碘光谱法测定非离子表面活性剂的临界胶束浓度

考察了碘光谱法测定非离子表面活性剂在水溶液中的临界胶束浓度（ｃｍｃ）的影响因素。欲得正确结果，须将碘－胶束溶液（不同浓度）放置，待碘的分配达到平衡（例如２４ｈ）后再进行测定，这样测得ＴｒｉｔｏｎＸ－１００、ＴｒｉｔｏｎＸ－３０５和单分散的纯化合物Ｃ１２Ｈ２５Ｏ（Ｃ２Ｈ４Ｏ）６Ｈ的ｃｍｃ分别为２．４×１０－４、３．５×１０－４和８．４×１０－５ｍｏｌ·ｄｍ－３，与文献中用表面张力法测得的结果一致。若按Ｒｏｓｓ和Ｏｌｉｖｅｒ将预先配好的溶液稀释后１小时内测定的方法，则所得结果偏低。只要测定时碘－胶束溶液已达平衡，则碘浓度在４～１２ｍｇ／１００ｍｌ范围内对ｃｍｃ的测定结果无明显的影响。文献中提到的碘浓度对ｃｍｃ测定值的影响可能是由于碘的分配未达平衡所致。     

碘电极测定饮用水中的碘和碘离子

应用碘电极 ,采用亚砷酸钠为碘的还原剂进行前处理 ,选用磷酸二氢钠为总离子强度缓冲液 ,测定了总碘及碘离子含量。建立的方法对三碘树脂净水器净化后的水进行了测定 ,结果良好。当总碘和碘离子的浓度在 10 -7～ 10 -4范围内时 ,相关系数为 0 .9999,回收率大于 98.1%。由实验测定的电位选择系数可见 ,该法选择性好 ,检测下限低。     

NULL和WILSON热力学模型在离子交换平衡系统中的应用研究

本文为应用Null和Wilson模型来描述Na~ —Ht体系的离子交换平衡,其结果今人满意。全文详述了理论处理和实验方法的具体过程,采用了NaCl溶液与H~-型国产732~*磺酸型树脂的平衡体系,在温度为25℃,溶液总浓度为0.2N、0.4N的条件下所测得的。实验数据通过理论计算所得的热力学平衡常数基本上为一定值。由本模型计算所得液—固两相的平衡组成与实验值偏差平均为5.1％,最大不超过9.3％。     

碱土金属在萃取剂与树脂间反应平衡常数的测定

研究了碱土金属离子在Ｄ００１树脂与８－羟基喹啉三氯甲烷溶液间的平衡常数Ｏ－ｔＫ的测定。其值依Ｍｇ、Ｃａ、Ｓｒ、Ｂａ次序减小。并得出萃取剂浓度［ＨＡ］。与金属离子在两相分配的关系。     

双水相胶束萃取苯酚

根据胶束的加溶原理和非离子表面活性剂系统在浊点温度以上自动分相的现象 ,采用TritonX - 10 0胶束系统萃取苯酚 .结果表明 :苯酚的比胶束加溶量与其在水相的平衡浓度成比例关系 .测定了比例系数 ,即加溶平衡常数 .由此建立了数学模型 ,讨论了表面活性剂浓度、溶质浓度、pH值等因素对萃取率的影响 .模型计算结果和实验结果都说明 ,调节pH值可以反萃取苯酚的原因是苯酚电离改变了加溶平衡常数     

草酸与乙醛酸的萃取分离

以草酸和乙醛酸的稀溶液为分离对象 ,采用三辛胺 (TOA)为萃取反应剂、正辛醇为稀释剂 ,研究了单溶质、双溶质有机酸的萃取分离特性 ,测定了溶液pH值、萃取反应剂的浓度等因素对双溶质有机酸萃取的影响 ,提出了萃取的化学反应发生在有机相中的假定 ,建立了TOA萃取草酸的数学模型 .实验结果表明 ,草酸与TOA的萃合物有 1∶1和 1∶2两种形式 .在本实验的条件范围内 ,草酸的分配系数较乙醛酸大 ,且随溶液pH值的增大而下降 ,草酸对乙醛酸的分离系数随pH值的增大而减小 .随萃取反应剂浓度的增大 ,两酸的分配系数皆随之增大 ,分离系数也随之增大 ,而且对于高浓度的萃取反应剂在较高的溶液pH值下草酸仍具有较大的分离系数 .采用单溶质萃取反应平衡常数及纯稀释剂中双溶质的分配系数预测双溶质萃取的结果 ,预测值与实验值相当接近     

三烷基氧膦络合萃取一元有机羧酸

络合萃取法对极性有机物稀溶液的分离具有高效性和高选择性。选择甲酸、乙酸、丙酸、丁酸为分离对象 ,三烷基氧膦 (TRPO)为络合剂 ,煤油为稀释剂 ,进行了系统的萃取相平衡实验 ,测定了络合剂浓度、稀释剂组成等因素对萃取平衡分配系数的影响。实验结果表明 ,溶质的亲油性对络合萃取平衡影响起主导作用 ;随TRPO浓度增大 ,萃取平衡分配系数呈增大趋势 ;随溶质初始浓度增大 ,有机相的溶质浓度向饱和萃取量接近 ;饱和萃取量随络合剂浓度的增大而增大。对相平衡分配系数进行拟合 ,精度令人满意。     

电位滴定-双氧水氧化法从海带中提取碘

将干海带在碳酸钠溶液中熬煮,滤液酸化并用双氧水氧化,采用电位滴定法控制氧化析碘过程;以低沸点有机溶剂为萃取剂,采用低温减压分离方法,实现有机溶剂和单质碘的分离,得到的碘收率较高（62.5%）,可用差量法称量。探索了滤液pH、双氧水浓度和萃取溶剂对实验结果的影响。分别采用碘量法和分光光度法检验了提取碘的纯度。研究结果表明：滤液pH为2.5～3.5时,用质量分数为2%的双氧水氧化析碘结果比较理想;与二氯甲烷相比,无水乙醚萃取含I₂水溶液效率更高。碘量法和分光光度法测定数据较为吻合,都可以用来测定水溶液的碘含量。     

碘化钾水溶液中碘在活性炭上的吸附等温线

测定了碘化钾水溶液中碘在活性炭上的吸附平衡数据，证明碘在液固两相中的平衡关系可用Ｆｒｅｕｎｄｌｉｃｈ方程式拟合，其平衡方程式为：ｘ／ｍ＝０．３８１Ｃ     

对碘沉淀法测定聚乙二醇浓度的改进

文献报道,碘沉淀法测定PEG的浓度范围在40～200ppm之间,为了测定更低浓度,我们提出在文献中的碘液外又加入硼酸溶液以测定聚乙二醇(PEG)溶液的浓度,这样就提高了PEG的测定精度,在520nm处用比色法测定,结果表明,PEG的浓度测定可降至2～20ppm之间,并且仍有良好的线性关系,此法可供评价超滤膜性能。     

A simple model for precisely describing liquid–liquid equilibrium and better understanding extraction mechanism

Describing distribution of solute equilibrium concentrations between two solvents is important for liquid–liquid equilibrium (LLE). Due to non-ideality of solutions, the distribution usually possesses non-linear characteristic. In this work, the non-ideality was simply represented by pseudo reaction (or chemical interaction) between the solute and the solvent without recourse to the complicated activity coefficient models. On this basis, a simple model, which combined physical partition and pseudo reaction equilibriums, was proposed and can precisely correlate various LLE systems, for example, the immiscible, the partially miscible, the organic, and even the electrolyte. More interestingly, the model can accurately reflect intrinsic mechanism by fitted parameters, that is, stoichiometric ratio of the pseudo reaction and total equilibrium constant for the interaction intensity. Besides, influence of the solute, the extractant, and temperature on the parameters was discussed deeply. This simple model is promising for precisely describing the LLE systems and better understanding their intrinsic extraction mechanism.     

活性炭纤维吸附填充床突破曲线预测(Ⅱ)实验及模型的验证

实验测定了活性炭纤维填充床吸附水中微量铅离子的突破曲线和吸附等温平衡数据,研究了活性炭纤维填充床的吸附性能。应用活性炭纤维吸附填充床突破曲线的精确解和两种近似解对实验数据进行了模拟。结果表明,本实验条件下理论计算值与实验数据均吻合较好;简单、计算速度快的拟对数概率密度函数近似解适用于模拟活性炭纤维填充床突破曲线;由突破曲线实验数据可方便准确地估算平衡常数;活性炭纤维吸附填充床内轴向弥散对突破曲线有较大影响,是不可忽略的因素。     

Acidization—VI: On the equilibrium relationships and stoichiometry of reactions in mud acid

A method is presented for determining the distribution of reaction products and the stoichiometric coefficient for the reaction of mud acid (HF/HCl) with various minerals. To illustrate the techniques, the dissolution of two common alumino-silicates, potassium feldspar and kaolinite, in mud acid is investigated for various temperatures and acid concentrations. After determining the product distribution from the ionic equilibrium relationships involving the various fluoride ion complexes, the stoichiometric coefficient [moles HF consumed per mole mineral dissolved] is arrived at through a numerical solution of the coupled equilibrium and mole balance equations. The HF acid stoichiometric coefficient was found to decrease significantly with increasing temperature and HCl acid concentration. This information is of great importance in determining design conditions for the matrix acid stimulation of oil reservoirs.In the above analysis we have found how the HF stoichiometric coefficient in the reaction between mud acid and two alumino-silicates varies with acid concentration and temperature. The HF stoichiometric coefficient is defined as the moles of HF acid consumed per mole of mineral dissolved. The information obtained in this study is of great importance in the design of the acid stimulation of well reservoirs. It was found that the same stoichiometric coefficient can result for two different sets of mud acid concentrations. Consequendy, one could evaluate which set of mud acid concentrations would be most economically feasible. In addition to the economical considerations, the prediction of the overall stoichiometric coefficient for the dissolution of a sandstone is of vital importance in determining the acid capacity number. From this number, one can calculate the penetration radius of the permeability front resulting from matrix acid stimulation of the reservoir.In calculating the stoichiometric coefficient we first determined the distribution of the aluminum-fluoride and silicon-fluoride complexes resulting from the dissolution of the mineral using the ionic equilibrium relationships. A numerical solution of the coupled mole balance and equilibrium equations was then carried out to determine the stoichiometric coefficient with respect to HF and HCl for the specified mineral dissolution. These results were found to agree satisfactorily with previously reported experimental values.The results of this analysis showed that the HF stoichiometric coefficient decreases with increasing temperature. In addition it was found to decrease during the course of the mud acid-mineral reaction. The most important results of this study are related to the variation of the HF stoichiometric coefficient with HCl concentration. This coefficient was found to be virtually independent of HCl concentration below concentrations of ca. 5 × 10^?2 M HCl. Above this concentration it was found to decrease significantly with increasing HCl concentration.A technique for estimating the overall stoichiometric coefficient for a sandstone from the coefficients of the individual minerals has been found to be in satisfactory agreement with the numerical technique involving the ionic equilibria for the sum of all minerals present which had to be carried out on the computer, for each sandstone composition.     

The removal of copper,cadmium, and lead ions from dilute aqueous solutions using foam fractionation

The removal of copper, lead and cadmium ions from aqueous solution by foam fractionation using sodium dodecylbenzene sulphonate (NaDBS) has been experimentally studied and theoretically predicted for solutions with a pH less than 4. A mathematical model of the system consisting of the equilibrium relations of chemical reactions occurring in the system was solved for the equilibrium concentration of all ions in the solution. Based on this equilibrium concentration and the effective radius of the hydrated ion, a modified theory of the Gouy-Chapman diffuse double layer⁽⁹⁾ was used to predict the distribution factor of the metal ions. The work was extended to systems containing two metal ions for the determination of the separability of the ions with respect to each other. It was found that the distribution factor for solutions containing one metal ion could be predicted theoretically for a bulk solution pH less than four. Deviation of results above this pH was attributed to the limitations of the bulk solution reaction model because it did not include reactions for the formation of poly hydroxyl and poly nuclear hydroxyl complexes. Good agreement was also obtained between experiment and theory in the separability study. The results indicate that the order of removal of the ions from solution is Pb⁺⁺ > Cd⁺⁺ > Cu⁺⁺. This sequence is the reverse order of the effective radii of the hydrated ions. The results support the fact that the mechanism for removal of the ions from solution is that of electrical attraction and that selectivity depends upon the charge and size of the hydrated ion.     

On the thermodynamics of solid solutions of polymer and salt

Solid solutions of poly(ethylene oxide) of different molecular masses (M_η from 6 × 10⁵ to 4 × 10⁶ g mol^?1) and lithium perchlorate (LiClO₄) were prepared by solution casting method. Salt concentrations of solutions vary between around 2 and 13 wt%. Thermodynamic properties of these solutions are reported in the range of low salt content. The solutions represent two‐phase systems mostly not in equilibrium at room temperature. They consist of neat crystalline PEO and an amorphous mixture of salt and polymer. Crystallinity of PEO in salt solutions stays constant with increasing salt content and is independent of molecular mass. Crystallinities serve determining share and composition of the amorphous phase. Glass transition temperature increases linearly with salt content in the amorphous phase. Depression of equilibrium melting points by addition of salt provides activity coefficients in solutions and allows for estimation of degrees of dissociation. Rate of crystallization of poly(ethylene oxide) depends exponentially on inverse undercooling. In that way, it is also coined by equilibrium melting point depression. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Optimization of the active component distribution through the catalyst bed

A variational problem was formulated to determine the optimal axially non-uniform catalyst activity distribution along the fixed catalyst bed. It was observed that the mass transport limitations or non-isothermal temperature profile are necessary conditions for potential optimization of the catalyst distribution along the bed length. Under isothermal conditions with linear dependence of the reaction rate on concentration at a constant mass transfer coefficient, the uniform distribution is optimal. Analytical solution for the first-order reaction and numerical solutions for power-law kinetics were found.     

基于矩法和时间域分析法研究稠密CO2中甲苯和对氯苯在硅胶固定床系统中的吸附和传递性质

Based on chromatographic theory, the moment method and the time-domain fitting analysis were applied to measure and evaluate the adsorption equilibrium constant and mass transfer properties (axial dispersion coefficient and effective intra-particle diffusivity) for toluene and p-dichlorobenzene on silica gel adsorbent in the subcritical and supercritical CO2. An apparatus based on supercritical fluid chromatography was established and the experiments were performed at temperatures of 298.15-318.15 K and pressures of 7.5-17.8 MPa. The two methods have been compared. The results show that for the systems studied here the moment method can give reasonable values for both adsorption equilibrium constant and mass transfer properties, but the time-domain analysis only can obtain the adsorption equilibrium constant. The dependence of adsorption equilibrium constant and mass transfer properties on temperature and pressure was investigated.     

Aggregation of lead phthalocyanine in blends with polycarbonate

The blends of a nonlinear optical dye with polycarbonate are described and comparisons are made with solutions of the dye in chloroform. Absorption spectra of blends with up to 1 wt % lead tetracumylphenoxy phthalocyanine showed the dye to be primarily in the monomer form. The monomer absorption spectrum and the measured extinction coefficient replicated those in chloroform solution. As the dye concentration increased to 20 wt %, the monomer intensity decreased and new spectral features characteristic of the dimer appeared. The spectra were resolved into contributions of monomer and dimer, and the concentration effect was analyzed according to the monomer/dimer equilibrium. Much higher monomer concentrations were achieved in polycarbonate blends compared to chloroform solutions. It was concluded that when the blends were quenched from the melt, the equilibrium established at the melt temperature was preserved in the solid state glass. Quenching the blend from different melt temperatures confirmed this interpretation. Extrapolation of the temperature dependent equilibrium constant to 25°C yielded a value close to that reported for chloroform solution at 25°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 104: 464–469, 2007     

Thermodynamics of wax formation in the fischer-tropsch synthesis products

A new method is suggested for calculating the thermodynamic equilibrium in a multicomponent multiphase system without chemical reactions. This method is based on ideas of statistical physics and non-equilibrium thermodynamics and includes numerical minimization of the Gibbs energy of the complex system. Component concentrations and the physically realizable roots of the equation of state are calculated as the steady state solutions of the set of ordinary differential equations that is implied by the procedure of seeking the probability maximum for the realization of the equilibrium distribution. The approach developed here is used to calculate the equilibrium distribution of the concentrations of vaporous, liquid, and solid substances in the Fischer-Tropsch synthesis products. A thermodynamic model of the formation of solid paraffins from the synthesis products is presented. The calculation of the properties of pure substances and liquid and gaseous products is based on the Lee-Kesler equation of state. The wax formation thermodynamics is considered in the regular solid solution approximation (Hildebrand-Scott model) and in the solid solution approximation taking into account the nonideality of the system (NRTL model). The calculated mass fractions of vaporous, liquid, and solid synthesis products are presented as a function of temperature for different values of the chain propagation constant.     

水盐体系汽液平衡的热力学模型研究

水盐体系的相平衡性质是化工单元操作的基础,在化学化工、海洋、地质等领域有着重要的研究价值。国内外许多学者对水盐体系汽液平衡进行了实验和理论的研究,构筑了各具特色的经验和半经验的模型。针对水盐体系,在NRTL理论的基础上,基于水化作用和混合盐假设建立了能够预测混合体系汽液平衡的活度系数扩展模型。通过对21组二元水盐体系和14组混合体系的关联计算,验证了该模型的可行性;同时,该模型可以采用二元体系参数直接预测计算混合水盐体系汽液平衡。