Thermodynamics of krypton adsorption on microporous carbon adsorbent at high pressures

The behavior of the thermodynamic functions for the adsorption system krypton—microporous carbon sorbent ACC is described. The dependences of the differential molar isosteric heat of adsorption, entropy, enthalpy, heat capacity, and differential molar energy of the adsorption system on the adsorption equilibrium parameters were studied over the temperature range from 178 to 393 K and at pressures ranging from 1 to 6?106 Pa. Consideration of the non-ideality of gas phase and non-inertness of the adsorbent leads to a temperature dependence of the thermodynamic functions of the studied adsorption system, especially in the range of high pressures of the adsorptive. The non-ideality of the gas phase and the energetics of the adsorbent—adsorbate system exert the most significant effect on the thermodynamic functions. The non-inertness of the adsorbent in the investigated range of parameters of the adsorption system has a weak effect on the thermodynamic functions of adsorption. In the region of high filling of ACC micropores, the entropy increases, indicating the existence of processes, which change the structure of the adsorbate in the micropores, in particular, to form associates.     

Adsorption complexes ‘zeolite–cationic surfactant’: properties and surface activity in a polymer composite material based on ultra-high-molecular-weight polyethylene

We investigated the adsorption of the cationic surfactant cetyltrimethylammonium bromide (CTAB) to zeolite from premicellar and micellar solutions, as well as some properties of the organically modified zeolite surface and the nature of its interfacial interaction with ultra-high-molecular-weight polyethylene (UHMWPE) in a UHMWPE-based polymer composite material (PCM). The formation mechanism of mono- and bimolecular adsorption layers of cetyltrimethylammonium cation and bromide anion to the clinoptilolite (Cli) surface was proposed, and the thermodynamic and kinetic characteristics of adsorption were determined. The surface texture of organically modified zeolite was studied by instrumental methods; the thermal stability limits of CTAB adsorption layers to zeolite surface and their decomposition behavior in inert and oxidizing media were established. The evaluation of the deformation and strength properties, the study of the supramolecular structure, and the calculation of the thermodynamic and kinetic parameters of the PCM crystallization process revealed that the filing with organically modified Cli increases the UHMWPE surface activity and improves their compatibility.     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.     

Chromatographic and Adsorption Properties of Antimony Pentoxide

The surface of antimony pentoxide was found to be convenient for analytical purposes in gas—solid chromatography. Its main advantage is the selective complete retention or some organic compounds. On the basis of this property, rapid determinations can be achieved.

The thermodynamic parameters for the adsorption of some representative organic compounds on antimony pentoxide have been determined. These values were then correlated with some physical properties of the compounds, thus enabling conclusions to be drawn about the nature of the forces responsible for the adsorption.     

氨基酸在固/液界面的吸附作用

本文介绍了氨基酸在固/液界面吸附等温线的特点,氨基酸液相吸附热力学和活性炭、硅胶、二氧化钛、氧化铝、蒙脱土等自水中吸附氨基酸的机制。     

Kinetic,isothermal and thermodynamic studies on Th(IV) adsorption by different modified activated carbons

In this study, the performance of modified adsorbents obtained from activated carbon for the adsorption of thorium(IV) ions from aqueous media was investigated. The analytical and spectroscopic methods such as FT-IR, BET, SEM and UV–Vis were used to examine the properties of the modified materials. According to the analysis results, the both adsorbents had large surface areas after modification. Then, temperature, pH, mixing time and solution concentration parameters were observed to determine optimum thorium adsorption conditions on modified materials. The obtained results from the experiments were applied different three kinetic models and adsorption isotherms and thermodynamic parameters were calculated and then all of the results were interpreted. The adsorption process for both adsorption systems was observed to be compatible with the pseudo-second-order kinetic model. The adsorption equilibrium data were best described by the Langmuir model for modified adsorbent with KMnO₄ and by the Freundlich model for modified adsorbent with NaOH. Furthermore, the calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed that the both adsorption processes were endothermic and spontaneous. The data show that modified adsorbents can be used as influential and low-cost adsorbents to remove thorium ion. Modified new adsorbents were highly selective for thorium ion in competitive adsorption studies.

     

Thermodynamics of methane adsorption on the microporous carbon adsorbent ACC

The behavior of the thermodynamic functions (differential molar isosteric heat of adsorption, entropy, enthalpy, and heat capacity) of the adsorption system methane—microporous carbon adsorbent ACC was analyzed at different adsorption equilibrium parameters in the temperature interval from 177.65 to 393 K and in the pressure range from 1 Pa to 6 MPa. The influence of the nonideal character of the gas phase and noninertness of the adsorbent were taken into account, which resulted in the appearance of the temperature dependence of the isosteric heat of adsorption, especially in the region of high pressures of the adsorptive. For the system studied, nonideality of the gas phase exerts the main effect on the thermodynamic functions of the adsorption system. In this interval of the parameters of the adsorption system, the correction to the noninertness of the adsorbent is not higher than 2.5%. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1765–1771, September, 2008.     

An experimental and molecular-statistical study of the adsorption of the iodobenzene, 2-iodothiophene, and isomeric iodoadamantane molecules on the graphite basal face surface

The thermodynamic characteristics of adsorption of iodobenzene, 2-iodothiophene, and 1- and 2-iodoadamantanes on the surface of graphitized thermal carbon black were determined experimentally. The influence of the special features of the molecular structure of the adsorbates on the thermodynamic characteristics of adsorption was studied. The atom-atom approximation of the semiempirical molecular-statistical theory of adsorption was used to calculate the thermodynamic characteristics of adsorption of the adsorbates using the newly determined potential function parameters of pair intermolecular interaction (φ(r)) of I with C atoms of the basal graphite face. For the example of isostructural monohalogenated benzenes, thiophenes, and adamantanes, a comparative analysis of the contributions of the F, Cl, Br, and I atoms to the thermodynamic characteristics of adsorption was performed for the nonspecific adsorption of these compounds on a plane graphitized carbon black surface.     

胡芦巴总皂苷在HPD 400A大孔树脂上的吸附性能研究

静态条件下,对胡芦巴中总皂苷在HPD 400A树脂的吸附平衡、吸附动力学、热力学进行了深入探讨,测定了不同温度下胡芦巴中总皂苷在该树脂上的吸附等温线,吸附动力学曲线以及热力学参数。结果表明,Freundlich方程可较好地描述胡芦巴中总皂苷在该树脂上的吸附平衡;吸附动力学规律可用二级速率方程表示,液膜扩散和颗粒内扩散是吸附的主要速率控制步骤,吸附活化能为8.314kJ/mol;热力学参数表明此吸附过程为吸热过程。     

INVESTIGATION OF THE INTERACTIONS BETWEEN WATER AND MODIFIED SILICA GEL BY IGC AND TPD

In this work, the thermodynamic parameters for the adsorption of water vapor on untreated silica gel and silica gel treated with hygroscopic salts and silane coupling agent were determined by Inverse Gas Chromatography (IGC) in the infinite dilution region. The desorption activation energies of the water vapor on virgin and modified silica gels were estimated by using the Temperature Programmed Desorption (TPD) technique. The interactions between the water and the virgin and modified silica gels were discussed. Results showed that the thermodynamic parameters and desorption activation energy of water vapour on the silica gels increase with decreasing pore size and increasing the surface hydrophilic properties. The desorption activation energy of virgin and modified silica gels was found to increase with increasing the thermodynamic parameters. The larger the adsorption parameters and the desorption activation energy were, the interactions between water and virgin and modified silica gels were.     

INVESTIGATION OF THE INTERACTIONS BETWEEN WATER AND MODIFIED SILICA GEL BY IGC AND TPD

1. INTRODUCTIONSilica gel is an amorphous inorganic polymer composed of siloxane (Si-O-Si) groups in the inner region and silanol (Si-OH) groups distributed on the surface [1]. Silanol groups can be easily functionalized by different chemical procedures. …     

Decoration of electrospun polyacrylonitrile nanofibers with ZnO nanoparticles and their application for removal of Pb ions from waste water

The adsorption behavior of lead (II) from aqueous solutions utilizing ZnO/polyacrylonitrile (PAN) nanofibers was studied. ZnO/PAN nanofibers were prepared by electrospinning method. The changes of the parameters of adsorbent amount, pH, contact time, and temperature were tested in the adsorption experiments. The adsorption was well described by the Langmuir adsorption isotherm model. The thermodynamic parameters indicate that the adsorption process is exothermic. The dynamic behavior of the lead (II) ions adsorption by PAN/ZnO nanofibers was well described by the pseudo-second-order kinetic model. The adsorbent can be regenerated by suitable desorption processes for multiple uses without significant loss of its adsorption capacity.     

Adsorption characteristics of poly(styrene-co-divinylbenzene) resin functionalized with methoxy and phenoxy groups for phenol

Two macroporous crosslinked poly(styrene-co-divinylbenzene) resins functionalized with methoxy and phenoxy groups, PVBME and PVBPE were prepared and their adsorption characteristics for phenol were studied in hexane as well as in aqueous solution. It was shown that the equilibrium adsorption capacity of phenol onto PVBPE was a little larger than that onto PVBME at the same temperature and equilibrium concentration. The adsorption onto PVBME in hexane can be correlated to Langmuir isotherm model, whereas the semi-empirical Freundlich isotherm model characterized the adsorption onto PVBPE better. The adsorption thermodynamic parameters were calculated and it was found that the adsorption enthalpy, adsorption free energy, and adsorption entropy were all negative, and the adsorption thermodynamic parameters onto PVBPE were more negative than the corresponding ones onto PVBME. The relationship of the adsorption capacity with the equilibrium concentration was linear in aqueous solution. The adsorption was hypersensitive to the solution pH in aqueous solution, and the optimum pH was determined to be 6.0. The adsorption dynamics of phenol onto PVBPE in aqueous solution was investigated and it was seen that the adsorption can be well fitted by the pseudo-first-order rate equation.     

Mechanism and Kinetics of the Sorption of Platinum, Palladium, and Gold on Activated Carbon from UV-Illuminated Chloride Solutions

The mechanism and kinetics of the sorption preconcentration of gold, platinum, and palladium on activated carbon from solutions exposed to ultraviolet (UV) radiation were studied. The thermodynamic parameters of sorption (sorption capacity and type of adsorption isotherm) were determined; the effect of pH was considered. An explanation of the mechanism of the effect of UV illumination on sorption preconcentration was proposed. It was demonstrated that UV illumination does not change thermodynamic parameters of sorption but significantly affects the kinetics of sorption preconcentration.     

Interaction of isoniazid drug with the pristine and Ni-doped of (4, 4) armchair GaNNTs: a first principle study

In this research, the interaction of isoniazid drug (INH) with the pristine and Ni-doped Gallium nitride nanotubes (GaNNTs) is investigated by using density function theory. The adsorption energy, deformation energy, natural bond orbital (NBO), quantum parameters, molecular electrostatic potential (MEP) and thermodynamic parameters of all adsorption models are calculated from optimized structures. The values of adsorption energy, enthalpy and Gibbs free energy of all adsorption models are negative and all adsorption process are favorable in view of thermodynamic points. It is notable that Ni-doped decrease adsorption strength and it is not suitable for INH adsorption on the GaNNTs surface. The MEP, NBO and maximum amount of electronic charge ΔN results demonstrate that the negative potential are localized around adsorption position and the positive potential are localized around INH molecule. The calculated results indicate that the GaNNTs is a good candidate to making absorber and sensor for detecting INH drug.     

Surface and Thermodynamic Parameters of Polymeric Surfactants from Recycled Poly(ethylene terephthalate)

Recycling of PET waste was carried out in presence of diethanolamine and manganese acetate as catalyst. The produced oligomers were reacted with stearic acid and polyethylene glycol, PEG, which have different molecular weights 400, 1,000, and 4,000 to produce nonionic polymeric surfactants having different hydrophilic‐hydrophobic balance (HLB). The surface tension, critical micelle concentration (CMC), and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration Γ_max, the area per molecule at interface A_min and the effectiveness of surface tension reduction (Π_CMC) were determined from the adsorption isotherms of the prepared surfactants. From the adsorption isotherm, some thermodynamic data for the adsorption process are calculated and discussed.     

The use of carbonaceous adsorbents for the extraction of silver ions from solutions and slurries

The adsorption of silver(I) ions from aqueous solutions on carbonaceous adsorbents synthesized from hard coals was studied. Adsorption isotherms were measured under static and dynamic conditions at various temperatures. Adsorption was shown to be maximum in alkaline media. The isotherms obtained at low silver concentrations were described by the Freundlich equation. A decrease in adsorption as the temperature increased was evidence that the process was exothermic. The kinetics of the process was studied and the thermodynamic parameters of adsorption determined.     

Adsorption of tetramethylsilane molecules on the basal face of graphite

The thermodynamic adsorption characteristics of tetramethylsilane (TMS) molecules on graphitized carbon black (GCB) were for the first time determined experimentally and by molecular statistics methods. The potential function parameters of pair molecular interactions (φ(r)) between Si and C atoms on the basal face of graphite were calculated in the atom-atom approximation of the semiempirical molecular-statistical theory of adsorption. The contributions of Si and C atoms to thermodynamic adsorption characteristics are compared for the example of nonspecific adsorption of TMS and isostructural neopentane molecules on the flat surface of GCB.     

Pulsed NMR method for determining the thermodynamic characteristics of adsorption processes in biopolymers

The efficiency of the pulsed NMR method in studying phenomena in the interphase layer of biopolymer-water systems within the framework of the Gibbs thermodynamic theory was examined. Relationships between the nuclear magnetic relaxation times and the chemical potential and surface tension coefficient at the interphase interface of the adsorption system were established. How the thermodynamic and relaxation parameters change during the formation of the adsorption Gibbs layer on various cellulose samples was demonstrated. An analysis of the state of the water in the adsorption layer was performed, and its mean thickness was determined.     

Modeling and Thermodynamics of Methylene Blue and Acid Blue 80 Adsorption onto Potato Residue Based Activated Carbon

A study was made on the adsorption kinetics and thermodynamics of methylene blue(MB) and acid blue 80(AB80) onto powder of activated carbon(PAC) prepared by chemical method from dry potato residue(DPR). The PAC was characterized by N₂ adsorption-desorption isotherms analysis and scanning electron microscopy. The ma- ximum adsorption capacities of PAC for MB and AB80 at 303 K are 532.19 and 156.22 mg/g, respectively. The results indicate that the adsorption kinetics of the selected dyes on PAC is well-described by the pseudo-second order model. And their thermodynamic data were analyzed via the isotherms of Langmuir, Freundlich, Redlich-Peterson, Toth and Sips, and the thermodynamic parameters were calculated. The results show that PAC is a fast and effective adsorbent for removing the cationic dyes from aqueous solutions.