New Ternary Phases in Some Alkaline-Earth Rare-Earth Sulfide Systems

New ternary alkaline-earth rare-earth sulfide phases of composition MLn₂S₇ where M = Ca or Sr and Ln = La, Nd, or Gd have been formed by open-system reactions in flowing H₂S. The phases have been characterized by X-ray powder diffraction and electron microprobe analysis. These compounds form as low-melting ( T _m approximately 1100°C) products when refractory compounds along the MS-Ln₂S₃ join are oxidized at high sulfur fugacities.     

Alkali Tungstates: Stability Relations in the Systems A2O WO3-WO3

Phase relations in the systems alkali monotungstate-tungsten trioxide were investigated in the range 600° to 1100°C.In the Li system, compounds with an A₂O/WO³ ratio of 1:2 and 1:4 are stable and melt incongruently at 745° and 805°C, respectively. In the Na system, the 1:2 compound melts congruently at 746°C, whereas the other 2 sodium tungstates (1:4 and 1:6) melt incongruently at 835° and 913°C, respectively. The K system includes compounds of 1:2, 1:3, 1:4, and 1:6 which melt incongruently at 684°, 842°, 912°, and 964°C, respectively. Eutectic points between the 1:l and 1:2 compounds in these respective systems are at 692°C and 56 mol%WO³, 622°C and 56.3 mol% WO³, and 633°C and 63 mol%WO³. In the Rb and Cs systems, the 1:2 and 1:3 compounds form complete solid-solution series, and their melting temperatures increase with increasing WO³ content, respectively, from 690° to 868°C and from 732° to 902°C. The 1:6 compounds are also stable in these systems and melt incongruently at 1040° and 1046°C, respectively.     

Lead-Ion Stability in Vitreous Systems

A new glaze composition was characterized and compared with one studied previously in order to evaluate structural model relating lead-ion stability and coloring-ion content to the vitreous system in which they are found. This model is based on the geometrical arrangement of the ionic network, depending in turn on the preferred coordination of the cations involved. The stability of the ionic structure, as indicated by release of Pb²⁺ on acid attack, is correlated with the coordination of sites occupied by network modifiers, i.e. cations producing cubic coordination were associated with increased Pb²⁺ release, whereas the opposite ccurred with those producing anti prismatic coordination.     

Equilibrium Phase Diagrams in the Systems PbO–Ag and CuO–Ag

Silver has played a critical role in the fabrication of metal/ high-T_c superconductor composites. Phase equilibrium in the binary PbO–Ag and CuO–Ag systems has been investigated using differential thermal analysis (DTA), thermogravimetry (TG), and X-ray diffractometry (XRD) techniques. Composition versus temperature diagrams have been established for these systems in air. Eutectic reactions CuO + Ag = L at a composition of Ag = 98.6 mol% and 932°± 3°C for the CuO–Ag system and PbO + Ag = L at a composition of Ag = 8.3 mol% and 825°± 3°C for the PbO–Ag system have been detected. The CuO–Ag system has two immiscible liquid phases in the composition regime of Ag = 30.6–98 mol%, and there are two immiscible liquid phases at the composition range of Ag = 11.7–95.7 mol% in the PbO–Ag system.     

Property Variation in Alkali Alkaline-Earth Metaphosphate Glasses

Coefficients of helium migration, coefficients of thermal expansion, and glass-transition temperatures were measured for several series of alkali alkaline-earth phosphate glasses. The helium permeability decreases with the field strength of alkali or alkaline-earth ions in the order Na⁺ > Li⁺ and Mg²⁺ > Ca²⁺ > Ba2+. The glass-transition temperature increases and coefficient of thermal expansion decreases with increasing field strength of alkali or alkaline-earth ions. The relationship of lower molar volume, corresponding to decreased coefficients of helium diffusivity reported for other glass-forming systems, occurs in the phosphate glasses.     

Nitrogen Dissolution in Sodium Alkaline-Earth Metaphosphate Melts

Phosphorus oxynitride glasses were prepared by remelting (5O – X )Na₂O · X BaO · 50P₂O₅, X = 0, 10, 20, 25, and 30, and 30Na₂O · 20MO · 50P₂O₅, M = Mg, Ca, Sr, and Ba', glasses in anhydrous ammonia. The nitrogen content depends upon the temperature and time of remelting in ammonia and the concentration and size of the alkaline-earth ion. Nitriding the starting glass decreased the dissolution rate in deionized water and thermal expansion coefficient and increased the dilatometric softening temperature and refractive index. The dissolution rate of the base glass in deionized water depended upon the concentration and size of the alkaline-earth ion, but for nitrided glasses, it was essentially independent of the alkaline-earth cation. The thermal expansion coefficient for all the oxynitride glasses decreased with increasing alkaline-earth concentration and cation field strength.     

超临界二氧化碳和脂质体系相平衡计算

对超临界CO2和一些脂质体系相平衡计算问题进行了研究.应用Peng-Robinson状态方程及Panagiotopoulos和Reid混合规则,改进能量参数a(T)后,用于计算脂质和超临界CO2组成的二元和三元体系的相平衡,结果与实验数据拟合精度较好.对于一些复杂的混合物如大豆油脱臭馏出物与超临界CO2体系,简化成拟三元、四元等体系进行了计算,计算结果达到一定的精度.     

水-异丙醚-苯酚和水-异丁醇-苯酚体系的液液平衡研究

水-异丙醚-苯酚体系的研究在工业上和环境保护上具有重要意义,但至今未见到液液平衡(LLE)数据的报导今报导了这一系统在两个工作温度的LLE数据.为了寻找萃取剂异丙醚的替代物,我们同时进行了水-异丁醇-苯酚体系的液液平衡研究. 在常压下使用GC-14B气相色谱仪,测定了319 K和329 K时水-异丙醚-苯酚体系的液液平衡(LLE)数据以及水-异丁醇-苯酚体系在319 K和333 K时的LLE数据.用内标法测定了这些体系中除水以外的各组分浓度.在水-异丙醚-苯酚体系中,异丙醚测量的根均方误差为1.4%;苯酚测量的根均方误差为4.6%.在水-异丁醇-苯酚体系中,异丁醇测量的根均方误差为3.1%:苯酚测量的根均方误差为4.6%. 文中给出了上述四个等温截面的LLE数据,同时也给出了相应示意图.2003年我们用工作曲线法(外标法)给出了水-异丙醚-苯酚在319K的等温截面图.两者比较,总体上是类似的,但内标法结果更可靠.这次的研究,还纠正了当时的一个错误估计.对于水-异丁醇-苯酚体系的液液平衡研究表明,异丁醇也是从废水中萃取苯酚的良好萃取剂.但是异丁醇的再生及其循环利用并不如异丙醚那样容易.     

Morphology and Stability of the Glass Phase in Glass Ceramic Systems

An explanation is given for the apparent stability of a minor phase in a two-phase system, such as a glass in a glass ceramic, even though normally the glass would be expected to dissolve completely into the crystalline phase. It is shown that the glass would be stable only if it is segregated to the triple-junction nodes and only if the dihedral angle is <π/3. The size and morphology of the glass pocket are obtained in terms of the interface energies, the undercooling below the solidus temperature, and the dihedral angle.     

High-Temperature Energy Relations in Borates: Alkaline-Earth and Lead Borate Compounds and Their Glasses

The high-temperature energy relations in some alkaline-earth and lead borate glasses and compounds of the same compositions are reported. The data obtained with a continuous high-temperature calorimeter and by solution calorimetry in 2 N nitric acid were combined to give heat content versus temperature curves from 25° to 1100°C. The heats of fusion, entropies of fusion, entropy changes vs. temperature, and the free-energy changes from crystal to glass at 25°C are given. Previously unavailable X-ray diffraction data for strontium diborate and calcium diborate are reported.     

Prediction of the Equilibrium Composition for High-Temperature Reaction Products in Complex Oxide Systems

Thermodynamic analysis of parallel-serial reaction in complex oxide systems is carried out. The use of the Karapet'yants method to supplement the refined Hooke-Jeeves method has made it possible to determine the optimum range of compositions studied and the most rational temperature interval for heat treatment of coatings. This makes it possible to substantially decrease subsequent experimental search and reduce it to a verification of the optimum interval that is thermodynamically identified.     

Metathetic Reaction in Reverse Micelles: Synthesis of Nanostructured Alkaline-Earth Metal Phosphates

For the past few years, hydroxyapatite (HAp) has been identified as a potential biomaterial due to its excellent biocompatibility and bioactivity. The preparation of nanostructured HAp with controlled powder characteristics is a pre-requisite for processing it into useful biocomposites. Here, the synthesis of nanorods of calcium hydroxyapatite (Ca-HAp), strontium hydroxyapatite (Sr-HAp), and barium hydroxyapatite (Ba-HAp) by exploiting the metathetic reaction taking place in reverse micelles in the presence of cetyltrimethylammonium bromide has been reported. Powder X-ray diffraction analysis and thermogravimetric measurements confirm the formation of monophasic Ca-HAp and Sr-HAp. The growth of nanorods was further confirmed using transmission electron microscopy studies. The average lengths of Ca-HAp and Sr-HAp were ∼60 and 30 nm, respectively. However, the preparation of Ba-HAp invariably yielded a multiphasic mixture with other competitive phases like BaHPO₄ and Ba(H₂PO₄)₂.     

Infrared Spectroscopy of Lead and Alkaline-Earth Aluminosilicate Glasses

Infrared spectroscopic studies of lead and alkaline-earth aluminosilicate glasses in the series x MO- x Al₂O₃ (1 - 2 x )SiO₂ M = Mg, Ca, Sr, Ba, and Pb; 0.05 x 0.275] were carried out in the range 2000 to 200 cm⁻¹. Three major absorption bands were observed in the 1100-, 800-, and 500-cm⁻¹ regions. The frequency and the intensity of the 1100-cm⁻¹ band varied linearly with composition. For a specific value of x , the changes in the frequency, intensity, and bandwidth of this band decreased in the order Mg > Ca > Sr > Pb > Ba and the apparent disorder in the glass structure, effected by the substitution of aluminum, increased in the direction Mg < Ca < Sr < Ba, with Pb in between Mg and Ca. The force constants and the bond orders of the Si-O and Al-O stretching vibrations in each of the glasses increased monotonically as Al/(Al + Si) decreased.     

非缓冲体系中性氨基酸的离子交换平衡

研究了非缓冲体系中性氨基酸在７３２型强酸性阳离子交换树脂上的离子交换平衡，并提出了平衡模型。该理论模型考虑了氨基酸的两性弱解离性质和树脂能团的能量非均一性，可以很好地关联氨基酸与Ｈ＾＋的二元离子交换平衡，并且通过两个二元体系ＶＡＬ／Ｈ＾＋和Ｎａ＾＋／Ｈ＾＋的平衡参数成功地预测了三元体系ＶＡＬ／Ｎａ＾＋／Ｈ＾＋的平衡关系，表明该模型可以描述非缓冲体系中性氨基酸的多元离子交换平衡。     

含乙醇胺二元体系汽液平衡的测定与推算

采用改进的Ｒｏｓｅ釜测定了单乙醇胺－水，二乙醇胺－水，单乙醇胺－二乙醇胺，３个二元体系的常减压汽液平衡数据，并用ＵＮＩＦＡＣ方法对实验数据进行了推算。数据经验符合热力学一致性。     

甲胺与水多元系常压汽液平衡研究

用新型泵式沸点仪测定了常压下一甲胺-二甲胺-三甲胺-水四元系在不同液相组成时的沸点;由所测的甲胺-水二元系数据,用过量自由焓Q函数间接法推算了与之平衡的汽相组成,再用最小二乘法求出甲胺与水间二元体系的液相活度系数模型参数：甲胺与甲胺间二元体系的液相活度系数模型参数则通过拟合它们与水构成的三元系获取;由所得的最佳二元系参数用于该体系四元系汽液相平衡数据的预测,将计算的泡点与实验测得的沸点作了比较,结果表明两者吻合良好。     

碱土金属溶剂萃取分离的新进展

本文就碱土金属离子萃取分离的进展情况,按萃取剂的分类进行了综述。     

Gravitational Search,Monkey, and Krill Herd Swarm Algorithms for Phase Stability,Phase Equilibrium,and Chemical Equilibrium Problems

Phase equilibrium calculations (PECs) and phase stability (PS) analysis of reactive and nonreactive systems problems are important for the simulation and design of chemical engineering processes. These problems, which are challenging, multi-variable, and non-convex, require optimization techniques that are both efficient and effective in finding the solution. Stochastic global optimization algorithms, especially swarm algorithms, are promising tools for such problems. In this study, monkey algorithm (MA), gravitational search algorithm (GSA), and Krill Herd algorithm (KHA) were used to solve PS, phase equilibrium, and chemical equilibrium problems. We have also studied the effect of adding a local optimizer at the end of the stochastic optimizer run. The results were compared to determine the strengths and weaknesses of each algorithm. When a local optimizer was used, MA was found to be a reliable algorithm in solving the problems. GSA had relatively the least numerical effort for all problems among the three algorithms but with low reliability. KHA was more reliable than other two algorithms without the use of a local optimizer. The performance of GSA, MA, and KHA was compared with firefly algorithm and cuckoo search (CS). In summary, this study found that CS algorithm was more reliable than the newly tested algorithms. Nevertheless, MA and GSA algorithms, when combined with a local optimizer, solve the thermodynamic problems as reliably and efficiently as CS.     

Equilibrium of Liquid Drops on Thin Plates; Plate Rigidity and Stability Considerations

Following an earlier paper, the equilibrium of an axisymmetric sessile drop resting on a thin, elastic plate has been considered using the minimum free energy hypothesis. A consequence is that although Young's equation is still obeyed at the triple line when considering the true contact angle, the apparent contact angle (i.e. with respect to the horizontal) invokes parameters other than simply the interfacial free energies, such as the drop volume and elastic properties of the solid. A quantitative estimate of apparent contact angle dependence on plate thickness has been made in the case of small drops. Finally, consideration of stability, again using the minimum free energy hypothesis, suggests that the axisymmetric configuration may not always be the most likely. This, it is conjectured, may have consequences in cell biology.     

Quantitative Analysis and Equilibrium Models of Selective Adsorption in Multimetal Systems Using a Bacterial Biosorbent

ABSTRACT

This study investigated the behavior of selective adsorption on the biomass of Pseudomonas aemginosaPU21 (Rip64) with solutions containing Pb, Cu, and Cd. Experiments were designed to quantitatively justify the biosorption preference of the biomass for the three metals. The multimetal adsorption equilibria were described by three models, two of which originated from single-component Langmuir isotherm, and the third one was established empirically. The multimetal adsorption results show that lead and copper significantly inhibited the adsorption of cadmium, while the effects of Cd on the adsorption of Cu and Pb were limited. Lead was found to exhibit a slightly higher inhibition effect on Cu when the two adsorbate coexisted. The data obtained from the ion-exchange systems indicate that Pb and Cu appreciably replaced the preadsorbed Cd ions from the biosorbent, but the competition of Pb and Cu for the adsorption sites was comparative. For three-metal biosorption with equal initial molar concentrations, the relative surface coverage of Pb, Cu, and Cd on the biomass was approximately 55, 40, and 5%, respectively. A modified Langmuir-type model (Model 2), which took account of the heterogeneity and specificity of the adsorption sites, described the experimental results better than the traditional Langmuir isotherm (Model 1) did. Of the three models examined, the empirical one (Model 3) showed the best fits for the two-metal adsorption data, whereas Model 2 had better prediction for the ternary adsorption results. In Model 3 the parameters determined from binary systems can be extrapolated to predict the adsorption equilibria of three-metal adsorption systems satisfactorily.