2A12铝合金在模拟溶液中的周浸腐蚀行为

采用干湿周浸实验、失重法和电化学阻抗谱研究了2A12铝合金在0.6mol/L NaCl和0.6mol/L NaCl 0.02mol/L NaHSO3两种溶液中的腐蚀行为与规律, 利用扫描电镜(SEM)、能谱(EDX)和红外光谱(FTIR) 观察分析腐蚀产物表面形貌、结构和组成,测试了材料的力学性能.研究表明,随腐蚀时间的延长,腐蚀产物不断增多,失重增加,力学性能下降,阻抗模值逐渐减小;腐蚀产物形貌以团状和块状为主,在0.6mol/L NaCl溶液中腐蚀产物主要为铝的氯化物和氧化铝,在0.6mol/L NaCl 0.02mol/L NaHSO3溶液中腐蚀产物主要为氧化铝、铝的硫酸盐水合物和铝的氯化物;由于NaCl和NaHSO3共同作用,2A12合金在0.6mol/L NaCl 0.02mol/L NaHSO3溶液中腐蚀电流密度高,阻抗模值相对较小,腐蚀速率较高,腐蚀后失重大,力学性能下降幅度较大,腐蚀更严重.     

模拟酸雨大气环境中Cl-浓度对镀锌钢腐蚀行为的影响

目的研究模拟酸雨环境中Cl-浓度对镀锌钢腐蚀行为的影响与作用机理。方法以p H为3.05的模拟酸雨溶液作为空白溶液,在每升空白溶液中分别加入0.01,0.1和0.5 mol的Na Cl,浸泡3天和7天后取出试样,进行形貌、成分分析以及电化学分析。结果浸泡后镀锌钢表面形成的腐蚀产物主要为Na Zn4SO4Cl(OH)6·6H2O。随着溶液中Cl-浓度的增加,镀锌钢的腐蚀电位逐渐减小,腐蚀电流密度逐渐增大,阻抗值逐渐减小。结论通过不同时间的浸泡,随着溶液中Cl-浓度的增加,镀锌钢表面腐蚀产物对基体都有一定的保护作用,但保护作用逐渐减小,尤其在浸泡3天时的变化最明显。     

四硼酸钠对AZ91D镁合金的缓蚀效果研究

选用无机环保型缓蚀剂四硼酸钠,研究了质量浓度不同的四硼酸钠对AZ91D镁合金的缓蚀效果,并采用电子显微镜对空白样品及添加缓蚀剂浸泡样品的腐蚀形貌进行了分析。结果表明,在室温下,四硼酸钠对AZ91D镁合金具有缓蚀效果,四硼酸钠溶液质量浓度为2. 4 g/L时的缓蚀效率可达到66. 46%;浸泡腐蚀与电化学腐蚀结果一致。     

纯铝在SO2气氛溶液中的腐蚀行为研究

采用扫描电镜（SEM/EDX）、失重法、交流阻抗谱和局部交流阻抗研究了纯铝1060在0.004mol/L Na2SO4 （pH=3.1）溶液中的腐蚀行为和规律。研究结果表明,纯铝1060在模拟溶液中连续浸泡720h后,材料质量损失与浸泡时间的关系符合指数规律即C=A·tⁿ;腐蚀产物形貌为不规则的团状或块状,分析表明腐蚀产物为氢氧化铝和硫酸铝水合物;交流阻抗结果显示纯铝1060腐蚀速率随浸泡时间的延长逐渐降低;局部交流阻抗图谱显示材料表面局部阻抗随时间而变化,并形成点蚀。     

咸水浸泡对珠江口滩涂围垦土壤重金属的去除效果

利用浸泡离心的方法,通过室内模拟实验,研究了浸泡时间、NaCl溶液浓度对土壤中6种重金属去除效果的影响,同时测定了NaCl浸泡前后土壤中重金属的形态变化.结果表明,浸泡时间为60d时达到最大去除率,分别为Cd30.3%、Zn22.0%、Pb9.4%、Cu8.0%、Cr12.6%、Ni9.9%;NaCl浓度为16 g/L时达到最大去除率,分别为Cd41.9%、Zn19.9%、Pb9.3%、Cu6.3%、Cr14.8%、Ni16.8%.重金属形态分析显示,NaCl浸泡能有效去除交换态、碳酸盐结合态和氧化物结合态的重金属,而对有机态和残渣态的重金属作用效果不明显.     

环氧富锌涂层对AZ91D镁合金的腐蚀防护能力研究

目的研究环氧富锌涂层对AZ91D镁合金的腐蚀防护能力。方法采用机械喷涂法在AZ91D镁合金表面制备一种保护性的环氧富锌涂层。采用电化学阻抗谱(EIS)研究环氧富锌涂层在0.5 mol/L的Na2SO4腐蚀溶液中的电化学腐蚀行为及其对镁合金的腐蚀防护能力。结果浸泡初期,环氧富锌涂层的阻抗谱中只出现一个时间常数,暗示着环氧富锌涂层优异的阻挡层作用;浸泡48 h后,环氧富锌涂层阻抗谱中出现两个时间常数,高频和低频时间常数分别对应环氧富锌涂层中高聚合的介电性质和锌粉的活性溶解;浸泡336 h后,环氧富锌涂层仍具有很高的阻抗模值,表明此时环氧富锌涂层对镁合金仍能提供良好的腐蚀防护。结论环氧富锌涂层在0.5 mol/L Na2SO4腐蚀溶液中能对AZ91D镁合金提供很好的腐蚀防护。     

有机/无机缓蚀剂在模拟混凝土孔隙液中对钢筋缓蚀作用对比研究

目的检测和评价五种有机/无机缓蚀剂在含3.5%NaCl的模拟混凝土孔隙液(SCP)中对Q235碳钢的缓蚀效果。方法采用动电位极化曲线和电化学交流阻抗谱(EIS)测试方法。结果综合评价后可知,0.0015 mol/L的D-葡萄糖酸钠具有最好的缓蚀效果,浸泡30 d后的Rct可达到282.7^4×104Ω·cm^2,此时的IE为99.99%,对Q235碳钢在模拟海水混凝土孔隙液中的腐蚀具有最佳应用价值。结论各缓蚀剂均存在最优浓度/配比,可使钢筋在含Cl-的SCP溶液中的点蚀电位(Eb)和电荷转移电阻(Rct)显著提高,且缓蚀效率(IE)随浸泡时间的延长而增大。     

锈层对船体钢耐腐蚀性能影响研究

选择5种不同类型的船体钢,在3%(质量分数)NaCl溶液中浸泡1 a,用金相显微镜观察内、外锈层形貌特征和腐蚀形貌,分析锈层下钢的腐蚀特征;记录自腐蚀电位(OCP)的变化,评价锈层对腐蚀倾向性的影响;利用电子探针(EMPA)分析锈层的形貌和内锈层元素分布;通过计算质量损失得到钢的平均腐蚀速率。结果表明,外锈层对钢腐蚀的影响较小;内锈层的缺陷与钢腐蚀形貌中的腐蚀坑对应;当钢中的Ni和Cr元素含量较高时,由于Cr元素在其内锈层和基体交界面富集,其平均腐蚀速率最小。     

纳米涂层/铝合金在不同pH值的海水溶液中的腐蚀行为研究

目的评价纳米涂层/铝合金在不同pH值海水溶液中的腐蚀行为。方法通过测试纳米涂层/铝合金试样在不同pH值海水溶液中的EIS值,分析试样阻抗谱图及Bode谱图的演化规律,建立不同EIS图谱的不同电极阻抗模型,并采用ZView软件解析涂层体系不同时期的电化学阻抗谱,获得涂层电阻的变化趋势,及不同pH值海水浸泡的纳米涂层体系腐蚀失效速度。结果随着浸泡时间的增加及pH值的降低,纳米涂层/铝合金体系腐蚀损伤失效速率在浸泡前期整体趋势增大,但中后期由于腐蚀产物逐渐堵塞了涂层的微孔,腐蚀介质向铝合金表面渗透的速率逐渐减小。结论 pH为2.0海水浸泡下的3涂层失效最快,其次是pH为4.0海水浸泡下的2涂层,最后为p H为6.0海水浸泡下的1涂层,该涂层体系应采用等效电路模型C进行拟合。     

两种紫铜在3.5％NaCl溶液中的腐蚀性能比较

采用极化曲线和交流阻抗技术,研究了2种紫铜在3.5％(质量分数)NaC1溶液中的腐蚀行为,比较了其耐腐蚀性能.结果表明,随着浸泡时间的延长,2种紫铜的自腐蚀电位先降低再升高,腐蚀速率先增大后减小.金相观察发现紫铜T2的第二相夹杂颗粒大小不均匀、晶粒粗大,经扫描电镜和能谱分析后发现其夹杂的成分不同,这是导致其耐蚀性能出现...     

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.     

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.     

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.     

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.     

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.     

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.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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