Analysis of trace mercury in water by solid phase extraction using dithizone modified nanometer titanium dioxide and cold vapor atomic absorption spectrometry

A new method for analysis of trace mercury in water samples was developed, based on the combination of preconcentration/separation using dithizone-modified nanometer titanium dioxide (TiO2) as a solid phase extractant and determination by cold vapor atomic adsorption spectrometry (CVAAS). Dithizone was dissolved with alcohol and loaded on the surface of nano-sized TiO2 powders by stirring. The static adsorption behavior of Hg2 on the dithizone-modified nanoparticles was investigated in detail. It was found that excellent adsorption ratio for Hg2 could be obtained in the pH range of 7-8 with an oscillation time of 15 min, and a 5 mL of 3.5 mol·L-1 HCl solution could quantitatively elute Hg2 from nanometer TiO2 powder. Common coexisting ions caused no obvious influence on the determination of mercury. The mechanisms for the adsorption and desorption were discussed. The detection limit (3σ) for Hg2 was calculated to be 5 ng·L-1. The proposed method was applied to the determination of Hg2 in a mineral water sample and a Zhujiang River water sample. By the standard addition method, the average recoveries were found to be 94.4%-108.3% with RSD (n = 5) of 2.9%-3.5%.     

雷达目标特征提取的一种方法

将小波变换和马氏距离相结合，提出了一种基于ISAR成像的雷达目标特征提取方法。对ISAR成像数据进行正交二进Symlet小波分解和门限处理，对数据进行压缩，然后计算压缩后坐标点的马氏（Mahalanobis)距离，得到目标稳定的特征向量。由实验结果看出，此向量具有在一定范围内的不变性，能够用于雷达目标识别。     

化学复合镀Ni-P-TiO_2光催化降解次甲基蓝

以钛酸丁酯为原料通过溶胶 凝胶法制备出粒径 30nm左右的纳米TiO2 ,利用化学复合镀在钢铁基底上形成Ni P 纳米TiO2 复合镀层 ,该复合镀层对次甲基蓝有较好的光催化降解作用 ,其催化性能与粉末状纳米TiO2 的催化性能大致相当。     

Kinetic Monte Carlo simulations of radiation induced segregation and precipitation

Kinetics of radiation induced segregation and precipitation in binary alloys are studied by Monte Carlo simulations. The simulations are based on a simple atomic model of diffusion under electron irradiation, which takes into account the creation of point defects, the recombination of close vacancy-interstitial pairs and the point defect annihilation at sinks. They can reproduce the coupling between point defect fluxes towards sinks and atomic fluxes, which controls the segregation tendency. In pure metals and ideal solid solutions, the Monte Carlo results are found to be in very good agreement with classical models based on rate equations. In alloys with an unmixing tendency, we show how the interaction between the point defect distribution, the solute segregation and the precipitation driving force can generate complex microstructural evolutions, which depend on the very details of atomic-scale diffusion properties.     

离子液体用于燃料油深度脱硫的研究进展

首先介绍了加氢催化脱硫和其他脱硫技术的特点,综述了近年来国内外利用离子液体在萃取脱硫、萃取脱硫与氧化脱硫耦合、萃取脱硫与生物脱硫耦合等方面的研究。认为离子液体萃取脱硫具有操作简便、可循环使用、无需氢气、环境友好、能深度脱硫等特点,是一项具有广阔发展前景的技术。若要实现该技术的工业化应用,还需进一步加强离子液体在合成工艺、脱硫选择性及回收再生等方面的研究。     

Formation of steady state size distribution of precipitates in alloys under cascade-producing irradiation

The effect of coherency loss on the development of precipitate size distribution under cascade-producing irradiation is considered. The nucleation of coherent precipitates, their growth followed by coherency loss and cascade-induced dissolution of large incoherent precipitates can occur simultaneously resulting in formation of a quasi-stationary size distribution of semicoherent precipitates. To describe this process we consider co-evolution of a mixed population of coherent, semicoherent and incoherent precipitates. Mathematically, the problem is formulated as a set of discrete rate equations of nucleation kinetics (the Master equation approach) which is also used for later stages of evolution. To solve the corresponding large set of equations (typically, more than 10⁵ equations) an efficient numerical method is developed. The simulation results obtained for material parameters and irradiation conditions typical for nuclear reactors show that the coherency loss affects considerably evolution of the precipitate population. Under certain irradiation conditions, both in solution-annealed alloys and in aged ones, the mean precipitate size and the number density during prolonged irradiation tend to steady state values, whereas the size distribution function of large precipitates narrows. The width of the quasi-stationary size distribution is controlled by cascade parameters. It was found that the asymptotic quasi-stationary state of the precipitate population may depend on initial state of the alloy.     

Mass transfer kinetics of neodymium(III) extraction by calix[4]arene carboxylic acid using a constant interfacial area cell with laminar flow

BACKGROUND: Thermodynamics and kinetics data are both important to explain the extraction property. In order to develop a novel separation technology superior to current extraction systems, many promising extractants have been developed including calixarene carboxylic acids. The extraction thermodynamics behavior of calix[4]arene carboxylic acids has been reported extensively. In this study, the mass transfer kinetics of neodymium(III) and the interfacial behavior of calix[4]arene carboxylic acid were investigated. RESULTS: The rate constant (K_ao) becomes constant when the stirring speed was controlled between 250 rpm and 400 rpm. The activation energy (E_a) was calculated to be 21·41 kJ mol^?1 or 88·17 kJ mol^?1 (dependent on temperature) from the slope of log K_ao against 1000/T. The linear relationship between the specific area and the extraction rate is the characteristic of an interfacial reaction control. The minimum bulk concentration of the extractant necessary to saturate the interface (C_min) is lower than 4·19 × 10^?4 mol L^?1. CONCLUSION: The effect of stirring speed, temperature, and species concentration on the extraction rate demonstrates that the extraction regime depends on the extraction conditions. The chemical reaction control governs the extraction regime at temperatures below 303 K and a mixed control regime occurs when the temperature is between 303 K and 318 K. The probable locale for the chemical reaction is at the liquid–liquid interface and the rate equation is deduced to be: ? d[Nd³⁺]_(a)/dt = k_f[Nd³⁺]_(a)[H₄A]_(o)^0·727[H⁺]_(a)^?0·978. The rate‐controlling step was suggested by the analysis of the experimental results. Copyright © 2008 Society of Chemical Industry     

调节剂对烷基水杨醛肟萃取铜铁的影响

烷基水杨醛肟虽然是一种高选择性的铜萃取剂，但单独使用时，萃取相易出现沉淀；反萃时，再生有机相出现乳化物，而且两相分离时间较长．将月桂醇、仲辛醇、壬基酚三种调节剂分别加入到萃取剂中，研究其对烷基水杨醛肟萃取及反萃行为的影响．结果表明，三种调节剂均可以解决上述问题，只是使萃取能力略有降低；壬基酚加入到烷基水杨醛肟中有助于提高铜铁分离系数，可达647．     

从水淬渣中回收镓的试验研究

对鼓风炉（ISP法）或烟化炉水淬渣中回收镓的工艺进行了研究。结果表明，利用浓硫酸恒温熟化的独特浸出工艺，克服硅对液固分离的影响；以伯胺N9123作为萃取剂在硫酸介质中萃取镓；获得了含镓品位为2.82%的富集物。     

用于快速P/G网分析的Cholesky分解法图模型

通过对Cholesky分解法求解线性方程组的分析，建立Cholesky分解法三角化对称正定阵的图模型，并基于该模型及Mesh结构P／G网络的自身特点，提出一个P／G网快速分析算法．实验证明，该算法能大大降低Mesh结构P／G网络的分析运算时间和内存占用．