气体在固体表面吸附的热力学模型及吸附等温式

描述气体在固体表面吸附的两个著名吸附等温式Langmuir公式和Bronauer—Emmett—Teller(B·E·T)公式可以由动力学方法和统计热力学方法导出。但在导出过程中,都要引进一些基本假定之外的附加限制和近似. 根据经典热力学的唯象特点,能建立气体在固体表面吸附的吸附表面相热力学模型.从吸附平衡是一种热力学相平衡这一观点出发,可以由相平衡原理十分简洁地导出Langmuir吸附等温式和多层吸附的B·E·T吸附等温式.     

气体在固体表面吸附等温式的热力学理论

气体在固体表面吸附等温式的热力学理论李学良，林建新（合肥工业大学化工学院，２３０００９）气体在固体表面吸附的等温式通常可由动力学、热力学或统计力学等传统方法￣［１］导出。但通常都只针对具体模型作推导，而很少对方法作较完整的论述。本文运用热力学方法，在...     

评Freundlich吸附等温式的推导

叙述了Freundlich吸附等温式的几种主要的推导方法,以及这些推导所反映的物理模型,并对它们进行了评价。     

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.     

偶氮苯硫醇衍生物自组装成膜过程考察

The formation kinetics of the self-assembled monolayer (SAM) of an azobenzenealkanethiol, denoted as AzoC2SH on surface was studied using electrochemical techniques, and the monolayers prepared at different assembly times and concentration were also investigated. A two-step adsorption kinetics has been confirmed: the fast adsorption process and the following long-term reorganization. The equilibrium constant(K)for the adsorption and the interaction factor between adsorbate-adsorbate molecules (δ) were evaluated based on the Frumkin isotherm and determined to be (3. 17±0. 13)× 106 mol•L(-1) and -0.34±0.04, respectively. The Gibbs free energy (G)of SAM was determined to be -(37. 07±0. 13)kJ•mol(-1).     

B-E-T吸附等温式的另一种建立方法

将多分子层气固吸附等效地视为链状分子的单分子层吸附,然后通过一个所谓的气固吸附Szyszkowski公式,同样能够建立起B-E-T吸附理论,并导出各种多分子层吸附的气固吸附等温式.     

Gibbs吸附公式在固-气和固-液界面吸附中的应用

Gibbs吸附公式本适用于各种界面的吸附研究 ,但由于有固体参与形成的界面界面能测定困难 ,至今Gibbs公式多只用于气 液界面的研究。本文讨论了Gibbs吸附公式在固 气和固 液界面吸附研究中的应用 ,主要是介绍将Gibbs公式与二维气体状态方程结合导出吸附等温式 ,因吸附而引起的固 气和固 液界面能变化规律 ,以及吸附过程中分子状态变化的有关信息     

大孔弱酸树脂对西索米星的吸附交换性能研究

通过离子交换实验,对不同类型的国产阳离子树脂进行筛选,得到用于分离提取西索米星的最佳的树脂.结果表明,大孔型弱酸性D1树脂对西索米星的吸附及解吸性能最好;D1树脂对西索米星的静态吸附量达20.92×104 μg/mL,动态吸附量为23.37×104 μg/mL;其吸附等温线符合Langmiur方程,相关系数达到0.9805;各种树脂的动态吸附量均比静态吸附量高.     

粘土对硒的吸附研究 Ⅱ

本文研究了在模拟地下水介质中，粘土对硒的吸附（解吸）规律和等温吸附方程。还对酸度，硒的化学状态和固液比变化对ＲＤ或Ｑ值的影响进行研究。     

推导一个表面张力等温式

本文试图从二点假设出发推导一个表面张力等温式：（１）溶液的表面张力是溶剂的表面张力和溶质的表面张力按其所占表面比率的相加,（２）溶质在表面的量与在体相中的量存在一个动态平衡。由此可导出如下表面张力等温式：σ＝σ０１－ａｃ１＋ｂｃ,其中常数ａ、ｂ具有物理意义。经实验数据的验证,该式在大多数情况下比Ｓｚｙｓｚｋｏｗｓｋｉ经验式更好     

聚氯乙烯微塑料对典型单羟基菲的吸附机制

为丰富微塑料与有机污染物间的相互作用机制相关数据,以3-羟基菲(3-OHP,C14 H10 O)为菲单羟基衍生物代表污染物,聚氯乙烯(PVC)微塑料为研究对象,研究了PVC微塑料在水环境中对3-OHP的吸附行为,并就相关吸附机制进行了深入探讨.该研究借助扫描电镜(SEM)、X射线衍射仪(XRD)、傅里叶红外光谱(FT-...     

Excess differential thermodynamic properties

A strategy is described for the systematic generation of a complete set of partial derivatives of the four energy functions from a basis set of five measured properties: V_m, S_m, C_p,m (δV_m/δT)_p and either (δV_m/δp)_T or (δV_m/δp)_s. The same set of equations applies to both pure substances and either real or ideal mixtures.

Examples are given of some excess differential properties of binary mixtures which exhibit unusual sensitivity to changes in composition.     

Adsorption of Heavy Metal Ions from Aqueous Solutions by Zeolite Based on Oil Shale Ash: Kinetic and Equilibrium Studies

Na-A zeolite was successfully synthesized via the alkaline fusion method with oil shale ash as the raw material. The adsorption capacity of it was tested by removing Cu²⁺, Ni²⁺, Pb²⁺ and Cd²⁺ from aqueous solutions. The results reveal the maximum adsorption capacity of adsorbent for Pb²⁺, Cu²⁺, Cd²⁺ and Ni²⁺ were 224.72, 156.74, 118.34 and 53.02 mg/g, respectively. The effects of contact time and pH value of solutions on the adsorption efficiency of the zeolite were evaluated. Besides, The equilibrium adsorption data and the batch kinetic data were correlated with Langmuir and Freundlich models and the pseudo-first-order and pseudo-second-order models separately. The results show that the Langmuir isotherm and the pseudo-second-order equation were more suitable for the adsorption of Na-A zeolite for the metal ions. In addition, Thermodynamic parameters of the adsorption(the Gibbs free energy, entropy, and enthalpy) were also evaluated and discussed. The results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions and the synthesized zeolite was an effective adsorbent for the removal of metal ions from aqueous solution.     

计算化学在分子轨道教学中的应用

分子轨道理论是理解分子电子结构与微观性质的重要理论之一,也是本科生与研究生结构化学教学中的重点与难点。学生对原子轨道组合形成分子轨道、分子轨道能级交叉混合等知识的理解缺乏形象直观、定量的认识。本文通过基于量子化学或密度泛函理论的Gaussian 03计算软件,计算、绘制并分析了F_2、O_2、N_2、HF、CO等的分子轨道能级图,将学生较难理解的内容定量、直观地呈现出来,形象地解释了分子轨道成键原则与电子填充原则等分子轨道理论中的重难点,加深了学生对分子轨道理论的理解,特别是sp轨道混杂导致的σ_(2p_z)与π_(2p)轨道能级交叉这一难点,激发了学生学习的主动性和积极性,提高了教学质量。在此基础上,利用分子轨道理论分析了CO_2的电子结构,使学生学会应用分子轨道理论解决实际问题,巩固了相关课堂理论知识。     

Adsorption and desorption kinetics of CmE8 on impulsively expanded or compressed air–water interfaces

The adsorption kinetics of C_mE₈ (m=10, 12, and 14) at an air–water interface are investigated. A pendant bubble is formed in aqueous surfactant solution and allowed to attain equilibrium. The bubble is then impulsively expanded or compressed with some change of area large enough to appreciably deplete or enrich the surface concentration and change the surface tension. The surfactant is then allowed to re-equilibrate. The surface tension evolution during this process is measured using video images of the pendant drop. The surface tension evolution is compared to mass transfer arguments. First, the re-equilibration of interfaces laden with C₁₄E₈ are studied. For compressed interfaces, surfactant must desorb to restore equilibrium. The surface tension rises more slowly than predicted by a diffusion-controlled evolution, implying that the re-equilibration is mixed diffusive-kinetic controlled. By analyzing the surface tension evolution in terms of a mixed kinetic-diffusive model, values for the kinetic constants for adsorption and desorption are found. These results are compared to those obtained previously for C_mE₈ (m=10 and 12). For all of these molecules, the adsorption rate constant is similar (β₁=5.6±1.0×10⁻⁶ cm³ (mol s)⁻¹). However, the desorption rate constant (₁) varies strongly. Increasing m by 2 lowers the desorption rate constant ₁ by nearly a factor of 15. This is consistent with an increased resistance to re-immersion into water with the length of a hydrocarbon chain.     

Adsorption Characteristics of Activated Carbon for the Reclamation of Eosin Y and Indigo Carmine Colored Effluents and New Isotherm Model

The adsorption response of eosin Y and indigo carmine acid dyes on activated carbon as a function of system temperature for a fixed concentration was investigated at various temperatures via adsorption isotherms and their thermodynamic quantities such as enthalpy, entropy, and Gibbs free energy changes. The adsorption data were exploited to develop a new adsorption isotherm. The new isotherm was developed with the spirit of solid–liquid phase equilibrium and regular solution theory. The proposed model has four adjustable constants and correlates adsorption isotherm in terms of the system temperature and melting temperature of the dye. The effect of pH on the removal of acid dyes was reported. The pH variation was observed to affect the adsorption efficiency. The removal of eosin Y and indigo carmine decreased from 99.4% to 82.6% and 92.38% to 79.48%, respectively, when the pH of the solution varied from 2 to 12. The thermodynamic analysis of the process reveals that the process of the removal of acid dyes is exothermic and spontaneous. Moreover, the kinetics parameters of the batch process are reported.     

Calculation of the surface charge and potential and of the structural component of disjoining pressure in an interlayer in KCl solutions between glass samples

The dependence of the Stern potential, ψ₁, of glass samples on the distance between these, H, has been theoretically calculated, while taking into account the Stern isotherm and the electroneutrality equation. Comparison of the theoretical dependences ψ₁(C)_H→∞ with those previously experimentally obtained enables one to calculate the energy of adsorption of OH ions on glass and, further, the dependence ψ₁(H). It has been shown that for pH 4–6 and C_KCl = 10^-2-10^-5 mol/L, the value of ψ₁ practically does not depend on H. The result obtained was used to calculate theoretically the ionic-electrostatic forces and to compute (from the experimental values of the interaction forces) structural forces U_s(H). The dependence thus obtained, U_s(H), is of exponential character.     

Aluminum-type superparamagnetic adsorbents: Synthesis and application on fluoride removal

Two effective types of superparamagnetic nano-scale adsorbents of bayerite/SiO₂/Fe₃O₄ have been synthesized via three sequential steps: chemical precipitation of Fe₃O₄, coating of SiO₂ on Fe₃O₄ using acidifying method, and further coating of bayerite (Al(OH)₃) on SiO₂/Fe₃O₄ adopting sol–gel (MASG) or homogeneous precipitation (MAHP) methods. The characteristics of MASG and MAHP were identified using the transmission electron microscopy (TEM) micrograph, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray powder diffractometer (XRD), and superconducing quantum interference device (SQUID). Removal of fluoride from aqueous solution was examined to evaluate the adsorptive capacity of MASG, MAHP, and commercial activated alumina (CA), and the effects of enclosure of Fe₃O₄ with SiO₂ for SiO₂/Fe₃O₄, MASG, and MAHP particles. Among the adsorbents tested under the same experimental condition, MASG is the most effective adsorbent, of which the adsorption capacities are 38 g/kg (based on adsorbent mass of adsorption in terms of equilibrium constant q_L of Langmuir isotherm), and can compete with CA even at a high pH value. The innovative superparamagnetic adsorbents synthesized in this study possess physicochemical stability at pH range of 6–8 and great potential in the adsorption processes due to not only their high adsorption capacity but also the conveniently magnetic separation which can overcome the difficulty in solid–liquid separation for nano-particles in solutions.     

十烷基硫酸钠-全氟辛酸钠混合表面活性剂在四氯乙烯-水界面上的吸附及胶团形成

测定了在30℃、总离子强度为0.1m时不同比例混合的十烷基硫酸钠(C₁₀SN_a)-全氟辛酸钠(7CFNa)在四氯乙烯-水界面的界面张力,研究混合溶液的界面性质及胶团形成,结果表明:(1)7CFNa与C₁₀SNa在混合溶液中,基本上各自独立形成胶团;(2)混合表面活性剂在四氯乙烯-水界面上的吸附与在正庚烷-水界面上吸附规律相同;(3)测定C₁₀SNa、7CFNa在不同油-水界面上的界面张力,证实碳氟链与碳氯链之间具有“互憎性”。     

中空介孔二氧化硅锚固聚偕胺肟吸附Cr(Ⅵ)

以硝酸铈铵为引发剂, 在自制的中空介孔二氧化硅(HMS)的空腔和通道内引发丙烯腈自由基聚合, 并将其氰基偕胺肟化, 用于制备具有吸附Cr(Ⅵ)的廉价有机无机复合吸附材料—中空介孔二氧化硅锚固聚偕胺肟. 通过傅里叶变换红外光谱(FTIR)、 扫描电子显微镜(SEM)及N₂吸附-脱附比表面分析对中空介孔二氧化硅锚固聚偕胺肟进行表征. 结果表明, 制备的中空微球直径约为400 nm, 其壁上孔径约为11.0 nm, 比表面积约为431 m²/g, 锚固聚偕胺肟后中空微球壁上孔道直径约为4.6 nm, 比表面积降低为347 m²/g. HMS锚固的聚偕胺肟对重铬酸钾溶液中铬的吸附量高达0.46 mmol/g, 吸附过程中伴随化学反应, 符合伪二级动力学模型, 可用作废水处理中重金属离子的高效廉价吸附材料.