Bayreuth 1998 – wissenschaftliches Programm

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SYA: Symposium Kolloide Systeme und Polyelektrolyte

SYA 1: Kolloidale Systeme und Polyelektrolyte

SYA 1.1: Vortrag

Montag, 9. März 1998, 10:00–10:20, H18

Precipitation of CaCO₃: nanoparticles and the effect of additives — •Jens Rieger, Thomas Frechen, Dirk Franke, Erich Haedicke, and Iris Rau — Kunststofflaboratorium, BASF AG

CaCO₃-incrustation in washing processes is caused by precipitation and crystal growth. For the further improvement of polymeric incrustation inhibitors in detergents it is essential to understand these processes on a molecular level. In order to reach this aim, we have established several experimental techniques which allow for the investigation of the precipitation of CaCO₃ in the time range from 20 msec to hours and from a few nanometers to millimeters - with and without additives. Our experiments show, e.g., that additive molecules which are used to prevent CaCO₃-incrustation cover the surface of CaCO₃- nanoparticles at the very beginning of the precipitation, thus preventing further growth of compact CaCO₃. The interplay between aggregation, agglomeration, and crystal growth has been examined. In order to understand the interaction of the additive molecules with the CaCO₃-particles we investigated the conformation, the dynamics, and the adsorption energies of these molecules at selected surface planes of Calcite (i.e., the stable modification of CaCO₃) by means of molecular modeling and molecular dynamics calculations.