斜发沸石对模拟核素CO2+的吸附/解吸动力学研究

以CO(NO3)2·6H2O为核素源、新疆某地所产斜发沸石为吸附剂,研究斜发沸石对Co2+的动力吸附/解吸效果.探讨了吸附时间、K+初始浓度与吸附量的关系.用pH值为6的水溶液对饱和吸附了Co2+的斜发沸石进行解吸.结果表明:斜发沸石对Co2+的吸附在2h能达到最大吸附率的99.5％,Freundlich吸附等温式能对...     

Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 µM, 0.9 µM, and 41.8 µM in 2002 to 37.5 µM, 1.3 µM, and 82.2 µM in 2006, respectively, while TP decreased from 2.1 µM to 1.7 µM. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 µM. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN:TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously.     

Base properties of zeolite catalysts

Distributions of base strengths were determined using indicator techniques and i.r. spectroscopic studies of acetic acid adsorbed on samples of faujasite-type zeolites. The results show that base sites of variou zeolites differ significantly in both their strength and nature. Among sodium forms of the zeolites, NaX appeared to exhibit higher strength and concentrations of base sites than NaY. For hydrogen-sodium forms, the situation was reversed: HNaY prevailed over HNaX. The total basicities of the hydrogen—sodium zeolites were considerably higher than those of the sodium forms, due to contributions from both hydroxyl groups and oxygen ions of (AlO₄)⁻ tetrahedra; whereas the latter exhibited Lewis basicity alone. Nonetheless, the higher basicities of the HNaY and HNaX zeolites do not correlate with their catalytic activity for decomposition of diacetone alcohol to acetone, a model base-catalysed reaction. The relatively poor conversions to acetone are examined within the context of base strengths and the high acidity of HNaX and HNaY since another reaction pathway, acid-catalysed formation of mesityl oxide, was also observed.     

Selection of geotextiles for use with synthetic drainage products

The selection of a geotextile to be used in conjunction with a synthetic core in a drainage layer should be part of the design process. Due to the large number of variables affecting the performance of the drainage layer it may be difficult to evaluate which geotextile would provide the best performance for a particular application. The decision analysis technique described in the paper provides a logical and methodical approach for comparing index or design test data to rank the geotextile in each performance area expected to affect the overall performance of the drainage layer.     

有机农药污染土壤的修复技术初探

中国农药使用量大,是农业面源污染中的主要污染物,因此,修复农药污染的土壤是农业面源污染治理的重点。叙述了农药污染土壤的化学、微生物、植物修复研究的进展,对今后农药污染土壤的化学和生物修复进行了展望。     

Enhanced generation of hydrogen,power, and heat with a novel integrated photoelectrochemical system

Hydrogen is an essential component of power-to-gas technologies that are needed for a complete transition to renewable energy systems. Although hydrogen has zero GHG emissions at the end-use point, its production could become an issue if non-renewable, and pollutant energy and material resources are used in this step. Therefore, a crucial step for the fully developed hydrogen economy is to find alternative hydrogen production methods that are clean, efficient, affordable, and reliable. With this motivation, in this study, an integrated and continuous type of hydrogen production system is designed, developed, and investigated. This system has three components. There is a solar spectral splitting device (Unit I), which splits the incoming solar energy into two parts. Photons with longer wavelength is sent to the photovoltaic thermal hybrid solar collector, PV/T, (Unit II) and used for combined heat and power generation. Then the remaining part is transferred to the novel hybrid photoelectrochemical-chloralkali reactor (Unit III) for simultaneous H₂, Cl₂, and NaOH production. This system has only one energy input, which is the solar irradiation and five outputs, namely H₂, Cl₂, NaOH, heat, and electricity. Unlike most of the studies in the literature, this system does not use only PV or only a photoelectrochemical reactor. With this approach, solar energy utilization is maximized, and the wasted portion is minimized. By selecting PV/T rather than PV, the performance of the panels is maximized because recovering the by-product heat as a system output in addition to electricity, and the PV/T has less waste and higher efficiency. The present reactor does not use any additional electron donors, so the wastewater discharge is only depleted NaCl solution, which makes the system significantly cleaner than the ones available in the literature. The specific aim of this study is to demonstrate the optimum operating parameters to reach the maximum achievable production rates and efficiencies while keeping the exergy destruction as little as possible. In this study, there are four case studies, and in each case study, one decision variable is optimized to get the desired performance results. Within the selected operating parameter range, all performance criteria (except exergy destruction) are normalized and ranked for proper comparison. The maximum production rates and efficiencies with the least possible exergy destruction are observed at the operating temperature of 30 °C. At 30 °C, 4.18 g/h H₂, 127.55 g/h Cl₂, 151 W electricity, and 716 W heat are produced with an exergy destruction rate of 95.74 W and 78% and 30% energy and exergy efficiencies, respectively.     

碳汇约束下的碳汇林生态效益优化模型研究

根据碳汇林发展现状及特点,综合考虑地区和树种等相关因素影响,运用区间规划方法,以生态效益最大化为优化目标,建立碳汇林生态效益优化模型,获取碳汇量约束下生态效益最大的造林决策方案。案例分析表明:通过模型优化,在满足碳汇约束的前提下优化方案可以提供更多的生态效益,较项目方案每年多收入[6 580.80,11 209.60]万元,提高了[14.35%,24.44%],充分发挥了碳汇林的生态效益潜能,使生态环境得到了明显的改善。     

Kinetics of collector adsorption on mineral surfaces

In the present study infrared attenuated total reflection (IR-ATR) was used to monitor the rate of in situ adsorption of heptyl xanthate on a layer of zinc sulphide synthesized on a germanium ATR crystal. The zinc sulphide surface was characterized using X-ray photoelectron spectroscopy (XPS). The absorbance of heptyl xanthate measured increased with increasing bulk concentration of the adsorbate up to an equilibrium plateau value corresponding to a fractional coverage of the surface sites of the substrate. For the adsorption from solutions of concentrations between 10⁻³ and 10⁻⁵ M, the rate of adsorption increased with increasing bulk concentration. At higher concentrations the measured absorbance should be corrected for the absorbance due to the concentration of xanthate in bulk solution. The present work provides a discussion of this correction. Assuming the adsorption stage to be rate-controlling and proportional both to the concentration of the adsorbing species in solution and unreacted surface area, a rate law governing this type of transient adsorption kinetics was derived. By means of absorbance data for the concentrations 0.1 and 0.01 mM, the rate constant of adsorption was calculated. From the initial part of a Langmuir adsorption isotherm, the absorbance at monolayer coverage and the equilibrium constant of adsorption could be estimated.     

On the relationship between stress and elastic strain for porous and fractured rock

Modeling the mechanical deformations of porous and fractured rocks requires a stress–strain relationship. Experience with inherently heterogeneous earth materials suggests that different varieties of Hooke's law should be applied within regions of the rock having significantly different stress–strain behavior. We apply this idea by dividing a rock body conceptually into two distinct parts. The natural strain (volume change divided by rock volume at the current stress state), rather than the engineering strain (volume change divided by the unstressed rock volume), should be used in Hooke's law for accurate modeling of the elastic deformation of that part of the pore volume subject to a relatively large degree of relative deformation (i.e., cracks or fractures). This approach permits the derivation of constitutive relations between stress and a variety of mechanical and/or hydraulic rock properties. We show that the theoretical predictions of this method are generally consistent with empirical expressions (from field data) and also laboratory rock experimental data.