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。     

关于差阻式仪器的几个技术问题

本文对差阻式仪器的几个重要问题,如差阻式仪器的国家标准、监测数据的质量控制、长期埋设仪器的现场鉴定、仪器测值异常的分析处理等进行了讨论,并提出了自己的意见,供有关科研人员进一步研究和参考.     

无粘结预应力蛋形消化池的施工技术

石家庄市桥东污水处理厂有6座11500m3无粘结预应力混凝土蛋形消化池,本文介绍其非预应力钢筋、模板体系、混凝土和预应力工程等结构施工成套技术。     

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。     

A frame-based knowledge representation model and its mapping to nested relations

The first part of this paper introduces the basic constructs of a frame representation model and gives a formal definition for them. Subsequently the nested relational model (NF²) is described as an extension of the classical relational model to support relation-valued attributes. In the second part of this paper both models are compared with each other and a mapping of frame representation structures to NF² structures is specified. The structural similarities between frames and NF² relations are made clear and it is shown that their main difference is due to the type polymorphism introduced by the concept hierarchy of the frame model. This causes type collisions to occur in the strictly typed NF² model when frames are directly mapped to NF² structures. Two solutions to this problem are suggested and compared. The paper concludes with a reformulation of query operations of the frame model in terms of NF² algebra operations.     

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。     

滚动转子式压缩机传热模拟

就滚动转子式压缩机的传热特性进行了分析。把压缩机分为15块，视摩擦损失和电机发热为内热源，考虑润滑油流动在传热过程中的影响，应用集中参数法对每块进行了能量分析，建立了传热数学模型并进行了计算。