利用吉布斯吸附等温式探索求解电解质溶液活度的新方法

以吉布斯吸附等温式积分式为基础,数学推证表面势的表达式,并应用表面势的数学表达式探求了一种测算电解质溶液活度系数的新方法.选取KIM计算电解质溶液溶质的活度系数公式为新方法的活度系数经验关系式的具体表达形式,利用实验直接测得的不同浓度下的表面张力数据,采用最优化拟合的方法,求算出活度系数经验关系式中的待定系数,从而可以求得不同浓度下的电解质溶液中的溶质的活度系数和活度.计算结果与KIM文献值对比,活度系数曲线在不同的坐标尺度下有很好的一致性,这使得通过测定电解质溶液表面张力测算其活度成为可能.     

双烃链正,负离子表面活性剂复合物水溶液的表面化学性质研究

本文研究了具有双烃链的正、负离子表面活性剂混合水溶液的表面和液相性质、。负离子表面活性剂是琥珀酸二己酯磺酸钠[简写为(C6)2SNa],正离子表面活性剂是氯化二正辛基羟乙基甲基铵[(C8)2NCl]和氯化辛基羟乙基二甲基铵[C8NCl]。为了增加复合物的溶解度,在铵基上引入了羟乙基。测定了表面张力-浓度关系,用GIBBS公式计算表面吸附量和吸附分子面积。结果表明,由于正、负表面活性离子之间的强烈相互作用,所研究的两种混合物体系的表面活性远高于单独的表面活性剂。在等摩尔混合和离子强度0.1mol/kg情况下,(C6)2SNa-(C8)2NCl体系的吸附层组成是对称的(摩尔比为1:1),且在临界胶团浓度(cmc)以上析出新相,表明此cmc实质上是复合物的溶解度;而(C6)2SNa-C8NCl体系的吸附层为不对称组成(摩尔比非1:1),在cmc以上可能形成相当大的胶团,两种体系混合溶液的起泡性有极大差异。     

用氯离子选择电极测定浓盐酸的活度系数及氯离子吸附效应的探讨

在25 ℃下, 用氯离子选择电极与玻璃电极组成电池测定了0.00498～15.02 molkg~(-1)浓度范围盐酸体系的电势, 发现用Nernst方程计算出的活度系数与文献值偏差极大。用氯离子吸附原理和形成吸附对的平衡原理导出的电势方程, 由此计算出的盐酸活度系数与文献值十分一致, 这表明氯离子在电极表面发生了特性吸附作用。     

疏水高分子单链在疏水表面上吸附和扩散过程的分子动力学模拟

采用分子动力学模拟方法研究不同聚合度(N)的聚乙烯(PE)单链在Si(111)表面上的吸附和扩散行为. 分别设置相对介电常数为1和78模拟无溶剂和不良溶剂环境. PE单链的平衡吸附构象均呈现为二维吸附构象, 但在这两种截然不同的环境中呈现不同的构象和动力学特征, 说明溶剂环境对于疏水高分子单链在疏水表面上的吸附和扩散起到了很大的作用. 吸附能与聚合度呈线性关系, 单位链长的平均吸附能是-0.38 kJ·mol^-1. 另外, 扩散系数(D)与聚合度之间的标度关系是D~N^-3/2.     

颗粒聚集体对两性SiO2颗粒无水泡沫表面性质的影响

基于Pickering乳液模板法, 合成了2种用于制备非水泡沫的不同相对两亲面积的Janus颗粒, 并合成了表面均匀修饰的颗粒作为对比. 通过调整油混合物的性质, 对颗粒在油气表面上的行为进行了测量和对比, 对颗粒团聚体在颗粒吸附中的作用进行了研究. 结果表明, 受颗粒表面接触角的影响, Janus颗粒的表面活性(表面张力降低能力与产生泡沫的体积)不总是大于均匀改性颗粒. 均匀改性颗粒和Janus颗粒均不是以单个颗粒形式从体相吸附至表面上, 而是以颗粒团聚体状态向表面移动, 并且需要颗粒团聚体的Cassie-Baxter复合表面的接触角约为90°, 而颗粒的本征接触角小于70.1°.     

水-短链醇二元溶液的表面吸附

基于表面聚集吸附(SAA)模型和Gibbs吸附微分方程,建立了二元液体混合物Gibbs表面过剩(Γ₂)和吸附层厚度(τ)代数方程,可在全浓度范围内预测Γ₂和τ随体相组成(如组分2的摩尔分数x_2,b)的变化.采用所建立的模型,研究了水(组分1)-短链醇(组分2)二元溶液的表面吸附行为,其在水表面的吸附趋势按甲醇、乙醇、异丙醇、正丙醇和叔丁醇的顺序依次增强,与其疏水性增强趋势一致,且其Γ₂和τ在低x_2,b区均依次增大,而在高x_2,b区均依次减小,是短链醇间吸附趋势和分子尺寸的差异所致.对于给定的短链醇体系,随着x_2,b的增大,Γ₂先急剧增大然后降低,呈现一个最大值,而其τ持续降低.     

表面等离子体子共振技术实时研究蛋白质在修饰表面的静电吸附行为

研究蛋白质在固相表面的静电吸附特性,进而控制蛋白质在修饰表面的静电吸附尤为重要,表面等离子体子共振可以检测金属表面吸附物质厚度和折射率的变化^[1]。这种技术已在研究生物分子相互作用^[2]和考察自组装单层的形成^[3]及蛋白质在固体表面吸附行为^[9-11]等方面得到广泛的应用。对蛋白质在固体表面吸附行为的研究多为考察不同的蛋白质在不同的修饰表面的吸附行为。然而,对蛋白质在修饰表面静电吸附的本质影响因素的研究却少有报道^[4]。本文使用表面等离子体子共振技术实时研究了蛋白质在甲羧基化葡聚糖修饰表面的静电吸附与溶液pH值及离子强度的依赖关系。     

二元表面活性剂水溶液表面张力及其表面过剩量摩尔分数的推算

对于水溶液中表面活性剂分子在表面相达到吸附平衡时,Rosen^[1]等人导出了如下相平衡计算方程式中α:活度,上标:s:表面相、b:体相,bo:参考态.α_i^bo:单一的i组分水溶液在其表面张力与系统表面张力相等时的体相活度.在Rosen等人的工作中对表面相的处理采用单参数的Margules活度系数关联式,对每一个实验点都求出一个参数β值,所得β值并不是一个常数。     

纳米SiO2与阳离子表面活性剂的相互作用及其诱导的正辛烷-水乳状液的双重相转变

研究了3种不同结构的水溶性阳离子表面活性剂对纳米二氧化硅颗粒的原位表面活性化作用, 它们分别是单头单尾的十六烷基三甲基溴化铵(CTAB)、单头双尾的双十二烷基二甲基溴化铵(di-C12DMAB)和双头双尾的Gemini型阳离子三亚甲基-二(十四酰氧乙基溴化铵)(II-14-3), 并通过测定Zeta电位、吸附等温线及接触角等参数对相关机理进行了阐述. 结果表明, 阳离子表面活性剂吸附到颗粒/水界面形成以疏水基朝向水的单分子层, 从而增强了颗粒表面的疏水性是原位表面活性化的基础. 通过吸附CTAB和II-14-3, 颗粒的疏水性适当增强, 能吸附到正辛烷/水界面稳定O/W(1)型乳状液; 而通过吸附di-C12DMAB所形成的单分子层更加致密, 颗粒的疏水性进一步增强, 进而使乳状液从O/W(1)型转变为W/O型; 当表面活性剂浓度较高时, 由于链-链相互作用, 表面活性剂分子将在颗粒/水界面形成双层吸附, 使颗粒表面变得亲水而失去活性, 但此时体系中游离表面活性剂的浓度已增加到足以单独稳定O/W(2)型乳状液的程度. 因此当采用纳米二氧化硅和di-C12DMAB的混合物作乳化剂时, 通过增加di-C12DMAB的浓度即可诱导乳状液发生O/W(1)→W/O→O/W(2)双重相转变.     

NiO表面磁性对分子吸附的影响的第一性原理研究

过渡金属氧化物广泛应用在当今能源与环境相关的催化领域,理解其表面化学性质以及结构-反应活性之间的关系对于先进催化材料的进一步发展以至理性设计至关重要.3d后过渡系金属(Mn,Fe,Co,Ni)的氧化物以其中金属离子独特的自旋状态和由此产生的铁磁/反铁磁性为典型特征.研究过渡金属氧化物的自旋状态以及磁性对表面化学的影响将使我们更加完整了解这些材料的表面化学.以NiO为代表的后过渡系金属岩盐结构一元氧化物具有反铁磁性,被经常作为反铁磁研究的模型体系.尽管在低温(低于其Neel温度)下NiO体相的完整晶体具有确定的反铁磁序,但是一系列最新研究表明,在条件变化时NiO表面的Ni离子可以产生不同的磁序.以此为背景,本工作以NiO为模型体系,采用DFT+U的第一性原理方法研究了NiO表面磁序对表面的小分子吸附活性的影响,包括表面吸附活性对各磁性相的表面取向以及吸附物种磁性的依赖关系.我们考察了NiO的5种反铁磁相和一种铁磁相,两个晶面NiO(001)和NiO(011),顺磁性分子NO和非顺磁性分子CO.我们发现表面能受磁性的影响较轻微,NiO(001)面上从49到54 meV/?2,NiO(011)面上从162到172 meV/?2.在NiO(001)面上,CO与NO都倾向于在Ni离子的顶位吸附.对于不同的体相磁序与表面取向,CO吸附能的变化范围为-0.33~-0.37 eV,NO吸附能的变化范围为-0.42~-0.46 eV.在NiO(011)表面,两种分子都倾向于吸附在由两个Ni离子构成的桥位.我们发现相对于NiO不同磁性相的体相长程磁序,吸附位点处构成桥位的两个Ni离子的局部磁矩相对取向对于分子的吸附具有更加显著的影响.计算得到NO在局部磁矩相对取向反平行(↑↓)吸附位点处的吸附能为-0.99~-1.05 eV,在局部磁矩相对取向平行(↑↑)吸附位点处吸附会增强,吸附能为-1.21~-1.30 eV.对于CO,尽管计算的吸附能在(↑↓)吸附位点(-0.73~-0.75 eV)与在(↑↑)吸附位点(-0.71~-0.72 eV)非常接近,两种吸附位点处的CO吸附时分子轨道杂化方式以及吸附后CO的局域电子态密度却具有明显不同的特征.本工作突出揭示了分子在过渡金属氧化物表面的多重吸附位点上吸附时吸附位点的局域磁矩相对取向对吸附性能的影响.     

Surface activity coefficients of ideal mixtures adsorbed on two-site heterogeneous surface model

The surface activity coefficients of ideal mixtures adsorbed on the heterogeneous surfaces have been calculated systematically by using the two-site heterogeneous surface model. The calculated results show that the apparent surface activity coefficients are always smaller than 1, i.e., negative-deviation from Raoult's law, which were always found experimentally. On the other hand, the calculated surface activity coefficients curves are always nearly symmetric if the total surface coverage is close to 1. This situation is comparable with those of adsorption from solutions. Therefore, the asymmetric curves for the surface activity coefficients may not be due to the heterogeneous of the surface, but due to the nonideal molecular interactions between the unlike components of the adsorbed mixture.     

Modeling spreading-pressure-dependent binary gas coadsorption equilibria using gravimetric data

The present work proposes an approach to building nonideal coadsorption models in a thermodynamically consistent fashion, including the effects of pressure and spreading pressure, from simple gravimetric measurements. This is an "inverse problem" of parameter determination from appropriate and limited experimental data.The approach relies on the nonideal adsorbed solution theory, which includes activity coefficients and their dependence on spreading pressure, and on an original form of the excess Gibbs energy of mixing. A fully analytical development leads to explicit relations between the infinite dilution activity coefficients and three sets of independent information: the parameters of this excess Gibbs function, the limiting slopes of measured binary gravimetric curves at two different total pressures, and the properties of the single-component isotherms. From there, the four parameters of the model may be determined quasi-analytically and uniquely. The method is exemplified with the coadsorption of CO(2) and CH(4) on activated carbon, and a heterogeneous set of data. On one hand, the total adsorbed mass of the two components is measured at 1 bar by "incremental gravimetry." On the other hand, data obtained from independent batch-type equilibration measurements at 2 bar allow a comparison of calculated and measured data for the individual component concentrations. It is emphasized, however, that only total adsorbed mass data are needed for application of the method.     

H2O/NaY吸附体系的热化学研究

用精密自动绝热量热计测定了在220-320K范围内, 不同含水量的H2O/NaY吸附体系的热容. 结果表明, 在这些吸附体系的Cp-T曲线上均没有水的固-液相变峰. 这说明即使在饱和吸附的情况下, 水分子仍以单分子层的形态存在于NaY表面上, 它们没有形成聚集态. 此外, 还测定了往饱和吸附的H2O/NaY中再加入不同量水后所组成的H2O/NaY体系的热容. 在这些Cp-T曲线上都出现了明显的相变峰. 所加之水一旦脱出, 则相变峰又消失. 这些水存在于分子筛颗粒之间只与外表面接触. 但仍受分子筛表面的影响. 所以它们的熔化热、熔化温度均比正常水的     

Studies of surface properties of Na- and La-montmorillonites

This paper presents possible applications of thermal analysis, sorptometry and porosimetry to study physico-chemical properties of Na- and La-montmorillonite samples, especially for determination of total surface heterogeneity. The quasi-isothermal thermogravimetric (Q-TG) mass loss and its first derivative (Q-DTG) curves with respect to temperature and time obtained during programmed liquid thermodesorption under quasi-isothermal conditions have been used to study adsorbed layers and heterogeneous properties of the Na- and La-montmorillonites. Calculations of the desorption energy distribution functions by analytical procedure using mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption under quasi-isothermal conditions of polar and non-polar liquid vapours preadsorbed on a material surface are presented. Parameters relating to porosity of samples were determined by sorptometry, mercury porosimetry and atomic force microscopy (AFM). From nitrogen sorption isotherms from sorptometry and porosimetry methods, the fractal dimensions of montmorillonites have been calculated. Moreover, a new approach is proposed to calculate fractal dimensions of materials obtained from Q-TG curve; this is compared with values obtained by the above methods. The total heterogeneous properties (energy distribution function and pore-size distribution functions) of samples studied were estimated. The radius and pore volume of the tested samples calculated on the basis of thermogravimetry, sorptometry and porosimetry techniques were compared and good correlations obtained.     

Surface Tension of the Liquid Hg-In Alloys

Abstract

The measurements of the surface tension of the liquid Hg-In alloys were made by means of a maximum drop pressure method. The surface tension increases monotonously with increasing the In concentration. It is thermodynamically shown that the composition of the Hg atoms adsorbed on the surface is larger than that in the bulk. Experimental results are compared with calculated results due to various model theories; in particular the hard sphere model with a density-dependent cohesive potential is found to be in qualitative agreement with experimental results of both surface tensions and its temperature coefficients.     

双子表面活性剂溶液的表面活性的研究

研究了阳离子型双子表面活性剂,二溴化-N,N'-二(二甲基烷基)乙(已)二铵,以及它们与阴离子表面活性剂十二烷基苯磺酸钠(SDBS)复配体系的表面活性,测定上述体系的平衡态表面张力。结果表明：双子表面活性剂的表面活性大大高于十二烷基三甲溴化铵(DTAB);对于两种双子表面活性剂,其表面活性和表面张力时间效应受其联接基团的影响远大于其烷基链的影响。双子表面活性剂与SDAB复配,其协同效应不如DTAB。动表面张力测定得到它们的各种参：t~i,t~m,γ~m,t*和n等值,结果表面双子表面活性剂的瞬时活性也高于DTAB。     

Determination of activity coefficients of binary adsorption solutions

Conclusions A method was prepared for calculating the activity coefficients of the components of adsorption solutions from specified curves, corresponding to constant values of the integral of the Gibbs equation, when binary gas mixtures are adsorbed on microporous adsorbents.Translated from Izvestiya Akademiya Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 166–168, January, 1972.     

The surface adsorption and micelle formation of the mixed aqueous solutions of fluorocarbon and hydrocarbon surfactants: II. Sodium perfluorooctanoate-sodium decylsulfate system

The adsorption and micellar behavior of the mixed solutions of sodium perfluorooctanoate (7CFNa) and sodium decylsulfate (C₁₀SNa) have been studied at constant ion strength of 0.1m. The adsorption was calculated from the surface (and interfacial) tension-concentration curves by applying Gibbs equation. It was found that the cmc's of 7CFNa and C₁₀SNa are of nearly the same value (1.66 × 10⁻²m and 1.45 × 10⁻²m, respectively), but γ_cmc of 7CFNa solution is ∼23 mNm⁻¹, which is much lower than that of C₁₀SNa solution. This implies that 7CFNa would have a much higher surface activity than C₁₀SNa and be adsorbed preferentially; for instance, 7CFNa has a surface mole fraction of about 0.8 in the saturated adsorption layer of the 1:1 mixed solution. The mole fractions of 7CFNa at the surface are always greater than those in the bulk solutions. The adsorption at the n- heptane-aqueous solution interface is quite different from that at the air-solution surface. Here C₁₀SNa is preferentially adsorbed owing to “Mutual phobicity” between the HC-chain of n-heptane and the FC-chain of 7CFNa at the interface. All the cmc's obtained from the γ-log m relations of 7CFNa (or C₁₀SNa) in the mixed solutions have nearly the same value and the cmc-x curves show a positive deviation from the ideal case. This further indicates that in the mixed solutions of fluorocarbon and hydrocarbon surfactants no completely miscible micelle but essentially the individual micelle of each surfactant exist due to the “Mutual phobicity” between FC- and HC-chain in the micellization process.     

活性炭自水溶液中吸附酚的研究：Ⅱ.酚类的竞争吸附

活性炭自水溶液中吸附酚的研究＊——Ⅱ．酚类的竞争吸附杨骏陈诵英彭少逸（中科院山西煤化所煤转化国家重点实验室，太原０３０００１）关键词动态法竞争吸附苯酚中图分类号Ｏ６４６．３１４本文的目的是采用动态法获取单组分体系－两种酚类化合物在活性炭上的吸附及扩散...     

Polysaccharides at interfaces 1. Adsorption of cholesteryl-pullulan derivatives at the solution-air interface. Kinetic study by surface tension measurements

The surface properties of a series of cholesteryl-pullulan (CHP) derivatives have been assessed by surface tension measurements at the solution-air interface. The results reveal that these properties are related to the nature of the hydrophobic cholesteryl group substituted in pullulan, and that the unsubstituted polysaccharide does not display any surface activity. The adsorption kinetics of such an amphiphilic macromolecule has been shown to be diffusion controlled, obeying the Ward and Tordai¨diffusional model only at low solution concentrations. In the 2 × 10⁻⁷–5 × 10⁻⁶ mol l⁻¹ concentration range for which this model is verified, the calculated diffusion coefficients are concentration dependent. The non-ideality of the system at higher concentrations may be explained both by the presence of solute/solute interactions in solution and in adsorbed monolayers, and by the existence of an adsorbed layer, even at time t₀, which prevents the process of adsorption from being governed only by diffusion.