Flocculation by cationic amphiphilic polyelectrolyte: Relating efficiency with the association of polyelectrolyte in the initial solution

Flocculation ability of an amphiphilic cationic polysaccharide with N-octyl-N,N-dimethyl-N-(2-hydroxypropyl)ammonium chloride groups attached to a dextran backbone, was evaluated in clay dispersions with respect to polycation dose and initial solution concentration and, consequently, its association state. According to turbidimetric results, the concentration of initial solution of polymer influenced, mainly, the width of the flocculation window (the polycation dose range where the minimum of the residual turbidity was obtained) since this flocculation characteristic increased with increasing this parameter. A significant change in flocculation performances was noticed when polymer concentration was above its critical aggregation concentration. Possible reasons for this dependence are discussed. The negative value of the zeta potential in the whole flocculation window and the floc size distribution point to contributions from both patch/charge neutralization and bridging mechanisms for the flocculation process.