纳米TiO2光催化氧化去除水中痕量双氯芬酸的研究

以TiCl4为前驱体,采用水解法经不同温度煅烧制备了具有不同理化性能的纳米TiO2光催化剂。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、物理吸附仪、紫外—可见光漫反射吸收光谱(UV-Vis DRS)等手段对纳米TiO2的晶相结构、粒径、孔径分布以及禁带宽度等进行了表征。以蒸馏水配制的双氯芬酸溶液为目标物,进行了纳米TiO2光催化氧化去除双氯芬酸的活性测试,研究了纳米TiO2的理化性能与光催化氧化活性之间的关系。结果表明,经400℃煅烧制得的纳米TiO2样品具有最高的光催化氧化活性,其在紫外光照射60min下对双氯芬酸的去除率为98%左右,比单独紫外光照射高出85百分点。纳米TiO2光催化氧化去除双氯芬酸的反应近似一级反应动力学模型,其中经400℃煅烧制得的纳米TiO2光催化氧化去除双氯芬酸的表观反应速率常数为0.054 54min-1,是普通商用TiO2的2倍左右,与德国Degussa P-25TiO2的光催化氧化活性最相近。     

焦炭负载改性纳米TiO2阳光催化降解染料模拟废水的初步研究

以焦炭为载体,Na2SiO3为粘结剂,制备了负载型铁改性纳米TiO2光催化剂,并研究了该催化剂在太阳光照射下降解亚甲基兰染料废水的效果,通过正交和单因素优化试验,探讨了影响染料废水降解效果的主要因素,研究结果表明,影响降解因素的大小次序是:煅烧时间＞铁掺杂量＞Na2SiO3质量百分比＞煅烧温度.本光催化剂制备的最佳制备条件是:以20%的Na2SiO3溶液为粘结剂,掺杂2%的Fe,400℃煅烧温度下煅烧3 h.以太阳光为光源,亚甲基兰染料废水的降解率可达到87.1%.     

焦炭负载改性纳米TiO2阳光催化降解染料模拟废水的初步研究

以焦炭为载体，Na2SiO3为粘结剂，制备了负载型铁改性纳米TiO3光催化剂，并研究了该催化剂在太阳光照射下降解亚甲基兰染料废水的效果，通过正交和单因素优化试验，探讨了影响染料废水降解效果的主要因素，研究结果表明，影响降解因素的大小次序是：煅烧时间〉铁掺杂量〉Na2SiO3质量百分比〉煅烧温度。本光催化剂制备的最佳制备条件是：以20％的Na2SiO3溶液为粘结剂，掺杂2％的Fe，400℃煅烧温度下煅烧3h。以太阳光为光源，亚甲基兰染料废水的降解率可达到87．1％。     

Mn掺杂TiO_2纳米材料的制备及可见光催化降解水中腐殖酸

以钛酸正丁酯为钛源,MnSO_4为锰源,采用溶胶-凝胶法,制备Mn-TiO_2光催化剂。经扫描电镜(SEM)、X射线粉末衍射(XRD)、光电子能谱(XPS)、紫外-可见漫反射(UV-vis DRS)等手段进行表征,同时通过对水中腐殖酸(HA)的降解实验,探讨不同煅烧温度下制备Mn-TiO_2的可见光催化性能。结果表明,在350~500℃煅烧下制备的Mn-TiO_2均为锐钛矿型,其光响应范围可不同程度拓宽到可见光区;煅烧温度是影响可见光催化活性的重要因素,过高或过低都不利,400℃煅烧制备的Mn-TiO_2催化剂可见光活性最佳;投加此催化剂1 g·L~(-1),对初始浓度5 mg·L~(-1)的HA水溶液可见光反应240min后,降解率达75.1%,且光催化反应过程符合准一级动力学,其表观速率常数为0.006 6 min~(-1)。     

煅烧氛围对N-TiO2可见光催化性能的影响

以钛酸丁酯为钛源,以尿素为氮源,采用溶胶-凝胶法制备TiO_2中间体,分别在空气和氮气氛围下煅烧制得N-TiO_2光催化剂,采用XRD、TEM、BET、UV-vis DRS、FT-IR、EDS和XPS等手段进行表征,以甲基橙溶液为目标污染物考察了其可见光催化性能。结果表明:N-TiO_2(N2)较N-TiO_2(空气)具有晶粒尺寸小、可见光响应性强和有效掺氮量高等优势;可见光持续光照240 min时,N-TiO_2(N2)对甲基橙溶液的光降解率达86.2%,较N-TiO_2(空气)提高近20%;N-TiO_2对MO的可见光降解反应符合假一级动力学方程,且N-TiO_2(N2)的表观速率常数是N-TiO_2(空气)的近5倍。N-TiO_2制备过程中采用N_2氛围下煅烧处理较空气氛围更有利于N元素的有效掺入,相应地,可见光催化活性更高。     

大尺寸大孔径TiO2/SiO2光催化剂的制备及甲醛去除研究

以大孔径SiO2为载体，通过钛酸丁酯溶液的浸渍、原位水解以及高温煅烧制备出大尺寸、大孔径的TiO2/SiO2光催化剂。利用自制空气净化装置对室内甲醛的清除进行研究，分别考察了TiO2的百分含量、紫外光光强、温度、湿度和空气流量等不同条件下TiO2/SiO2光催化剂对除去甲醛效率的影响。结果表明，反应温度从10～50℃依...     

多孔MoS2/g-C3N4材料对水环境中四环素的降解

通过浸渍-高温煅烧法制备多孔MoS_2/g-C_3N_4光催化剂,采用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、N2吸附-解吸、紫外-可见光(UV-vis)漫反射吸收光谱对材料进行表征;并在可见光照射下,对四环素(TC)进行光催化降解。结果表明,催化剂量为2.0 g·L-1、pH为5.0时,对TC的去除效果最好,可见光照射180 min,MoS_2/g-C_3N_4(1.0%-MC)复合材料对TC的降解率可达80.6%。反应完成后,复合材料循环利用5次,其降解效率仍保持在70.0%以上。浸渍-高温煅烧法所制备的MoS_2/g-C_3N_4光催化剂具有良好的应用前景。     

Pd/N共掺杂TiO_2的制备及其光催化降解苯酚的研究

将纳米管钛酸浸入含尿素和金属(Pd)硝酸盐的乙醇溶液中,乙醇超声挥发后所得样品先在空气气氛、600℃下煅烧,再在H2气氛、400℃下热还原制备得到Pd/N共掺杂TiO2光催化剂(Pd/N-TiO2)。利用光电子能谱(XPS)仪研究了催化剂表面N、Pd元素的化学态。结果表明,N元素以Ti—O—N形式存在,Pd元素以单质金属状态存在。考察了Pd/N-TiO2的紫外光光催化降解苯酚的活性,与单纯TiO2光催化剂和N掺杂TiO2光催化剂相比,Pd/N-TiO2活性明显提高。研究了催化剂用量、苯酚初始浓度和pH、O2流量以及外加双氧水等条件对紫外光光催化降解苯酚的活性的影响,得到光催化降解苯酚的最佳工艺条件:苯酚初始质量浓度为120mg/L,催化剂用量为0.10g/L,苯酚溶液初始pH为8,O2流量为80mL/min,加入适量双氧水。     

亚甲基蓝表面修饰纳米TiO2降解造纸废水动力学

以亚甲基蓝(MB)作为表面修饰剂,采用简单的化学吸附法制备亚甲基蓝表面修饰的纳米TiO2光催化剂(TiO2-MB)。经表面修饰后,TiO2-MB光催化剂波长响应范围红移至可见光区575 nm处。探讨了光催化剂量、光照时间和溶液pH值对TiO2-MB光催化降解造纸废水的影响;研究了纳米TiO2-MB对造纸废水的暗吸附规律和光降解性能。结果表明:纳米TiO2-MB对造纸废水的吸附规律都较好地符合Langmuir和Freundlich吸附等温模型,属于吸热反应;光催化降解动力学符合Langmuir-Hinshelwood动力学模型。在160 W高压汞灯光照80 min,3.0 g/L纳米TiO2-MB光催化降解pH=2.0的造纸废水(COD:2 069.8 mg/L),COD去除率可达94.7%,处理效果远高于避光条件下。光催化剂经8次使用仍具有较高的催化活性。     

Fe/Si/TiO2三元复合光催化剂的性能研究

用溶胶-凝胶法制备了Fe/Si/TiO2三元复合光催化剂,利用X射线衍射(XRD)和紫外-可见漫反射光谱(DRS)对样品进行了分析表征,并以甲基橙为模拟污染物,考察了其光催化活性.结果表明,Fe/Si/TiO2三元复合光催化剂与TiO2相比,光催化活性明显提高;当煅烧温度为900℃、添加Fe的摩尔分数为0.050%时,光催化活性最佳.     

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.     

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.     

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.     

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.     

Radionuclides and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

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.