Adsorption of Supercritical Fluids

Adsorption isotherms for supercritical fluids are calculated using lattice theory. Results are compared with experimental data for methane on graphon and for carbon dioxide on coal. It is shown that the model reflects the peculiar features in adsorption isotherms of supercritical fluids (in particular, a maximum in the adsorption with increasing pressure). The analysis shows that there is two layer adsorption over a wide range of densities.     

Magnetic Suspension Balance For Simultaneous Measurement of a Sample and the Density of the Measuring Fluid

This paper deals with gravimetric measurements of adsorption equilibria of gases on the surface of porous solids with a new type of magnetic suspension balance. Items discussed include the measurement of adsorption data at high pressure and temperature as well as the simultaneous measurement of adsorption and the density of the adsorptive gas using only one magnetic suspension balance. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermodynamic Description of Excess Isotherms in High-Pressure Adsorption of Methane, Argon and Nitrogen

In the present work the supercritical fluids argon, methane and nitrogen were picked out as examples, and the results of analysis concerning the adsorption of these fluids at activated carbon Norit R1 (Norit company, Germany) and SCS-3 (ISPE, Kiev) at different temperatures up to a pressure of 50 MPa are presented and discussed in this paper. The principle of working of the measuring device is described in this context as well.A three-parameter isothermal equation is used to represent the adsorption equilibrium. The isothermal equation is based on a physical model concept which has already been used for the modelling of adsorption processes with a pressure up to 15 MPa.     

Adsorption equilibria of CO/H2 with a magnetic suspension balance: Purely gravimetric measurement

Adsorption equilibria of pure gases and binary gas mixtures can be measured with a new magnetic suspension balance. For this measurement no additional concentration measurement is required, neither for the gas phase nor for the adsorbed phase. The new instrument allows gravimetric adsorption measurements in a wide range of pressure (UHV...50 MPa) and temperature (210 K...570 K) to be performed. The experimental procedure and the instrument set up is fairly easy and can be compared to pure gas adsorption experiments. The new instrument and experimental procedure have been tested by performing coadsorption measurements with CO/H₂ mixtures on a commercial 5A zeolite.This revised version was published online in November 2005 with corrections to the Cover Date.     

Adsorption of Pure Gases and Mixtures on Porous Solids up to High Pressures

Physisorption equilibria of multicomponent gases on microporous solids like zeolites or activated carbons are considered. An overview about adsorption measurements of pure gases H₂, He, O₂, N₂, Ar, CO₂, CO, CH₄, C₂H₄ and C₂H₆ and some of their mixtures in the pressure range vacuum < p < 50 MPa at different temperatures 10^∘C–70^∘C were investigated. Also a thermodynamic formalism based on a modified van Ness method and on a new 3 parameter Isotherm equation (3-PIG) to describe the excess amount adsorbed was developed. Results are shown and discussed. Dedication to the memory of W. Schirmer.     

The magnetic suspension balance in high pressure measurements of pure gases

In the present work the supercritical fluids argon, methane, nitrogen, carbon dioxide, ethane, ethylene and propane were picked out as examples, and the results of analysis concerning the adsorption of these fluids at activated carbon Norit R1 (Norit Company, Germany) and SCS-3 (ISPE, Kiev) at different temperatures up to a pressure of 50 MPa are presented and discussed in this paper. The principle of working of the measuring device is described in this context as well.A three-parameter isothermal equation is used to represent the adsorption equilibrium. The isothermal equation is based on a physical model concept which has already been used for the modelling of adsorption processes with a pressure up to 15 MPa.This revised version was published online in November 2005 with corrections to the Cover Date.     

Experimental Determination and Analysis of High Pressure Adsorption Data of Pure Gases and Gas Mixtures

Adsorption data of the pure gases ethane, methane and their mixtures on zeolite 13X and the pure gases carbon dioxide, nitrogen and their mixtures on activated carbon Norit R1 were measured gravimetrically at a temperature of 298 K and pressures up to 15 MPa. From the total loads the partial loads were calculated by the modified van Ness approach. The calculated loads show a good agreement with the experimental data.     

Simultaneous Determination of Aluminum and Iron in High Salt Content Matrices by Adsorptive Stripping Voltammetry. Application to Dialysis Fluids

A new analytical procedure for the simultaneous determination of aluminum(III) and iron(II) in two kinds of dialysis fluids (peritoneal and hemodialysis fluids) by differential pulse adsorptive stripping voltammetry (DPAdSV) is described. The voltammetric measurements were performed using, as working electrode, a stationary mercury electrode, and a platinum electrode and a Ag|AgCl|KCl_(sat.) electrode as auxiliary and reference electrodes, respectively, employing acetate buffer solutions at different pH as supporting electrolyte. As complexing agents, Solochrome Violet RS, Palatine Chrome Black 6BN, Chromazurol S and Eriochrome Black T were employed. For both elements, the accuracy, expressed as relative recovery R%, was very satisfactory being in the range 94–105%, the precision as repeatability, expressed as relative standard deviation s_r%, was lower than 6%, while the limits of detection were of the order of a few units of μg/L. The analytical voltammetric procedure has been validated by comparison with spectroscopic (graphite furnace atomic absorption spectroscopy, GFAAS) measurements.     

Infrared Spectroscopic Study on Adsorption of Acetonitrile from Solution onto Several Oxide Surfaces at High Pressure

Adsorption of acetonitrile from toluene solution at a liquid-solid interface under pressures of up to 300 MPa was investigated by IR spectroscopy. The CN stretching vibration bands (v_CN) of adsorbed acetonitrile were observed at higher frequencies than those of the same species in the liquid phase. The shift on alumina-pillared montmorillonite (ALPM) was the largest (ca. 8 cm^-1) for the adsorbents studied. The v_CN intensities of adsorbed acetonitrile on ALPM and on alumina (Al₂O₃) considerably increased with increased pressure, indicating an increase acetonitrile adsorption due to compression. It was concluded that the total volume of the system was reduced by adsorption, and that the reduction was brought about not only by the formation of an adsorption bond but also by the change in the solvation of the adsorbate in the adsorbent pore.     

Application of a magnetic suspension balance to the oxidation study of the zirconium based alloys under high pressure water vapour

The fuel claddings in the Pressurised Water Reactor are corroded in water at high temperature and high pressure. The technical device ableto follow continuously the corrosion rate in conditions close to this medium does not yet exist. That is the reason why a high pressure thermogravimetric installation based on magnetic suspension has been designed to study in situ the oxidation kinetics of the zirconium based alloys under water vapour until 50 bars of pressure at 415°C. The accuracy of measurements is about 5·10⁻⁵ g under 2 bars, and 10⁻⁴ g under 50 bars. The reproducibility of measurements was verified and the deviation regarding post test weighing at room temperature is around 5·10⁻⁵ g what is clearly satisfying. Finally, the results presented in this work allow validating the high pressure thermogravimetric measurements obtained with this magnetic suspension device.     

紫草油有效成分的高效液相色谱测定法及其在超临界流体萃取制备紫草油中的应用

紫草提取制备成的紫草油能够预防及治疗婴儿尿布疹、皮肤溃烂、湿疹等多种皮肤疾患,临床应用非常广泛,超临界流体萃取是紫草有效成分提取的优选方法.该文建立了紫草油有效成分的高效液相色谱(HPLC)测定方法,并以紫草油所含的有效成分含量为评价指标,采用三因素三水平正交试验法对紫草超临界流体萃取制备过程中的几个重要因素(萃取压力...