Study of the concentration and separation of cadmium with microcrystalline phenolphthalein modified by crystal violet

A new method for cadmium separation and concentration with microcrystalline phenolphthalein modified by crystal violet (CV) was developed in the paper. In the presence of potassium iodide (KI) and CV, cadmium are quantitatively absorbed on microcrystalline phenolphthalein in the pH range 1.0-6.0 as the forms of water-insoluble ion-associated complexes (CdI₃⁻)·(CV⁺) and (CdI₄²⁻)·(CV⁺)₂. Effect of different parameters such as phenolphthalein amount, stirring time, the concentration of CV and KI, various salts and metal ions was studied in detail. During the present study, a significant enhancement of the extraction of cadmium was observed. Cd(II) can be completely separated from Zn(II), Fe(II), Co(II), Ni(II), Mn(II), Cr(III) and Al(III) in this microcrystalline system and well concentrated without the interference of these metal ions at high level. The possible reactive mechanism of cadmium concentration has been discussed. Analytical results obtained by this new method were very gratifying.     

State-of-the-art of membrane bioreactors: Worldwide research and commercial applications in North America

Membrane bioreactor (MBR) technology is advancing rapidly around the world both in research and commercial applications. Despite the increasing number of studies and full-scale applications of MBR systems, directions and trends in academic research as well as commercial developments require further analysis. This paper aims to critically characterize and review worldwide academic research efforts in the area of MBRs as well as focus attention to commercial MBR applications in North America. A total of 339 research papers published in peer-reviewed international journals from 1991 to 2004 and a total of 258 full-scale MBR installations in North America were used as the database for the analysis provided in this paper. After a surge of MBR publications in 2002, research appears to have reached a plateau in the last 3 years using both submerged and external MBR units. Although much of the pioneering research occurred in Japan, France and the UK, countries such as South Korea, China and Germany have significantly contributed to the research pool in the last 5 years. The primary research focus has been on water filtration MBRs with limited growth in extractive and gas diffusion MBRs which still hold un-tapped potential. Fundamental aspects studied in academic research predominantly involve issues related to fouling, microbial characterization and optimizing operational performance. Research in North America presents a unique picture as a higher ratio of industrial wastewater treatment and side-stream MBR applications have been studied compared to other parts of the world. For MBR commercial application, the North America installations constitute about 11% of worldwide installations. Zenon occupies the majority of the MBR market in North America, whereas Kubota and Mitsubishi-Rayon have a larger number of installations in other parts of the world. Due to more stringent regulations and water reuse strategies, it is expected that a significant increase in MBR plant capacity and widening of application areas will occur in the future. Potential application areas include nitrate removal in drinking water treatment, removal of endocrine disrupting compounds from water and wastewater streams, enhancing bio-fuels production via membrane assisted fermentation and gas extraction and purification MBRs.     

EXAMINATION OF THE SURFACE FREE ENERGY AND ACID-BASE PROPERTIES OF CELLULOSE BY THE COLUMN WICKING TECHNIQUE AND THE CRITICAL PACKING HEIGHT/DENSITY

INTRODUCTIONThe wicking technique has been used to determine the surface energy components of solids[1-7]. Generally, thereare two wicking processes in practice, i.e. thin layer wicking and column wicking. A comparison of the twowicking techniques made by van Oss et al.[2], shows that column wicking has a problem of showing differentpacking density due to some kinds of powder materials, i.e. clay can not give good repacking reproducibility[2].But thin layer wicking has a problem in sample…     

Simultaneous Determination of Aluminum and Iron in High Salt Content Matrices by Adsorptive Stripping Voltammetry. Application to Dialysis Fluids

A new analytical procedure for the simultaneous determination of aluminum(III) and iron(II) in two kinds of dialysis fluids (peritoneal and hemodialysis fluids) by differential pulse adsorptive stripping voltammetry (DPAdSV) is described. The voltammetric measurements were performed using, as working electrode, a stationary mercury electrode, and a platinum electrode and a Ag|AgCl|KCl_(sat.) electrode as auxiliary and reference electrodes, respectively, employing acetate buffer solutions at different pH as supporting electrolyte. As complexing agents, Solochrome Violet RS, Palatine Chrome Black 6BN, Chromazurol S and Eriochrome Black T were employed. For both elements, the accuracy, expressed as relative recovery R%, was very satisfactory being in the range 94–105%, the precision as repeatability, expressed as relative standard deviation s_r%, was lower than 6%, while the limits of detection were of the order of a few units of μg/L. The analytical voltammetric procedure has been validated by comparison with spectroscopic (graphite furnace atomic absorption spectroscopy, GFAAS) measurements.     

Behavior of rifampicin in association with<Emphasis Type="Italic"> β</Emphasis>-cyclodextrin in aqueous media: a spectroscopic and conductometric study

The behavior of rifampicin (D) with -cyclodextrin (-CyD) in aqueous media (W) has been examined by means of UV-vis spectroscopy and conductivity measurements over the temperature range 15–30 °C. The UV-vis study has been used to characterize the systems. The estimated molar absorption coefficient for D/CyD/W system was 10757±280 M^–1 cm^–1 in comparison to the value of 6133±99 M^–1 cm^–1 for D/W system. The conductivity was measured (i) as a function of [D] for binary D/W systems, (ii) as a function of [CyD], keeping the concentration of drug constant, for D/CyD/W system, and (iii) as a function of [D] in the presence of a constant cyclodextrin concentration. Two transition points were observed for D/CyD/W system at constant [CyD], which were assigned as cac-1 and cac-2. The stoichiometry of the association was estimated from the conductivity data. This was obtained from [drug] value at which the change in slope of occurs. The standard free energy change, of aggregation was also calculated from the critical concentration data. An attempt has also been made to estimate the stoichiometry of -cyclodextrin:rifampicin association.     

BaLaB_9O_（16）中Ce~（3＋）敏化Dy~（3＋）发光的机理

在紫外光激发下，研究了ＢａＬａＢ９Ｏ（１６）中Ｄｙ（３＋）、Ｃｅ（３＋）的发光光谱、激发光谱、发光强度及荧光寿命随着组成变化的规律性．结果表明：Ｄｅ（３＋）对Ｄｙ（３＋）的发光有相当强的敏化作用，Ｃｅ（３＋）→Ｄｙ（３＋）的能量传递效率可高达９３％，能量传递的机理为电偶极－偶极相互作用的共振传递．根据３４９ｎｍ激发下Ｄｙ（３＋）发光强度与浓度的关系，证明了Ｄｙ（３＋）发光的自身浓度猝灭机理也为电偶极－偶极相互作用．     

Hydrogen Gas Sensing of High Electrical Conducting-P2O5-SiO2 Glasses Prepared by Sol-Gel Process

High proton-conducting P₂O₅-SiO₂ glass was applied to the electrolyte of the hydrogen concentration cell for hydrogen gas sensing. 5P₂O₅·95SiO₂ glass was prepared using the sol-gel method and its electrical conductivity and electromotive force were measured at 50°C as a function of both the ambient humidity and hydrogen gas concentration. The electrical conductivities increased with increasing humidity and reached 10^–2 S/cm at 90% relative humidity. The electromotive force of the hydrogen concentration cell, where the glass was used as a membrane, showed good Nernstian response to hydrogen pressure in the high relative humidity region.     

新型氧离子导体La2Mo1.8Ga0.2O9陶瓷的合成及其电性能

通过高温固相合成法首次合成了La₂Mo_1.8Ga_0.2O₉陶瓷样品. 粉末XRD结果表明, 该样品为单一立方相La₂Mo₂O₉结构. 以陶瓷样品为固体电解质、多孔性铂为电极, 采用交流阻抗谱、气体浓差电池、氧泵等方法研究了样品在600～1000 ℃下各种气氛中的离子导电特性. 结果表明, 氧浓差电池电动势的实测值与理论值吻合得很好, 氧离子迁移数为1, 表明该陶瓷样品在该温度下氧气气氛中为一纯氧离子导体; 氧泵(氧的电化学透过)实验结果进一步证实了该样品在氧气气氛中为一纯氧离子导体; 在氧分压p(O₂)＝10^－5～10⁵ Pa的高氧分压气氛中, 电导率与氧分压变化基本无关, 表明在该氧分压范围内样品为纯离子导体, 这与氧浓差电池电动势测定结果相吻合; 在低氧分压为10^－5～10^－15 Pa范围内, 总电导率随氧分压降低而稍有升高, 表明在该氧分压范围样品为氧离子与电子的混合导体; 在600～1000 ℃下氧离子电导率＞10^－2 S•cm^－1, 显著高于母体La₂Mo₂O₉的氧离子电导率, 1000 ℃时的氧离子电导率为0.07 S•cm^－1.     

Determination of Aggregation Parameters of Hexadecyltrimethylammonium Bromide from Probe Absorption

The mean aggregation number (n) and the critical micelle concentrations (CMC) of reverse micelles formed by hexadecyltrimethylammonium bromide have been determined by means of an optical absorption probe (acridine orange). The procedure to obtain these quantities from absorption spectrophotometric measurements is described. The CMC and mean aggregation number are in satisfactory agreement with published results obtained from more sophisticated methods.     

The solubilization of alcohols in micellar solutions

The specific conductivities of dodecyldimethylbenzylammonium bromide (C12BBr) have been determined in aqueous butanol and aqueous benzyl alcohol solutions in the temperature range of 5-40°C. From these data the temperature dependent critical micelle concentration (cmc) was determined. The molar fraction of alcohol in the micelle was estimated using the theory suggested by Motomura et al. for surfactant binary mixtures. The thermal properties such as standard Gibbs free energy, enthalpy and entropy of solubilization of alcohols in the micelles were estimated for the phase separation model. The change in heat capacity upon solubilization of alcohol in the micelle has been estimated form the above properties. This revised version was published online in July 2006 with corrections to the Cover Date.