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  • 1975-1979  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 255 (1977), S. 140-152 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary The interaction between three solids (hematite, silica and graphitized carbon) with some polyanions (sodiumtripolyphosphate, ethane-I,I-diphosphonate, phosphonoacetate, α-phosphonopropionate and mellitic acid) in aqueous solution was studied by measuring adsorption, electrokinetic potential and heat of immersion. It was observed that there are great differences in the interaction of the three solids investigated. Polyanions adsorb strongly at the hematite solution interface over a very wide range of pH, whereby a significant increase of pH is observed. In addition, since the particles are already negatively charged at pH 〉 4 it is concluded that chemisorption is involved. With increasing pH adsorption decreases. In the case of hydroxyethane-1,1-diphosphonate adsorption passes a minimum at pH ≈9. ζ-potential is significantly less dependent on pH and passes a broad maximum at pH≈8. In case of hydroxyethane-1,1-diphosphonate ζ-potential increases with pH monotonously. It follows from measurement of heats of immersion that the enthalpy of interaction is approximately zero. Consequently, the process is mainly governed by entropy change. Adsorption of polyanions on silica is very small and occurs at pH 〈 IEP (= pH 1,3) only, as could be shown by measuring adsorption and ζ-potential. At pH 〉 2 the presence of polyanions does not affect the ζ-potential of the quartz particles. Quite different is the interaction between graphitized carbon particles and various polyanions. No adsorption has been observed of phosphorous containing polyanions even on positively charged particles. Mellitic acid adsorbs strongly under these conditions whereby IEP is shifted from pH 6,3 to 5,3, approximately. If the methyl group of hydroxyethane-1,1-diphosphonate is substituted by a phenyl this compound adsorbs at the carbon interface. It is likely to assume that the π-electrons of the ring systems of adsorbent and adsorbate are involved in the adsorption of aromatic compounds.
    Notes: Zusammenfassung Durch Messungen der Adsorption, des elektrokine-tischen Potentials ζ und der Immersionswärmen wurde die Wechselwirkung zwischen drei Pigmenten (Hä-matit, Quarz, graphitierter Ruß) und einige Poly-anionen (Natriumtriphosphat, 1-Hydroxyäthan-1,1-diphosphonat, Phosphonoacetat, α-Phosphonopropio-nat und Mellitsäure) untersucht. Dabei zeigte sich, daß die Pigmentoberflächen mit den Anionen sehr unterschiedlich reagieren. An Hämatit werden die Polyanionen über einen sehr weiten pH-Bereich stark adsorbiert, wobei eine deutliche Zunahme des pH-Wertes beobachtet wird. Da gleichzeitig die (bei pH 〉 4) bereits negative Partikelladung stark erhöht wird, beruht die Wechselwirkung sehr wahrscheinlich auf einer Chemisorption der Polyanionen an der Hämatitoberfläche. Mit steigenden pH-Werten nimmt die Adsorptionsdichte stark ab, bei Hydroxyäthandiphosphonat durchläuft sie ein Minimum bei etwa pH 9. Das ζ-Potential ist deutlich geringer pH-abhängig als die Adsorption. Es durchläuft ein breites Maximum (ca. pH 8), bei Hydroxyäthandiphosphonat nimmt es jedoch mit steigendem pH zu. Aus der Messung der Immersionswärmen folgt, daß die Wechselwirkung zwischen Hämatit und den Polyanionen annähernd ohne Enthalpieänderung verläuft und folglich wesentlich durch die Entropie kontrolliert werden muß. Die Adsorption der Polyanionen an Quarz ist sehr gering und erfolgt nur unterhalb des IEP (pH 1,3). Das zeigen sowohl direkte Adsorptionsbestimmungen als auch die Messungen des ζ-Potentials, denenzufolge die Gegenwart der Polyanionen bei pH 〉 2 keinen Einfluß auf die Höhe des ζ-Potentials der Quarzteilchen hat. Davon verschieden sind die Verhältnisse der Wechselwirkung bei graphitiertem Ruß. Hier erfolgt auch bei positiver Partikelladung keine Adsorption der untersuchten phosphorhaltigen Polyanionen. Dagegen wird Mellitsäure unter diesen Bedingungen stark adsorbiert und verschiebt den IEP von etwa pH 6,3 auf pH 5,3. Substituiert man in Hydroxyäthandiphosphonsäure die Methyl- durch eine Phenylgruppe, so wird auch diese Verbindung an graphitiertem Ruß adsorbiert. Bei der Adsorption von aromatischen Verbindungen an graphitiertem Ruß ist daher eine Wechselwirkung zwischen den π-Elek-ktronensystemen von Adsorbens und Adsorbat anzunehmen.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 257 (1979), S. 292-301 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary The interaction ofγ-Al2O3 with three homologous n-alkyl-benzene sulfonates and different polyanions as well as with mixtures of surfactants and polyanions has been investigated by measurements of adsorption and electrokinetic potentials at 70 °C. The adsorption isotherms of the anionic surfactants at pH 7 follow the Langmuir adsorption equation. The interaction with the alumina surface consists in a hydroxyl ion exchange as is indicated by the observed liberation of hydroxyl ions during the adsorption. At higher surfactant concentrations hydrophobic bonding of the surfactant ions in the adsorption layer contributes to the interaction. This is shown by the fact that even above the isoelectric point (IEP) a significant adsorption occurs, and that even far below the IEP the negative electrokinetic potential is approximately constant. The adsorption isotherms of Na5P3O10, HEDP and citrate at pH 7 follow the high affinity type indicating that these polyanions exert a stronger interaction with the alumina surface than the surfactants. The adsorption is specific and very strong even at pH 10. The adsorption of the surfactants is highly inhibited at pH 7 and 9 by STP, HEDP or citrate, sometimes even at very small concentrations of the polyanions. The polyanions themselves are strongly adsorbed at the same time. At lower pH values, on the other hand, the adsorption of the surfactants is only little influenced by the polyanions although the latter are strongly adsorbed.
    Notes: Zusammenfassung Durch Messung der Adsorption und des elektrokinetischen Potentials wurde die Wechselwirkung vonγ-Al2O3 mit 3 homologen n-Alkylbenzolsulfonaten, mit verschiedenen Buildern (Na5P3O10, HEDP, Citronensäure, NTA und Na2SO4) sowie Aniontensid-Builder-Gemischen bei 70°C untersucht. Die Adsorptionsisothermen der Aniontenside bei pH 7 folgen der Langmuirschen Adsorptionsgleichung. Die Wechselwirkung mit der Al2O3-Oberfläche erfolgt unter Hydroxylionenaustausch, wie durch die beobachtete Freisetzung von Hydroxylionen bei der Adsorption nachgewiesen wurde. Bei höheren Tensidkonzentrationen kommt noch die hydrophobe Wechselwirkung der Tensidionen untereinander in der Adsorptionsschicht hinzu. Sie äußert sich darin, daß auch oberhalb des isoelektrischen Punktes (IEP) noch eine deutliche Adsorption stattfindet und daß auch weit unterhalb des IEP noch ein praktisch konstantes negatives ζ-Potential aufrechterhalten wird. Die Adsorptionsisothermen von Na5P3O10, 1-Hydroxyäthan-1,1-diphosphonsäure (HEDP) und Citronensäure bei pH 7 folgen dem High-Affinity-Typ und deuten eine stärkere Wechselwirkung mit der Al2O3-Oberfläche an, als sie bei den Aniontensiden gegeben ist. Die Adsorption erfolgt spezifisch und ist selbst bei pH-Werten 〉 10 noch sehr stark. Die Adsorption der Aniontenside in Gegenwart der Polyanionen verläuft sehr unterschiedlich. Während Na2SO4 die Adsorption der Tenside geringfügig verstärkt, werden diese in Gegenwart typischer Builder (Na5P3O10, HEDP und Citronensäure) bei pH 7 und 9, teilweise bereits bei sehr geringen Builderkonzentrationen, überwiegend von der Festkörperoberfläche verdrängt. Gleichzeitig werden die Builderionen selbst stark adsorbiert. Völlig verschieden ist der Verlauf der Konkurrenzadsorption Builder/Tensid im sauren pH-Bereich. Hier beeinflu\t die Gegenwart der Builder die Tens idadsorption nur geringfügig, obwohl die Builder selbst stark adsorbiert werden.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 253 (1975), S. 643-657 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The interaction ofγ-Al2O3 and polyanions of different classes of substances was investigated by means of adsorption and measurements of the electrokinetic potential. Whereas the isotherm (pH 7, 25 °C) of sodium sulfate is of theLangmuir type those of sodiumtripolyphosphate, mellitic acid, ethanehydroxy-1. 1-dip hosphonic acid, phosphonoacetic acid, α-phosphonopropionic acid, and nitrilotriacetic acid are of the high affinity type. Some polyanions attack the alumina surface strongly through the formation of soluble Al-complexes. Because of this effect the scale of equilibrium concentration is shifted towards the origin, and consequently the slope of the isotherm is affected in a complicated fashion. Therefore, it is impossible to calculate the affinity between anions and solid surface from the rise of the isotherms. On the other hand a ratio of surface coverage and molecular cross section derived from the values of saturation enables to establish a sequence of affinities. Adsorption is strongly pH-dependent. A significant decrease is observed with increasing pH. Adsorption is increased with increasing temperature. Since adsorption enthalpies of alumina in the solutions of the polyanions are about those in pure water, entropy should control the adsorption process. The IEP of the solid is about 9. A very small shift of IEP is observed in the presence of sodium sulfate whereas those of the polyanions cause a strong one in the direction towards lower pH (pH 〈 2). In addition a significant increase of pH is observed when the solid is dispersed in the solutions of polyanions. All data indicate that chemisorption of the investigated polyanions at the alumina surface occurs whereas for sulfate physisorption probably takes place.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 1979-02-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 5
    Publication Date: 1979-12-01
    Print ISSN: 0029-554X
    Electronic ISSN: 1878-3759
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Published by Elsevier
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  • 6
    Publication Date: 1977-02-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 7
    Publication Date: 1975-08-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 8
    Publication Date: 1979-03-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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