Starch-based flocculants prepared by a reactive deep eutectic solvent based on solid-phase method

Flocculation is one of the most widely used and economical pretreatment methods in water treatment. In this study, we developed a reactive deep eutectic solvent (DES) formed by 2, 3-epoxypropyl trimethyl ammoniumchloride (GTA) and urea, which was used as a reaction reagent and diffusion agent. DES has a strong hydrogen bond breaking effect and can penetrate into the starch granules, while mechanical force was introduced to fragment and refine the starch granules, destroying their internal structure and further promoting the penetration of DES, which was realised under the dual action of DES and mechanical force to achieve the starch-based flocculant (St-GTA) preparation. Gel permeation chromatography, Fourier transform infrared spectroscopy (FTIR) and ¹H NMR nuclear magnetic resonance spectroscopy (NMR) were used to characterise the prepared St-GTA, and its flocculation performance and flocculation mechanism were investigated by zeta potential and UV-Vis absorption tests. The flocculation efficiency of St-GTA on the simulated kaolin wastewater was systematically investigated, and its flocculation effect on other colloidal contaminants and real wastewater was also studied. The results showed that the dosage of St-GTA only needed to be 0.4 mg/L to achieve a removal rate of 98.5 % for the simulated kaolin wastewater, and its removal rate for the rest of the colloidal pollutants and the real wastewater could all reach 98 %. Therefore, the starch-based flocculant can be used as a new type of flocculant for wastewater treatment and has shown excellent properties, demonstrating its potential as a sustainable alternative to traditional flocculants.