旋转薄膜浆态光催化反应器

在分析现有光催化反应器特点的基础上,提出了一种新型的旋转薄膜式浆态光催化反应器（RFFS）。用商品化光催化剂Degussa P25,以苯酚模型有机物为降解对象,对比了RFFS与传统鼓泡浆态光催化反应器（TBS）的性能,研究了RFFS的光催化性能。结果表明,与传统浆态光催化反应器相比,RFFS具有较高的光催化性能,尤其是能够在较高的光催化剂浓度下运行。在光催化体系的循环流速大于2.7 L·min-1、供气流量为1.0 L·min-1、催化剂浓度为3.0 g·L-1的条件下,RFFS比传统浆态鼓泡光催化反应器的降解速率提高1.6倍。RFFS利用旋转浆态薄膜强化了光催化反应体系的传质,同时提高了体系中光催化剂对光能的利用率,较好地解决了光在传统浆态体系中的传递问题,为开发新型的具有工业应用前景的光催化反应器提供了方案。苯酚在RFFS中的降解动力学符合表观一级动力学模型,理论值与实验结果吻合较好。     

反应器型式对有机废水光催化氧化特性的影响

采用浆态光催化反应器对苯甲酰胺模拟废水光催化氧化特性进行了研究。探讨了催化剂的用量、污染物的初始浓度、反应时间、空气流量等操作参数对鼓泡式、循环式等形式的浆态光催化反应器内苯甲酰胺模拟废水光催化氧化特性和动力学的影响。结果表明,浆态光催化降解过程中污染物的浓度越低效果越好,催化剂的用量存在适当值;不同操作条件对不同形式浆态光催化反应器内苯甲酰胺模拟污染物光催化降解性能的影响不近相同。在所考察的污染物初始浓度、催化剂量和空气流量范围内,反应器中苯甲酰胺光催化氧化速率均符合拟一级动力学方程。与鼓泡式浆态光催化反应器相比,所开发的循环式浆态光催化反应器在空气作用下能更好地改善催化剂与气体和废水的混合效果,进而提高了光催化剂的利用效率,能更有效降解有机污染物;而且空气利用量小,能够大大降低浆态床光催化氧化处理废水的运行成本。     

光催化降解水中苯酚的研究

采用WL-TiO2型光催化剂,对水中的苯酚进行光催化降解：探究了该催化剂的光催化氧化机理,并考察了不同类型的TiO2、催化剂投放量、苯酚浓度、降解温度、溶液的pH值以及光源和光强等因素对降解率的影响。试验结果表明,浓度为14mg／L的苯酚溶液,用WL-TiO2光催化剂,光催化降解3h,可以将溶液中的苯酚完全降解。     

固定式填充复合床光催化反应器降解亚甲基蓝的研究

设计了一种固定式填充复合床光催化反应器,以普通玻璃片和玻璃螺旋圈为载体,用溶胶-凝胶法制备了负载型TiO2薄膜光催化剂。利用紫外光为光源,采用难降解物质亚甲基蓝在不同初始浓度、pH值和光强等因素下的光催化降解脱色反应速率考察了该反应器的工艺特性,试验结果表明:该种反应器的最佳操作条件为反应器中同时放置普通玻璃片TiO2薄膜光催化剂和玻璃螺旋圈TiO2薄膜光催化剂,溶液pH值为7.5,光源光强为650W,光照时间为180min。当进水亚甲基蓝的质量浓度为8.0mg/L时,在此条件下的降解脱色效率为93.83%,且其设计易于实现产业化。     

纳米二氧化钛光催化降解苯酚水溶液

以P 25纳米TiO2 作为光催化剂,在环状光催化反应器中进行了苯酚水溶液的光催化降解性能研究。系统考察了溶液的pH、P 25用量、银掺杂量、苯酚的初始质量浓度等因子对苯酚溶液光催化降解过程的影响。结果表明,在pH=7时,苯酚水溶液降解率达97 4%,强酸和强碱条件均不利于苯酚的降解;质量浓度50mg/L的苯酚水溶液,P 25用量为50mg,UV辐照30min时降解率为95 6%;质量浓度100mg/L的苯酚水溶液,P 25用量为150mg,UV辐照60min时降解率为95 4%;银掺杂P 25增加了其光催化活性,用质量分数为10%的硝酸银水溶液掺杂制备的复合光催化剂,苯酚的降解率比未掺杂时增加16 5%。     

浆态光催化反应器有机模拟废水光催化氧化特性与动力学

采用循环式浆态光催化反应器对苯甲酰胺模拟废水光催化氧化特性和动力学进行了研究,系统地考察了操作条件对模拟污染物光催化降解的影响,并与搅拌式和鼓泡床式浆态光催化反应器中苯甲酰胺的降解效果进行对比.结果表明,循环式浆态光催化反应器中光催化剂的用量、污染物的初始浓度和初始pH值对模拟污染物光催化降解性能的影响存在适宜值;体系中H₂PO^-₄、Cl^-、Cu²⁺、Al³⁺对其光催化降解过程有明显的抑制作用.与传统的搅拌式和鼓泡床式浆态光催化反应器相比,循环式浆态光催化反应器中催化剂和废水的混合效果较好,光利用率高,较大程度上减少催化剂的用量和提高废水处理能力.同时,对不同催化剂的用量和污染物初始浓度下的光催化氧化反应动力学研究表明,此过程符合拟一级动力学,催化剂表面反应速率常数k₀和催化剂吸附平衡常数K_TiO2分别为0.0279 min^-1和17.99 L•g^-1.     

三相流化床中光催化降解反应特性的研究

在设计并建立的流态化光催化反应器中,采用负载型光催化剂对甲基橙水溶液进行了光催化降解实验研究。优化了三相流化状态下光催化反应器的操作条件, 其结果为:气体流量200-250Lh-1,液体流量30 Lh-1,催化剂用量为1.5gkg-1处理液;考察了该反应器中催化剂的使用寿命,为光催化降解技术的工业应用研究提供了参考。     

钒-氮共掺杂TiO2光催化降解苯酚试验研究

采用溶胶-凝胶法制备了钒-氮共掺杂TiO2光催化剂,对苯酚溶液进行了光催化降解试验研究,考察了在模拟太阳光条件下,pH、曝气量、苯酚溶液初始和催化剂投加量对钒-氮共掺杂TiO2光催化剂降解苯酚溶液的影响。结果表明,在试验条件下,以800 W氙灯为光源,反应溶液pH=6,曝气体积流量75 mL/min,苯酚溶液初始质量浓度小于80mg/L,催化剂投加量1.5 g/L时,苯酚溶液降解率最高;钒-氮共掺杂TiO2光催化剂重复使用7次后,对苯酚的光催化活性没有明显下降,具有良好的重复使用性。可为钒-氮共掺杂TiO2的应用推广提供依据。     

SO2-4/TiO2光催化降解邻硝基苯酚

采用硫酸溶液浸渍处理TiO2制得SO2-4/TiO2光催化剂.考察了光催化剂对邻硝基苯酚溶液的光催化行为.发现SO2-4/TiO2的光催化活性高于TiO2,浸渍液中H2SO4的浓度和催化剂的焙烧温度对SO2-4/TiO2的催化活性有一定的影响,H2SO4溶液的最佳浓度为0.5 mol·L-1,最佳焙烧温度为500℃.催化降解过程符合一级反应动力学规律.     

环管式反应器中亚甲基蓝的光催化降解反应

采用环管式反应器,以Degussa P25为光催化剂和亚甲基蓝染料为代表性污染物,测定了20℃时亚甲基蓝在P25上的吸附,采用Langmuir等温吸附模型来拟合该实验数据;并测试了反应器中的紫外光分布,同时考察了P25颗粒剂量和空气流量对该三相鼓泡淤浆床反应器中液相光催化降解反应的影响.实验结果表明,最佳的P25光催化剂颗粒和空气流量分别为0.5g/L和800mL/min.     

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.