直接熔融缩聚法合成PLGA的表征及其生物相容性研究

本文旨在探究一条更加适合用于医学研究的高分子材料PLGA的合成途径。首先在无催化剂、高真空条件下直接熔融缩聚合成聚乳酸-聚乙醇酸(PLGA)的无规则共聚物,对其合成反应体系的最佳温度范围、反应时间进行确定,然后对反应产物的分子量、结构、亲水性能、热性能以及不同比例LA/GA的产物特性粘数等物化性质进行表征,对合成的高分子材料PLGA的生物相容性进行分析与讨论。结果显示在无催化剂、高真空、160~175℃、LA/GA的比例为3∶7左右、反应时间60 h左右下合成的高分子材料PLGA具有较稳定的物化性质和较好的生物相容性,可以作为以后用于医学研究的高分子材料PLGA的合成途径。     

可生物降解材料在水环境领域中的研究进展

随着环境与能源等矛盾问题的日益突出,研究和开发可生物降解材料是解决环境污染问题的极为有效地途径,引起许多科研工作者的关注。作为20世纪80年代后发展起来的新型材料,在环保领域起到了独特的作用。本文概述了近些年来,可生物降解高分子材料在环境方面的研究状况。结合污水处理生物反硝化工艺,展望了可生物降解高分子材料在水环境领域的研究前景。     

两性高分子絮凝剂的结构与性能的研究

以天然高分子植物粉 F691为原料 ,通过羧甲基化、接枝共聚和曼尼期 ( Mannich)三步反应合成出两性天然高分子改性絮凝剂 ( CGAAC)。研究了阴 /阳取代度、接枝率等结构因素对 CGAAC絮凝性能的影响 ;并将 CGAAC对高岭土的絮凝性能与阴离子絮凝剂 CGA和阳离子絮凝剂 PAM-C进行了对比 ,实验结果表明 :该絮凝剂具有最佳用量范围较宽、p H值使用范围较宽的特点     

可降解塑料及聚氨酯研究现状与发展趋势

在环境危机日益严重、环境保护的要求日益迫切的形势下,降解塑料已成为高分子材料领域的研究热点。聚氨酯材料在包装和医疗领域具有广泛的应用,其可降解化研究具有重要的科学和社会意义。总结和回顾了可降解聚氨酯材料领域的现状及发展历程,阐述了其性能特点及需要解决的技术问题与难点,展望了本领域未来的发展趋势。     

天然高分子絮凝剂及其在水处理的应用

天然高分子絮凝剂具有传统絮凝剂和其他合成聚合物不具备的优点,现已得到国内外的广泛重视。概括了以淀粉、壳聚糖、木质素和植物胶为原料改性而成的天然高分子有机絮凝剂的研究与应用概况,并对它们在废水处理中的应用和发展进行了综述。     

高分子螯合剂在废水处理中的应用

以螯合树脂为代表的高分子螯合剂作为一种新型材料,在各种工业中使用已非常引人注目。特别是由于螯合树脂液态化,水溶性高分子螯合剂,即高分子重金属捕收剂的研究成功,并在水处理行业中取得的卓越成效而崭露头角。随着使用技术的进步,使用量将急剧增加。它是一种卓越的水处理技术,有很快普及的希望。一、概述高分子重金属捕收剂在化学工业上又称为两性高分子表面活性剂。根据其母体的化学结构不同可分为物性不同的线状结构和立体架桥结构两大类,前者称为高分子螯合剂,后者称为螯合树脂:     

基于混合遗传算法的模拟电路自动设计研究

模拟电路在电子系统设计中具有重要意义．模拟电路设计包括电路拓扑结构设计和元件值设计，这两个方面对计算机辅助模拟电路设计都很重要．但是，传统的遗传算法在不断进化电路元件值时效率低．因此，本文提出一种具有超突变和精英策略的混合遗传算法HME-GA．该方法不仅可以用来设计电路的拓扑结构，而且可用于设计电路的元件值．实验结果表明，HEM-GA算法优于简单遗传算法GA，可作为计算机辅助模拟电路设计的有效方法，在模拟电路自动化设计中具有非常重要的意义和巨大的应用潜力．     

具有重金属捕集功能的高分子絮凝剂MAC去除Cd2+的性能研究

以壳聚糖、巯基乙酸为原料,通过酰胺化反应合成了一种具有重金属捕集功能的新型高分子絮凝剂--巯基乙酰壳聚糖(MAC),研究了其对含Cd2+废水水样的处理性能,并对影响处理性能的因素(pH、有机络合剂及浊度等)进行了探讨.结果表明,该絮凝剂对Cd2+有很好的捕集功能,采用不同相对分子质量、不同脱乙酰度的壳聚糖合成的MAC,...     

聚硅酸硫酸铝铁的合成及其性能研究

聚硅酸金属盐类无机高分子絮凝剂是当前用于给水和废水处理领域的新型高效水处理药剂。本文设计了一系列试验,用工业水玻璃和化学试剂合成了聚硅酸硫酸铝铁复合絮凝剂,并检验其除浊性能。结果证明,聚硅酸硫酸铝铁絮凝剂在较低pH值制备比较稳定,适用废水酸度范围广,絮体小,沉速快,除浊效率高,是一种具有广泛应用前景的无机高分子絮凝剂。     

用四乙烯五胺制得的高效除油乳选剂及性能

研究了用四乙烯五胺与甲醛、尿素、环氧氯丙烷合成高分子浮选剂的条件，并用充气浮选法考察了产品性能。浮选剂的合成分两步，首先用四乙烯五胺、甲醛、尿素进行Ｍａｎｎｉｃｈ反应制得聚和单体，然后用聚合单体与一定比例的环氧氯丙烷聚合和季铵化。着重研究了四乙烯五胺与环氧氯丙烷的不同摩尔比对产物性能的影响，并把其产物的浮选性能与用甲胺、二甲胺、二乙胺、二乙醇胺制得产物的浮选性相比，结果表明：四乙烯五胺与环氧氯丙烷     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.