Abstract: Deacetylchitins of similar molar mass (6.1, 6.9, 7.2×10~5 g·mol~(-1)) but different aminecontent(93%, 78%, 62%) were tested as flocculants for bentonite suspensions. Flocculant performance was assessed by determining the turbidity change of the suspensions with time, the extent of the deacetylchitin adsorption and the electrokinetic potential of the treated particles. The suspension concentration was kept constant at 2 g (bentonite).dm~(-3) in 10~(-3) mol·dm~(-3) NaCl solution; pH was varied from 3 to 6. It was found that bridging was the predominant mechanism of the flocculation, but neutralization of the particle charge by the adsorption of macroelectrolytes did play a contributory role in the destabilization of the suspensions.
Similar experiments were carried out using a nonionic acrylamide of high molar mass (1～3×10~6 g·mol~(-1). The efficacy of flocculation by polymer bridging did not counteract the increasing self-repulsion of the bentonite particles with increasing pH which produced poor floc formation.

Key words: Deacetylchitin, Bentonite suspension, Floceulation, Bridging mechanism