Cu-Mn-Ce ternary mixed-oxide catalysts for catalytic combustion of toluene

Cu–Mn, Cu–Mn–Ce, and Cu–Ce mixed-oxide catalysts were prepared by a citric acid sol–gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu–Mn–Ce ternary mixed-oxide catalyst with 1:2:4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu–Mn–Ce catalyst, a portion of Cu and Mn species entered into the Ce O_2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu–Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu–Mn and Cu–Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.     

独立学院教学中的四忌

独立学院的学生与母体高校学生相比有一定的特殊性。独立学院的教学如若完全沿用母体高校的方法和要求，势必会出现一些问题和矛盾。为此，在独立学院教学中，教师应注意四忌。     

高铁酸盐氧化絮凝去除含油污水中的油

油田产出的油、水经分离后会产生大量的含油污水,选用高铁酸钾对污水进行处理已成为人们关注的一个问题。用荧光比色法测定非均相固-液悬浮体系中油含量的实验证明:(1)高铁酸盐在含油污水中的初始反应速度快,可将大部分有机物氧化;(2)氧化法处理含油污水受多种因素的影响;(3)高铁直接氧化和芬顿氧化法均可比较彻底地处理油田含油污水。用高铁氧化法处理含油污水技术上很有发展前景,各种浓度的污水经处理后都可达到国家排放标准。     

Seasonal Variation of Chemical Composition in Fine Particles at Gosan, Korea

PM_2.5 aerosol samples were collected at Gosan in Jeju Island during six intensive measurement periods between November 2001 and August 2003. In order to investigate the chemical composition of fine particles, major ion components, trace elements, and elemental and organic carbon were analyzed. Quite different seasonal characteristic in the chemical composition of fine particles was observed. The concentration of most secondary aerosol components showed a summer minimum and a winter maximum with higher correlation between them at Gosan. This fact clearly reveals the possibility of long-range transport of such pollutants in winter. On the other hand, OC and EC had the highest concentration and good correlation with ion components, such as K⁺, Ca²⁺ in fall. It means that biomass burning could significantly influence the ambient fine carbonaceous particulate in fall, which was primarily long-range transported.     

重金属铅,镉,锌对小麦DNA构象的影响

采用紫外吸收谱法，研究了不同浓度铅，镉，锌对小麦ＤＮＡ构象的影响。结果显示重金属铅，镉，锌均可影响小麦ＤＮＡ构象，使其紫外吸收峰值发生变化。其中，铅离子对小麦ＤＮＡ构象影响最大，５０μｇ／ｍｌ＾ｐｂ＾２＋处理使小麦出现明显减色反应，１０００μｇ／ｍｌｐｂ＾２＋处理使其沉淀析出；镉离子对小麦ＤＮＡ构象影响不大，可使其产生轻微减色反应，低浓度锌离子使小麦ＤＮＡ发生增色反应，而高浓度使小麦ＤＮＡ发生减色     

参数化绘图系统的开发与应用

探讨了参数化绘图系统开发的基本算法、功能和要求及开发步骤,简单介绍了国内外参数化CAD的应用情况。     

Growth and phosphate uptake kinetics of Microcystis aeruginosa under various environmental conditions

Growth and uptake of exogenous phosphate by Microcystis aeruginosa in batch culture under different temperature, photoperiod, and turbulence were studied by the method of phosphate isotope tracer. Relatively high temperature, long photoperiod and strong turbulence increased the cell density of M. aeruginosa in these batch cultures. The initial rapid uptake of phosphate by M. aeruginosa was independent of the temperature, photoperiod, and turbulence. Similarly, maximum exogenous phosphate uptake was not related to these environmental factors. However, elevated temperature and turbulence shortened the time, required to obtain maximum P accumulation. The growth of M. aeruginosa could alleviate the phosphorous leakage. Total amounts of exogenous phosphate uptake to M. aeruginosa and the phosphorus leakage of M. aeruginosa were significantly influenced by the growth state of M. aeruginosa closely correlated with the environmental factors. The maximum volume of exogenous phosphate uptake to M. aeruginosa was 46% of added exogenous phosphate in water with 16 hours of photoperiod. Thus, total amounts of exogenous phosphate uptake to M. aeruginosa were more strongly affected by the photoperiod length than temperature and turbulence.     

水中典型光敏剂引发金雀异黄酮三线态敏化光降解机理

金雀异黄酮(genistein,Gs)在水体中频繁检出,其环境行为备受关注。为深入探讨水中溶解性有机质(DOM)激发三线态敏化Gs间接光降解的机理,以3-甲氧基苯乙酮(3-MAP)、亚甲基蓝(MB)、2-萘乙酮(2-AN)和2-苯甲酮(BP)模拟DOM引发三线态光敏化反应,阐明Gs发生间接光降解活性与敏化剂性质、pH值的关系。通过光化学实验结合密度泛函理论计算发现,激发态能量高的BP或3-MAP对Gs的敏化效率低,二者虽可与Gs发生能量或电子转移敏化,但对λ290 nm的模拟太阳光吸收少,因此激发态产率低;激发态能量低的MB或2-AN对Gs的敏化效率高,且随pH升高而增强,因二者能吸收较多的模拟太阳光,激发态产率高。以MB为例,发现Gs分子形态几乎不能被光敏化降解(pH≤5); Gs由一价阴离子逐渐解离成二、三价阴离子,kin增大102倍(pH 6～12),说明Gs不同解离形态的敏化光降解活性具有显著差异。因Gs阴离子更易发生敏化光降解,因此带正电荷的MB分子比中性分子态的2-AN更易与Gs阴离子结合,表现出更高的敏化能力,相同pH (9或12)条件下,敏化光降解速率相差25～47倍。敏化剂三线态性质及pH值对Gs光敏化降解的影响机理,对于深入认识化学组成复杂的环境DOM的光化学活性具有重要意义。     

植物-微生物修复石油烃污染土壤与根际微生态环境变化

石油烃作为一类持久性难降解有机污染物对土壤环境质量产生严重的危害。以天津大港油田原油污染土壤中筛选出的耐低温高效石油烃降解菌为靶细胞,以小麦、紫花苜蓿作为供试植物,利用盆栽试验,对植物-外源菌协同修复体系中的脱氢酶活性和土壤微生物多样性进行研究,分析其变化及其与石油烃降解率的关系。结果表明植物-微生物协同修复对石油烃具有较好的降解能力,其中小麦-固定化外源菌组具有最高的降解率,石油烃含量从最初的30 600 mg獉kg-1下降为24 300 mg獉kg-1,降解率为20.6%,并且其试验后期石油烃的降解率最大,远远高于其他时期,表现出良好的修复潜力。外源菌投加的初始阶段会迅速提高脱氢酶活性,然而这种影响随着降解时间延长而逐渐减弱。初期脱氢酶活性与总石油烃的降解存在较好的相关性,脱氢酶活性可以在一定程度上表征土壤石油烃的降解情况。微生物多样性与总石油烃降解也存在一定的相关性。     

The role of solubility on the rejection of trace organics by nanofiltration membrane: exemplified with disinfection by-products

Environmental Science and Pollution Research - Interactions of trace organic compounds (TOrCs) with polymeric nanofiltration (NF) membrane can affect their rejection. It is desirable to investigate...