复合载体对选择性催化还原催化剂低温脱硝性能的影响

采用浆液浸涂法在堇青石蜂窝陶瓷载体上涂覆Al2O_3-TiO_2-ZSM-5分子筛复合载体,并通过浸渍法负载活性组分Mn-Fe-Ce,制备了M/ATZ-CC选择性催化还原催化剂。考察了催化剂的低温脱硝活性和抗水性能,表征了催化剂的物性参数和氨-程序升温脱附性能。实验结果表明,M/ATZ-CC催化剂具有优异的脱硝活性和抗水性能,在反应温度为160℃、水蒸气加入量为10%(φ)、NO体积分数为0.1%、n(NH_3)∶n(NO)=1、O_2体积分数为3.0%、体积空速为3 000~10 000 h~(-1)的条件下,NO去除率在80%以上。表征结果显示,该催化剂的比表面积、孔径、弱酸酸量、中强酸酸量和总酸量得到了显著提高。     

N235萃取含盐酸性废水中的盐酸

以N235为萃取剂、甲苯为稀释剂萃取模拟含盐酸性废水(简称废水)中的盐酸。最佳实验条件为:振荡时间20 min,初始废水中盐酸浓度0.75～2.45 mol/L,V(N235):V(N235+甲苯)=0.3～0.7,V(N235+甲苯):V(废水)=0.5～1.0。在初始废水中盐酸浓度为1.00 mol/L、不含无机盐、V(N235):V(N235+甲苯)=0.4、V(N235+甲苯):V(废水)=1.0的条件下,振荡20 min后萃取液中盐酸浓度为0.80 mol/L、n(盐酸):n(N235)=0.88。当废水中氯化钠浓度大于2.0 mol/L时,氯化钠的加入对N235萃取盐酸有促进作用;硫酸钠的加入对N235萃取盐酸具有抑制作用。     

二硫化碳萃取—气相色谱法同时测定含盐酸废水中的甲苯、邻氯甲苯、对氯甲苯和氯化苄

建立了二硫化碳萃取—气相色谱法同时测定含盐酸废水中甲苯、邻氯甲苯、对氯甲苯和氯化苄的方法,并应用于实际水样的测定。采用二硫化碳萃取含盐酸废水中的甲苯、邻氯甲苯、对氯甲苯、氯化苄,待测物质经30QC3/AC20（30 m×0.32 mm×0.50 μm）毛细管柱气相分离。采用保留时间定性,外标法定量。实验结果表明,甲苯、邻氯甲苯、对氯甲苯和氯化苄的质量浓度在0.2~100.0 mg/L范围内与对应的峰面积呈良好的线性关系,检出限分别为0.09,0.12,0.13,0.10 mg/L。该方法的精密度和准确度较高,相对标准偏差小于2%,加标回收率在96.4%~101.0%之间。     

Mn-Ce/Ti-Zr-柱撑膨润土催化剂低温选择性催化还原法脱硝

以改性的有机膨润土为原料,制备Ti、Zr共柱撑有机膨润土(Ti-Zr-OPILC),并通过浸渍法负载Mn、Ce,制备得催化剂Mn-Ce/Ti-Zr-OPILC,运用XRD、BET分析了催化剂的物理化学特性,并考察了催化剂对NO低温选择性催化还原反应的催化活性.实验结果表明:催化剂的比表面积得到很大提高,Mn和Ce在载体上分散性较好;在反应温度为220℃、体积空速为40 000 h-1、n(NH3)∶n(NO)为1、初始NO体积分数为0.06％、O2体积分数为3.6％时,对NO去除率高达95％以上.     

磷钨酸催化合成混合二元酸二丁酯

采用混合二元酸和正丁醇为原料,以自制磷钨酸为催化剂,甲苯为带水剂,合成了混合二元酸二丁酯.通过均匀设计和单因素实验研究得到混合二元酸二丁酯合成的最佳工艺条件:n(正丁醇):n(混合二元酸)为3.0,催化剂与混合二元酸的质量比为2.2%,甲苯在反应体系中的质量分数为22%,反应时间为2.0 h.在最佳工艺条件下反应的酯化率为99.44%.     

电子束辐照分解甲苯的初步实验研究

进行了电子束辐照分解甲苯的静态实验研究,实验结果表明,电子束辐照能够有效地分解甲苯,在850keV、11kGy电子束的辐照下,初始质量浓度为1 000~3 000m g/m3的甲苯去除率可以达到77%以上,且甲苯去除率随吸收剂量的增加而提高。甲苯辐照分解的主要产物是苯甲醛和甲酸,此外还有少量苯、苯酚等。进一步验证了.OH在甲苯分解中的重要作用。     

生物滴滤法处理喷漆废气

采用生物滴滤系统处理喷漆废气,在研究了混合气体中甲苯与二甲苯之间相互作用的基础上,对生物滴滤系统净化喷漆废气的稳定性进行了研究。实验结果表明:在挂膜启动阶段,进气流量为22.5 m3/h、空塔停留时间为33.9 s、进气甲苯质量浓度为400~1 500 mg/m3的条件下,最终甲苯去除率可稳定在97%以上;在总进气质量浓度为1 000 mg/m3的条件下处理甲苯和二甲苯混合气体,混合气体中甲苯与二甲苯存在相互抑制作用,且甲苯对二甲苯的抑制作用更强;在进气流量为20.0 m3/h、空塔停留时间为38.0 s、进气中总挥发性有机物(TVOCs)质量浓度为300~900 mg/m3的条件下处理喷漆废气,平均TVOCs去除率为90.84%,出口二甲苯质量浓度低于GB16297—1996《大气污染物综合排放标准》中规定的排放限值(二甲苯质量浓度为70 mg/m3),基本满足排放要求。     

恒沸精馏法分离回收阿维菌素生产残液中的甲苯和乙醇

在阿维菌素精制工艺中 ,乙醇和甲苯被共用作溶剂及浸泡剂。乙醇与甲苯的混合液在常压下、温度为 76 .7℃时即共沸 (乙醇的沸点为 78.4℃ ,甲苯的沸点为 110 .8℃ ) ,这种残液如不处理则会带来严重的环保问题。此残液无法用普通精馏法分离 ,我们采用恒沸精馏法将其进行分离回收 ,取得了较好的效果。1　残液组成　　以某生物农药厂阿维菌素精制工艺的废溶剂为试验原料 ,其中甲苯的质量分数为 12 %～ 16 %、乙醇的质量分数为 75 %～ 80 % ,其余为水和少量杂质。2　分离原理　　通过在二元共沸物中引入第 3组分 (夹带剂 ) ,使其与乙醇、甲苯形成…     

二级膜分离—冷凝—吸附工艺处理石化罐区废气

采用二级膜分离—冷凝—变压吸附工艺回收处理含有高浓度挥发性有机物和苯系物的炼厂罐区外排"呼吸气"。结果表明,进气的非甲烷总烃质量浓度范围41 000～182 000 mg/m~3,进气中苯、甲苯和二甲苯的质量浓度分别为400～1 400 mg/m~3,150～1 600 mg/m~3,300～2 100 mg/m~3时,尾气中非甲烷总烃质量浓度始终低于80mg/m~3,去除率均高于99.9%,苯、甲苯和二甲苯的去除率分别为99.6%、99.6%和99.8%。抗冲击负荷实验将进气量提高50%,尾气中非甲烷总烃质量浓度仍低于80 mg/m~3。二级膜单元可以高效浓缩轻烃,既回收获得可燃气,又解决了轻烃积累所造成的尾气超标难题。     

Ti-MCM-41分子筛对Cr(Ⅵ)的吸附性能

以发烟硅胶为硅源、钛酸四丁酯为钛源,采用水热合成法制备了一系列不同n(Si)∶n(Ti)的Ti-MCM-41分子筛,采用XRD、UV-Vis、BET及ICP技术对其进行了表征,考察了其对溶液中Cr(Ⅵ)的吸附性能及重复使用性能。结果表明:制备的Ti-MCM-41分子筛保持了MCM-41的介孔结构,但随着Ti含量的增加分子筛的比表面积、孔径和总孔体积均降低;在初始Cr(Ⅵ)质量浓度为100 mg/L、Ti-MCM-41分子筛(投料n(Si)∶n(Ti)为40)投加量为1 g/L、吸附时间为60 min、吸附温度为323 K、溶液pH为6的条件下,Cr(Ⅵ)吸附率可达96.3%;Ti-MCM-41分子筛对Cr(Ⅵ)的吸附符合Langmuir等温吸附模型;Ti-MCM-41分子筛的重复使用性能良好。     

Distribution of Cd,Ck, Pb and Zn in Soil and Vegetation Compartments in Stands of Five Boreal Tree Species in N.E. Sweden

Concentrations and total quantity of cadmium (Cd), cupper (Cu),lead (Pb) and zink (Zn) were determined in biomass and soil compartments in a replicated tree species experiment with 27-yr-old stands growing on former farmland in N.E. Sweden. Sequentialextractions of soil samples were performed in order to estimate the exchangeable and an organically bound fraction of each element. The tree species included were Picea abies (L.)H. Karst., Pinus sylvestris L., Pinus contorta Dougl., Larix sibirica Ledeb., and Betula pendula Roth.Tree species influenced the rate of removal of Cu, Pb and Zn incase of stemwood harvesting, and of Cd, Cu and Zn in the case ofwhole-tree harvesting. B. pendula and P. abies had higher quantities and average concentrations of Zn in the biomass. For all species, >50% of the Zn in the stems was found in the bark. P. abies and L. sibirica had higher quantities of Cu in the biomass than the other species.P. abies and P. contorta had high quantities of Cd inthe biomass in relation to the other species. Branches and stembark contained high concentrations of Cd and Pb in relation to foliage and stemwood. Dead branches had especially high concentrations of Pb. The high accumulation rate of Zn in thebiomass of B. pendula was related to a low exchangeable amount of Zn in the A horizon. In the superficial centimeters ofthe A horizon, a depletion similar to that found for Zn was detected for Cu, whereas for Cd and Pb, no correlations were found between quantities of elements in the trees and element pools in the soil.     

Programs assessing implementation and effectiveness of state forest practice rules and BMPs in the West

The major forest nonpoint source control programs in the West are largely regulatory, either under forest practices acts (California, Idaho, New Mexico, Nevada, Oregon, and Washington) or a streamside management act (Montana). These programs and the specific rules they enforce continue to undergo intensive scrutiny. Still, the questions are the same for these regulatory programs as for states that base nonpoint source control on voluntary BMPs (Arizona, Colorado, Utah, Wyoming). Are the rules or BMPs being applied, and are they effective in reducing nonpoint source pollution to levels that protect beneficial uses of water? The level of debate about forestry in the West has resulted in detailed monitoring and research to answer these questions. In the past, state agencies have assumed levels of BMP compliance based on the percent of operations without enforcement actions. These estimates are being replaced by statistically valid and reproducible monitoring of forest practices rules and BMP compliance levels. BMP effectiveness is being assessed using both qualitative and quantitative methods. This can involve field assessments, process-based research, and control watershed studies. Some trend monitoring is also beginning. With the regional implementation rate for forestry BMPs at about 94% and rising, it is likely that effectiveness testing will continue to be a priority and consume the majority of assessment resources for this region.     

High Immobilization of NH4+ in Danish Heath Soil Related to Succession,Soil and Nutrients: Implications for Critical Loads of N

During recent decades heathlands havechanged into grasslands in regions with high atmosphericnitrogen deposition. In regions with intermediatedeposition level (e.g., Denmark) changes have been lesspronounced which may be due to delay or decrease inresponse of the ecosystem. The mor layer (O horizon) mayplay an important role for this delay due to high sinkstrength for N. In this study, the capacity for netNH₄ ⁺ immobilization and mineralization wasstudied during short- and long-term incubations (2–36 days)of mor samples from Danish dry inland heaths. High short-term capacity for net NH₄ ⁺ immobilization wasfound to be a general characteristic of Danish heath morlayers both under heather (Calluna vulgaris) andcrowberry (Empetrum nigrum ssp nigrum), the latterdominating late stages in heathland succession. The netNH₄ ⁺ immobilization was higher under youngcompared to old or dead vegetation, and higher on lessnutrient poor soils than on extremely nutrient poor soils.The addition of N, P and C stimulated CO₂ productionand net NH₄ ⁺ immobilization, but not net Nmineralization. The immobilization of ¹⁵NH₄ ⁺caused release of dissolved organic N, increased N anddecreased C/N ratio in the microbial biomass, and indicatedgrowth of microorganisms with other metabolic abilitiesthan the indigenous population. No evidence was obtained ofstabilization of immobilized ¹⁵NH₄ ⁺ intosoil organic matter during the experiment. On background ofthe results and current knowledge it was concluded that therecognition of the high capacity for net NH₄ ⁺immobilization in mor layers does not allow for a raiseof critical loads for N for northern dry inland heaths.     

Starch-plastic materials—Preparation,physical properties,and biodegradability (a review of recent USDA research)

Recent starch-plastic research at the National Center for Agricultural Utilization Research is reviewed and related worldwide efforts are noted. Properties of starch that influence its formulation and performance in plastics are discussed. Methods are given for preparation of starch-poly(methyl acrylate) graft copolymer, starch-poly(ethylene-co-acrylic acid), and starch-poly(ethylene-co-acrylic acid)-polyethylene plastics. Their physical properties are discussed, as is degradability by enzymes or amylolytic organisms from soil, ponds, and streams.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Application of Cellulose Microfibrils in Polymer Nanocomposites

Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents.     

四氮唑废水处理工艺设计

高浓度、高盐分的四氮唑生产废水通过三效蒸发浓缩,馏出液经铁炭氧微电解和混凝预处理,再采用水解酸化一接触氧化一反应二沉主体组合工艺进行处理。研究了该工艺所需构筑物和设备的设计与选型。该工艺在正常运行条件下,处理后出水pH6～9,COD 302mg／L,BOD5 108mg／L,SS30mg／L,色度36倍,水质达到GB8978--1996（污水综合排放标准》三级标准。     

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.     

Reconstruction of Long-Term Changes in Lake water Chemistry,Zooplankton and Benthos of a Small,Acidified High-Mountain Lake: Magic Modelling and Palaeolimnogical Analysis

Starolesnianske pleso is a small and shallow acid lake in the High Tatra Mountains, situated at 2000 m above sea level, on granitic bedrock, with sparse and thin soil cover. When detailed measurements began in the 1980s Starolesnianske pleso had pH below 5 and only one species of cladoceran zooplankton, the ubiquitous Chydorus sphaericusPalaeolimnological investigations show changes in cladoceran zooplankton and chironomid zoobenthic assemblages since about 1920 and a major change in 1970–1980. The dynamic acidification model MAGIC was used to reconstruct changes in water chemistry over the past 150 years. The results from MAGIC agree well with the sediment record; pH levels gradually decreased from 6.5 in the mid-1800s to about 5.6 in 1920 (first response in biota) to below 5.0 by 1970, and concentrations of inorganic aluminium rose dramatically beginning about 1960. In the 1990s the lake water chemistry showed clear signs of reversal in acidification brought about by a major decline in S deposition.     

Does Soil Acidification Affect Spruce Needle Chemical Composition and Tree Growth?

In 1994, a large survey of soil chemistry was undertaken in thecounty of Värmland in central Sweden (Lundström et al., 1998).The southern part of the county was affected by soilacidification whereas there were no such indications in thenorthern part. To investigate the influence of soil chemistryon the trees at the specific sites, the survey was continued byan analysis of needle chemistry (Norway spruce) which wasundertaken at 150 of the 180 sites, and of tree growth at 65 ofthe 180 sites. Growth was expressed as a ratio between expectedgrowth, estimated with a national, empirical growth model, andthe growth observed in the field. In statistical analyses,using rank correlation, PCA and PLS, there were only weakindications of an influence of soil chemistry on needlechemistry and on tree growth. A moderate correlation betweennitrogen and sulphur in needles was found, which wasinterpreted as an effect of deposition and of processes in thetree canopy. No obvious regional pattern of the growth ratiowas found, in contrast to the clear pattern of soilacidification. The statistical analysis could not with anycertainty point out any of the soil chemistry variables asespecially important for the tree growth ratio.     

Heavy Metals Removal by Biosorption and Flotation

The removal of a mixture of heavy (toxic) metal cations (copper, nickeland zinc) from liquid effluents was investigated in this study at pilotscale, using counter-current contact mode. The innovative processinvolved the abstraction of metal ions onto fungal biosorbents, followedby the application of flotation for the subsequent solid/liquid separationof biomass particles. The ability of microorganisms to remove metal ionsfrom aqueous solutions is a well-known phenomenon. Nevertheless,engineering considerations are very important in decisions, concerningthe commercial future of biosorption and practical solutions are neededfor certain problems, such as the efficient post-separation ofmetal-loaded biomass. The two processes (flotation and biosorption) caneffectively operate in combination, in what it was termed biosorptiveflotation process. The sorbents may be recycled, after appropriate elutionof metals, as well as the treated (clean) water.