B,N和Ce共掺杂TiO2催化剂光催化活性研究

采用溶胶-凝胶法制备出B,N和Ce共掺杂TiO2光催化剂,并用XRD、SEM等表征了其结构特征。以酸性大红染料溶液的光催化降解为探针反应,考察了制备条件对共掺杂TiO2催化剂活性的影响。结果表明,在400℃,当B,N和Ce的原子比为1∶2∶0.1,焙烧3 h时,光催化剂活性最大,大红染料的降解率达到98%。     

B,N和Ce共掺杂TiO_2催化剂光催化活性研究

采用溶胶-凝胶法制备出B,N和Ce共掺杂TiO2光催化剂,并用XRD、SEM等表征了其结构特征。以酸性大红染料溶液的光催化降解为探针反应,考察了制备条件对共掺杂TiO2催化剂活性的影响。结果表明,在400℃,当B,N和Ce的原子比为1∶2∶0.1,焙烧3 h时,光催化剂活性最大,大红染料的降解率达到98%。     

V/Ce共掺杂TiO2光催化降解甲醛的实验研究

采用溶胶-凝胶法制备了不掺杂、V掺杂、Ce掺杂、V/Ce共掺杂纳米TiO2光催化剂,并将其分别负载于瓷砖上,利用X射线衍射分析（XRD）和扫描电镜分析（SEM）技术对薄膜样品的结构和形貌进行了表征。通过对甲醛的降解实验评价光催化剂的光催化活性。实验结果表明,光催化剂的负载量、共掺杂离子的掺杂量、掺杂配比、煅烧温度影响纳米TiO2的光催化活性。V/Ce共掺杂TiO2光催化剂产生了协同效应,其光催化活性优于纯TiO2和单掺杂TiO2样品。     

V/Ce共掺杂TiO2光催化降解甲醛的实验研究

采用溶胶凝胶法制备了不掺杂、V 掺杂、Ce掺杂、V/Ce共掺杂纳米TiO₂光催化剂，并将其分别负载于瓷砖上，利用X射线衍射分析（XRD）和扫描电镜分析（SEM）技术对薄膜样品的结构和形貌进行了表征。通过对甲醛的降解实验评价光催化剂的光催化活性。实验结果表明，光催化剂的负载量、共掺杂离子的掺杂量、掺杂配比、煅烧温度影响纳米TiO₂的光催化活性。V/Ce共掺杂TiO₂光催化剂产生了协同效应，其光催化活性优于纯TiO₂和单掺杂TiO₂样品。     

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。     

铂铈共掺杂纳米TiO2的制备、表征及光催化性能

以钛酸四丁酯为前驱体，过氧化氢为氧化剂，采用简单易行的低温氧化法制备出晶粒尺寸较小（平均尺寸25nm）的二氧化钛纳米粒子。通过贵金属Pt掺杂TiO2（Pt-TiO2）、稀土元素Ce掺杂TiO2（Ce-TiO2）和Pt、Ce共掺杂TiO2（Pt／Ce-TiO2）的掺杂的方法对二氧化钛进行改性。通过XRD，XPS，TEM，紫外漫反射等表征手段对制备的样品进行表征。通过可见光下降解罗丹明B来测试其光催化活性。实验结果表明，由ce掺杂的TiO2光催化剂对有机污染物的最大降解能力略大于Pt掺杂的TiO2，2种元素进行共同掺杂时对应的TiO2光催化剂降解能力最大。     

CF-TiO2的制备及其在模拟太阳光下的光催化性能

以十六烷基三甲基溴化铵(CTAB)和氟化钠分别为碳源和氟源,采用溶胶-凝胶法制备了CF-TiO2光催化剂,并对其进行了SEM、XRD、N2吸附、XPS、UV-visDRS和PL表征。研究了CF-TiO2在模拟太阳光下光催化降解亚甲基蓝溶液的活性,并讨论了氟掺杂量以及CTAB加入量对催化性能的影响。结果表明,CF-TiO2为锐钛矿型,孔结构丰富、比表面积大,氟碳共掺后使TiO2光催化剂的禁带宽度变窄为2.40 eV,在可见光区吸收增强,有效提高TiO2在模拟太阳光下的光催化活性,而且当n(F/Ti)(氟钛摩尔比)为0.1,加入碳源CTAB量为2 g时,其光催化活性最好。     

Ce掺杂的CNTs-TiO2光催化剂制备及其NO氧化性能

为探讨湿法脱硫后光催化在烟气脱硝方面的应用潜力,采用溶胶-凝胶法制备了金属、非金属掺杂的CNTs-TiO_2复合光催化剂,并在模拟烟气条件下对所得催化剂的NO氧化性能进行了测试与对比筛选,通过SEM、BET、XRD、Raman、XPS、DRS等手段进行表征。结果表明:TiO_2的氧化效率最低,掺杂金属比掺杂非金属的光催化剂的氧化效率略高,复合CNTs的光催化剂的氧化效率明显提高;CNTs-Ce/TiO_2比表面积较大,Ti—O键长最短,从而有利于光生电子沿Ti—O键向CNTs转移,可形成更多的三价铈氧化物,有利于催化剂表面的氧吸附;带隙宽度较低以及极大的紫外光吸光度,在NO氧化性能测试中表现出最优异的脱除效率,与TiO_2相比,效率提升了19%,与CNTs-TiO_2相比,效率提升了13%。进一步分析可知:Ce和CNTs具有协同作用,Ce掺杂TiO_2可以有效抑制光生载流子的结合,从而提高光催化活性;复合CNTs提高了催化剂比表面积并促进了氧空位的形成,从而促进整个催化氧化反应。     

纳米Bi2O3/TiO2复合光催化剂的制备及性能研究

以光催化效果为评价标准，采用超声波作用下水解法制备Bi2O3／TiO2复合光催化剂，考察了水解条件和Bi2O3掺入量等制备条件对复合光催化剂性能的影响。结果表明，与传统制备方法相比，该方法操作简单、快速；当水和乙醇的比例为4：1时所得样品的光催化活性最好；Bi2O3的掺入拓宽了TiO2对光的吸收范围，提高了TiO2的光催化活性，掺入量（Bi2O3）为0．25％复合光催化剂催化活性最高；复合光催化剂对多种水溶性染料均具有较好的处理效果。     

Ag~+-TiO_2/AC复合材料的可见光吸附-光催化协同作用

采用水热法制备活性炭负载银掺杂纳米Ti O2复合材料(Ag+-Ti O2/AC),对样品进行了TEM、XRD、FT-IR和UV-Vis表征,分析了Ag+-Ti O2/AC的微结构、吸收谱特性和掺杂银离子后的半导体带隙变化,并研究了其在可见光下对甲基橙溶液(MO)的降解性能。结果表明,水热法不需要高温处理即可得到高活性的锐钛矿相纳米Ti O2,Ag+掺杂和AC负载均明显提高Ti O2光催化剂的光催化活性,在可见光下光照180 min,0.2 g/L的Ag+-Ti O2/AC对10 mg/L的甲基橙溶液的降解率为73.7%,主要由于存在持续的活性炭局域强吸附-Ti O2光催化降解协同作用,明显提高了甲基橙的降解效率。     

Half-lives of tetra-, penta-, hexa-, hepta-, and octachlorodibenzo-p-dioxin in rats,monkeys, and humans--a critical review

The elimination half-lives (t1/2) in Sprague-Dawley rats for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2, 3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD) were estimated in long-term studies by Schlatter, Poiger and others. Furthermore, there are some published half-lives of TCDD in adult humans. The average half-life of TCDD in adult humans is approximately 2840 days, while in Sprague-Dawley rats the average t1/2 of TCDD is 19 days. The t1/2 of TCDD in humans is about 150 times that of rats. This factor was used to calculate the t1/2 values of the other polychlorinated dibenzo-p-dioxins (PCDDs) in humans from the rat data. Furthermore, the terminal t1/2 values of PCDDs in adult humans were calculated from the regression equation: logt1/2H = 1.34 logt1/2R + 1.25 which was recently established for 50 xenobiotics (t1/2H = terminal half-lives in days for humans, t1/2R = terminal half-lives in days for rats). The following terminal half-lives in adult humans were obtained: 12.6 years for 1,2,3,7,8-PeCDD, 26-45 years for 1,2,3,4,7,8-HxCDD, 80-102 years for 1,2,3,4,6,7,8-HpCDD and ca. 112-132 years for OCDD. These half-lives of PCDDs are critically compared with measured t1/2 values of PCDDs and other persistent organic pollutants in rats, monkeys and humans.     

Phthalic acid esters in grains,vegetables, and fruits: concentration,distribution, composition,bio-accessibility,and dietary exposure

Environmental Science and Pollution Research - Grain, vegetable, and fruit samples were collected from Xi’an City in Northwest China and analyzed for the characteristics, bio-accessibility,...     

Polychlorinated-naphthalenes, -biphenyls, -dibenzo-p-dioxins, -dibenzofurans and p,p'-DDE in bluefin tuna,swordfish, cormorants and barn swallows from Italy

Concentrations of p,p'-DDE, polychlorinated biphenyl congeners (PCBs), polychlorinated-dibenzo-p-dioxins (PCDDs), -dibenzofurans (PCDFs) and -naphthalenes (PCNs) were measured in bluefin tuna, swordfish, common cormorants, and barn swallows collected from Italy. Average concentrations of PCBs in livers of tuna, swordfish, cormorant, and swallows were 930, 745, 1420 and 1230 ng PCBs g-1, w.w. respectively. p,p'-DDE was found in tuna, swordfish, cormorant, and swallow livers at mean concentrations of 82, 135, 166 and 95 ng DDE g-1, w.w. respectively. PCNs were found in all the samples analyzed, although at concentrations less than those reported for biota from the Baltic Sea. PCBs, particularly, non-ortho coplanar PCBs accounted for 80-90% of the total TEQs in tuna and swordfish. Relative contribution of PCDDs/DFs to TEQs was greater in cormorants and swallows compared to that in fishes. PCDD/DF congeners accounted for up to 80 and 45% of the total TEQs in cormorants and swallows, respectively.     

Toxicity, dioxin-like activities, and endocrine effects of DDT metabolites—DDA, DDMU, DDMS, and DDCN

Background, aim, and scope  

2,2-bis(chlorophenyl)-1,1,1-trichloroethane (DDT) metabolites, other than those routinely measured [i.e., 2,2-bis(chlorophenyl)-1,1-dichloroethylene (DDE) and 2,2-bis(chlorophenyl)-1,1-dichloroethane (DDD)], have recently been detected in elevated concentrations not only in the surface water of Teltow Canal, Berlin, but also in sediment samples from Elbe tributaries (e.g., Mulde and Havel/Spree). This was paralleled by recent reports that multiple other metabolites could emerge from the degradation of parent DDT by naturally occurring organisms or by interaction with some heavy metals. Nevertheless, only very few data on the biological activities of these metabolites are available to date. The objective of this communication is to evaluate, for the first time, the cytotoxicity, dioxin-like activity, and estrogenicity of the least-studied DDT metabolites.     

Sorption of lambda-cyhalothrin,cypermethrin, deltamethrin and fenvalerate to quartz,corundum, kaolinite and montmorillonite

Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1–100 μg/l. Sorption to centrifuge tubes used in the batch experiments accounted for 25–60% of total sorption. Net sorption was obtained from total sorption after subtracting the amounts of pyrethroids sorbed to centrifuge tubes used. All isotherms could be fitted by the Freundlich equation with n ranging between 0.9 and 1.1. Bonding affinities per unit surface area decreased in the order: corundum>quartz>montmorillonitekaolinite. A similar sequence as found for the total surface tension of the minerals. All minerals showed the same selectivity order with respect to sorption affinity of the four pyrethroids: lambda-cyhalothrin>deltamethrin>cypermethrin>fenvalerate, which shows that the most hydrophobic compound is sorbed most strongly. Stereochemical properties of the four pyrethroid formulations may also contribute to the selectivity pattern.     

Migration,remittances, livelihood trajectories,and social resilience

We argue that all aspects of demographic change, including migration, impact on the social resilience of individuals and communities, as well as on the sustainability of the underlying resource base. Social resilience is the ability to cope with and adapt to environmental and social change mediated through appropriate institutions. We investigate one aspect of the relationship between demographic change, social resilience, and sustainable development in contemporary coastal Vietnam: the effects of migration and remittances on resource-dependent communities in population source areas. We find, using longitudinal data on livelihood sources, that emigration and remittances have offsetting effects on resilience within an evolving social and political context. Emigration is occurring concurrently with, not driving, the expansion of unsustainable coastal aquaculture. Increasing economic inequality also undermines social resilience. At the same time diversification and increasing income levels are beneficial for resilience.     

Transformations,Lifetimes, and Sources of NO2, HONO,and HNO3 in Indoor Environments

Recent research has demonstrated that nitrogen oxides are transformed to nitrogen acids in indoor environments, and that significant concentrations of nitrous acid are present in indoor air. The purpose of the study reported in this paper has been to investigate the sources, chemical transformations and lifetimes of nitrogen oxides and nitrogen acids under the conditions existing in buildings. An unoccupied single family residence was instrumented for monitoring of NO, NO₂, NO_y, MONO, HNO₃, CO, temperature, relative humidity, and air exchange rate. For some experiments, NO₂ and HONO were injected into the house to determine their removal rates and lifetimes. Other experiments investigated the emissions and transformations of nitrogen species from unvented natural gas appliances. We determined that HONO is formed by both direct emissions from combustion processes and reaction of NO₂ with surfaces present indoors. Equilibrium considerations influence the relative contributions of these two sources to the indoor burden of HONO. We determined that the lifetimes of trace nitrogen species varied in the order NO ~ HONO > NO₂ >HNO₃. The lifetimes with respect to reactive processes are on the order of hours for NO and HONO, about an hour for NO₂, and 30 minutes or less for HNO3. The rapid removal of NO₂ and long lifetime of HONO suggest that HONO may represent a significant fraction of the oxidized nitrogen burden in indoor air.     

Lead,mercury, cadmium,chromium, nickel,copper, zinc,calcium, iron,manganese and chromium (VI) levels in Nigeria and United States of America cement dust

This study was aimed at investigating the relative abundance of heavy metals in cement dust from different cement dust factories in order to predict their possible roles in the severity of cement dust toxicity. The concentrations of total mercury (Hg), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), manganese (Mn), lead (Pb), iron (Fe) and chromium (VI) (Cr (VI)) levels in cement dust and clinker samples from Nigeria and cement dust sample from the United States of America (USA) were determined using graphite furnace atomic absorption (GFAAS), while Zn and Ca were measured by flame atomic absorption spectrophotometry (FAAS), and Cr (VI) by colorimetric method. Total Cu, Ni and Mn were significantly higher in cement dust sample from USA (p < 0.05), also, both total Cr and Cr (VI) were 5.4–26 folds higher in USA cement dust compared with Nigeria cement dust or clinker (p < 0.001). Total Cd was higher in both Nigeria cement dust and clinker (p < 0.05 and p < 0.001), respectively. Mercury was more in both Nigeria cement dust and clinker (p < 0.05), while Pb was only significantly higher in clinker from Nigeria (p < 0.001). These results show that cement dust contain mixture of metals that are known human carcinogens and also have been implicated in other debilitating health conditions. Additionally, it revealed that metal content concentrations are factory dependent. This study appears to indicate the need for additional human studies relating the toxicity of these metals and their health impacts on cement factory workers.