Search results for "Selective adsorption"
showing 10 items of 18 documents
Adsorptionseffekte als Fehlerquellen bei Lichtzerstreuungsmessungen
1956
Es werden die Einflusse der Adsorption von Hochpolymeren aus den Losungen auf Lichtzerstreuungsmessungen untersucht. Zunachst wird die Adsorption aus Losung an Glaswolle und Glaspulver in verschiedenen Losungsmitteln gemessen. Es zeigt sich, das sowohl Konzentrationserniedrigung, bestimmt im Differentialrefraktometer, wie auch eine Abnahme des Molekulargewichtes, aus der Lichtzerstreuung bestimmt, infolge selektiver Adsorption auftreten. Beim Schutteln der Losungen tritt als weiterer Effekt ein Abbau der Kettenmolekule ein. Beim Filtrieren von Losungen nehmen durch Adsorption im Filter Konzentration und Molekulargewicht ab. Die Abnahme wachst mit der Feinheit des Filters, d. h. mit seiner O…
Study of Selective Adsorption of Gases by Calorimetry
2013
This chapter is devoted to the study of coadsorption of gases in nanoporous solids by using the differential calorimetry. In the first part, the thermodynamic principles of adsorption of gases are recalled. Some of them have already presented in chapter one. However a special attention has been paid here to the determination of the adsorption enthalpies and entropies and we focused on the selective adsorption of binary mixtures. Then the specific experimental technique based on the combination of differential calorimetry with manometry and gas phase chromatography or mass spectrometry is shown in details. In the last part, the thermodynamic concepts on coadsorption are illustrated with expe…
Selective adsorption of oppositely charged PNIPAAM on halloysite surfaces: a route to thermo-responsive nanocarriers.
2018
Halloysite nanotubes were functionalized with stimuli-responsive macromolecules to generate smart nanohybrids. Poly(N-isopropylacrylamide)-co-methacrylic acid (PNIPAAM-co-MA) was selectively adsorbed into halloysite lumen by exploiting electrostatic interactions. Amine-terminated PNIPAAM polymer was also investigated that selectively interacts with the outer surface of the nanotubes. The adsorption site has a profound effect on the thermodynamic behavior and therefore temperature responsive features of the hybrid material. The drug release kinetics was investigated by using diclofenac as a non-steroidal anti-inflammatory drug model. The release kinetics depends on the nanoarchitecture of th…
Study on the sensitive and selective adsorption voltammetry of vanadium with antipyrylazo III (APA III)
1994
The sensitive and selective adsorption voltammetric determination of the vanadium(V)-antipyrylazoIII complex in HAc-NaAc solution is investigated. The V-complex is strongly adsorbed onto a stationary Hg-electrode and is reduced at a potential more negative than that corresponding to the reduction of its ligand. The conditions for determining vanadium are investigated and the mechanism of the reduction peak of the vanadium complex is discussed, as also the influence of foreign ions on the determination of vanadium. An at least 20-fold excess of foreign ions does not cause any interference. The detection limit is 4×10−10 mol/l V with 3 min enrichment time.
Selective adsorption of ethyl mercaptan on NaX zeolite.
2008
Adsorption on microporous solid is an alternative technique to remove mercaptans from natural gases. The present study gives equilibrium adsorption data on NaX faujasite for some pure gases representative of natural gas impurities (ethyl mercaptan, toluene and n-heptane) and their binary mixtures. The first part of the paper is devoted to the adsorption of pure gases. Experimental results show that the zeolite has a high adsorption affinity for ethyl mercaptan, toluene and n-heptane. In the second part, we examine adsorption isotherms for binary mixtures of ethyl mercaptan and toluene or n-heptane over a large domain of composition. Coadsorption enthalpies are also determined. These experim…
Adsorption of p-Xylene/m-Xylene Gas Mixtures on BaY and NaY Zeolites. Coadsorption Equilibria and Selectivities
1997
Coadsorption of the gases p-xylene and m-xylene on BaY and NaY was studied at 150 °C in the range of pressure 10-2-3 hPa. For BaY coadsorption isotherms and single-component adsorption isotherms are perfectly superimposed in the whole range of investigated pressure. The capacity of adsorption of BaY is 3 molecules α-1 for each single component as well as for each mixture under 3 hPa. For NaY coadsorption isotherms lie between those of single p-xylene and m-xylene. The capacity of adsorption of NaY for mixtures is in proportion to the composition of the initial adsorptive mixture and varies from the capacity of adsorption for single p-xylene (3.3 molecules α-1) to that for single m-xylene (3…
Selective adsorption of formaldehyde and water vapors in NaY and NaX zeolites
2019
International audience; Coadsorption of formaldehyde and water vapors on NaX and NaY zeolites is studied at 298 K in the pressure range 0-2 hPa by manometry coupled with gas phase chromatography and calorimetry. Coadsorption isotherms, adsorption selectivities and coadsorption heats are measured. Results show that the coadsorption process is selective for water at low filling and for formaldehyde at high filling. The adsorption selectivity for formaldehyde over water is however too low to consider the possibility of using such adsorbents for the development of air handling units. On the other hand, a preliminary study carried out on the adsorption of formaldehyde and water in pure gas phase…
Measurements of thickness dispersion in biolayers by scanning force microscopy and comparison with spectroscopic ellipsometry analysis.
2007
Measuring the thickness of biological films remains a difficult task when using differential measurements by atomic force microscopy (AFM). The use of microstructured substrates combined with a selective adsorption constitutes an alternative to tribological measurements. The statistical thickness analysis of biological layers, especially via the dispersion measurements, can provide a way to quantify the molecular orientation. AFM thicknesses were then compared with those obtained optically by spectroscopic ellipsometry (SE) and surface plasmon resonance enhanced ellipsometry (SPREE). The biolayers could then be modeled using a vertical gradient of optical index, which reflects height disper…
Surfactant-Assisted Synthesis of Mesoporous Alumina Showing Continuously Adjustable Pore Sizes
1999
Porous materials displaying tailor-made pore sizes and shapes are particularly interesting in a great variety of real and potential applications where molecular recognition is needed, such as shape-selective catalysis, molecular sieving, and selective adsorption. Classically, apart from silica, materials most commonly used for catalysis and catalyst supports have been those based on high surface aluminas, owing to their thermal, chemical, and mechanical stability and their low cost. Earlier aluminas with high surface areas (~500 m/g) had been prepared using structure-directing agents. However, they were X-ray amorphous materials and their porosity was purely textural, characterized by wide …
Exploiting the Colloidal Stability and Solubilization Ability of Clay Nanotubes/Ionic Surfactant Hybrid Nanomaterials
2012
Halloysite clay nanotubes are functionalized by exploiting the different charges between the inner positive and the outer negative surfaces; accordingly, a selective adsorption is pursued by employing anionic and cationic surfactants. The obtained hybrid materials dispersed in aqueous phase are studied from the physicochemical viewpoint to investigate the colloidal stability that is a crucial parameter for applications. It is demonstrated that the adsorption of anionic surfactant into the HNTs lumen increases the net negative charge of the nanotubes enhancing the electrostatic repulsions and consequently the dispersion stability. The solubilization capability of these functionalized nanotub…