Fenton试剂氧化降解聚丙烯酰胺的机理研究

Fenton试剂法是在一定条件下Fe2 + 催化分解H2 O2 产生·OH的高级氧化技术 ,在处理有机废水中应用广泛。本文采用Fenton试剂法氧化降解水溶液中的聚丙烯酰胺 ,降解率在 90 %以上。此外 ,本文对反应机理进行了探讨。     

TiO2光催化氧化降解印染废水的研究

对TiO₂光催化剂处理实际印染废水的可行性进行了试验研究，探讨了印染废水的CODcr去除率和脱色率随光照时间、光催化剂用量、光照强度、试液初始pH值和H2O2加入浓度等因素影响的变化规律。试验结果表明, TiO2光催化CODcr能有效降解印染废水，使其CODcr和色度显著降低。     

The mechanisms of oxidative degradation of biomedical polymers by free radicals

Degradation is an essential factor in polymer biocompatibility. The physiological environment of the human body can be aggressive to polymers. Most implanted polymers suffer degradation and the kinetics and mechanisms of the processes can be significantly affected by various biologically active species, especially enzymes, lipids, peroxides, free radicals, and phagocytic cells. Iron enhances the toxicity of oxygen free radicals. Superoxide and hydrogen peroxide can interact to form the very toxic hydroxyl radical in the presence of iron. The data have shown that the hydroxyl radical is likely to be one of the main causes of polymer degradation in implantable devices. © 1994 John Wiley & Sons, Inc.     

氧化降解法制备羧基封端的液体氟橡胶

以偏氟乙烯-六氟丙烯共聚物(VDF-HFP)为原料,采用氧化降解法合成了羧基封端的液体氟橡胶,通过傅里叶变换红外光谱法、凝胶渗透色谱法、乌氏黏度计和电位滴定仪表征了产物.结果表明,产物在1 766 em-1处出现羧基基团的特征峰,其重均分子量比VDF-HFP有较大程度的降低,这与特性黏数的结果一致;产物的羧基质量分数为...     

The inhibition of the thermal oxidative degradation of polypropylene by various phenanthrols

All isomers of phenanthrol, 1-, 2-, 3-, 4-, and 9-phenanthrol, were prepared and the inhibitory effect of these compounds on the thermal oxidative degradation of isotactic polypropylene was examined by conventional oxygen uptake. The phenanthrols were found to be much more effective antioxidants than commercial 2,6-di-tert-butyl-4-methyl-phenol (abbreviated as BHT), and phenanthrene itself hardly showed any inhibitive effect. The effect of the phenanthrols was largely dependent on the position of the hydroxy group; the order of the effect was as follows: 1- > 4- > 2- > 3- > 9-phenanthrol > BHT. The phenanthrols were also good inhibitors of the radical polymerization of methyl methacrylate, and a fairly good correlation was observed between oxygen uptake and radical polymerization data.     

二氧化氯氧化降解三元采出液技术研究

三元复合驱采出液由于聚合物、碱、表面活性剂的存在,使采出液的粘度增加,乳化严重,油水分离困难,传统的应用于水驱、聚驱采出液的处理技术不能满足三元复合驱采出液的处理要求。本文研究了ClO2氧化降解三元采出液的效果,并且找出了ClO2的最优反应条件,结果表明,反应温度为45℃,采出液中ClO2浓度40mg·L-1,加酸量为0.5%,反应2h以上,采出液粘度可由16.65mPa·s下降到2.9mPa·s,阴离子表面活性剂浓度可由0.16mg·L-1下降到0.10mg·L-1。处理后的三元采出液的腐蚀率在腐蚀三级标准的范围内。     

Solubilization of Neyveli lignite by oxidative degradation: A potential source of carbochemicals

The recent and possible future shortages of petroleum-derived hydrocarbons for use as starting materials for the synthesis of organic chemicals/products have stimulated renewed interest in the use of coal as raw material for chemical production. Oxidatively solubilized coal and or lignite (OSC) in alcohol is a potential substitute for value added carbo-chemicals of the future. Phenomenal increase in the solubility of lignite in organic solvent consequent on treatment with dilute nitric acid under mild conditions was considered to be an expedient pathway for its direct utilization. The primary requirements for the solubilization are generation of functional groups like free carboxyl groups and size degradation. For the desired product the reaction should also be guided in such a manner, so that the aromatic/hydroaromatic moieties of the coal/lignite are preserved. The present study aims at the selection of the required reaction parameters for the conversion of lignite to such a product. Characterization of the original lignite and the products have been done chemically and spectroscopically. FT-IR, ¹³C (solid state) and ¹H NMR spectra have shown that substances posses both aromatic and aliphatic characteristics. The dominant functional groups which contribute to the reactivity of the substances are phenolic and carboxylic acids.     

Study of local oxidative degradation in polypropylene impact copolymer by energy dispersive X-ray system

Summary In this study, the thermal oxidative degradation of a polypropylene (PP) impact copolymer was examined using a transmission electron microscope equipped with an energy dispersive X-ray system (TEM/EDX). The oxidative behavior was visually captured by oxygen line analysis. The oxidation resistance of the ethylene-propylene rubber (EPR) phase was considerably higher than that of the PP matrix, indicating that the degradation behavior of the PP impact copolymer was heterogeneous. It was found that the higher resistance of the EPR phase originated from its primary structure by ¹³C-NMR measurement.     

Chemiluminescence of isotactic polypropylene induced by photo‐oxidative degradation and natural weathering

The analysis of the chemiluminescence (CL) kinetic parameters (induction time, oxidation rate, and activation energy) after the UV irradiation and outdoor exposure of isotactic polypropylene (i‐PP) films have been studied. The initial CL emission intensity increased with increasing photodegradation time of i‐PP films. On photodegradation, the activation energies were found to decrease linearly with time of UV‐irradiation and outdoor exposure. The slopes of these linear dependences were used to indicate the degree of photodegradation of the polymer and also for the characterization of the stabilizing effect of the additive. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4623–4629, 2006     

超细水雾协同甲烷氧化菌降解与抑制甲烷爆炸的实验研究

搭建了半封闭的实验管道平台,开展了不同喷雾量的超细水雾降解与抑制甲烷爆炸的实验研究,分析了甲烷氧化菌的形态,抑爆过程中火焰变化,管道内部最大爆炸超压,平均升压速率的变化规律。结果表明：含甲烷氧化菌-无机盐的超细水雾能够有效降解甲烷,喷雾量越大,降解甲烷的速率越快,当甲烷的体积分数为9.5%,在喷雾量达到0.7 ml,立即引爆后的火焰亮度和火焰传播速率明显高于降解时间为360 min且二次喷雾量为0.7 ml的工况。喷雾量从0.7 ml增加至4.9 ml,无论近端还是远端最大爆炸超压均呈现下降的趋势,对于近端的平均升压速率也呈现下降的趋势。以无机盐为培养基的甲烷氧化菌和超细水雾降解与抑制甲烷爆炸具有协同作用,能够在一定时间内有效降解甲烷。     

非催化条件下H_2O_2对淀粉的氧化降解行为

在非催化条件下,H2O2可以有效地对淀粉进行氧化降解。H2O2用量由2 mL增加至12 mL的过程中,淀粉的粘度下降百分率由3.49%增加至57.91%,继续增加H2O2的用量,淀粉的粘度下降百分率不再明显变化。对降解时间的研究表明,最佳反应时间为120 min,延长反应时间,淀粉的粘度反而有所增加。在18~70℃的范围内,H2O2对淀粉的氧化降解性能先增加后减弱,在60℃时达到最好,淀粉的粘度下降百分率为52.36%。在H2O2的作用下,淀粉中羟基部分被氧化为羧基或醛基,另外淀粉分子链中的1,4位的环间苷键也可能被打断,从而使淀粉的粘度下降。     

Mechanisms of oxidative degradation. I. Oxidation of synthetic rubbers catalyzed by metallic ions

The oxidative stability of rubbers depends on the structure of the rubber and the impurities contaminating the rubber. It is known that the oxidation of natural rubber is accelerated by the presence of metallic impurities. Besides GR-S rubber and nitrile rubber, the effects of metallic impurities on the oxidation of new rubbers, especially those introduced after the discovery of Ziegler-Natta catalyst, have not been reported. In the first part of this paper, the theoretical background on the mechanisms of metalcatalyzed oxidation is given. Most of the early work was carried out for the oxidation of hydrocarbons in the liquid phase. The difficulties in applying the liquid-phase results to the oxidation of high polymers in the solid phase are mentioned. The new rubbers used for this study are polyisoprene, polybutadiene, cis-poly-1,3-butadiene, styrenebutadiene copolymer, butyl rubber, ethylene-propylene terpolymer (EPT), propylene oxide rubber, polyacrylic rubber, and butadiene-acrylonitrile rubber. The effects of stearic acid and various stearates on the oxidation of these rubbers are presented. The number of electrons transferred by the metal ion during redox reactions was found to be related to the effectiveness of the ion as a catalyst. Both the high and low oxidation states of the metal ion were shown to be active catalysts, supporting the accepted theory of metal catalysis through a hydroperoxide decomposition mechanism.     

Durability of radiation-sterilized polymers. I. Estimation of oxidative degradation in polymers by chemiluminescence

In relation to sterilization of medical supplies, the degree of degradation by γ-ray and electron beam irradiations of homopolypropylene (HP), copolypropylene (CP, coplymer including 6% of ethylene unit) and polymethylpentene were compared, and chemiluminescence (CL) of irradiated polymers were measured. HP degraded extremely around the sterilization dose (2.5 Mrad) by either γ-ray or electron beam irradiations. In the case of CP and polymethylpentene, stabilities of polymers far differed between γ-ray and electron beam irradiations. The polymethylpentene was more stable than the polypropylenes against irradiation. The counts of CL emitted by recombination of peroxy radical (ROO ·) increased with increasing dose, reflecting degrees of oxidation of polymers. The degradation of polymers was independent of irradiation sources, rather it depended on the degree of oxidation. It was found that CL analysis are favorable for estimation of degradation in irradiated polymers.     

Photo‐oxidative degradation in polyisoprene: surface characterization and analysis by atomic force microscopy

Surface adhesion and surface mechanical properties of natural rubber cast films have been investigated by atomic force microscopy (AFM) before and after UV irradiation. Analysis in the force versus distance (F–d) mode probed changes in tip‐to‐surface adhesion. Adhesion was observed to increase as a result of exposure, in accord with the prediction that generation of polar groups in the surface should promote a hydrophilic transition. The hydrophilicity also gives rise to a stronger adhesive contribution from a meniscus force, as demonstrated by comparison of results obtained in air for irradiated and as‐received samples. Calculated values of work of adhesion, based on the Johnson–Kendall–Roberts model, reflected the changes in surface chemistry and the effects of the fluid environment. The outcomes of F–d analyses revealed both tip indentation and polymer extension; the former was fitted to expressions derived from the Snedden formalism, followed by calculation of an effective Young's modulus. Good agreement was obtained for as‐received surfaces with bulk measurements. The photochemistry predicts chain scission events which are likely to account for the observed softening of the polymer. © 2001 Society of Chemical Industry     

Formation of hydroperoxy‐ and hydroxyalkenals during thermal oxidative degradation of sesame oil monitored by proton NMR

The usefulness of ¹H nuclear magnetic resonance (NMR) for studying oil oxidation processes was tested. Refined sesame oil was submitted to oxidative conditions at 70 °C with circulating air, and the status of the sample was studied daily by ¹H NMR. This technique permits the determination of the proportions of the acyl groups in the oil throughout the oxidation process and, at the same time, allows monitoring of the formation and degradation of primary oxidation compounds, as well as of the formation of secondary oxidation products. Generation of the geno‐ and cyto‐toxic oxygenated aldehydes 4‐hydroxy‐, 4‐hydroperoxy‐ and 4,5‐epoxy‐trans‐2‐alkenal was proved.     

The thermo–oxidative degradation of acrylonitrile–butadiene–styrene copolymers during processing as studied by chemiluminescence

The glow curve obtained upon processing acrylonitrile–butadiene–styrene copolymers (ABS), through various machines, reaches a peak at 180°C. The proper assignment of that peak has required the study of the chemiluminescence (CL) shown by related polymers such as: polybutadiene (PB), styrene–acrylonitrile copolymer (SAN), and polyacrylonitrile (PAN). Three hydroperoxide types associated with the structural units, that is, 1, 2, and cis- and trans-1,4, exhibiting CL peaks at 180, 240, and 340°C, respectively, have been identified in the PB sample. The activation energy (E_a), recorded for the hydroperoxides thermal decomposition, was 15.0 ± 1.0, 17.85 ± 0.9, 20.7 ± 0.8 kcal/mol. PAN shows a CL peak at 180°C. Its occurance is related to the color developed during the thermal treatment. That PAN peak has been attributed to the hydroperoxides generated on the acrylonitrile units neighboring the azomethinic structures. The corresponding E_a is 23.3 ± 1.0 kcal/mol. The same peak (having an identical position and E_a) has been identified with processed ABS and SAN copolymers. As is evident by CL studies, the processing induced oxidation mainly occurs within the SAN phase of the ABS copolymers, though it was also noted within 1,2 units of the PB phase.     

Evaluation of a gas chromatogram of a mixture containing aldehydes and aldehydic esters obtained by oxidative degradation of the positional isomers of methyl octadecenoate

A simple method is described to evaluate gas chromatograms of mixtures containing aldehydes and aldehydic esters obtained by ozonolysis of mixtures of positional isomers of methyl octadecenoate. The evaluation is based on the assumption that the process of ozonolysis and the subsequent reduction of the ozonides is independent of the double bond position. This implies the formation of equivalent amounts of aldehydes and aldehydic esters, which results in certain ratios between the values of gas chromatographic peak areas of degradation products from the same molecule. These ratios can be calculated for a flame-ionization detector. Peak area values of partly or completely fused peaks can then easily be corrected.     

Kinetics of the oxidative color removal and degradation of bromophenol blue with hydrogen peroxide catalyzed by copper(II)-supported alumina and zirconia

Copper-supported alumina and zirconia catalysts were prepared and their catalytic activity towards the oxidative color removal and degradation of bromophenol blue with H₂O₂ was investigated. The rate of reaction with alumina is greater than that with zirconia, which ascribed to the increased amount of copper loaded on the catalyst as well as to the increased surface area. A brown intermediate (peroxo-compound), formed at the early stages of the reaction, inhibited the reaction rate. The rate of reaction increased with increase in pH of the medium as well as with added chloride ions. Both catalysts are very stable and can be used for several times without notable loss in their catalytic activities.     

Investigation of the influence of blast-furnace slag on the resistance of concrete against organic acid or sulphate attack by means of accelerated degradation tests

Replacement of ordinary Portland cement (OPC) by blast-furnace slag (BFS) alters the durability behaviour of concrete. In this research, the influence of BFS on the concrete's acid or sulphate resistance is investigated by accelerated degradation tests and the results are related to microstructural and physico-chemical parameters.A significant reduction of acid deterioration was recorded for BFS concrete, which is mainly attributed to the different chemical composition of the binder. General durability indicators like open porosity cannot solely explain the different performances of OPC and BFS concrete. In contrast, the resistance of concrete cyclically and partially submerged in sulphate solutions decreases when high amounts of cement are replaced by BFS. Crystallisation pressure causes more severe deterioration in these cases.