Sorptionsverhalten von Polyvinylpyrrolidon an Tonmineralen: Struktur und Eigenschaften des Adsorbats
Sorptionsverhalten von Polyvinylpyrrolidon an Tonmineralen: Struktur und Eigenschaften des Adsorbats
The Thesis contains principal and environmentally oriented studies regarding the behaviour of the polymer Poiy(vinyl pyrollidone) (PVP) while adsorbing on mineral clays. The thesis' target was to characterize the adsorbed structure respectively the minerals tactoidal structure in the presence o...
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Personal Name(s): | Hild, A. (Corresponding author) |
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Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich, Zentralbibliothek, Verlag
1999
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Physical Description: |
IV, 192 p. |
Document Type: |
Report Book |
Research Program: |
Addenda |
Series Title: |
Berichte des Forschungszentrums Jülich
3623 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
The Thesis contains principal and environmentally oriented studies regarding the behaviour of the polymer Poiy(vinyl pyrollidone) (PVP) while adsorbing on mineral clays. The thesis' target was to characterize the adsorbed structure respectively the minerals tactoidal structure in the presence of PVP. Investigations in the ternary system mineral - PVP - anionic tensid were done to clear up the influence of PVP on the absorption of amphophilic substances on mineral clays. Further on quantitative investigations were done to determine the adsorbed amount on Na-kaolinite, Ca-bentonite and Na-montmorillonite. These investigations were done by registrating adsorption isotherms, and by using electrokinetical, calorimetric, UV-vis, X-ray diffractive, fluorescence spectroscopic,turbidimetric and viscosimetric methods and by investigating the sedimentation of the systems. Negative charged layer silicates show a great adsorption capacity for PVP. In this case so-called highaffinity isotherms are found. Calorimetric measurements show the strength of binding of each single adsoption site being low in the order of physical interactions. The increase of entropy due to replacement of bound water is another reason for polymer adsorption. It was shown that there are built up flat structures by the adsorbed matter at low adsorption amounts not depending on the molecular mass of the polymer due to expansion processes at the surface. At higher amounts of adsorption the thickness of the adsorped layer increases quickly with increasing molecular mass of the polymer. A similar course the radii of gyration of the free PVP-molecule solution show. So no significant differences in conformations exist between PVP in the solubilized and adsorbed state. Within the bounds of these investigations a six-layer-structure can be derived for coated Ca-bentonite. This result is In agreement with other Investigations concerning the tactoidal structure. A model was developed to describe the interactions of PVP with Na-montmorillonite in dispersion while adsorption. At lower degrees of surface loading there is built up a compact polymer-structure between the surfaces of the alumino-silicates. At increasing coating of the silicate with PVP a more voluminous structure of the adsorbat at the outer surfaces of a double-tactoid Is built up together with the compact structure between the layers mentioned above. During the investigations concerning the adsorption taking place in the ternary system Na-montmorillonite - Na-dodecylsulfate (SDS) - PVP synergistic as well as antagonistic effects are observedfor the adsorption of PVP and SDS. In this way at Na-montmorillonite there are adsorbed lower amounts of PVP-SDS-aggregates compared to free PVP. In contrast PVP-Ioaded Na-montmorillonite shows higher amounts of adsorbed SDS. he adsorption behaviour of the modified surfaces concerning SDS depends strongly on the present structure of the adsorbed polymer. There are two different kinds of adsorption sites observed for the adsorption of SDS at montmorillonite particles modified with PVP. At lower amounts of coating for all different loaded minerals SDS is adsorbed specific at the positive edges of the montmorillonite. Further at higher loaded PVP-montmorillonites an interaction of SDS with the more voluminous structures of the adsorbate is observed. Therefor it is possible to overcome the anion exclusion volume existing at the negative charged montmorillonite surfaces and to build PVP-SDS-aggregates at the mineral surface. By modifing the surfaces of montmorillonite with the neutral polymer PVP the adsorption of arganic anions like SDS can be strengthened significantly. For example the amount of adsorbed SDS at Namontmorillonite is about 50 times higher after surface-saturation with PVP. This yields to a surface of the adsorbing species containing amphiphilic polymer-tenside-aggregates being able to solubilize low soluble components like pyrene or chlorphenoles. By the described PVP-SDS-coated layer silicates the group of "organo clays" containing non-ionic and cationic tensides is enlarged with the anionic tensides.Using this results it can be explained why layer silicates rnodifled with macromolecules and biomolecules (e.g. humic acids) In soli display a store for harmful organic substances. |