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Temperature effects on the adsorption of polyvinyl alcohol on silica

100%
Wiśniewska M.
Open Chemistry
|
2012
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vol. 10
|
issue 4
1236-1244
EN
The influence of temperature on the adsorption of polyvinyl alcohol (PVA) on a silica surface was studied from 15–35°C. The structure of the polymer adsorption layer was determined from spectrophotometric, viscosity and thermogravimetric measurements. The amount of PVA adsorbed, macromolecules’ conformation in solution, thickness of the polymer adsorption layer, and changes in the heating curve of SiO2 with adsorbed polymer were determined. Temperature influences the PVA chain conformation in solution and the structure of the polymer adsorption layer. A temperature rise causes relaxation of polymer coils which results in an increase in the linear dimensions of PVA chains in the solution, the creation of a thicker adsorption layer, and an increase in polymer adsorbed. Polymer adsorption on the silica surface also causes changes in the heating curve of these systems. The mass losses due to heating are smallest for the systems obtained at 15°C because the least polymer is adsorbed at this temperature. [...]
2
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Influence of the Electrolyte Type on the Adsorption and Electrokinetic Properties of the Ionic Polyamino Acids – Cr2O3 system

63%
Ostolska I., Wiśniewska M.
Annales Universitatis Mariae Curie-Skłodowska, sectio AA – Chemia
|
2013
|
vol. 68
|
issue 1-2
EN
The influence of a kind of support electrolyte on the ionic polyamino acids adsorption at the chromium (III) oxide – polymer solution interface was investigated. The NaCl and CaCl2 were used as the background electrolytes. In order to determine the effect of the electrolyte, the same value of ionic strength of the test solutions were taken. It was proved that formation of intermolecular and intramolecular complexes in the presence of divalent calcium ions is responsible for essential changes in polymer adsorption. Related to the ionic character of polyamino acid two different adsorption behaviours can be observed. The increase of the ASP adsorption amount in the presence of calcium ions may be explained by formation of complexes between the dissociated carboxylic groups and Ca2+ ions. The opposite situation takes place in the case of polylysine – the application of CaCl2 results in the dramatic decrease in the polymer adsorption caused by blocking the active sites available for LYS macromolecules. In order to make a comprehensive analysis, the zeta potential and surface charge density measurements were performed taking into account the kind of the background electrolyte. The above-mentioned tests were carried out in the absence and presence of the polyamino acid at two different concentrations – 10 and 100 ppm respectively.
3
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Comparison of stability properties of poly(acrylic acid) adsorbed on the surface of silica, alumina and mixed silica-alumina nanoparticles - application of turbidimetry method

45%
Wiśniewska M., Urban T., Nosal-Wiercińska A., Zarko V., Gun’ko V.
Open Chemistry
|
2014
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vol. 12
|
issue 4
476-479
EN
The influence of anionic poly(acrylic acid) - PAA addition on the stability of synthesized silica, alumina and mixed silica-alumina suspensions as a function of solution pH was studied. The turbidimetry method was used to monitor the changes of the examined systems stability over time. The calculated stability coefficients enabled estimation of polymer adsorption influence on stability of metal oxide suspension. It was shown that the alumina suspension without the polymer is the most unstable at the pH values 6 and 9, whereas the silica polymer was most unstable at pH 3. PAA with higher molecular weight (240 000) is a relatively effective stabilizer of all investigated adsorbents (except silica at pH 3). These properties of poly(acrylic acid) are highly desirable in many branches of industry (e.g. production of cosmetics, pharmaceuticals, paints) where polymers are widely used as effective stabilizers of colloidal suspensions.
4
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Effect of solution pH on the stability of mixed silica -alumina suspension in the presence of polyacrylic acid (PAA) with different molecular weights

39%
Wiśniewska M., Terpiłowski K., Chibowski S., Urban T., Zarko V., Gun’ko V.
Open Chemistry
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2013
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vol. 11
|
issue 1
101-110
EN
The influence of solution pH (in the range 3–9) on mixed silica-alumina suspension in the absence and presence of polyacrylic acid (PAA) was studied. The composition of the adsorbent was SiO2 (97%) and Al2O3 (3%). The turbidimetry method was applied to record changes in the stability of the investigated systems as a function of time. It was shown that the suspension without the polymer is less stable at pH 3, whereas at pH 6 and 9, the systems were stable. PAA with molecular weights 100 000 and 240 000 at pH 3 (improvement of system stability conditions) and PAA 2 000 at pH 6 (deterioration of suspension stability) have a great effect on the silica-alumina suspension stability. The stabilization-flocculation properties of polyacrylic acid are a result of a specific conformation of its chains on the solid surface where it depends on the solution pH and the polymer molecular weight.
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