自溶液中的吸附XII.活性炭自水中吸附芳香化合物的热力学研究

测定了25℃和35℃时活性炭自水中吸附苯甲酸,邻苯二甲酸,邻羟基苯甲酸,间羟基苯甲酸,对羟基苯甲酸,苯酚和邻苯二酚共七种芳香化合物的等温线,计算了吸附过程的△G,△H和△S.七种芳香化合物的-△G都在5.9～7.7kcal.mol[-1]的范围内,差别不大;-△h都小于-△g的值;△s则都是正的。这些结果表明熵变是这类体系的吸附过程的重要驱动力,而且往往是主要驱动力,在液相吸附中,溶质的吸附必伴随着溶剂的脱附,前者是熵减少的过程,后者是熵增加的过程。因为上述芳香化合物的摩尔体积约是水(溶剂)的5～7倍,也就是说,吸附1摩尔的溶质将伴随5～7摩尔的水由表面脱附。因此,由于水的脱附引起的熵增加远远超过溶质吸附所引起的熵减少,这可以解释为何这类体系的吸附过程的熵变总是相当大的正值,根据这个理论,可以设想倘若溶剂的摩尔体积与溶质的相近或比溶质的更大时,吸附过程的熵变可能出现负值,文献中的一些数据支持了这一推测。     

酚醛型吸附树脂吸附VB12的热力学研究

研究了酚醛型附树脂JDW-2对VB12的吸附。在304-322K和研究的浓度范围内，JDW-2对VB12吸附平衡数据符合Freundilch吸附等温方程。Freundilich吸附等温线和等量吸附焓表明：JDW-2对VB12吸附是吸热过程。测试了VB12在JDW-2上的吸附焓、自由能和吸附熵，并对吸附行为作了合理解释。     

新型吸附树脂对苯乙酸的吸附热力学研究

研究了苯乙酸在新型超高交联树脂AH、NDa-150和大孔吸附树脂(Amberlite XAD-4)上的平衡吸附数据，测定了288K、303K和318K温度下的吸附等温线，结果表明吸附过程符合Langmuir吸附等温方程。苯乙酸在AH、NDa-150上的吸附容量分别比在Amberlite XAD-4上的吸附容量最高高出90％、113％，这主要归因于AH、NDa-150表面的极性基团及树脂的微孔结构．Langmuir吸附等温线、相对吸附容量以及等量吸附焓变表明，苯乙酸在AH树脂上的吸附是物理吸附和化学吸附共同作用的结果．对苯乙酸被3种树脂吸附的吸附焓变、自由能变、吸附熵变也作了计算，并对吸附行为作了合理的解释。     

吸附树脂对山梨酸的吸附作用及其热力学性质

大孔吸附树脂;吸附树脂对山梨酸的吸附作用及其热力学性质     

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...     

热力学标准态

热力学标准态姚天扬（南京大学化学系２１００９３）在化学热力学中标准状态（简称标准态ＳｔａｎｄａｒｄＳｔａｔｅ）是一个重要而抽象难懂的概念，它贯穿整个化学热力学。波及化学动力学及统计热力学。本文将从物理化学教学角度对标准态作一较全面的论述。标准态概念化...     

气相色谱吸附过程的热力学函数变化及规律探讨 II: 吸附熵变的计算方程与硅胶对直链烷的吸附

本文从吸附平衡的定义导出一个较为合理的方程, 并据此计算了9个有机化合物在硅胶表面吸附过程的焓变和熵变, 所得结果进一步验证了热力学补偿效应、同系物碳数关系和等热力学等规律.     

粒度对纳米氧化镁吸附苯的热力学性质影响

以纳米氧化镁与水溶液中的苯作为吸附体系,研究了纳米氧化镁的粒度对吸附热力学性质的影响。实验结果表明,纳米氧化镁的粒度对吸附标准平衡常数、标准摩尔吸附吉布斯自由能变、标准摩尔吸附焓变和标准摩尔吸附熵变均有较大影响;并且随着纳米氧化镁粒度的减小,吸附标准平衡常数增大,标准摩尔吸附吉布斯自由能变、标准摩尔吸附焓变和标准摩尔吸附熵变均降低。     

超高交联吸附树脂对苯甲酸的吸附研究

用新合成的NJ－8超高交联吸附树脂吸附苯甲酸，并与Amberlite XAD-4进行比较。从静态平衡吸附行为及其热力学性质讨论吸附机理。动态穿透吸附实验进一步验证了NJ－8提高交联吸附树脂对苯甲酸的吸附能力约为Amberlite XAD-4的1.6倍。     

焙烧态镁铝水滑石对诺氟沙星的吸附行为研究

采用共沉淀法合成镁铝水滑石(LDH),用X-射线衍射(XRD)、扫描电镜(SEM)等表征了产物,研究了400℃焙烧后LDH(LDO)的结构、成分及吸附率的变化,通过静态吸附实验考察了LDO对诺氟沙星的吸附性能。结果表明,在固液比1∶500、pH=5.0、吸附温度25℃、离子强度0.1 mol/L的条件下吸附1 h对诺氟沙星(20 mg/L)的吸附率达91.25%。吸附过程符合Langmuir等温线方程,理论平衡吸附量达到32.05 mg/g,推断焙烧态镁铝水滑石对诺氟沙星的吸附是以表面吸附为主的自发反应。     

合成氨反应动力学平衡常数与热力学平衡常数的关系

根据当前普遍被接受的氨合成和氨分解机理,明确了氨合成及分解反应的速度控制步骤,确定了氨合成和氨分解反应的动力学方程,进而导出合成氨反应的动力学平衡常数表达式,与热力学平衡常数进行了比较,明确了2者之间的关系。有助于理解合成氨热力学平衡常数与反应速率的关系。     

Adsorption Equilibrium of Alkanes on a High Surface Area Activated Carbon Prepared from Brazilian Coconut Shells

Adsorption equilibria of methane, ethane, and n-butane on a high surface area activated carbon prepared from Brazilian coconut shells is examined in this study. The material shows high capacities for the alkanes tested. A group-contribution theory is used to predict adsorption isotherms for all three components with very good accuracy employing one set of model parameters. The theory is also used to observe trends in isosteric heat of adsorption as a function of loading at various temperatures.     

Multicomponent Equilibrium Adsorption on Heterogeneous Adsorbents

A generalized method for prediction of multicomponent adsorption is suggested based on representing that adsorbent volume as energetically inhomogeneous. The method depends on extending the Polanyi potential theory to mixture adsorption. The main feature of the method is that, at constant partial pressure and temperature the composition of an adsorbed phase is not uniform over its volume. Results of applying this theory to non-porous adsorbents have been considered. The prediction ability of the theory is confirmed for the strongly non-ideal system acetone–chloroform–graphitized carbon black. It was shown that the departure from ideal behavior of adsorbed phase is quite close to that for the liquid mixture. Another system considered was oxygen–nitrogen–anatase at 78 K. Although this mixture is ideal, it has been found that there is significant variation in composition over the adsorbed layer due to the difference in the interactions of the quadrupolar N₂ molecule and nonpolar O₂ molecule with the anatase surface.     

Correlation of Adsorption Equilibrium Data for Water Vapor on F-200 Activated Alumina

Single component adsorption equilibrium data for water vapor on commercially available activated alumina F-200 measured in a previous study (Serbezov, 2003) is correlated by two adsorption isotherm equations, both of which are based on the adsorption potential theory. The first equation is the well known Dubinin-Astakhov (D-A) equation. The second equation is obtained from a methodology proposed by Kotoh et al. (1993). It is referred to as a dual mechanism adsorption potential (DMAP) equation because it is a linear combination of two D-A terms with n = 1 where each term accounts for a specific mechanism of water retention. The D-A equation has two fitting parameters; the DMAP equation has three fitting parameters. The DMAP model provides a better fit for the adsorption data than the D-A model, while neither model describes the desorption data well. Analysis of the DMAP equation parameters shows that most of the water is retained by virtue of capillary condensation. In addition to fitting the experimental data, the heat of adsorption was calculated as function of the relative humidity and adsorbent loading. When capillary condensation is present, the heat of adsorption is only slightly higher than the latent heat of vaporization.     

气体超临界吸附研究进展

综述了近年来国内外学者对超临界气体在固体表面吸附的研究情况。指出了气体在临界温度以上吸附与临界温度以下吸附的不同之处;对现行的关于超临界气体的吸附理论研究进行了讨论,并在此基础上提出了研究中存在的总是及进一步的研究方向。     

氢原子在Be(0001)表面吸附的密度泛函理论研究

采用第一性原理的密度泛函理论研究单个氢原子和多个氢原子在Be(0001)表面吸附性质.给出了氢吸附Be(0001)薄膜表面的原子结构、吸附能、饱和度、功函数、偶极修正等特性参数.同时也讨论了相关吸附性质与氢原子覆盖度(0.06-1.33ML)的关系.计算结果表明:氢原子的吸附位置与覆盖度之间有强烈的依赖关系,覆盖度低于0.67ML时,氢原子能量上易于占据fcc或hcp的中空位置;覆盖度为0.78ML时,中空位与桥位为氢原子的最佳吸附位;覆盖度在0.89到1.00ML时,桥位是氢原子吸附能量最有利的位置;以上覆盖度中Be(0001)表面最外层铍原子的结构均没有发生明显变化.当覆盖度为1.11-1.33ML,高覆盖度下Be(0001)表面的最外层铍原子部分发生膨胀,近邻氢原子渗入到铍表面次层,氢原子易于占据在hcp和桥位.吸附结构中的氢原子比氢分子中的原子稳定.当覆盖度大1.33ML时,计算结果没有发现相对于氢分子更稳定的吸氢结构.同时从分析偶极修正和氢原子吸附垂直高度随覆盖度的变化关系判断氢覆盖度为1.33ML时,在Be(0001)表面吸附达到饱和.     

Metastable Phase Equilibrium of the Quaternary System Na+, Rb+, Mg2+//Cl--H2O at 298.2 K

The component solubilities, densities and refractive indices of the quaternary system Na⁺, Rb⁺, Mg²⁺//Cl^--H₂O at 298.2 K were measured using an isothermal evaporation method. Based on the gathered data, a metastable phase diagram, a water content diagram, and a density/refractive index vs. composition diagram were constructed. The results show that this system is of a complex type with a double salt rubidium carnallite (RbCl·MgCl₂·6H₂O) formed at 298.2 K. Double salt rubidium carnallite, whose component point locates in its own crystallization zone in the dry salt phase diagram, belongs to congruent double salt at 298.2 K. Accompanied by the double salt that was formed, there are two invariant points in the phase diagram that cosaturated with three salts and an equilibrated solution. The cosaturated salts for the two invariant points are MgCl₂·6H₂O+RbCl·MgCl₂·6H₂O+ NaCl and NaCl+RbCl+RbCl·MgCl₂·6H₂O, respectively. Both invariant points are commensurate invariant points in the evaporation process, and the two invariant points are evaporative dry points. The sizes of the crystalline regions of the salts are in the order of NaCl > RbCl > RbCl·MgCl₂·6H₂O > MgCl₂·6H₂O.     

ZrO_2表面上Zr~(3+)中心上的O_2吸附平衡

以ESR为主要研究手段,研究了一种最可几粒径为9.8 nm的ZrO_2样品在室温不 同气体（He,H_2,O_2,空气,温空气）中及经不同温度处理后ZrO_2中Zr~(3+)中 心信号的变化。根据ZrO_2样品中Zr~(3+)浓度在室温下对于介质气体中O_2分压改 变的响应极快及Zr~(3+)浓度在室温下对于介质气体变化可逆性等特点提出, ZrO_2中Zr~(3+)中心绝大多数存在于样品的表面上,Zr~(3+)是ZrO_2晶体表面上那 些O~(2-)配位不饱和的Zr原子点位。ZrO_2表面上ESR活性Zr~(3+)中心的数目与其 上氧吸附平衡有关。由ESR法对ZrO_2样品中Zr~(3+)中心的定量和对ZrO_2晶体的粒 度分析,推测ZrO_2表面上Zr~(3+)中心是那些位于ZrO_2微晶的晶角处O~(2-)配位 不饱和的Zr原子。