石墨相氮化碳协同UV-H_2O_2光催化降解亚甲基蓝

以三聚氰胺为前驱体,经热解—回流法制备了石墨相氮化碳(g-C3N4),采用XRD、FTIR、SEM、EDS、PL等技术对g-C_3N_4进行了表征。研究了g-C_3N_4在UV-H_2O_2体系中对废水中亚甲基蓝(MB)的光降解效果。实验结果表明,UV+g-C_3N_4催化剂+H_2O_2体系能协同降解MB,在初始MB质量浓度为20 mg/L、初始废水p H为5、废水体积为250 mL、g-C_3N_4加入量为0.10 g、H_2O_2浓度为0.4 mmol/L、反应温度为25℃的优化工艺条件下,紫外光照射70 min时MB脱色率达98.32%。g-C_3N_4催化剂具有较好的重复使用性能,使用5次后MB脱色率仍保持在95.10%。     

Effects of Coastal Lighting on Foraging Behaviorof Beach Mice

Abstract:  Introduction of artificial light into wildlife habitat represents a rapidly expanding form of human encroachment, particularly in coastal systems. Light pollution alters the behavior of sea turtles during nesting; therefore, long-wavelength lights—low-pressure sodium vapor and bug lights—that minimize impacts on turtles are required for beach lighting in Florida (U.S.A.). We investigated the effects of these two kinds of lights on the foraging behavior of Santa Rosa beach mice (  Peromyscus polionotus leucocephalus ). We compared patch use and giving-up densities of mice for experimental food patches established along a gradient of artificial light in the field. Mice exploited fewer food patches near both types of artificial light than in areas with little light and harvested fewer seeds within patches near bug lights. Our results show that artificial light affects the behavior of terrestrial species in coastal areas and that light pollution deserves greater consideration in conservation planning.     

二溴硝基甲烷在紫外光照条件下的光降解

以二溴硝基甲烷为研究,采用单一控制变量法研究了光照强度、初始物浓度、自由氯、溴离子、pH值等影响因子对二溴硝基甲烷光降解的影响,探讨了二溴硝基甲烷的光降解动力学规律.结果表明：二溴硝基甲烷在紫外光条件下的降解遵循一级反应动力学规律,其光降解效率随二溴硝基甲烷初始浓度的增加而减小,随光照强度和pH值增加而增加;溴离子的存在能促进二溴硝基甲烷的光降解;添加自由氯能够显著加快二溴硝基甲烷的光降解效率,并且会使二溴硝基甲烷在光降解的过程中转化为以一溴一氯硝基甲烷为主的其他卤代硝基甲烷.此研究结果可为水处理过程中控制二溴硝基甲烷的形成、降低水质安全风险提供参考.     

轻质高强多功能点阵夹层结构研究进展

根据材料类型和点阵结构,对点阵夹层结构进行了分类简述,并从静态、动态力学性能上,分析了各类点阵夹层结构的优缺点。简要叙述了设计过程中,综合考虑材料、结构以及功能等影响因素,针对不同使用工况的要求,可对各影响因素进行匹配设计,以实现传热特性、电磁波屏蔽特性、声学特性等不同的功能性需求。然后介绍了复合点阵夹层结构(嵌锁组装、模具热压成形、穿插编织)和金属点阵夹层结构(冲压成形、挤压线切割、拉伸网折叠、搭接拼装、熔模铸造以及增材制造)的主要制造工艺。最后提出如何将设计因子与多目标进行匹配及优化设计,是轻质高强点阵夹层结构的重点研究方向,轻质高强点阵夹层结构将朝多材料及多结构复合方向发展,开发新的制造工艺,提高费效比,是点阵夹层结构材料需解决的问题。     

Mesoporous WO3-graphene photocatalyst for photocatalytic degradation of Methylene Blue dye under visible light illumination

Advanced oxidation technologies are a friendly environmental approach for the remediation of industrial wastewaters. Here, one pot synthesis of mesoporous WO_3 and WO_3-graphene oxide(GO) nanocomposites has been performed through the sol–gel method. Then, platinum(Pt) nanoparticles were deposited onto the WO_3 and WO_3-GO nanocomposite through photochemical reduction to produce mesoporous Pt/WO_3 and Pt/WO_3-GO nanocomposites. X-ray diffraction(XRD) findings exhibit a formation of monoclinic and triclinic WO_3 phases. Transmission Electron Microscope(TEM) images of Pt/WO_3-GO nanocomposites exhibited that WO_3 nanoparticles are obviously agglomerated and the particle sizes of Pt and WO_3 are ~ 10 nm and 20–50 nm, respectively. The mesoporous Pt/WO_3 and Pt/WO_3-GO nanocomposites were assessed for photocatalytic degradation of Methylene Blue(MB) as a probe molecule under visible light illumination.The findings showed that mesoporous Pt/WO_3, WO_3-GO and Pt/WO_3-GO nanocomposites exhibited much higher photocatalytic efficiencies than the pure WO_3. The photodegradation rates by mesoporous Pt/WO_3-GO nanocomposites are 3, 2 and 1.15 times greater than those by mesoporous WO_3, WO_3-GO, and Pt/WO_3, respectively. The key factors of the enhanced photocatalytic performance of Pt/WO_3-GO nanocomposites could be explained by the highly freedom electron transfer through the synergetic effect between WO_3 and GO sheets, in addition to the Pt nanoparticles that act as active sites for O2 reduction, which suppresses the electron hole pair recombination in the Pt/WO_3-GO nanocomposites.     

有机硅改性环氧树脂的光固化动力学与性能研究

目的研究紫外光固化有机硅改性环氧树脂的固化行为和性能。方法通过介电分析(DEA)研究光引发剂、热引发剂及有机硅含量对紫外光固化脂环族环氧树脂反应过程的影响,利用热重(TG)、差示扫描热(DSC)和显微硬度仪对有机硅树脂改性环氧树脂性能进行分析。结果发现光引发剂与热引发剂对固化效率可起到协同互补的作用,增加光引发剂和热引发剂的浓度,可缩短引发时间,加快固化速率,提高固化效率。与纯环氧树脂相比,有机硅改性环氧树脂的固化效率和初始分解温度都有所下降,但高温阶段降解速率明显降低,500℃的残炭率也得到提高。当加入质量分数为10%的有机硅时,固化物表现出较好的耐热性能,树脂维氏硬度可达31.75HV。结论紫外光可以很好地固化有机硅改性环氧树脂。     

Photocatalytic degradation of phenol

In this study photocatalytic degradation of phenol in thepresence of UV irradiated TiO₂ catalyst andH₂O₂was investigated. Effects of TiO₂ andH₂O₂concentrations and pH on photocatalytic degradation were examined. The rate constants for photocatalytic degradation wereevaluated as a function of TiO₂ and H₂O₂ concentrations and pH of the solution. It was found thatphotodegradation is an effective method for the removal of phenoland disappearance of phenol obeyed first order kinetics. The amount of CO₂h produced during photocatalytic degradation wascorresponding to the complete mineralization. Photodegradationcan be an alternative method for the treatment of phenol containing wastewaters.     

Seasonal characteristics of haze observed by continuous visibility monitoring in the urban atmosphere of Kwangju, Korea

Continuous visibility monitoring has been carried out inKwangju, Korea since May 1999. The total light extinctioncoefficient b _ext measured by a transmissometer andreveals seasonal trends in urban visual air quality,especially under hazy conditions with a visual range of lessthan 15 km. Seasonal atmospheric visibility under lowrelative humidity during the winter was observed to be betterthan during any other seasons. Summertime visibility wasseverely degraded due to highly increased light scattering byhygroscopic particles under high humidity atmosphericconditions. Visibility during spring and fall was alsomoderate. However, yellow sand in spring caused the lowestvisibility conditions over the measurement area for a fewdays. With continuous monitoring using the transmissometer,the daily average seasonal visual range was measured to be13.1, 9.2, 11.0, and 13.9 km in spring, summer, falland winter, respectively. Under the atmospheric humiditycondition less than 60%, visual range was observed tobe 16.1, 13.9, 15.1, and 16.6 km in spring, summer,fall, and winter, respectively. The mean light extinctionbudget by sulfate and nitrate aerosols was determined to bethe highest value of 63.71% during the summer and thelowest value of 27.08% during spring. During the `yellow sand dust' period, a mean light extinction budget by soil particles was estimated to be at an unusually high value of 44.22%.     

UV-B辐射对小麦叶抗氧化系统的影响

研究了温室种植的小麦在０（ＣＫ）、８．８２ｋＪ／ｍ＾２（Ｔ１）和１２．６ｋＪ／ｍ＾２（Ｔ２）三种剂量的紫外线Ｂ（ＵＶ－Ｂ）辐射下抗氧化系统的变化及其原因。ＵＶ－Ｂ辐射诱导了Ｈ２Ｏ２的合成，还原型抗坏血酸和还原型谷胱甘肽含量的增加、过氧化氢酶、愈创木酚过氧化物酶、抗坏血酸过氧化物酶和谷胱甘肽还原酶活性升高，而类胡萝卜素稍有所降低、超氧歧化酶（ＳＯＤ）活几乎不受ＵＶ－Ｂ辐射影响，分析表明，ＵＶ－Ｂ辐射     

Enhanced cyanogen chloride formation after UV/PS and UV/H2O2 pre-oxidation and chlorination in natural river water

Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H₂O₂) have attracted much attention in recent years as advanced oxidation processes for water treatment. However, it is not all clear how these two methods affect the formation of cyanogen chloride (CNCl) in the subsequent water chlorination process. In this study, it was found that both UV/H₂O₂ and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers. Glycine, uric acid, arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl. The results showed that compared with chlorination alone, pre-oxidation by UV/H₂O₂ and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95% during post-chlorination process. However, they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold. In a more detailed investigation, pre-oxidation of histidine formed highly reactive intermediates to chlorine, leading to increased CNCl formation and chlorine consumption. The results showed that the precursors of CNCl was altered after pre-oxidation, and need to be re-evaluated.