Flocculation efficiency of modified water soluble chitosan versus commonly used commercial polyelectrolytes

Aim of this work was to evaluate the flocculation efficiency of a modified, water soluble chitosan versus various commercial products such as: chitosan, PolyDADMAC and positively charged polyacrylamide. The flocculation properties were investigated in dispersions of the clay type Blauton by means of turbidity measurements, colloid titration and measurements of the floc size. It was found that flocculation occurs even before the Blauton surface charge neutralization is achieved. The modified chitosan was more effective than the commercial one in Blauton's settling. Modified chitosan in comparison to the commercial products demonstrated not only a wider flocculation window, but also a higher efficiency since lower amounts of polymer were required for the flocculation of Blauton. Finally, the use of modified chitosan resulted in an increase of the critical polymer concentration above which restabilization of Blauton occurs. (C) 2010 Elsevier Ltd. All rights reserved.