Effect of polyelectrolyte structural features on flocculation behavior: Cationic polysaccharides vs. synthetic polycations

Growing demand for environmentally friendly technologies promotes the interest in investigation of natural flocculants and development of new ways of their derivatization aimed to find a compromise between cost, efficiency, and safety in polyelectrolyte applications. Recent progress in cationization of natural starch [T. Heinze et al., Macromol. Mater. Eng. 2002,287,495] allowed obtaining cationic starch derivatives (2-hydroxy-3-trimethylammoniumpropyl starch chloride) with very high substitution degrees (up to 1.54) that made them together with aminopolysaccharide chitosan the most promising candidates to replace synthetic flocculants in various industrial sectors. In this paper the flocculation efficiency of chitosan, cationic polyacrylamide copolymers (Praestols), and two series of cationic starch derivatives varying in substitution degree and amylose/amylopectin ratio is investigated to answer the following questions: do cationic polysaccharides and synthetic polymers show comparable efficiency; does high degree of starch functionalization significantly improve its flocculation behavior in comparison with commercially available starch products; and whether the amylose/amylopectin ratio (i.e. ratio of linear/branched polymers) plays a role in flocculation behavior of highly substituted cationic starch derivatives.