改性粉煤灰处理低浓度含磷废水的研究

以酸改性粉煤灰为吸附剂,处理低质量浓度(1 mg/L左右)磷酸盐溶液,探讨了改性剂的种类、改性剂用量、吸附剂用量、反应时间、pH以及温度对除磷效果的影响.结果表明:(1)经过酸改性后粉煤灰的磷去除率显著提高,而且硫酸改性粉煤灰的除磷效果更好,磷去除率最高可达97.68％.(2)最佳条件:选择硫酸用量为5 mL/g进行改性,硫酸改性粉煤灰投加量为2.0g,反应时间为60 min,pH为7.2～10.8,温度为25℃(即室温).(3)改性粉煤灰对磷的吸附更符合Freundlich吸附等温模型,既有物理吸附,也有化学吸附,并以Ca、Mg氧化物与磷形成磷的沉淀物为主.     

纳米零价铁颗粒除磷反应机理

从溶液化学与固相表征两方面对纳米零价铁(NZVI)去除水中磷酸根(PO3-4)的机理进行初步探究。分别研究不同初始p H值、溶解氧(DO)对NZVI除磷效果的影响,结果表明,酸性环境(p H为3.0~7.0)有利于NZVI除磷,且初始p H值越低,磷去除率越高;好氧环境较厌氧环境更利于磷的去除,DO8.0 mg/L时对磷酸根的去除率是厌氧条件(DO0.1 mg/L)下的2倍。采用Na OH对反应后含磷NZVI进行解析,发现磷解析率不到30%,说明吸附并非NZVI除磷惟一作用机理。微米铁、NZVI和Ca(OH)2等7种不同去除材料中以Ca(OH)2的共沉淀作用去除率最大(99.9%),NZVI次之(87.2%),表明NZVI除磷机理中还存在共沉淀作用。采用多种固相表征手段对NZVI除磷前后进行分析:扫描电子显微镜(SEM)显示反应后出现不规则颗粒;X射线衍射(XRD)表明Fe3(PO4)2是主要反应产物;X射线光电子能谱(XPS)分析未发现磷被还原成低价态。研究表明,NZVI可有效去除水中磷酸根,主要去除机理包括:NZVI对磷酸根的吸附作用、NZVI在水中腐蚀产生的Fe2+离子对磷酸根的化学沉淀作用及铁氢氧化物与磷酸根的共沉淀作用。     

硅锰复合物的水热合成及对水中Cu~(2+)的吸附

为了提高吸附剂在低p H条件下去除水中重金属离子的效率,通过水热法合成了一种硅锰复合材料。利用N2-吸附脱附、透射电子显微镜(TEM)以及X射线衍射(XRD)技术对制备的材料进行了表征;并将其用于吸附水中的Cu~(2+),研究了Si O2掺杂量、溶液p H值、初始Cu~(2+)浓度以及吸附时间对吸附效果的影响。结果表明:与纯δ-Mn O2相比,当Si O2含量为7.5%~15%,硅锰复合物对Cu~(2+)的吸附量受溶液p H影响较小,在溶液p H=2~4范围内有更高的Cu~(2+)吸附量;等温吸附曲线符合Langmuir等温吸附模型,计算饱和吸附量为84.68~71.12 mg,与实验值十分接近。     

铁负载阴离子交换树脂高效除磷研究

针对污水处理生化出水高磷酸盐浓度对水体富营养化影响的问题,采用阴离子交换树脂(AER)为基质材料,利用树脂上—NH2官能团中的N原子与Fe3+发生配位聚合,制备了除磷聚合配位交换吸附剂(Fe—PLE)。并采用Langmuir和Freundlich等温吸附方程对Fe—PLE和原AER进行了比较,发现Fe—PLE更加趋向化学吸附类型,且Fe—PLE最大吸附容量达到93.05 mg/g,比AER提高了47.98%。通过SEM、EDS、FT-IR及TGA对吸附前后Fe—PLE和AER的表征比较,认为通过配位作用形成Fe—O配位键是Fe—PLE的可溶性无机磷吸附效率提高的主要原因。通过静态吸附实验考察了吸附时间、p H和竞争性阴离子对AER和Fe—PLE吸附的影响,结果显示,Fe—PLE吸附平衡时间为1.5 h,比AER稍高;2种吸附填料都在p H 7.0时效率最高,AER的磷吸附效率对p H较为敏感,Fe—PLE能够在相对较宽的p H范围内保持高去除率;竞争性阴离子对AER磷吸附的负面影响较大,而Fe—PLE依靠其Fe—O的配位作用具有一定的抗干扰能力。通过4次循环再生实验,Fe—PLE表现出良好再生能力的同时磷有较高的回收利用率。     

铁屑粉煤灰组合处理含磷废水

实验研究了铁屑粉煤灰组合处理含磷废水的除磷效果.通过单因素实验,考查了铁屑粉煤灰质量比、反应时间、pH值和投加量对除磷效果的影响.实验结果表明,该法除磷的最优条件为铁屑和粉煤灰的质量比为2∶1,反应时间为20 min,pH值为6,投加量为20 g/L.在最优实验条件下磷的去除率达到了97.5％.对比了该法和粉煤灰吸附法与传统铁屑法的除磷效果.与单一粉煤灰吸附法和传统铁屑法除磷的结果相比较,铁屑粉煤灰组合除磷的方法具有明显优势.     

水铁矿吸附磷酸根的影响因素

为了修复水体富营养化,选取了人工合成的水铁矿作为除磷吸附剂。通过批量实验研究了震荡速度、吸附时间、吸附剂投加量、溶液初始p H、含磷初始浓度、反应温度和共存离子等因素对吸附作用的影响。结果表明:水铁矿的吸附具有快速吸附,缓慢平衡的特点;随着投加量的增加,溶液中磷酸根的去除率逐渐增加;溶液初始p H在酸性条件下,溶液中磷酸根的去除率最好;在室温25℃下,水铁矿对不同浓度的磷酸根溶液均具有很好的吸附效果;溶液共存离子的存在对磷酸根去除率有一定影响,HCO_3~-的影响最大。     

粉煤灰碎砖颗粒除磷实验研究

磷含量过高会导致水体富营养化。人工湿地除磷简单经济,但常用填料砾石除磷能力有限。通过等温吸附实验和人工湿地模型实验研究粉煤灰碎砖颗粒的除磷效果,实验结果表明,Langmuir和Freundlich吸附方程可较好地描述吸附过程,粒径为4～6 mm的粉煤灰碎砖颗粒对磷素的理论饱和吸附量为21 277 mg/kg。当初始溶液...     

掺杂改性对Mn-Ce/TiO_2低温SCR催化剂性能的影响

分别掺杂十六烷基三甲基溴化铵(CTAB)、Al_2O_3和Si O_2对Mn-Ce/Ti O_2催化剂进行改性,并运用XRD、BET和SEM对改性前后的催化剂进行表征。结果表明,掺杂CTAB改性效果最为明显,在140℃时NOx去除率即达到84%。掺杂Al2O3也有一定的优化效果,而掺杂Si O_2改性效果不明显。BET表征显示,CTAB能明显增大催化剂的比表面积和总孔容。XRD和SEM表征发现,掺杂CTAB未改变催化剂晶相结构和表面形态。     

UV/Fenton氧化处理PVA溶液

为了对PVA(聚乙烯醇)溶液中PVA去除进行研究,采用UV/Fenton氧化技术氧化处理PVA溶液。探究了UV/Fenton氧化PVA溶液的影响因素,主要研究了反应时间、初始p H、H2O2/COD和H2O2/Fe2+,获得了各个因素对PVA溶液COD去除率的影响规律以及PVA溶液经处理后的B/C(BOD5/COD)变化规律。实验表明,随着H2O2/COD投加比的增加,COD去除率不断增加,B/C呈现先增加后减少的现象;随初始p H的增加,COD去除率以及B/C均呈现先增加后减少的现象;随着H2O2/Fe2+不断增加,COD去除率以及B/C均呈现先增加后减少的现象;随反应时间的增加,COD去除率以及B/C均增加之后趋于稳定。当H2O2/COD=1.5,p H=4,H2O2/Fe2+物质的量之比为10,T=30 min时COD去除率效果比较好,经过处理之后溶液的B/C由0.1增至0.6,可生化性提高,为后续生物处理创造条件。     

改性矿化垃圾对渗滤液生化出水中COD和氨氮的吸附

用矿化垃圾作为吸附剂吸附处理生化后的垃圾渗滤液,利用单因素变量法研究了改性温度、p H、吸附剂投加量和反应时间对吸附效果的影响,并采用红外光谱和电镜扫描对矿化垃圾进行表征。结果表明:矿化垃圾改性温度为700℃,水样p H值为9,吸附剂用量为60 g/L,反应时间为10 h时,COD和氨氮去除率分别达到58.38%和79.77%,平衡吸附量分别为11.68 mg/g和1.58 mg/g;动力学数据拟合COD和氨氮吸附过程均符合拟二级动力学方程即吸附速率被化学吸附所控制;等温方程拟合表明,矿化垃圾对COD和氨氮的吸附分别属于多层吸附和单层吸附;红外光谱分析结果显示,吸附过程中OH、C=O和C—O 3种基团起主要作用;电镜扫描结果显示,矿化垃圾改性前、后和吸附前、后内部结构均发生变化。     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

Knowledge transfer initiative between molecular biologists and environmental researchers and regulators

A Natural Environment Research Council (NERC) funded Knowledge Transfer (KT) workshop was held in the United Kingdom (UK) to identify the needs and opportunities in the application of molecular biology and ‘omics’ techniques to environmental monitoring and risk assessment. Attendees highlighted a lack of effective communication between end-users and researchers as well as difficulties with data interpretation as reasons behind the slow uptake of molecular biology and omics techniques. A number of promising areas in which new techniques could be implemented at a practical level in the very near future were identified, thereby raising the profile of these recent technologies and providing vital proof of concept work. Molecular taxonomy, bacterial source tracking and pre-screening of chemicals for potential toxicities were all viewed as areas in which omics and molecular techniques could have immediate value, with the aim of reducing cost, increasing efficiency and providing more comprehensive data of improved quality.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine～ amitrole～ simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K_ow) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.