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。     

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.     

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.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

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.     

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.     

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.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.     

Biochemical interaction of six op delayed neurotoxicants with several neurotargets

Abstract

Five organophosphorous insecticides: Leptophos, EPN, Cyano‐fenphos, trichloronate and salithion proved to cause irreversible ataxia not only to chicken but also to mice and sheep. TOCP was included as a reference. Cyanofenphos blocked the catecholamine B‐receptor binding activity with ³H‐norepinephrine at a level similar to that of the specific inhibitor propranolol in the mouse heart preparation. In the lamb heart preparation, the B‐receptor was more sensitive to Leptophos, salithion and TOCP than to propranolol. The six compounds and their oxons were screened for their in‐vitro inhibition to monamine oxidase (MAO), acetyl cholinesterase (AChE) and neurotoxic esterase (NTE) in the brain of either mouse, lamb or chicken. It is believed that their AChE inhibition stands for their acute toxicity, while NTE inhibition is responsible for their paralytic ataxia.     

Phytoextraction of lead-contaminated soil using vetivergrass (<Emphasis Type="Italic">Vetiveria zizanioides</Emphasis> L.), cogongrass (<Emphasis Type="Italic">Imperata cylindrica</Emphasis> L.) and carabaograss (<Emphasis Type="Italic">Paspalum conjugatum</Emphasis> L.)

Background, Aims and Scope The global problem concerning contamination of the environment as a consequence of human activities is increasing. Most of the environmental contaminants are chemical by-products and heavy metals such as lead (Pb). Lead released into the environment makes its way into the air, soil and water. Lead contributes to a variety of health effects such as decline in mental, cognitive and physical health of the individual. An alternative way of reducing Pb concentration from the soil is through phytoremediation. Phytoremediation is an alternative method that uses plants to clean up a contaminated area. The objectives of this study were: (1) to determine the survival rate and vegetative characteristics of three grass species such as vetivergrass, cogongrass and carabaograss grown in soils with different Pb levels; and (2) to determine and compare the ability of the three grass species as potential phytoremediators in terms of Pb accumulation by plants. Methods The three test plants: vetivergrass (Vetiveria zizanioides L.); cogongrass (Imperata cylindrica L.); and carabaograss (Paspalum conjugatum L.) were grown in individual plastic bags containing soils with 75 mg kg⁻¹ (37.5 kg ha⁻¹) and 150 mg kg⁻¹ (75 kg ha⁻¹) of Pb, respectively. The Pb contents of the test plants and the soil were analyzed before and after experimental treatments using an atomic absorption spectrophotometer. This study was laid out following a 3 × 2 factorial experiment in a completely randomized design. Results On the vegetative characteristics of the test plants, vetivergrass registered the highest whole plant dry matter weight (33.85–39.39 Mg ha⁻¹). Carabaograss had the lowest herbage mass production of 4.12 Mg ha⁻¹ and 5.72 Mg ha⁻¹ from soils added with 75 and 150 mg Pb kg⁻¹, respectively. Vetivergrass also had the highest percent plant survival which meant it best tolerated the Pb contamination in soils. Vetivergrass registered the highest rate of Pb absorption (10.16 ± 2.81 mg kg⁻¹). This was followed by cogongrass (2.34 ± 0.52 mg kg⁻¹) and carabaograss with a mean Pb level of 0.49 ± 0.56 mg kg⁻¹. Levels of Pb among the three grasses (shoots + roots) did not vary significantly with the amount of Pb added (75 and 150 mg kg⁻¹) to the soil. Discussion Vetivergrass yielded the highest biomass; it also has the greatest amount of Pb absorbed (roots + shoots). This can be attributed to the highly extensive root system of vetivergrass with the presence of an enormous amount of root hairs. Extensive root system denotes more contact to nutrients in soils, therefore more likelihood of nutrient absorption and Pb uptake. The efficiency of plants as phytoremediators could be correlated with the plants’ total biomass. This implies that the higher the biomass, the greater the Pb uptake. Plants characteristically exhibit remarkable capacity to absorb what they need and exclude what they do not need. Some plants utilize exclusion mechanisms, where there is a reduced uptake by the roots or a restricted transport of the metals from root to shoots. Combination of high metal accumulation and high biomass production results in the most metal removal from the soil. Conclusions The present study indicated that vetivergrass possessed many beneficial characteristics to uptake Pb from contaminated soil. It was the most tolerant and could grow in soil contaminated with high Pb concentration. Cogongrass and carabaograss are also potential phytoremediators since they can absorb small amount of Pb in soils, although cogongrass is more tolerant to Pb-contaminated soil compared with carabaograss. The important implication of our findings is that vetivergrass can be used for phytoextraction on sites contaminated with high levels of heavy metals; particularly Pb. Recommendations and Perspectives High levels of Pb in localized areas are still a concern especially in urban areas with high levels of traffic, near Pb smelters, battery plants, or industrial facilities that burn fuel ending up in water and soils. The grasses used in the study, and particularly vetivergrass, can be used to phytoremediate urban soil with various contaminations by planting these grasses in lawns and public parks. ESS-Submission Editor: Dr. Willie Peijnenburg (wjgm.peijnenburg@rivm.nl)