介孔TiO2纤维的制备及其光催化性能

采用溶胶-凝胶和水蒸气活化热处理技术制备了介孔TiO2纤维,考察了各种因素对介孔TiO2纤维光催化活性的影响,并对介孔TiO2纤维结构进行了表征。介孔TiO2纤维的最佳制备条件：n（TBOT）∶n（C6H10O3）∶n（H2O）∶n（C3H8O）=1∶0.4∶2.0∶16,搅拌时间80min,Si与Ti的摩尔比为0.15,采用分段程序升温工艺,活化温度为700℃。所得介孔TiO2纤维比表面积为127.7m2/g,最可几孔径为7.3nm,具有极高的热稳定性及抗晶型转变能力,反应时间75min时活性艳红X-3B降解率为99.3%。     

电炉炼锡废渣制备白炭黑

以电炉炼锡废渣为原料,经过酸浸处理去除Fe元素后,再用沉淀法制备白炭黑。探索了制备白炭黑的最佳工艺条件。分别采用XRD、FTIR、SEM及粒度分析等技术表征了白炭黑产品的物相、形貌、粒径及其分布。实验结果表明,制备白炭黑的最佳工艺条件为:Na OH溶液浓度8 mol/L、固液比1∶10(干燥废渣质量与Na OH溶液体积比,g/m L)、搅拌速率300 r/min、反应温度90℃、反应时间6 h。在最佳工艺条件下制备的白炭黑产品中Si O2质量分数达92.8%。表征结果显示,所制备的白炭黑产品是由近似球形的颗粒聚集而成的无定形非晶体水合二氧化硅,粒径为95~200 nm的颗粒约占87.5%。     

碱性氧化焙烧回收含铬污泥中的铬

采用碱性氧化焙烧工艺回收含铬污泥中的铬,以浸出渣作为焙烧填料,最佳工艺条件为：含铬污泥加入量10g,浸出渣加入量8g,焙烧温度700℃,焙烧时间40min,n（Cr2O3）：n（NaNO3）：n（Na2CO3）：n（NaOH）=1：2：3．5：10。在此条件下,碱性氧化焙烧工艺铬浸出率高达98％以上。     

用CO_2改性碱渣废水强化炼油废水的硝化效能

针对炼油废水缺乏碱度而硝化效能受限问题,以CO_2曝气处理后的改性碱渣废水为碱度补充剂,按一定配比加入炼油废水好氧阶段以强化硝化效能。实验结果表明:经流量为1 L/min的CO_2连续曝气处理5 h后,碱渣废水p H可降至7.2~7.8,钙元素质量浓度可降低90.65%,并去除了部分汞、砷等有毒重金属;将该改性碱渣废水以1∶99的体积比加入炼油废水并进行生化处理,COD去除率可达90.2%;相较于未补充碱渣的炼油废水,出水ρ(NO3--N)提高25%~30%,硝化细菌菌群密度增加52%,污泥絮体形态结构未发生改变。     

化学还原法回收含银电镀废液中的银

以Na2S2O4为还原剂,采用化学还原法回收某电镀厂含银电镀废液中的银。实验结果表明,在n(Na2S2O4)∶n(Ag+)=2.5、反应温度35℃、废水pH7.5、搅拌速率300r/min的条件下,Ag+回收率达到99.92%。对回收的银粉进行X射线衍射和扫描电子显微镜分析,分析结果表明回收的银粉纯度较高,成球形。     

化学沉淀法去除焦化废水中的氨氮

采用化学沉淀剂MgCl2 ·6H2 O和Na2 HPO4·12H2 O(或MgHPO4·3H2 O)与焦化废水中的NH+ 4 反应 ,生成磷酸铵镁沉淀。探讨了不同操作条件对氨氮去除率的影响。在pH为 8 5～ 9 5的条件下 ,投加的药剂Mg2 + ∶NH+ 4 ∶PO3 -4(摩尔比 )为 1 4∶1∶0 8时 ,废水氨氮的去除率达 99%以上 ,出水氨氮的质量浓度由 2 0 0 0mg/L降至 15mg/L。     

炼油废水污泥脱水工艺条件的优化

采用化学除油降黏—污泥调理—离心脱水工艺处理某炼油厂废水处理系统的混合污泥,并对工艺条件进行优化。实验结果表明,最佳的工艺条件为:化学除油降黏阶段处理体系的pH=4,反应温度35℃,H2O2加入量2 g/L,m(H2O2)∶m(Fe2+)=4,反应时间60 min;污泥调理反应阶段的CaO加入量7.0 g/L;离心脱水阶段在分离因数为1 558时脱水5 min。在此条件下,得到的泥饼的含水率为70.0%~75.0%(w),含油率小于2%(w),污泥比阻约为3.0×107 s2/g。     

乙烯废碱液的ZnO沉淀法脱硫过程优化与动力学研究

采用ZnO沉淀法对乙烯废碱液进行脱硫,通过正交实验确定的最佳工艺条件为:反应温度80～85℃,n(ZnO)∶n(Na2S)=0.9,反应时间150min。在上述最佳工艺条件下,废碱液脱硫率和ZnS质量分数可分别达88%和95%以上。动力学研究结果表明,ZnO沉淀法的脱硫速率可用简化的Na2S浓度的幂函数模型描述,该模型的Na2S转化率计算值与实验值吻合良好。     

并流加料沉淀法处理含铜锌废水同时形成类水滑石污泥

分别采用传统沉淀法和并流加料沉淀法处理含铜锌废水,考察了废水进样速率、废水pH、搅拌速率对重金属离子残留质量浓度的影响。采用FTIR、XRD和SEM表征了所得污泥的物相和形貌。实验结果表明:并流加料沉淀法所得滤液中Zn~(2+)、Cu~(2+)和Al3+的质量浓度远低于传统沉淀法;在废水进样速率1.0 mL/min、废水pH 9、搅拌速率500 r/min的最佳工艺条件下,滤液中Cu~(2+)和Zn~(2+)基本没有残留,Al3+质量浓度仅为0.2 mg/L,达到工业排放标准;所得污泥结晶度良好,为类水滑石Cu_3Zn_3Al_2(OH)_(16)CO_3·4H_2O(PDF#37-0629)结构。     

气浮—磁分离工艺处理含油废水

采用气浮—磁分离工艺处理某石化企业的含油废水,重点考察了磁分离单元的工艺条件对除油率的影响。实验结果表明磁分离单元的最佳工艺条件为:絮凝剂聚合氯化铝加入量25 mg/L,磁种加入量100 mg/L,磁场强度40 mT,搅拌条件为先以150 r/min的转速搅拌2 min,再以50 r/min的转速搅拌5 min。在最佳工艺条件下进行气浮—磁分离工艺除油实验,在进水油质量浓度平均为29.5 mg/L时,气浮单元出水油质量浓度平均为8.5 mg/L,除油率平均为71.1%;磁分离单元出水油质量浓度平均为4.7 mg/L,除油率平均为44.1%;总除油率平均为83.8%。     

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.     

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.     

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。     

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.     

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.     

Characterization of air emissions and residual ash from open burning of electronic wastes during simulated rudimentary recycling operations

Air emissions and residual ash samples were collected and analyzed during experiments of open, uncontrolled combustion of electronic waste (e-waste), simulating practices associated with rudimentary e-waste recycling operations. Circuit boards and insulated wires were handled separately to simulate processes associated with metal recovery. The average emissions of polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDFs) were 92 ng toxic equivalency (TEQ)/kg [n = 2, relative standard deviation (RSD) = 98%] and 11 900 ng TEQ/kg (n = 3, RSD = 50%) of the initial mass of the circuit boards and insulated wire, respectively. The value for the insulated wire is about 100 times higher than that for backyard barrel burning of domestic waste. The emission concentrations of polybrominated dibenzodioxins and dibenzofurans (PBDD/PBDFs) from the combustion of circuit boards were 100 times higher than for their polychlorinated counterparts. Particulate matter (PM) sampling of the fly ash emissions indicated PM emission factors of approximately 15 and 17 g/kg of the initial mass for the circuit boards and insulated wire, respectively. Fly ash samples from both types of e-waste contained considerable amounts of several metallic elements and halogens; lead concentrations were more than 200 times the United States regulatory limits for municipal waste combustors and 20 times those for secondary lead smelters. Leaching tests of the residual bottom ash showed that lead concentrations exceeded U.S. Environmental Protection Agency landfill limits, designating this ash as a hazardous waste.     

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.     

Solubility and Potential Mobility of Heavy Metals in Two Contaminated Urban Soils from Stockholm,Sweden

The solubility and potential mobility of heavy metals (Cd, Cu,Hg, Pb and Zn) in two urban soils were studied by sequential andleaching extractions (rainwater). Compared to rural (arable) soils on similar parent material, the urban soils were highlycontaminated with Hg and Pb and to a lesser extent also with Cd,Cu and Zn. Metal concentrations in rainwater leachates were related to sequential extractions and metal levels reported fromStockholm groundwater. Cadmium and Zn in the soils were mainly recovered in easily extractable fractions, whereas Cu and Pb were complex bound. Concentrations of Pb in the residual fractionwere between two- and eightfold those in arable soils, indicatingthat the sequential extraction scheme did not reflect the solidphases affected by anthropogenic inputs. Cadmium and Zn conc. inthe rainwater leachates were within the range detected in Stockholm groundwater, while Cu and Pb conc. were higher, whichsuggests that Cu and Pb released from the surface soil were immobilised in deeper soil layers. In a soil highly contaminatedwith Hg, the Hg conc. in the leachate was above the median concentration, but still 50 times lower than the max concentration found in groundwater, indicating the possibilityof other sources. In conclusion, it proved difficult to quantitatively predict the mobility of metals in soils by sequential extractions.     

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.     

Biodegradation of Injection Molded Starch-Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Blends in a Natural Compost Environment

Injection molded specimens were prepared by blending poly (hydroxybutyrate-co-valerate) (PHBV) with cornstarch. Blended formulations incorporated 30% or 50% starch in the presence or absence of poly-(ethylene oxide) (PEO), which enhances the adherence of starch granules to PHBV. These formulations were evaluated for their biodegradability in natural compost by measuring changes in physical and chemical properties over a period of 125 days. The degradation of plastic material, as evidenced by weight loss and deterioration in tensile properties, correlated with the amount of starch present in the blends (neat PHBV < 30% starch < 50% starch). Incorporation of PEO into starch-PHBV blends had little or no effect on the rate of weight loss. Starch in blends degraded faster than PHBV and it accelerated PHBV degradation. Also, PHBV did not retard starch degradation. After 125 days of exposure to compost, neat PHBV lost 7% of its weight (0.056% weight loss/day), while the PHBV component of a 50% starch blend lost 41% of its weight (0.328% weight loss/day). PHB and PHV moieties within the copolymer degraded at similar rates, regardless of the presence of starch, as determined by ¹H-NMR spectroscopy. GPC analyses revealed that, while the number average molecular weight (Mn) of PHBV in all exposed samples decreased, there was no significant difference in this decrease between neat PHBV as opposed to PHBV blended with starch. SEM showed homogeneously distributed starch granules embedded in a PHBV matrix, typical of a filler material. Starch granules were rapidly depleted during exposure to compost, increasing the surface area of the PHBV matrix.