Interaction of cationic starch and dissolved colloidal substances from paper recycling, characterized by dynamic surface measurements

Modified starch with cationic as well as hydrophobic units can be used to remove negatively charged substances due to recycling processes of paper, so called stickies. teractions between different types of starch and a negatively charged model suspension, obtained by heating up common newspaper, have been studied using polyelectrolyte titration, nephelometric turbidity measurement, and determination of the carbon content. In addition, we were able to show that the dynamic interface tension is a very suitable property to characterize the surface active compounds in the model suspension which allows receiving additional information about the sticky content of the waste water. ectrolyte complexes were formed by adding cationic starch to the anionically charged model suspension. At a certain mixing ratio their precipitation leads to a significant reduction of the turbidity and the carbon content, whereas the surface tension increases due to sticky removal. Among starches with the same degree of cationic charge, those with the highest hydrophobicity were the most effective.