COLLOID AGGREGATION - NUMERICAL-SOLUTION AND MEASUREMENTS

Citation
Kh. Gardner et al., COLLOID AGGREGATION - NUMERICAL-SOLUTION AND MEASUREMENTS, Colloids and surfaces. A, Physicochemical and engineering aspects, 141(2), 1998, pp. 237-252
Citations number
38
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry Physical
ISSN journal
0927-7757
Volume
141
Issue
2
Year of publication
1998
Pages
237 - 252
Database
ISI
SICI code
0927-7757(1998)141:2<237:CA-NAM>2.0.ZU;2-K
Abstract
A model has been developed that describes the kinetics of particle agg regation by a numerical solution of the von Smoluchowski equation. Whi le the complete model incorporates surface chemical phenomena, this pa per discusses only the physical aggregation process, and focuses on lo ng-term aggregation where aggregates composed of many primary particle s (up to 2000) are formed. Model simulations were compared with labora tory experiments that were conducted with hematite spheres aggregating with no applied shear stress. Comparison was achieved by minimizing t he sum of squared differences between the model and experimental data using two fitting parameters: the collision efficiency and the fractal dimension of the aggregates. The model was sensitive to the two param eters, which had a small degree of dependence on one another as eviden ced by the orientation of the joint confidence regions. Estimates of t he fractal dimension varied inversely with collision efficiency and we re between 1.25 and 1.5; lower than many estimates by others for diffu sion-controlled processes but consistent with cluster-cluster aggregat ion of aggregates comprised of very dense particles. The collision eff iciency was estimated to be 1 x 10(-4) for slow aggregation conditions , and 2 x 10(-4) under rapid aggregation; these values reflect inclusi on of hydrodynamic interactions and their significance in a system dom inated by differential settling. (C) 1998 Elsevier Science B.V. All ri ghts reserved.