TiO2/SiO2/γ-Fe2O3的表征及其光催化降解染料废水

以γ-Fe2O3为磁性核心,通过溶胶-凝胶法制备出三层结构的复合光催化剂TiO2/SiO2/γ-Fe2O3.通过X射线衍射、扫描电镜、透射电镜、振动样品磁强计和紫外-可见分光光谱分析进行表征.SiO2包覆膜可以减弱内层γ-Fe2O3对光催化效果的不利影响,有效地阻隔高温时γ-Fe2O3磁核与TiO2之间的熔结.以亚甲基...     

混合菌降解模拟聚乙烯醇(PVA)废水性能研究

从纺织废水污泥中筛选出了具有PVA降解能力的混合菌B07.通过正交实验得出其降解PVA的最佳条件:温度为35℃,pH为7,氮源为牛肉膏.在此条件下,B07对PVA1799模拟废水处理96 h时COD的去除率达64%.同时考察了PVA聚合度和醇解度对其降解性能的影响,结果表明,PVA聚合度越大,醇解度越高,其降解效率越差...     

洋河水库水华优势种演替的原因分析

针对鱼腥藻和微囊藻这2种洋河水库水华暴发常见优势藻,研究了其在不同温度及硝态氮浓度下的生长情况。结果表明,在温度15～25℃,硝态氮浓度0.05～10 mg/L的范围内,温度的升高、硝态氮浓度的增加,对鱼腥藻的生长影响不明显,却能够明显地促进微囊藻的增长。15℃或0.05 mg/L硝氮条件下,鱼腥藻的比增长速率高于微囊藻,而25℃或10 mg/L硝氮时,微囊藻的比增长速率分别达到了0.425 d-1和0.466 d-1,明显超过鱼腥藻。洋河水库逐年升高的硝态氮浓度以及夏秋季节比较适宜的温度促进了微囊藻的增长,可能是洋河水库水华优势种由螺旋鱼腥藻向微囊藻转变的重要因素。     

ZnO的制备及其光催化性能

分别采用草酸沉淀法和柠檬酸络合法制备了纤锌矿型ZnO,通过X射线粉末衍射仪、扫描电子显微镜和透射电子显微镜对ZnO的结构和形貌进行了表征,并研究了所制备的ZnO对溶液中甲基橙的光催化降解性能.实验结果表明:草酸沉淀法制备的ZnO为小颗粒堆积而成的空心类柱状体,柠檬酸络合法制备的ZnO为小球形颗粒;草酸沉淀法制备的ZnO...     

复合型CoO／TiO2光催化剂降解亚甲基蓝动力学研究

以钛酸四丁酯为前驱体,采用溶胶凝胶法,制备了CoO掺杂的TiO2光催化剂。利用X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、紫外可见漫反射（UV—visDRS）对催化剂进行了分析、表征。以中压汞灯为光源,研究了亚甲基蓝（MB）在CoO／TiO2微粒水悬浮液中的降解动力学。结果表明：所制备的催化剂活性组分主要是锐钛矿型的二氧化钛和CoO固溶体,粒径为25～30nm,分布均匀。亚甲基蓝的光催化降解动力学满足一级动力学,在一定的浓度范围内,反应速率常数随初始浓度增大而减少,适当的掺钴量可以有效地提高TiO2光催化活性,其最佳掺杂量重量百分比为0．25％。     

Environmental analysis of groundwater in Mecosta County, Michigan

Groundwater withdrawal has major economic, social, and environmental implications. In Michigan, recent legislative activity has begun to address the issue of groundwater sustainability. However, more hydrologic data are needed to help inform policy and legislation. A study was conducted in Mecosta County, Michigan to: (1) determine if a relationship could be established between land use/land cover and groundwater quality; and (2) develop a conceptual model for the shallow groundwater system of the study region. In general, groundwater quality was good, with below detection levels of E. coli, low total bacterial counts, and relatively low nutrient concentrations. No statistically significant associations were found between the bacterial numbers and either land use or the physical/chemical attributes measured, which may be because the scale of our spatial analysis was too coarse to detect patterns. Finer-scale, localized processes may have a greater influence on microorganism growth and abundance than coarser-scale, regional processes in this area. Our groundwater analysis suggested that shallow groundwater flow paths are generally consistent with regional surface water flow networks, and that shallow groundwater levels in most of the region have fluctuated within 1–2 m over the past 30 years, with no obvious increasing or decreasing trend.     

The use of oxyhalogen in photocatalytic reaction to remove o-chloroaniline in TiO2 dispersion

Photodecay of o-chloroaniline (o-ClA) in various combinations of UV sources, TiO2, and oxyhalogens was investigated. To improve the conventional photocatalytic process by using UV/TiO2, the addition of oxyhalogens (ClO3(-), BrO3(-) and IO3(-)) into UV/TiO2 system was studied and the effect in such addition is very encouraging for all the selected additives. Oxyhalogens are capable of deferring the electron-hole recombination of TiO2 which significantly improved its catalytic performance. The presence of IO3(-) in UV/TiO2 resulted in the fastest o-ClA decay among three oxhalogens at the same dosage. The decay of o-ClA in UV/TiO2/oxyhalogen process is characterized by a two-stage pseudo-kinetics, where a faster initial decay was followed by a retardation state. A mathematics model was successfully established for the prediction of the two-stage decay of o-ClA in UV/TiO2/IO3(-) with any designed [IO3(-)] concentration.     

Removal of phenylurea herbicide monuron via riboflavin-mediated photosensitization

Photodegradation of the phenylurea herbicide monuron by using riboflavin (Rf), a sensitizer, was investigated by varying the doses of monuron and Rf in this work. An enhanced photochemical effect was observed in the process compared with the direct photolysis by using UV irradiation only. The reaction time was greatly shortened from more than 60 min (direct photolysis) to 8-30 min depending on the doses of initial concentration of monuron ([M]0) and Rf. A modified hyperbola model was found to be useful to determine the reaction kinetics and thereafter the performance on the photodegradation of monuron sensitized by Rf. Two measurable characteristic constants (initial decay rate and total removal index) were used to quantify the reaction. The maximum removal difference compared with the direct photolysis and Rf-sensitization was investigated. It was found that the improvement of the process depended on both the [M]0 and the doses of Rf.     

Dacthal and chlorophenoxy herbicides and chlorothalonil fungicide in eggs of osprey (Pandion haliaetus) from the Duwamish-Lake Washington-Puget Sound area of Washington state, USA

Current-use chlorophenoxy herbicides including 2,4-dichlorophenoxyacetic acid, dicamba, triclopyr, dicamba, dimethyl tetrachloroterephthalate (DCPA or dacthal), and the metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and the fungicide, chlorothalonil, were investigated in the eggs of osprey (Pandion haliaetus) that were collected from 15 sites from five study areas Puget Sound/Seattle area of Washington State, USA. DCPA differs from acidic chlorophenoxy herbicides, and is not readily hydrolyzed to free acid or acid metabolites, and thus we developed a new method. Of the 12 chlorophenoxy herbicides and chlorothalonil analyzed only DCPA could be quantified at six of these sites (2.0 to 10.3 pg/g fresh weight). However, higher levels (6.9 to 85.5 pg/g fresh weight) of the unexpected DCPA structural isomer, dimethyl tetrachlorophthalate (diMe-TCP) were quantified in eggs from all sites. diMe-TCP concentrations tended to be higher in eggs from the Everett Harbor area. As diMe-TCP is not an industrial product, and not commercially available, the source of diMe-TCP is unclear. Regardless, these findings indicate that DCPA and diMe-TCP can be accumulated in the food chain of fish-eating osprey, and transferred in ovo to eggs, and thus may be of concern to the health of the developing chick and the general reproductive health of this osprey population.     

Dissipation of carbofuran and carbaryl on Oolong tea during tea bushes, manufacturing and roasting processes

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranol-N-methylcarbamate) and carbaryl (1-naphthyl-N-methylcarbamate) are insecticides widely used in tea plantations. The objective of the present study was to evaluate the dissipation of carbofuran and carbaryl during the growth periods of Oolong tea, processing and roasting. Analysis of the residual insecticides was carried out using high-pressure liquid chromatography with a post-column fluorescence detector. Results showed that in the tea field carbofuran dissipated faster then carbaryl. Manufacturing processes of Oolong tea further reduced the carbofuran and carbaryl contents. The persistence of carbofuran and carbaryl was decreased with increasing roasting temperature. From the results, we conclude that the presence of carbofuran and carbaryl in tea can be reduced by proper field management, manufacturing and roasting processes.