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951.
表面活性剂改性4A分子筛对Cr(VI)的吸附行为 总被引:1,自引:0,他引:1
采用浸渍法对4A分子筛进行表面改性,通过引入阳离子表面活性剂,使4A分子筛表面附着季铵型阳离子,并与反离子Br-形成"阴离子交换膜",从而促使更多的Cr(VI)阴离子通过离子交换吸附到改性4A分子筛上,通过X-射线衍射(XRD)和傅里叶变换红外光谱(FTIR)对样品的物相结构和组成进行表征分析。研究表明,表面活性剂的类型和疏水碳氢链结构会影响4A分子筛的吸附能力,十八烷基三甲基溴化铵(OTAB)碳氢链长,在分子筛表面形成的双分子层密,对Cr(VI)的吸附量最大。采用准一级、准二级、Elovich和Bangham动力学模型对六价铬的吸附数据进行拟合,其中准一级动力学方程最符合十八烷基三甲基溴化铵改性分子筛的吸附行为。同时,分别从Langmuir和Redlich-Peterson等温吸附模型获得六价铬的最大吸附量为13.98 mg/g,且改性分子筛以均一表面吸附为主。 相似文献
952.
Ying Wang Juying Wang Jingli Mu Zhen Wang Ziwei Yao Zhongsheng Lin 《Environmental science and pollution research international》2014,21(1):148-158
Predicted no-effect concentration (PNEC) is often used in ecological risk assessment to determine low-risk concentrations for chemicals. In the present study, native marine species were selected for toxicity testing. The PNECs for three polycyclic aromatic hydrocarbons (PAHs), specifically phenanthrene (Phe), pyrene (Pyr), and benzo[a]pyrene (BaP), were derived from chronic and acute toxicity data with log-normal statistical methods. The achieved PNECs for Phe, Pyr, and BaP were 2.33, 1.09, and 0.011 μg/L, respectively. In Jinzhou Bay and the Shuangtaizi River Estuary of Liaodong Bay in the Bohai Sea, China, the surface water concentrations of the three PAHs were analyzed by gas chromatography–mass spectrometry. Based on two probabilistic ecological risk assessment (PERA) methods, namely probabilistic risk quotient and joint probability curve, the potential risk of Phe, Pyr, and BaP in Jinzhou Bay and Shuangtaizi River Estuary was assessed. The same order of ecological risk (BaP > Phe > Pyr) was found by both models. Our study considered regional characteristics of marine biota during the calculation of PNECs, and the PERA methods provided probabilities of potential ecological risks of chemicals. Within the study area, further research on BaP is required due to its high potential ecological risk. 相似文献
953.
Rongfei Zhang Dongsheng Jiang Liujun Zhang Yibin Cui Mei Li Lin Xiao 《Environmental science and pollution research international》2014,21(3):2141-2153
This paper's survey of the pollution of the Wujin'gang River is important because it is one of the main rivers flowing into Meiliang Bay of Lake Taihu in eastern China. Trace metals (TMs) in this paper are described according to their pollution index (P i). Cluster analysis and correlation analysis are utilized for group sites and to assess co-contamination. Toxicity effect analysis was conducted using individual sediment quality guideline quotients (SQGQs) and mean SQGQs. The results showed that sediment from the Wujin'gang River basin was affected by nutrients, heavy metals, and polycyclic aromatic hydrocarbons (PAHs), which are an essential contamination source for both Meiliang Bay and Zhushan Bay of Lake Taihu. The discharge of TMs has significant correlations to total nitrogen (TN) and total phosphorus (TP); however, no significant correlations were observed between the content of PAHs and TMs. Toxicity effect results show that sediment in the Wujin'gang River basin threatens sediment-dwelling organisms. The harmful effect was mainly caused by heavy metals especially Cd, Cr, Ni, and Cu. Sediment dredging is an effective way to control pollution from internal rivers especially for the pollution of TN and heavy metals in the Wujin'gang River basin. 相似文献
954.
本文采用多层次转型理论的分析框架,回顾了国内外延伸生产者责任(EPR)制度的理论和实践进展,对比了EPR制度倡导者最初提出的创新导向的制度设计,与当前各国实践中基于成本—效益平衡所开展的政策评估研究,指出两者在是否应该将激进的可持续转型作为EPR基本政策目标上观点不同,其原因在于政策的技术创新激励效果难以通过可测量的政策评估方法进行有效考察,由此造成两者在EPR政策调整方向上的分歧:前者坚持EPR制度设计应该进一步完善个体责任原则,以激励生产者创新和采纳绿色技术,推进生产消费模式的系统转型;而后者则强调在现有管制框架下简化制度设计,重点完善循环处理基础设施及其管理效率。这种分歧不仅影响到发达国家EPR制度的演化,也深刻影响了发展中国家EPR制度的移植和建构。结论以中国电子废物管理实践为例,提出构建包含三个层次的演化经济学分析框架,考察EPR制度建构过程中,微观层次的企业技术选择,中观层次的供应链治理结构变动,和宏观层次的再生资源产业转型,以系统考察制度发展对技术创新的激励效果。 相似文献
955.
There is much discussion within the sustainable development community regarding climate stabilization and particularly, finding
environmentally equitable ways to address emission reductions. Knowing the current level of emission is only one variable
in this complex picture. While the rate of emissions is clearly a problem, the overall increase in GHG concentration in the
atmosphere is ultimately the main driver of anthropogenic warming. Therefore, it is also important to understand the cumulative
emissions, those which have taken us to the current condition. This research presents a case study of six countries to compare
the emissions per capita and cumulative emissions during the past 200 years. It is known that carbon emissions are closely
related to economic activities, but here we show that some countries have reached per capita emissions plateaus at different
levels while others are still rising. Specifically, one approach toward socioeconomic development, in terms of energy–economy,
reaches a plateau at 10 Mt carbon per person, which the United Kingdom and South Korea have attained. The US occupies another
emission regime at 20 Mt carbon per person. Developing economies such as India and China are considerably below these levels,
and unless they follow other integrated economic/environmental solutions, they will continue to increase their per capita
emissions during development. 相似文献
956.
Keigo Akimoto Fuminori Sano Takashi Homma Kenichi Wada Miyuki Nagashima Junichiro Oda 《Sustainability Science》2012,7(2):157-168
This study focuses on analyses of greenhouse gas (GHG) emission reductions, from the perspective of interrelationships among
time points and countries, in order to seek effective reductions. We assessed GHG emission reduction potentials and costs
in 2020 and 2030 by country and sector, using a GHG emission reduction-assessment model of high resolution regarding region
and technology, and of high consistency with intertemporal, interregional, and intersectoral relationships. Global GHG emission
reduction potentials relative to baseline emissions in 2020 are 8.4, 14.7, and 18.9 GtCO2eq. at costs below 20, 50, and 100 $/tCO2eq., corresponding to +19, −2, and −7 %, respectively, relative to 2005. The emission reduction potential for 2030 is greater
than that for 2020, mainly because many energy supply and energy-intensive technologies have long lifetimes and more of the
current key facilities will be extant in 2020 than in 2030. The emission reduction potentials in 2030 are 12.6, 22.0, and
26.6 GtCO2eq. at costs below 20, 50, and 100 $/tCO2eq., corresponding to +19, −2, and −7 %, respectively, relative to 2005. The emission reduction potential for 2030 is greater
than that for 2020, mainly because many energy supply and energy-intensive technologies have long lifetimes and more of the
current key facilities will be extant in 2020 than in 2030. The emission reduction potentials in 2030 are 12.6, 22.0, and
26.6 GtCO2eq. at costs below 20, 50, and 100 /tCO2eq., corresponding to +33, +8, and −3 %, respectively, relative to 2005. Global emission reduction potentials at a cost below
50 $/tCO2eq. for nuclear power and carbon capture and storage are 2.3 and 2.2 GtCO2eq., respectively, relative to baseline emissions in 2030. Longer-term perspectives on GHG emission reductions toward 2030
will yield more cost-effective reduction scenarios for 2020 as well. 相似文献
957.
958.
Pinus roxburghii (chir-pine) and Quercus leucothchophora (banj-oak) are dominant forests of mountainous part of the Uttarakhand Himalaya. The continued anthropogenic disturbance
is opening the canopy, forming canopy gaps and as a result forest fragments are developing. Thus, the present study aims to
analyze variations in species richness and vegetational parameters in relation to canopy gaps in forests. Total species richness
was greater in open canopied forest compared to moderate and close canopied forests. In comparison between oak and pine forest,
it was greater in oak forest while the proportion of common species was low between oak—pine forests. Mean species richness
did not significantly vary from one canopy gap to another as well as in oak and pine dominated forest. This indicated that
dominant forest types played an important role to form the community structure. The shrubs richness were greater in closed
canopy and between the forests it was greater in pine forest. Tree and shrub density was low in open canopy while herb density
was high in moderate canopy. Thus, this study indicated that the dominant canopy species play an important role in deciding
the community structures especially the distribution of under canopy species. These parameters should be considered for conservation
and maintenance of plant biodiversity of a region. 相似文献
959.
Chuen-Jinn Tsai Chia-Hung Lin Yu-Min Wang Cheng-Hsiung Hunag Shou-Nan Li Zong-Xue Wu 《Journal of the Air & Waste Management Association (1995)》2013,63(3):319-332
Abstract An efficient venturi scrubber system making use of heterogeneous nucleation and condensational growth of particles was designed and tested to remove fine particles from the exhaust of a local scrubber where residual SiH4 gas was abated and lots of fine SiO2 particles were generated. In front of the venturi scrubber, normal-temperature fine-water mist mixes with high-temperature exhaust gas to cool it to the saturation temperature, allowing submicron particles to grow into micron sizes. The grown particles are then scrubbed efficiently in the venturi scrubber. Test results show that the present venturi scrubber system is effective for removing submicron particles. For SiO2 particles greater than 0.1 μm, the removal efficiency is greater than 80–90%, depending on particle concentration. The corresponding pressure drop is relatively low. For example, the pressure drop of the venturi scrubber is ~15.4 ± 2.4 cm H2O when the liquid-to-gas ratio is 1.50 L/m3. A theoretical calculation has been conducted to simulate particle growth process and the removal efficiency of the venturi scrubber. The theoretical results agree with the experimental data reasonably well when SiO2 particle diameter is greater than 0.1 μm. 相似文献
960.
Brian K. Gullett Paul W. Groff M. Linda Lin James M. Chen 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1188-1194
Pilot-scale tests were conducted to develop a combined nitrogen oxide (NOx) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium- and titanium-based composite honeycomb catalyst and enhanced urea (NH2CONH2) were used with a natural-gas-fired furnace at a NOx concentration of 110 ppm. Changes in SNCR chemical injection temperature and stoichiometry led to varying levels of post-furnace ammonia (NH3), which acts as the reductant feed to the downstream SCR catalyst. The urea-based chemical could routinely achieve SNCR plus SCR total NOx reductions of 85 percent with less than 3 ppm NH3 slip at reductant/NOx stoichiometries ranging from about 1.5 to 2.5 and SCR space velocities of 18,000 to 32,000 h?1. This pilot-scale research has shown that SNCR and SCR can be integrated to achieve high NOx removal. SNCR provides high temperature reduction of NOx followed by further removal of NOx and minimization of NH3 slip by a significantly downsized (high-space velocity) SCR. 相似文献