Simultaneous static and dynamic light scattering is proposed to measure heteroaggregation rate constants in binary colloidal mixtures. The experimental study will be performed on carboxyl (A) and zwitterionic (B) latex particles. Absolute formation rate constants for all dimers (AA, AB and BB) will be measured as a function of solution pH and ionic strength. The experimental data will be compared to the theory of Derjagurin, Landau, Vervey and Overbeek (DLVO). The authors will investigate the limits of validity of DLVO-theory for small separation distances (< 1 nm) of the barrier in the particle-particle interaction potential, where the theory apparently fails. The proposed work has relevance to stabilization, coagulation and deposition of colloidal particles in various natural and industrial processes such as water purification, mineral processing, filtration, transport of microorganisms in groundwater and medical applications.
