl2和CHCl3.电解中间体的生成和降解速率随废水中Cl-初始浓度的增加而增大.据此,导出苯酚在含Cl-体系中电化学氧化的反应途径.     

中孔石墨碳负载TiO2复合材料光催化降解罗丹明B和苯酚

以26nm单分散的SiO2球为模板,苯乙烯为碳源,Ni为催化剂,在950℃合成了比表面积为298.2m2/g的中孔石墨碳材料.采用粉末X射线衍射、低温N2吸附、热重分析和透射电镜等对碳材料进行了结构表征.结果发现,通过Ni的催化作用,可在较低温度下得到高度石墨化的中孔碳材料.采用溶胶-凝胶法将TiO2负载在中孔石墨碳材料上,形成TiO2/石墨碳复合材料.以罗丹明B和苯酚的光催化降解为探针反应,考察了TiO2/石墨碳复合材料的光催化降解活性.结果表明,在紫外光照射下,罗丹明B和苯酚在该复合材料上的光催化降解反应遵循一级反应动力学,复合材料对罗丹明B和苯酚的光催化降解活性明显高于相同条件下制备的纯锐钛矿型TiO2.     

TiO2光催化降解4-氯苯酚过程中的电分析监测

采用循环伏安法和紫外光谱法对有机物的光催化降解进行机理研究和在线监测.以标准光催化剂DegussaP25在紫外光照射下催化降解4-氯苯酚,发现在降解过程中至少有两对氧化还原中间产物对苯二酚-苯醌和羟基氢醌-羟基苯醌.由4-氯苯酚及中间产物的电极响应,可以观测到它们在光催化降解过程中的含量变化,从而对整个过程实现在线监测,并由此全面了解光催化反应机理.从不同反应时间后测得的紫外光谱可以看到,苯环特征峰逐渐消失.这表明4-氯苯酚的苯环逐渐被打开,直至被彻底降解.     

金属钯纳米颗粒/氮化钛复合材料对水中2,4-二氯苯酚的电催化氢化脱氯（英文）

随着社会经济的快速发展,含氯有机物,特别是含氯苯系物,在农业、化工和医药等领域的使用量逐年增多,而使用过程中不合理的排放和控制致使含氯苯系物对生态环境,特别是水体环境的污染日趋严重.含氯苯系物具有高致毒致癌性,易生物富集,且很难被完全降解矿化,已被国家环保局认定为优先控制污染物.常规的废水处理工艺,如吸附、氧化及生物降解等,效率不高,且具有二次污染风险.电催化氢化脱氯技术是一种新型特别针对废水中含氯有机污染物的处理工艺,是通过在阴极电解还原水,原位生成原子态氢,以进攻苯环上C.Cl键,通过C.Cl键断裂H原子取代,使含氯苯系物完全转化为苯系物,达到去毒去害化的目的,近年来越来越受到研究者的关注.在整个电催化氢化脱氯技术中,高效稳定的电催化剂合成是关键,决定着脱氯效率、脱氯动力学、产物选择性及能量的利用率.本文报道了一种简易、无需添加任何表面活性剂的湿式还原法制备金属钯/氮化钛(Pd/TiN)和金属钯/碳(Pd/C)复合材料.在该复合材料中,金属钯颗粒具有均一的纳米尺寸(约5.0 nm)和球状形貌,且均匀分布在TiN和C载体上.作为针对水体中代表性含氯苯系物2,4-二氯苯酚的电催化氢化脱氯反应催化剂,Pd/TiN所展现的活性和稳定性均优于TiN和Pd/C,这源于TiN载体的促进作用.当TiN与Pd复合时,相应形成的Pd-TiN界面可改变Pd表面的电子结构,进一步优化Pd产活性氢及其吸附活化2,4-二氯苯酚的性能,因而其催化氢化脱氯活性增加.阴极工作电压是该催化反应中一个重要操作参数,决定了电催化氢化脱氯的效率和最终产物的构成.实验表明,.0.80 V vs Ag/AgCl是最佳操作电压,此时2,4-二氯苯酚的电催化氢化脱氯效率最高,可达到93.27%,且可实现最大程度的2,4-二氯苯酚向苯酚转化.脱氯反应路径研究发现,在Pd/TiN催化剂上2,4-二氯苯酚脱氯反应路径为2,4-二氯苯酚→对位一氯苯酚,邻位一氯苯酚→苯酚,但Pd/TiN对邻位和对位的C.Cl键断裂基本没有选择性.本文提供了一种新的有效调控Pd材料电催化氢化脱氯性能的方法,可望用于其他氢化反应体系的高效催化剂的设计合成,同时可推动电催化氢化脱氯技术在环境污染修复中的应用.     

阴极脱氯协同多孔Ti/BDD电极阳极电催化氧化对氯苯酚

本文主要研究阴极脱氯协同阳极(多孔Ti/BDD 电极)电催化氧化对于对氯苯酚的电化学降解过程. 在有无阳离子交换膜电解槽体系下电化学降解对氯苯酚的实验结果表明,对氯苯酚的矿化主要在阳极区进行;无隔膜电解槽体系下,对氯苯酚在阴极还原形成的氯离子迁移到阳极,在阳极表面进一步生成了具有强催化氧化作用的活 性氯,与阳极产生的羟基自由基协同降解对氯苯酚;在阳离子交换膜电解槽体系下,阴极产生的氯离子难以通过阳离子膜迁移至阳极区,无隔膜电解槽呈现出更好的降解效率. 结合高效液相色谱技术确定阳极室的中间产物为对苯二酚、邻苯二酚、对苯醌和苯酚等,阴极室的主要产物是苯酚,并根据中间产物提出了对氯苯酚的降解路径.     

苯酚和氯苯酚的Pt／TiO2催化光解

在TiO_2和Pt/TiO_2催化作用下水溶液中苯酚、对氯苯酚、2,4-二氯苯酚和2,4,6-三氯苯酚均能发生光致降解(λ≥345nm)。在固定于反应器内壁的薄层Pt/TiO_2催化作用下,这些化合物的光致降解均呈现一级反应动力学;表观反应速率常数K_(ob)的相对大小为:苯酚<对氯苯酚<2,4-氯苯酚<2,4,6-三氯苯酚。少量H_2O_2(1.9×10~(-2)mol·L~(-1))能提高这些化合物的光解速率。光照1.0～5.0h后这些化合物的降解率大于97％,COD去除率大于95％。     

Plasma-induced Degradation of Chlorobenzene in Aqueous Solution

Liquid-phase degradation of chlorobenzene (CB), induced by contact glow discharge electrolysis under various reaction conditions, such as, the initial solution pH, current intensity, volume of solution and iron salts was investigated. Experimental results indicated that, in the absence of catalysts, the depletion of CB followed first-order kinetics, where the observed value of the first-order rate constant ‘k’ is directly proportional to the applied current intensity and inversely proportional to the solution volume. Initial solution pH had little effect on the value of k. HPLC and IC analyses showed that the major intermediate products were chlorophenols, phenol, organic acids and chloride ions. During the treatment, a lot of hydrogen peroxide was formed. Role of Fenton’s reaction was examined. A reaction pathway is proposed based on the degradation kinetics and the distribution of intermediate products.     

Production of hydrogen-rich gas and multi-walled carbon nanotubes from ethanol decomposition over molybdenum modified Ni/MgO catalysts

A series of molybdenum modified Ni/MgO catalysts(Ni-Mo/MgO) with different loading ratios of Ni : Mo were prepared by impregnation method. Ethanol decomposition to co-produce multi-walled carbon nanotubes and hydrogen-rich gas at temperatures of 600–800 ℃ was investigated over the synthesized Ni-Mo/MgO catalysts. The results showed that the catalytic activity depended strongly on the reaction temperature and loading ratio of Ni : Mo. According to the gaseous and solid products obtained, the reaction pathways for ethanol decomposition were suggested.     

C/Fe-Bi_2WO_6光催化氧化诺氟沙星废水的效能及其机理

采用树脂碳化和水热两步法制备C/Fe-Bi_2WO_6光催化剂,对不同光催化剂光催化降解诺氟沙星溶液的去除效果进行对比研究。考察了条件因素对诺氟沙星(NOR)溶液在模拟太阳光下光催化氧化降解的影响规律。结果表明,在实验条件下,NOR光催化氧化降解符合L-H拟一级反应动力学模型,在NOR溶液初始浓度10 mg/L、溶液p H=7.0、催化剂用量0.75 g/L、H_2O_2浓度为200 mg/L、500 W氙灯照射60 min条件下,NOR完全分解,表观速率常数K_(app)为0.0751 min-1。采用分子荧光光谱法,对C/Fe-Bi_2WO_6光催化氧化去除NOR体系中羟基自由基生成规律进行研究,并推测了反应机理。结合LC-MS的分析结果,推测了NOR可能的降解路径和中间产物。     

CF2Cl2 decomposition over nanocrystalline MgO: evidence for long induction periods

CF(2)Cl(2) has been found to react with nanoscale MgO at 325 degrees C and higher temperatures. In excess of the halocarbon, the reaction results in the formation of MgF(2) as a predominant solid product, with CCl(4), and CO(2) formed as the main gaseous products. The kinetics of the process is characterized by a prolonged induction period, which is as long as 8.5 h at 325 degrees C. The length of the induction period decreases with temperature increase and becomes negligible at 500 degrees C. Complete CF(2)Cl(2) mineralization has been achieved in an excess of MgO at 450 degrees C. Detailed HRTEM and EDX analysis has shown that the induction period involves the formation of small amounts of magnesium halides on the oxide surface and results in its reconstruction leading to initial oriental ordering of the nanocrystals followed by substantial changes in the bulk composition of the nanoparticles. The reaction proved to be structurally sensitive. It has been found that deep fluoridation is possible only for nanoscale MgO samples. The use of samples with lower surface areas results in lengthening of the induction period and decrease of the reaction depth. The MgO transformation to MgF(2) has been found to result in a surface area decrease by more that an order of magnitude as a result of intense sintering of magnesium fluoride under the reaction conditions.     

Photocatalytic debromination of decabromodiphenyl ether by graphitic carbon nitride

The graphitic carbon nitride(g-C3N4) is found to be an efficient photocatalyst for the reductive degradation of decabromodiphenyl ether(BDE209) under UV irradiation(>360 nm).g-C3N4 was prepared by heating dicyandiamide.X-ray diffraction,X-ray photoelectron spectroscopy,and UV-vis spectra were used to characterize the properties of as-prepared catalysts.The photoreductive degradation kinetics of BDE209 was further investigated under different reaction conditions.The degradation of BDE209 is a stepwise process,and the bromines at meta positions are much more susceptible to remove than those at the ortho and para positions.A possible photoreductive mechanism was also proposed.     

原油中有机硫化物成因的硫酸盐热化学还原反应模拟研究

原油中部分有机硫化物来源于硫酸盐热化学还原反应。利用高压釜在高温高压含水条件下对正戊烷 硫酸镁反应体系进行了热模拟实验研究。通过气相色谱仪、微库仑仪、毛细管气相色谱/脉冲火焰光度检测器、红外光谱仪及X射线衍射仪,对气、油、固三相产物进行了分析。结果表明,硫酸盐热化学还原反应在425℃~525℃可以进行,主要生成氧化镁、炭、硫化氢、二氧化碳以及硫醇、硫醚和噻吩类等有机硫化物。根据动力学模型计算出该反应活化能为58.0kJ/mol。     

Glycoside bond cleavage in the radiolysis of aqueous solutions of methylglycosides and disaccharides

The kinetics of formation of methylglycoside and disaccharide radiolysis products resulting from the O-glycoside bond cleavage was studied, and the yields of these products were determined. It was found that oxygen inhibits these processes. The findings suggest that the fragmentation reaction of C’₂ radicals plays an important role in the formation of carbohydrate degradation products in the radiolysis of aqueous carbohydrate solutions.     

Degradation kinetics of phenol and its decomposition products in the electrolyte cathode of direct-current atmospheric-pressure discharge

The degradation kinetics of phenol and the formation kinetics of its decomposition products in the liquid cathode (distilled water) of direct-current atmospheric-pressure discharge in air have been experimentally measured. The processes occurring in the liquid phase have been simulated on the basis of the previously proposed reaction kinetics scheme complemented by phenol decomposition reactions and the formation/decay reactions of its degradation products.     

FTIR Investigation of UHMWPE Oxidation Submitted to Accelerated Aging Procedure

In the present study, an accelerated ageing by oxidative degradation of UHMWPE in hydrogen peroxide solution was performed and the inhibition with ascorbic acid (vitamin C) was analyzed. Both systems were extensively characterized by Fourier Transformed Infrared Spectroscopy (FTIR). Different chemical groups of UHMWPE associated with the degradation reaction were monitored for over 120 days in order to evaluate the possible oxidation mechanisms involved and the inhibitory behavior of vitamin C. The results have provided strong evidence that the oxidation mechanism is rather complex, and 2 stages with their own particular first-order kinetics reaction patterns have been clearly identified. Furthermore, the vitamin C has proven to be an efficient antioxidant for UHMWPE under the evaluated conditions.     

Photodegradation Kinetics of Fexofenadine Hydrochloride Using a LC Method

The kinetics of photodegradation of the antihistamine fexofenadine hydrochloride using a stability-indicating high performance liquid chromatography (HPLC) method is demonstrated. The degradation was carried out in methanol and in water solutions, prepared from coated tablets, in quartz cells under UV light at 254 nm. The kinetics parameters of order of reaction and the rate constants of the degradation were determined for both solvents. The degradation process of fexofenadine hydrochloride in solutions can be described by second-order kinetics under the experimental conditions used in this study. The obtained results show that the HPLC method is satisfactory in the determination of the kinetics of degradation of fexofenadine hydrochloride in the presence of its photolytic degradation products.