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duanlin_nk银虫 (小有名气)
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Es&t_Jul 6 2007
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Suppression of Dioxin Emission in Co-Incineration of Poly(vinyl Chloride) with TiO2-Encapsulating Polystyrene Jeongsoo Choi, Oksun Kim, and Seung-Yeop Kwak* Hyperstructured Organic Materials Research Center (HOMRC), and School of Materials Science and Engineering, Seoul National University, San 56-1, Shillim-dong, Gwanak-gu, Seoul 151-744, Korea Received for review January 22, 2007 Revised manuscript received May 29, 2007 Accepted May 31, 2007 Abstract: This paper presents an approach to the suppression of the emission of dioxin and its precursors as a result of the co-incineration of poly(vinyl chloride) (PVC) with TiO2-encapsulating polystyrene (TEPS), in which TiO2 nanoparticles with the capacity to adsorb dioxin and its precursors are encapsulated without significant agglomeration. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to show that spherical PS particles encapsulating a uniform dispersion of TiO2 nanoparticles are obtained through the dispersion polymerization of styrene in an aqueous ethanol medium. To facilitate the encapsulation, the surface of the TiO2 nanoparticles was modified with a polymerizable organic silane linker prior to polymerization. For comparison purposes, experiments were performed in which PVC was co-incinerated with neat PS (PVC/PS), TiO2-encapsulating PS (PVC/TEPS), and mechanically mixed TiO2/PS (PVC/PS-MTiO2). Qualitative and quantitative investigations of the suppression of the emission of a model dioxin and its precursors were performed by analyzing the exhaust gases from the co-incinerations using gas chromatography/mass spectrometry (GC/MS). The results show that the addition of TiO2 nanoparticles into co-incineration systems reduces the concentration of the dioxin and its precursors in exhaust gases. Moreover, the quantitative removal efficiencies for PVC/TEPS and PVC/PS-MTiO2 indicate that the suppression is successfully enhanced by the TiO2-encapsulation: increases in the dispersity of the nanoparticles result in improved adsorption of the dioxin and its precursors. ************************************************************ Role of Divalent Cations in Plasmid DNA Adsorption to Natural Organic Matter-Coated Silica Surface Thanh H. Nguyen* and Kai Loon Chen Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 3230 Newmark Laboratory, Urbana, Illinois 61801, and Department of Chemical Engineering, Environmental Engineering Program, Yale University, New Haven, Connecticut 06520-8286 Received for review February 19, 2007 Revised manuscript received May 16, 2007 Accepted May 18, 2007 Abstract: The adsorption kinetics of supercoiled and linear plasmid DNA onto a natural organic matter (NOM)-coated silica surface are acquired using a quartz crystal microbalance with dissipation monitoring (QCM-D) in the presence of common divalent electrolytes CaCl2 and MgCl2. The adsorption kinetics of both DNA are noticeably higher in the presence of CaCl2 compared to MgCl2. We hypothesize that specific bridging between the DNA phosphate groups and NOM carboxyl functional groups in the presence of Ca2+ cations may lead to more efficient attachment than in the presence of Mg2+ cations, which are only likely to allow for charge neutralization. The influence of background Na+ cations on the adsorption kinetics in the presence of CaCl2 is found to be insignificant, while the presence of Na+ leads to slower attachment kinetics in MgCl2. Rinsing the DNA layer adsorbed in the presence of CaCl2 with a solution of low NaCl concentration followed by deionized water does not result in observable detachment, indicating irreversibility of DNA adsorption. Instead, softening of the DNA layer adsorbed in the presence of CaCl2 with background Na+ occurs with the rinses due to the increase in electrostatic repulsion between the phosphate functional groups along the DNA backbone. In the case of the DNA layer adsorbed in the presence of CaCl2 without background Na+, softening of the layer does not occur with the rinses. ************************************************************ Cyclodextrin Enhanced Biodegradation of Polycyclic Aromatic Hydrocarbons and Phenols in Contaminated Soil Slurries Ian J. Allan,* Kirk T. Semple, Rina Hare, and Brian J. Reid School of Environmental Sciences, University of East Anglia, NR4 7TJ Anglia, United Kingdom, Department of Environmental Science, Lancaster University, LA1 4YQ Lancaster, United Kingdom, and ALcontrol Laboratories, CH4 8RD Chester, United Kingdom Received for review February 27, 2007 Revised manuscript received June 1, 2007 Accepted June 4, 2007 Abstract: This work aimed to evaluate the relative contribution of soil catabolic activity, contaminant bioaccessibility, and nutrient levels on the biodegradation of field-aged polycyclic aromatic hydrocarbons and phenolic compounds in three municipal gas plant site soils. Extents of biodegradation achieved, in 6 week-long soil slurry assays, under the following conditions were compared: (i) with inoculation of catabolically active PAH and phenol-degrading microorganisms, (ii) with and without hydroxypropyl--cyclodextrin supplementation (HPCD; 100 g L-1), and finally (iii) with the provision of additional inorganic nutrients in combination with HPCD. Results indicated no significant (p < 0.05) differences between biodegradation endpoints attained in treatments inoculated with catabolically active microorganisms as compared with the uninoculated control. Amendments with HPCD significantly (p < 0.05) lowered biodegradation endpoints for most PAHs and phenolic compounds. Only in one soil did the combination of HPCD and nutrients consistently achieve better bioremediation endpoints with respect to the HPCD-only treatments. Thus, for most compounds, biodegradation was not limited by the catabolic activity of the indigenous microorganisms but rather by processes resulting in limited availability of contaminants to degraders. It is therefore suggested that the bioremediation of PAH and phenol impacted soils could be enhanced through HPCD amendments. In addition, the biodegradability of in situ and spiked (deuterated analogues) PAHs following 120 days aging of the soils suggested that this contact time was not sufficient to obtain similar partitions to that observed for field-aged contaminants; with the spiked compounds being significantly (p < 0.05) more available for biodegradation. ************************************************************ |
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