TiO2光催化剂的负载技术研究进展

TiO2是光催化反应中的一种研究较为广泛的光催化剂,具有优异的光催化特性,在废水处理、空气净化等环保领域具有诱人的应用前景.对近年来国内外TiO2光催化剂的载体和负载技术进行了综述,为今后开发新型、高效、实用的光催化剂提供借鉴.     

光催化剂载体及其固定化方法的研究进展

负载型光催化剂是将光催化剂负载固定于载体上而得到的一种复合型光催化材料。在参考近年来国内外光催化领域研究的基础上,对负载型光催化剂的载体的作用、选择的一般原则、常用载体的类型等进行了概述。从负载型光催化剂的负载固定的形式入手,重点综述了近年来光催化剂的负载固定化方法的研究进展,同时提出了目前负载型光催化剂研究的热点和发展趋势。     

聚苯胺改性负载型纳米二氧化钛的研究

采用悬浮聚合法制备聚苯乙烯微珠载体,通过矿化接枝技术将溶胶-凝胶法制备的纳米二氧化钛负载在微珠载体上,制成负载型纳米二氧化钛光催化剂。利用导电聚苯胺对负载型纳米二氧化钛光催化剂进行可见光改性研究,通过XRD,SEM等方法对负载型纳米二氧化钛光催化剂进行表征;通过光催化降解甲基橙实验评价了导电聚苯胺改性负载型纳米二氧化钛光催化剂在可见光条件下的光催化活性。实验结果表明：导电聚苯胺对负载型纳米二氧化钛光催化剂的改性,可有效改善负载型纳米二氧化钛光催化剂在可见光条件下的光催化性能,降解率提高了24.5%。     

固载粘结剂对二氧化钛光催化性能的影响

以磷酸铝和水溶性聚丙烯酰胺为粘结剂,玻璃为载体,制备了负载型TiO2光催化剂.通过甲基橙脱色率和COD(chemical oxygen demand)为检测手段,比较两种固载粘结剂对TiO2光催化性能的影响.结果表明两种负载型光催化剂对甲基橙脱色都具有较好的效果,但有机粘结剂的使用不利于光催化过程中COD值的降低.另外研究了固载粘结剂对负载型光催化剂寿命的影响, 实验证明两种固载型光催化剂在使用50 h后仍具较好的光催化活性.     

氧化亚铜基复合光催化剂的研究进展

氧化亚铜在光催化、太阳能电池、传感器等领域有着广阔的应用前景。结合氧化亚铜光催化剂的研究方向,综述了改善其光催化性能的常用方法,包括形貌尺寸改进、掺杂、金属负载和半导体复合等。介绍了几种具有代表性的氧化亚铜基复合光催化剂,包括金属-氧化亚铜复合光催化剂、氧化亚铜-半导体复合光催化剂、氧化亚铜-碳材料复合光催化剂和三元复合光催化剂,阐述了它们各自的反应机理。最后对氧化亚铜基复合光催化剂今后的发展进行了展望。     

纳米矿物材料负载TiO_2在污水处理中的研究进展

非金属矿物以其特殊的纳米孔道结构和形态成为纳米TiO2的理想光催化载体,本文系统论述了非金属纳米矿物／纳米TiO2复合光催化剂在污水处理中的研究和应用,重点介绍了非金属纳米矿物载体及其种类、负载工艺和负载趋势的研究现状,并对负载型光催化剂存在的问题进行了简述。     

半导体光催化剂载体的研究进展

光催化技术是一项新型的绿色环保技术,半导体光催化剂光催化技术在水制氢和污水处理领域具有诱人的应用前景,但是粉末型光催化剂的不足大大制约了其大规模的应用,因此负载型光催化剂应运而生。通过查阅大量资料,对近年来国内外各种光催化剂载体进行了综述,介绍了各种光催化剂载体的优点与不足,为未来开发新型、高效、实用的光催化剂载体提供借鉴,并对未来合适的光催化剂载体进行了展望。     

矿物负载纳米TiO2光催化复合材料的研究进展

综述了国内外有关矿物负载纳米TiO2光催化复合材料的研究和应用现状,重点介绍了矿物载体以及负载方法的研究进展,评述了各载体及负载方法的特点,并展望了负载型TiO2光催化剂的研究发展方向.     

微球负载TiO2催化剂的制备与降解苯酚性能

以粉煤灰中分离的微珠为载体,采用溶胶.凝胶法制备了负载型TiO2光催化剂,通过XRD、SEM技术对粉煤灰微珠负载TiO2光催化剂的晶型结构和形貌进行了表征;采用悬浮体系以苯酚为降解对象,研究了TiO2 光催化活性.结果表明:负载TiO2催化剂在悬浮体系中具有较高的光催化活性,催化剂负载4次,500℃煅烧2h,降解苯酚的能力最强,在苯酚浓度为102 mg/L,120 min降解率达到60%.     

介孔材料负载光催化剂在废水处理中的应用

介孔材料已成为光催化领域中的研究热点之一。介绍了介孔材料负载光催化剂的优点、制备方法、光催化机理,重点概述了它在废水中的应用及对其活性的影响因素,并对其存在的问题和应用前景进行分析。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.