Microplastics (MP) that are widespread in aquatic environments around the world is one of the biggest environmental problems and poses a major threat not only to the aquatic ecosystem but also to humans [1]. Flocculation is one of the ways of removing microplastics from water. The flocculants currently used are synthetic and therefore not only contribute to environmental pollution but also can be toxic [2]. Therefore, the main objective of this work was to synthesize cationic starches and to explores them use as flocculants for the removal of microplastics from water.
Sixteen cationic starch derivatives were synthesized by the etherification reaction of potato starch and various amounts of (3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHTAC) as a cationization agent (CA) in aqueous medium with or without CaO and CaCl\(_{2}\) additives. The cationic starch selected for the flocculation study was obtained at the molar ratio of starch : CHTAC : CaO/CaCl\(_{2}\) : NaOH : H\(_{2}\)O of 1 : 0.21 : 0.04/0.1 : 0.31 : 3.1, at a temperature of 45 °C, and the reaction duration of 16 hours.
The flocculation properties of synthesized cationic starch were tested using two aqueous model systems, namely, those of kaolin and industrially produced polyethylene (PE) microparticles as well as an aqueous microdispersions of artificially obtained polystyrene (PS) and polypropylene (PP) particles. The amount of microplastic particles in water ranged from 500 to 1500 mg/l and the optimum amounts of cationic starch required to destabilize the tested suspensions were established. In was determined that cationic starch concentration of 0.6, 1, 1, and 7.5 mg/l was required to destabilize the aqueous suspensions of PE, PP, PS and kaolin, respectively. The performed studies have shown that cationic starches have suitable properties to be applied as biopolymer-based flocculants for removing microplastics from water.