Flocculation of montmorillonite dispersions based on surfactant-polymer interactions

A two-step flocculation process is described in which a polycation (polydiallyldimethylammonium chloride) is adsorbed on to negatively charged montmorillonite particles, followed by the addition of an anionic surfactant [sodium dodecyl sulfate (SDS)]. At a 1:1 molar ratio, optimal flocculation is obtained owing to the formation of an insoluble surfactant-polymer complex in the presence of the particles. The precipitation of the insoluble complex is also dependent on the SDS and polymer concentrations, and occurs at a 1:1 SDS:monomer molar ratio. From adsorption isotherms of the polymer-particle and surfactant-polymer systems, the adsorption energy was calculated and subsequently a flocculation mechanism is suggested.