活性炭固定床吸附分离溶液中表面活性剂和多环芳烃

利用活性炭固定床吸附分离表面活性剂和多环芳烃(PAH)的混合溶液,选取了具代表性的表面活性剂(TX100)和PAH(菲(PHE)等)。实验结果表明,流量越低、活性炭填充量越多、表面活性剂浓度越高、PAH浓度越低,越有利于表面活性剂的回收和PAH的去除。定义了有效回收时间,该时间是指PAH穿透10%的时间与表面活性剂穿透90%的时间之差,该时间越长,越有利于表面活性剂的回收。采用BDST和Thomas模型对TX100和PHE进行了吸附模拟,效果均较好;BDST模型拟合结果表明,当活性炭对TX100的吸附接近饱和时仍对PHE有较强的吸附能力。活性炭固定床吸附分离法可节约运行成本0.06元/L。     

活性炭吸附黏胶纤维生产废气中的CS2

分别采用静态吸附和柱穿透吸附研究了活性炭对黏胶纤维生产废气中CS₂的吸附性能,考察了温度、水蒸气含量和预吸附H₂S时间对活性炭吸附CS₂效果的影响。实验结果表明：活性炭静态吸附CS₂的吸附等温线可用D-R方程很好地拟合,吸附温度升高,活性炭对CS₂的吸附量降低;Y-N方程能很好地拟合CS₂在活性炭上的柱吸附穿透过程,吸附温度升高,CS₂在活性炭上的吸附穿透时间缩短;进气水蒸气含量增大,吸附穿透时间缩短;预吸附H₂S时间延长,活性炭对CS₂的吸附穿透时间缩短;脱附温度升高,CS₂脱附率和脱附速率均加快。     

活性炭固定床上液相污染物的吸附透过行为

测定了四种活性炭在常温下对异丙醇-水溶液的静态吸附等温线,并对其中三种活性炭作了固定床的动态吸附透过曲线。文章对吸附平衡和透过行为进行了讨论。此外,文章还讨论了与总传质系数代表值有关的问题,强调了开展表面扩散系数和孔扩散系数测试研究的重要性。     

GC-MS在电子束辐照降解甲苯中的应用

用甲苯作为挥发性有机化合物的代表物质,建立了活性炭吸附-二硫化碳解吸气相色谱-质谱分析方法,对电子束辐照甲苯的静态实验和动态实验进行了定性、定量分析。实验结果表明：电子束辐照能有效地降解甲笨,其降解率随吸收剂量的增加而增大;同时,甲苯降解过程中也会生成部分有毒有害物质。该分析方法的检出限为0．02mg／L,工作曲线的线性范围为10～1000mg／L,相关系数为0．9998,活性炭吸附、解吸甲苯的加标回收率大于90％。     

挥发性有机物的物化性质与活性炭饱和吸附量的相关性研究

采用kc-4．0型颗粒活性炭对甲苯、对二甲苯、乙酸甲酯、乙酸乙酯、乙醇、正丙醇进行吸附实验,研究挥发性有机物的物化性质与活性炭饱和吸附量之间的相关性。实验结果表明,活性炭对乙酸甲酯、乙醇和正丙醇的吸附性能较差,对乙酸乙酯、甲苯和对二甲苯的的吸附性能较好,饱和吸附量最大的是甲苯（达312．92mg／g）,饱和吸附量最小的是乙酸甲酯（为224．93mg／g）。6种挥发性有机物的吸附等温线用Langmuir方程进行拟合,效果良好。挥发性有机物的比蒸发速度、饱和蒸气压和电离势能与活性炭饱和吸附量具有显著的相关性。比蒸发速度越快、饱和蒸气压越高或电离势能越大,活性炭饱和吸附量越小。     

轻烃类VOCs在活性炭上的动态吸附行为

采用BET,XRD,FTIR技术对两类椰壳活性炭进行了表征,考察了空速和吸附温度对正戊烷和正己烷动态吸附穿透容量(DPC)及穿透时间的影响,并对正戊烷和正己烷的二元竞争吸附过程进行了研究。结果表明:两类活性炭材料的组成和官能团结构相似,具有大量微孔的片状活性炭(FAC)有利于轻烃类VOCs的吸附;采用FAC吸附正己烷时,DPC对空速和温度变化不敏感;二元竞争吸附过程中,开始阶段正戊烷和正己烷同时被吸附,随后已被吸附的正戊烷被强吸附质正己烷部分置换,直至正己烷吸附饱和,与一元吸附相比,正己烷的DPC和饱和吸附容量略有增加,正戊烷的DPC和饱和吸附容量大幅降低。     

活性碳纤维吸附废气中的丙烯酸和甲苯

采用动态吸附法探讨了在活性碳纤维对模拟废气中丙烯酸和甲苯的吸附过程中,各因素对活性碳纤维穿透吸附量和饱和吸附量的影响。实验结果表明,在模拟废气中丙烯酸质量分数为0.2%、双柱塞泵流量为6.1mL/h、载气流量为1.60L/min的条件下,穿透时间为10min,活性碳纤维的穿透吸附量为227.5mg/g,饱和吸附时间为40min,活性碳纤维的饱和吸附量为460.0m g/g。     

碱改性活性炭对VOCs的吸附性能

选用3种经氢氧化钠改性的活性炭,研究了其对4种代表性VOCs(丁酮、乙酸乙酯、甲苯和四氯化碳)的吸附规律。结果表明:活性炭经碱改性后吸附性能有较大改善,吸附量的大小与其比表面积呈正相关性,而其比表面积多为微孔提供;改性活性炭对有机气体的吸附以物理吸附为主;吸附质的相对分子质量、密度、熔点与其在改性活性炭上的吸附量具有线性相关性,而沸点、饱和蒸气压、分子动力学直径则与吸附量无明显相关性;对于同一吸附剂,170℃再生时的性能最好,130℃次之,210℃最差。     

自制ZSM-5分子筛对甲苯气体的吸附-脱附性能

考察了自制ZSM-5分子筛对甲苯气体的吸附-脱附性能,并与市售MCM-22分子筛进行了对比实验。实验结果表明:在吸附温度为25℃、进口甲苯质量浓度为840mg/m3、吸附气体流速为0.016m/s、床层高度为15cm的条件下,出口甲苯质量浓度达到0.8mg/m3时的穿透时间为82min,吸附效率为4.26mg/g;在脱附温度为80℃、脱附气体流速为0.016m/s的条件下,脱附35min时出口甲苯质量浓度达到最大,为1220mg/m3。自制ZSM-5分子筛的吸附-脱附性能优于市售MCM-22分子筛。     

用微孔填充理论研究活性炭对有机气体的吸附性能

用微孔填充理论研究了活性炭C40／4对丙酮、甲苯、二氯甲烷有机气体的吸附性能,测试了该活性炭对3种有机气体在不同温度下（288．15,293．15,298．15K）的吸附结果。用D—R方程处理了实验数据,建立了3种有机气体在活性炭C40／4上的等温吸附模型,并将实验测试值与理论预测值进行了比较。实验结果表明：微孔填充理论及D—R方程可很好地描述活性炭C40／4对有机气体的吸附性能,理论预测值与实验测试值的平均相对误差小于3％;有机气体分压较高时,由于发生毛细凝聚,理论预测值较实验测试值偏低。     

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.     

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.     

Bioassessment of silvicultural impacts in streams and wetlands of the Eastern United States

Bioassessment is a useful tool to determine the impact of logging practices on the biological integrity of streams and wetlands. Measuring biota directly has an intuitive appeal for impact assessment, and biota can be superior indicators to physical or chemical characteristics because they can reflect cumulative impacts over time. Logging can affect stream and wetland biota by increasing sedimentation rates, altering hydrologic, thermal, and chemical regimes, and changing the base of food webs. Biotic impacts of logging on streams compared to wetlands probably differ, and in this paper we review some of those differences. In streams, invertebrates, fishes, amphibians, algae, and macrophytes have been used as indicators of logging impacts. In wetlands, bioassessment is just beginning to be used, and plants and birds are the most promising indicator taxa. Various best management practices (BMPs) have been developed to reduce the impacts of logging on stream and wetland biota, and we review quantitative studies that have evaluated the efficacy of some of these techniques in streams and wetlands in the eastern United States. Remarkably few studies that address the overall efficacy of BMPs in limiting biotic changes in streams and wetlands after BMP implementation have been published in scientific journals, although some work exists in reports or is unpublished. We review these works, and compile conclusions about BMP efficacy for biota from this body of research.