Structural characteristics and flocculation properties of amphoteric starch

Starch ampholytes (AmS) – cationic starch succinates – with the degree of substitution according to cationic groups of 0.29 or 0.36 and the degree of substitution according to anionic groups from 0.11 to 0.34 were prepared by succinylation of precationized starch. FT-IR spectra confirmed the incorporation of carboxylic groups into the backbone of cationic starch. Scanning electron microscopy was used for evaluation of the granular structure and surface morphology of modified polysaccharides. The decrease in accessibility of cationic quaternary ammonium groups in AmS was detected by means of polyelectrolyte titration. Colloidal dispersions of AmS were verified in the flocculation of kaolin suspensions and the sedimentation of wastewater sludge. Their flocculation performance was studied in connection with ξ-potential measurements and compared with that of cationic starch. The main advantage of AmS application is broadening of the flocculation window. The mechanism of flocculation by starch ampholytes has been proposed.