A novel way to obtain effective cationic starch flocculants

Abstract

A novel way to obtain an effective flocculant based on biodegradable starch was found. The medium-substituted (DS from 0.10 to 0.54) cationic starches (CS) with preserved microgranular form was synthesised by the reaction of potato starch with 2,3-epoxypropyltrimethylammonium chloride using the semi-dry process. The cationic starch derivatives were characterised by Fourier Transform infrared spectroscopy, X-ray diffraction and 1H-NMR, and their pasting and swelling properties were investigated. High-performance flocculant was obtained using intense mechanical shearing of aqueous cationic starch slurry. Swollen CS microgranules were crushed by the applied mechanical shearing and low-viscosity, stable CS aqueous dispersions were prepared. Sheared CS have a higher accessibility to polyanions, a lower molecular weight and a markedly higher flocculation efficiency—a lower minimum dose, while maintaining wide flocculation window. The flocculation mechanism of the kaolin suspension by sheared CS was proposed.