Measurement of Absolute Coagulation Rate Constants for Colloidal Particles: Comparison of Single and Multiparticle Light Scattering Techniques
✍ Scribed by Helmut Holthoff; Artur Schmitt; Antonio Fernández-Barbero; Michal Borkovec; Miguel ángel Cabrerı́zo-Vı́lchez; Peter Schurtenberger; Roque Hidalgo-álvarez
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 169 KB
- Volume
- 192
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
the measurement of colloidal stability have been per-The absolute coagulation rate constants of monodisperse spherical formed almost since colloidal science exists ( 1 -4 ) . In colloids in aqueous suspension were measured at the early stage of spite of the existence of various experimental methods for the coagulation processes by using two different techniques: single the measurement of absolute aggregation rate constants, particle light scattering (SPLS) and simultaneous static and dycommonly accepted, reliable methods for routine meanamic light scattering (SLS / DLS). Single particle light scattering surements of this kind are lacking. determines the cluster-size distribution directly by counting the num-Not only is the availability of such methods of central ber of different clusters during the coagulation process and therefore importance for the various applications mentioned above, but can be used to test the kinetic growth model used for obtaining the coagulation rate constants. The simultaneous static and dynamic accurate measurements of absolute rate constants on welllight-scattering method is an in-situ experiment, where the average characterized systems are of much interest from the theoreticluster size is estimated by simultaneous static and dynamic lightcal point of view as well. At present, no satisfactory quantitascattering measurements at different angles on a multiangle fibertive theory of the currently existing data on aggregation optics-based setup. A combined evaluation of the static and dynamic rate constants is available. The widely accepted theory of light-scattering data permits the determination of the absolute rate Derjaguin, Landau, Verwey, and Overbeek (DLVO) is able constants without the explicit use of light scattering form factors to explain the qualitative features of the coagulation proand hydrodynamic properties for dimers. In this paper, we compare cesses, but it fails in predicting the coagulation rate constants results obtained with both techniques. Good agreement was found quantitatively. In the regime of fast coagulation, which was for the absolute coagulation rate constants of two different latex thought to be an entirely diffusion-controlled process, the particle suspensions. Furthermore, we show that the two techniques complement one another and the limitations of the first are overcome discrepancy in the rate constants could be reduced by introby the second and vice versa. ᭧ 1997 Academic Press ducing a hydrodynamic correction accounting for the en-Key Words: aggregation rate constant; colloid stability; simultahanced friction coefficient of two approaching particles (5, neous static and dynamic light scattering; single particle light scat-6). In the regime of slow coagulation, the DLVO-theory tering.
underestimates the rate constants dramatically and surface heterogeneities have been suggested to represent the origin of these discrepancies (7). Therefore, accurate measurecle counting technique with simultaneous static and dynamic 463