Q235钢在海洋铁细菌作用下的腐蚀行为研究

采用开路电位、电化学极化曲线、电化学阻抗谱(EIS)等方法研究了海洋铁细菌作用下Q235钢的腐蚀行为与腐蚀机理。扫描电子显微镜(SEM)形貌分析结果表明有大量的杆状铁细菌附在Q235钢铁表面。在海洋微生物的影响下,Q235钢的开路电位变小,腐蚀倾向与腐蚀率变大。EIS结果表明在海洋铁细菌作用下Q235钢的交流阻抗模值减少,而且大大降低了Q235钢的极化电阻和表面膜的电阻。微生物的附着促进了钢材表面的溶解,使其表面氧化膜层消失,进而形成了疏松不致密的生物膜层,从而加速了其腐蚀进程。     

Q235钢在模拟自然环境下失效行为的电化学研究

采用电化学阻抗谱(EIS)和阴极极化曲线研究了Q235钢在薄液膜条件下的大气腐蚀过程,探讨了液膜厚度、Cl-和腐蚀产物对Q235钢失效过程的影响.结果表明液膜厚度会影响O2的扩散过程,并进一步影响腐蚀速率;C1～环境下,Q235钢腐蚀产物分成2层,外层为多孔疏松层,内层主要为α-FeOOH和γ -FeOOH组成的锈层,...     

安徽省内电网设备常用钢材大气腐蚀试验研究

目的针对在安徽省内H1、R1及T28三个站点自然环境下暴露1年后的Q235、40Cr及镀锌钢,开展腐蚀速率、腐蚀产物及腐蚀层形貌的研究,探讨其大气腐蚀机理。方法采用称量法计算腐蚀质量损失,通过光学及电子显微镜法观察腐蚀层表面及截面形貌,用电子能谱仪测试微区成分,用X-射线衍射法测试腐蚀层的物相构成。结果 Q235、40Cr的大气腐蚀产物为Fe OOH、Fe3O4、Fe(OH)3及FeSO4,镀锌钢则为Zn O及Zn SO4。Q235、40Cr腐蚀层表面分布着绒球状的α-FeOOH及片状的γ-FeOOH,镀锌钢大气腐蚀层致密,但T28站点镀锌钢表面形成点状的腐蚀坑,腐蚀防护能力降低。结论同一站点三种钢腐蚀速率大小次序为40CrQ235镀锌钢,站点R1钢的腐蚀速率最大,站点T28的腐蚀速率最小。     

储罐用钢在3.5%NaCl溶液中的腐蚀行为研究

目的对比研究三种油气储罐在水压试验时的腐蚀行为特征。方法选用9Ni钢、Q235碳钢、304L不锈钢储罐用材料以及3.5%NaCl模拟海水溶液,采用开路电位、电化学阻抗谱、动电位极化曲线测试方法研究三种储罐用钢在模拟海水中的电化学腐蚀特征,同时结合浸泡质量损失试验和微观腐蚀形貌进行分析。结果 9Ni钢、Q235碳钢、304L不锈钢稳定后的开路电位(vs.SCE)分别为-0.55、-0.64、-0.10m V,Rt值分别为2 792、1 765、125 100,平均腐蚀深度分别为0.070 6、0.160 3、0.002 5 mm/a。微观腐蚀形貌显示,9Ni钢和Q235碳钢表面发生明显的腐蚀,而304L不锈钢只发生轻微的点蚀。结论在3.5%NaCl模拟海水溶液中,304L不锈钢最耐腐蚀,Q235碳钢最易腐蚀,9Ni钢居于两者之间。因此在9Ni钢和Q235碳钢储罐海水试压过程中需要采取临时保护。     

模拟南海大气环境下耐候钢腐蚀性能研究

目的通过室内模拟南海大气环境加速腐蚀试验,对比分析几种钢腐蚀性能优劣,为开发耐南海大气腐蚀用钢提供数据支撑和理论依据。方法分别选用Q235B,Q355和Q500q E三种材料作为研究对象,采用中性盐雾试验方法模拟南海苛刻大气环境对试样进行耐蚀性测试,通过试样表面形貌观察、腐蚀质量损失计算和电化学分析等手段研究其腐蚀行为机制。结果 Q235B表面最先被腐蚀产物完全覆盖,腐蚀速率始终大于另外两种材料。Q355和Q500q E表面膜初期起到延缓腐蚀作用,其中以Q500q E极化阻抗最大,腐蚀表面最为平整。结论模拟南海大气环境下三种试验钢耐蚀性能排序为Q500q EQ355Q235B。     

碳钢和耐候钢在盐雾环境下的腐蚀行为研究

目的研究Q235钢和耐候钢在3.5%(质量分数)NaCl盐雾/干燥循环加速腐蚀试验中的腐蚀过程,比较它们的耐腐蚀性。方法采用腐蚀失重分析、X-射线衍射分析、扫描电镜观测和电化学测试等进行研究。结果 Q235钢和耐候钢的锈层没有明显的保护作用,但耐候钢的耐蚀性略优于Q235钢。结论在模拟海洋大气环境中,该耐候钢没有优越性,说明该耐候钢不适用于海洋大气环境中。     

浸泡时间对X60钢SRB电化学腐蚀行为影响研究

利用极化曲线,电化学阻抗谱,扫描电镜,能谱分析和微生物分析等方法对X60钢在灭菌培养基和接种硫酸盐还原菌(SRB)培养基中浸泡2h和浸泡240h后的腐蚀行为进行了对比研究.结果表明:浸入初期,相比灭菌介质,含SRB介质中X60钢表面上SRB的初始吸附成膜具有一定的保护作用,这使其耐蚀性能有所提高.浸泡2h后,SRB菌落代谢过程的阴极去极化作用使X60钢表面产生明显点蚀形貌,加速了X60钢的腐蚀,使其耐蚀性能下降.     

钢铁材料在黄河三门峡水库中的腐蚀行为

目的获取典型钢铁材料在黄河三门峡水库中长期暴露的腐蚀结果和腐蚀行为。方法采用暴露腐蚀试验,将1种碳钢、3种低合金钢和3种不锈钢材料在三门峡水库中暴露1,2,5,8 a,用金相显微镜测量各材料的点蚀深度,观察腐蚀形貌,并计算其腐蚀速率。结果在三门峡水库中暴露8 a,碳钢和低合金钢的腐蚀行为基本相同,4种钢暴露1 a的平均腐蚀速度接近,为0.047~0.050 mm/a,暴露1~8 a,Q235B的平均腐蚀速度为0.040 mm/a,X70,X80和D36钢的平均腐蚀速度与Q235B相差不大,分别为0.039,0.034,0.037 mm/a。暴露1 a后,0Cr13表面有蚀点,最大点蚀深度为0.010 mm,暴露8 a后,0Cr13试样的边角、钻孔处出现溃烂、穿孔。暴露8 a后,304和316L的最大点蚀深度均小于0.1 mm。结论 Q235B,X70,X80,D36在黄河三门峡水库中的腐蚀行为基本相同,它们在第1年的腐蚀速度较大,暴露1 a后腐蚀速度略有降低。0Cr13腐蚀严重,暴露8 a,发生腐蚀溃烂、穿孔现象。304和316L在三门峡水库中有很好的耐蚀性。     

316L不锈钢在南海环境中的缝隙腐蚀行为研究

目的 研究316L不锈钢在南海环境中的缝隙腐蚀行为.方法 利用自主设计的实海实验装置,在南海170 m水深的位置开展316L不锈钢缝隙腐蚀实验.利用光学显微镜观察试样的腐蚀形貌,利用扫描电子显微镜(SEM)观察腐蚀产物膜的微观形貌,结合能谱仪(EDS)分析腐蚀产物膜的微区成分,并利用荧光显微镜观察缝隙腐蚀试样表面微生物...     

Q235碳钢在石化大气环境中初期腐蚀行为

在武汉石化厂区内对Q235碳钢进行了半年的化工大气环境下的暴晒试验,测量了钢的初期腐蚀速率;利用扫描电镜、XRD观察分析了暴晒后样品的锈层特征;对带锈试样进行了交流阻抗测量.结果显示,Q235碳钢暴晒半年后腐蚀产物主要有Fe2(SO4)3·nH2O,FeSO4·nH2O,FeOOH,Fe(OH)(SO4)(H2O),腐...     

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.     

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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Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.