Cluster discrimination in electrostatic heteroaggregation processes

Abstract

Electrostatic heteroaggregation processes arising in 1:1 mixtures of oppositely charged microspheres at low and very low electrolyte concentrations were investigated by means of single-cluster light scattering. Cluster discrimination, i.e., the fact that clusters differing by only one constituent particle behave quite differently, was found for monomers and dimers. This effect was recently predicted by Brownian dynamic simulations but, to the best of our knowledge, not yet confirmed by experiments. The experimental data were confronted with the simulations and a good qualitative and quantitative agreement was obtained. The origin of the cluster discrimination phenomenon could be related to the range of the attractive electrostatic interactions.

Electrostatic heteroaggregation regimes in colloidal suspensions

“…Hence, in addition to the monomer discrimination already found at intermediate electrolyte concentrations, also a "dimer discrimination" is now observed. Dimer discrimination increases when the electrolyte concentration decreases, and, hence, it is an effect related to the range of the particle interactions [2,27]. We want to point out that this feature is quite reproducible even when no electrolyte was added.…”

“…This means that clusters with an even number of particles disappear faster than those composed by an odd number of particles. The first experimental support for this hypothesis has been reported recently [27].…”

“…The average particle diameter of both systems was 2a = (525 ± 17) nm. In a previous work [27], we checked that both systems have similar absolute electrophoretic mobilities but of opposite signs at the working pH.…”

“…Nevertheless, experimental studies about the cluster-size distributions (CSD) are scarce in the literature [2,27]. The CSDs are discussed in Section 5.1.…”

Fractal Structures and Mechanisms in Coagulation/Flocculation Processes in Environmental Systems: Theoretical Aspects

“…Such systems are too complicated to allow for the development of exact analytical theories, but computer simulations based on the concepts presented in Sections 4.1-4.3 can help to understand their behaviour. For example, simulations of the coagulation of a system made up of dissimilar A and B particles have been reported [73][74][75][76] and compared with experiment. The structures and growth kinetics of clusters formed by both A and B particles having variable sticking probabilities, and the influence of their relative concentrations, have been investigated in order to determine the influence of the unsuccessful A-A and B-B collisions on the rate of A-B aggregation, and to determine optimal coagulation conditions.…”