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Understanding the degradation behavior of azo dyes in photocatalytic wastewater treatment is of fundamental and practical importance for their application in textile-processing and other coloration industries. In this study, quantum chemistry, as density functional theory, was used to elucidate different degradation pathways of azo pyridone dyes in a hydroxyl radical (HO?)-initiated photocatalytic system. A series of substituted azo pyridone dyes were synthesized by changing the substituent group in the para position of the benzene moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The effect of dye molecular structure on the photocatalytic degradation reaction mechanism was analyzed and quantification of substituent effects on the thermodynamic and kinetics parameters was performed. Potential energy surface analysis revealed the most susceptible reaction site for the HO? attack. The calculated reaction barriers are found to be strongly affected by the nature of substituent group with a good correlation using Hammett σp constants and experimentally determined reaction rates. The stability of pre-reaction complexes and transition state complexes were analyzed applying the distortion-interaction model. The increased stability of the transition state complexes with the distancing from the substituent group has been established. 相似文献
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Some emerging technologies are expected to be pivotal for solving many of the environmental challenges faced today, especially those related to energy. However, many of these technologies may incur significant environmental impacts over their life cycle, while having environmental benefits during their use. This paper presents results of a Life Cycle Assessment (LCA) of a proposed type of nanophotovoltaic, quantum dot photovoltaic (QDPV) module. The LCA is confined to the stages of raw materials acquisition, manufacturing, and use. The impacts of QDPV are compared with other types of PV modules and energy sources - both renewable and nonrenewable. To provide a comprehensive comparative assessment, QDPV modules were compared with mature as well as emerging PV types for which data are available. Comparative assessment with other types of energy sources includes coal, oil, lignite, natural gas, diesel, nuclear, wind, and hydropower.QDPV modules may have the potential to overcome two current barriers of solar technology: low efficiencies and high manufacturing costs. If higher efficiencies are realized, QDPV modules could pave the way to large scale implementation of solar energy, helping nations move toward greater energy independence. On the other hand, candidate materials as quantum dots for solar cell applications are mostly compound semiconductors such as cadmium selenide, cadmium telluride, and lead sulfide which may be toxic and for which renewable options are limited. Toxic effects of these materials may be exacerbated by their nanoscale features.The LCA was carried out using the software SimaPro, and the Ecoinvent Life Cycle Inventory (LCI) database supplemented with available literature and patent information. Our results indicate that while QDPV modules have shorter Energy PayBack Time (EPBT), lower Global Warming Potential (GWP), SOx and NOx emissions than other types of PV modules, they have higher heavy metal emissions, underscoring the need for investigation of emerging technologies, especially nano-based ones, from a life cycle perspective. QDPV modules are better in all impact categories assessed than carbon-based energy sources but they have longer EPBT than wind and hydropower and higher GWP. 相似文献
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Behavior and prediction of photochemical degradation of chlorinated polycyclic aromatic hydrocarbons in cyclohexane 总被引:3,自引:0,他引:3
The photochemical degradation of 11 chlorinated polycyclic aromatic hydrocarbons (ClPAHs) and the corresponding 5 parent PAHs was examined to simulate the compound’s fate on aerosol surfaces. All the ClPAHs and PAHs decayed according to the first-order reaction rate kinetics. The photolysis rates of ClPAHs varied greatly according to the skeleton of PAHs; the rates of chlorophenanthrenes (ClPhes) and 1-chloropyrene were higher than those of corresponding parent PAHs, whereas chlorofluoranthenes, 7-chlorobenz[a]anthracene and 6-chlorobenzo[a]pyrene were more stable under irradiation compared to respective parent PAH. Considering the photoproducts of ClPhes detected, the oxidation could occur immediately at positions of the highest frontier electron density. Finally, the quantitative structure-property relationship models were developed for direct photolysis half-lives and average quantum yields of the ClPAHs and parent PAHs, in which the significant factors affecting photolysis were ELUMO+1, total energy and surface area, and ELUMO, ELUMO − EHOMO and total energy, respectively. 相似文献
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Mingjie Zhang Gang Yang Shuai Liu Jiahui Yu Hongzhe Li Liwen Zhang Yipei Chen Ruitang Guo Tao Wu 《环境科学学报(英文版)》2022,34(6):163-174
Due to the ever-tightening regulation on mercury emission in recent decades, there is an urgent need to develop novel materials for the removal of elemental mercury at coal-fired power plants. In this study, a series of MoS2 quantum dots (QDs)-based MoS2/HKUST-1 composite materials were prepared. It is found that MoS2 QDs were encapsulated by HKUST-1 and enhanced the crystallinity and specific surface area of HKUST-1. The MoS2/HKUST-1 showed excellent performance in catalytic oxidation of Hg0 as compared with pristine HKUST-1. It is found that surface layer of lattice oxygens is active and participates in Hg0 oxidation, while the consumption of surface oxygens then leads to the formation of oxygen vacancies on the surface. These vacancies are effective in the adsorption and dissociation of O2, which subsequently participates in the oxidation of Hg0. Moreover, the study on the influence of commonly seen gas components, such as SO2, NO, NH3 and H2O, etc., on Hg0 oxidation demonstrated that synergistic effects exist among these gas species. It is found that the presence of NO promotes the oxidation of Hg0 using oxygen as the oxidant. 相似文献
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Shuqin Liu Rui Wu Xi Yang Shuting Fang Zhangmin Xiang Shenghong Yang Gangfeng Ouyang 《Frontiers of Environmental Science & Engineering》2022,16(9):116
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N-Nitrosodimethylamine (NDMA) is a potent carcinogen that yields a cancer risk of 10−6 at concentrations as low as 0.7 ng L−1. Tentative guideline values are set at 3 ng L−1 in California, USA; 9 ng L−1 in Ontario, Canada; 40 ng L−1 nationwide in Canada; and 100 ng L−1 by the World Health Organization. NDMA is a great concern in treating reclaimed water as well as drinking water. UV degradation can be considered effective degradation method. A 1-log reduction of NDMA is achieved by 1000 mJ cm−2 of a 254-nm low pressure (LP) mercury UV lamp. However, a higher degradation efficiency than that provided by LP lamps is desired in practical treatment. In this study, the effects of wavelength and water quality were investigated to achieve higher degradation efficiency. The effects of wavelength were examined by comparing three UV lamps: a 222-nm Kr Cl Excimer UV lamp, a 254-nm LP mercury UV lamp, and a 230- to 270-nm filtered medium pressure (FMP) mercury UV lamp. The 222-nm lamp and FMP lamp achieved 4 times and 2.8 times higher degradation efficiency, respectively, than the conventional 254-nm LP lamp. Effects on water quality were also simulated by using absorption spectrum data of nitrate solutions and process water from a drinking-water treatment plant. In the simulation, the 222-nm lamp was affected by UV-absorbing compounds in the water, whereas the FMP lamp showed more stable degradation efficiency. Appropriate use of these three types of lamps could enhance the efficiency of degradation of NDMA. 相似文献
8.
A rapid and high-throughput quantum dots bioassay for monitoring of perfluorooctane sulfonate in environmental water samples 总被引:1,自引:0,他引:1
Zhang J Wan Y Li Y Zhang Q Xu S Zhu H Shu B 《Environmental pollution (Barking, Essex : 1987)》2011,159(5):1348-1353
Currently HPLC/MS is the state of the art tool for environmental/drinking water perfluorooctane sulfonate (PFOS) monitoring. PFOS can bind to peroxisomal proliferator-activated receptor-alpha (PPARα), which forms heterodimers with retinoid X receptors (RXRs) and binds to PPAR response elements. In this bioassay free PFOS in water samples competes with immobilized PFOS in ELISA plates for a given amount of PPARα-RXRα. It can be determined indirectly by immobilizing PPARα-RXRα-PFOS complex to another plate coated with PPARα antibody and subsequent measuring the level of PPARα-RXRα by using biotin-modified PPARα-RXRα probes-quantum dots-streptavidin detection system. The rapid and high-throughput bioassay demonstrated a detection limit of 2.5 ng L−1 with linear range between 2.5 ng L−1 and 75 ng L−1. Detection results of environmental water samples were highly consistent between the bioassay and HPLC/MS. 相似文献
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Arzu HatipoĞlu 《毒物与环境化学》2013,95(3):147-162
The kinetics of the photocatalytic degradation of 10 different dichlorophenols and dichloroanilines have been investigated experimentally and theoretically. With the intention of finding certain molecular indices in order to determine the degradation rates of aromatic pollutants, geometry optimizations of the compounds have been performed with the semiempirical PM3 method. The molecular orbital calculations have been carried out by an SCF method using the RHF formalism. The correlations between the apparent first-order rate constants and the calculated molecular properties of the compounds have been examined. Four different structure–activity relationships have been developed expressing the logarithms of the rate constants in terms of the Hammett constants, electron densities of the substituents, the coefficients and the energies of the highest occupied molecular orbitals HOMO, and 1-octanol/water partition coefficients log?K OW. 相似文献