Flocculation of sulfamerazine suspensions by a cationic polymer.

Flocculation by a cationic polymer of sulfamerazine suspensions containing a wetting agent was evaluated. Suspensions with sufficient surfactant concentrations to ensure complete wetting were deflocculated. When the anionic surfactant, dioctyl sodium sulfosuccinate, was used as a wetting agent, the suspensions were flocculated over a limited polymer concentration range. Flocculation was attributed to simultaneous interaction of a polymer molecule with more than one particle. At higher polymer concentrations, the particles were covered completely with polymer, leading to repulsion between the particles and deflocculation of the suspensions. The polymer concentration required for flocculation provided evidence for interaction between the anionic surfactant and the cationic polymer. Suspensions containing a nonionic surfactant also were flocculated using various polymer concentrations. When a surfactant mixture was employed in the suspensions, the peak sedimentation volume of flocculated systems and the concentration of polymer at the peak depended on the surfactant mixture composition.