Thermodynamic behavior and applications of KMnO4 in cerium separation process using cyanex 923

In this work, studies were carried out on the extraction properties of Mn(II) and MnO4- in sulfuric acid medium using Cyanex 923. Effects of different variables on the extraction of Mn(II) and MnO4-, such as the concentrations of acid, the extractant, and the temperature, were investigated. Results indicated that Mn(II) was extracted weakly by Cyanex 923; however, MnO4- could be strongly extracted into the organic phase. The extraction mechanism of MnO4- was proposed, and the influence of MnO4- on the extraction of cerium was identified when KMnO4 as oxidizer added into the bastnasite sulfuric acid leaching liquor. As MnO4- was easier to be extracted into the organic phase than Ce(IV) and then lost its ability for oxidization, a new device was designed to realize sufficient oxidization of cerium from III to IV, and which has been applied to industrialization.

Theoretical estimation of thermodynamic properties of the system PS/PPO on the basis of modified combining rule of Sanchez-Lacombe lattice fluid model

The three scaling parameters described in Sanchez-Lacombe lattice fluid theory (SLLFT), T*, P* and rho* of pure polystyrene (PS), pure poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and their mixtures are obtained by fitting corresponding experimental pressure volume-temperature data with equation-of-state of SLLFT. A modified combining rule in SLLFT used to match the volume per mer, v* of the PS/PPO mixtures was advanced and the enthalpy of mixing and Flory-Huggins (FH) interaction parameter were calculated using the new rule. It is found that the difference between the new rule and the old one presented by Sanchez and Lacombe is quite small in the calculation of the enthalpy of mixing and FH interaction parameter and the effect of volume-combining rule on the calculation of thermodynamic properties is much smaller than that of energy-combining rule. But the relative value of interaction parameter changes much due to the new volume-based combining rule. This effect can affect the position of phase diagram very much, which is reported elsewhere [Macromolecules 34 (2001) 6291]

Formation of epsilon-FeXN/BN magnetic nanocomposite and its thermodynamic and kinetic analyses

A nanocomposite of nanometer-sized magnetic granular epsilon-FeXN embedded in a nonmagnetic amorphous boron nitride matrix was prepared by ball milling mixture of alpha-Fe and hexagonal boron nitride in argon atmosphere. The grain size of the epsilon-FeXN alloy was about 10-20 nm. The nitrogen concentration in the epsilon-FeXN alloy increases with extending milling time. Both thermodynamic calculation and the present experiment show that iron and nitrogen atoms have higher alloying driving force than iron and boron atoms. Analyses of thermodynamics and kinetics about formation of the epsilon-FeXN alloy suggested that the formation of the epsilon-FeXN alloy is related to amorphization of the hexagonal boron nitride and refinement of the alpha-Fe. II was found from the present experiment that a critical grain size of the alpha-Fe reacting with nitrogen in the amorphous boron nitride is about 8 nm.

CRYSTAL-STRUCTURE AND THERMODYNAMIC PARAMETERS OF NYLON-1010

WAXD, SAXS, FTIR, DSC and density techniques have been used to investigate the crystal structure, crystal density rho(c), amorphous density rho(a), equilibrium heat of fusion DELTAH(m)degrees and equilibrium melting temperature T(m)degrees. By extrapolating the straight lines in the FTIR absorbance against density plot to zero intensity, rho(c) and rho(a) were estimated to be 1.098 and 1.003 g/cm3 respectively. The rho(c) obtained was too low in value. From X-ray diffraction patterns of uniaxially oriented fibres, the crystal structure of Nylon-1010 was determined. The Nylon-1010 crystallized in the triclinic system, with lattice dimensions: a = 4.9 angstrom, b = 5.4 angstrom, c = 27.8 angstrom, alpha = 49-degrees, beta = 77-degrees, gamma = 63.5-degrees. The unit cell contained one monomeric unit, the space group was P1BAR, and the correct value of rho(c) was 1.135 g/cm3. The degree of crystallinity of the polymer was determined as about 60% (at RT) using Ruland's method. SAXS has been used to investigate the crystalline lamellar thickness, long period, transition zone, the specific inner surface and the electron density difference between the crystalline and amorphous regions for Nylon-1010. The analysis of data was based upon a one-dimensional electron-density correlation function. DELTAH(m)degrees was estimated to be 244.0 J/g by extrapolation of DELTAH(m)degrees in the plot of heat of fusion against specific volume of semicrystalline specimens to the completely crystalline condition (V(sp)c = 1/rho(c)). Owing to the ease of recrystallization of melt-crystallized Nylon-1010 specimens, the well-known Hoffman's T(m)-T(c) method failed in determining T(m)degrees and a Kamide double extrapolation method was adopted. The T(m)degrees value so obtained was 487 K.

Variation in joint mode of the tropical Indian-Pacific Ocean thermodynamic anomaly

Previous research has defined the index of the Indian-Pacific thermodynamic anomaly joint mode (IPTAJM) and suggested that the winter IPTAJM has an important impact on summer rainfall over China. However, the possible causes for the interannual and decadal variability of the IPTAJM are still unclear. Therefore, this work investigates zonal displacements of both the western Pacific warm pool (WPWP) and the eastern Indian Ocean warm pool (EIOWP). The relationships between the WPWP and the EIOWP and the IPTAJM are each examined, and then the impacts of the zonal wind anomalies over the equatorial Pacific and Indian Oceans on the IPTAJM are studied. The WPWP eastern edge anomaly displays significant interannual and decadal variability and experienced a regime shift in about 1976 and 1998, whereas the EIOWP western edge exhibits only distinct interannual variability. The decadal variability of the IPTAJM may be mainly caused by both the zonal migration of the WPWP and the 850 hPa zonal wind anomaly over the central equatorial Pacific. On the other hand, the zonal migrations of both the WPWP and the EIOWP and the zonal wind anomalies over the central equatorial Pacific and the eastern equatorial Indian Ocean may be all responsible for the interannual variability of the IPTAJM.

海相碳酸盐－稀土元素共沉淀过程中的分异作用研究

本文主要运用稳定加液－反应系统对海水中方解石和文石形成时稀土元素的共沉淀现象进行了分析，研究了稀土元素在固-液体系中的迁移、转化和分配。进而在对其定量描述的前提下，研究了稀土元素共沉淀对各种反应条件的响应，并对共沉淀行为的机制进行了探讨。 本实验首先运用pH测试、高精度滴定分析等手段测定了实验中的一些基本参数，如[H+]、碱度和[Ca2+]，根据计算结果获得了各碳酸体系要素，并以此为基础建立了5℃、15℃和25℃及pCO2=0.003atm下海水中方解石或文石的沉淀动力学方程。实验结果表明： 1）在各条件下，方解石或文石的沉淀速率（R）和其在海水中过饱和度（Ω）存在很好的线性相关性，即海相碳酸盐的沉淀动力学方程可以通过下面的基本表达式来表示：LogR=k*Log(Ω-1)+b ； 2）过高的稀土元素浓度会对文石或方解石的沉淀产生抑制作用，进而对共沉淀过程中YREEs的分异和分馏产生一定的影响。相比方解石而言，文石的沉淀动力学过程承受稀土元素的干扰能力更强； 3）不同温度下得到的方解石或文石各自的沉淀动力学方程存在明显的差异，表明这一过程受热力学因素控制。相对于方解石而言，温度对文石的沉淀动力学的影响更为显著。 与前人研究不同的是，本实验中YREEs的浓度设定在非常低的范围内，从而避免了过高浓度YREEs对方解石或文石沉淀动力学过程的干扰。在最终的反应液中，各种实验条件非常接近自然环境。有关稀土元素的共沉淀行为主要得出以下定性或定量化结论： 1）YREEs在随方解石或文石的共沉淀过程中，均发生了强烈的分异作用。在方解石实验中，稀土元素的分异系数分布曲线呈凸状分布；而在文石实验中，稀土元素的分异系数随原子序数的增加逐渐减小，遵循镧系收缩的规律。总的来说，稀土元素，尤其轻稀土元素在文石中的分异作用要强于方解石。 2）无论是方解石还是文石，沉淀速率对YREEs的分异作用都有着明显的影响。在方解石中，YREEs的分异系数随沉淀速率的增加呈一致性递减趋势；而在文石中，其分异系数对文石沉淀速率有着截然不同的响应：轻稀土元素（La, Ce, Nd, Sm, Eu, Gd）的分异系数随文石沉淀速率的增加而下降，而重稀土元素（Ho, Y, Tm, Yb , Lu）的分异系数则随文石沉淀速率的增加呈上升趋势。 3）在方解石中YREEs的分异系数之间存在非常好的相互关系，表明这些元素是以成比例的方式参与共沉淀。整个谱系呈现中等强度的分馏，MREE相对于LREE和HREE要更为富集；在文石中由于沉淀速率的作用不同，只有Y、Ho、Yb、Lu等元素的分异系数之间有较好的相互关系。YREEs出现了差异性的强烈分馏，在新生成沉淀中轻稀土元素相对于重稀土元素强烈富集。 4）YREEs在溶液中和碳酸盐晶体表面的碳酸根配位形式对YREEs在共沉淀过程中的分异作用极为重要，YREEs在碳酸盐晶体表面的吸附是整个谱系发生分馏效应的关键环节。对于文石来讲，晶体中有效YREE离子和Ca离子半价大小之间的相近程度是其分馏效应的关键因素；而对于方解石来说，YREEs在方解石晶格中的安置就是其分馏效应的关键控制因子，但在晶格安置中起到关键作用的是YREEs和方解石中O原子之间离子键M-O的键长，而非离子半径。 5）综合YREEs在方解石中的分异作用和分馏效应，我们认为M2(CO3)3-CaCO3和MNa(CO3)2-CaCO3是最为可能的两种固体溶液形成模式。 最为重要的是，对比我们的实验结果与前人在灰岩、叠层石、微生物成因碳酸盐等方解石质载体中的研究成果，两者之间出现了非常好的一致性。我们认为方解石质载体将是重建古海水中稀土元素相关信息的重要工具。相比之下，文石质载体不适合作为类似的载体。

Electrochemical and thermodynamic investigation of diniconazole and triadimefon as corrosion inhibitors for copper in synthetic seawater

This paper presents the investigation of diniconzole and triadimefon as chemical corrosion inhibitors for freshly polished copper in synthetic seawater (3.5% NaCl solution). Determination of weight loss, polarization curves, electrochemical impedance spectroscopy (EIS), and SEM, were performed to analyze the inhibiting performance of these compounds. Polarization curves show that they act as mixed-type inhibitors. EIS indicates that an adsorption film of the inhibitors is formed on copper surface. The highest values of inhibition efficiency are respectively, 99.2% and 97.3% at 100 mg/L concentration. Thermodynamic calculation suggests that chemisorptions between the compounds and copper are accordance with Langmuir adsorption isotherm. (C) 2010 Elsevier Ltd. All rights reserved.

Heat capacity enhancement and thermodynamic properties of nanostructured amorphous SiO2

The heat capacity of nanostructured amorphous SiO2 (na-SiO2) has been measured by adiabatic calorimetric method over the temperature range 9-354 K. TG and differential scanning calorimeter (DSC) were also employed to determine the thermal stability. Glass transition temperature (T-g) for the two same grain sizes with different specific surface of naSiO(2) samples and one coarse-grained amorphous SiO2 (ca-SiO2) sample were determined to be 1377, 1397 and 1320 K, respectively. The low temperature experimental results show that there are significant heat capacity (C-P) enhancements among na-SiO2 samples and ca-SiO2. Entropy, enthalpy, Gibbs free energy and Debye temperature (theta (D)) were obtained based on the low temperature heat capacity measurement of na-SiO2. The Cp enhancements of na-SiO2 were discussed in terms of configurational and vibrational entropy. (C) 2001 Elsevier Science B.V. All rights reserved.