Synthesis and application of a biodegradable polysilicate iron zirconium-starch composite coagulant for efficient drinking water treatment

We report the synthesis and performance evaluation of a novel inorganic–organic composite coagulant, polysilicate iron zirconium chloride modified starch (PFZS-CS), prepared via an aqueous-phase synthesis method. PFZS-CS integrates natural, biodegradable starch with metal-based coagulants, offering enhanced charge neutralization and adsorption bridging effects. Under optimal synthesis conditions (45 °C, 5.2 g etherification agent, 0.2 g NaOH, starch/Si mass ratio 0.1) and usage parameters (pH 7, dosage 80 mg·L −1 , 30 min sedimentation), PFZS-CS achieved turbidity and UV₂₅₄ removal efficiencies of 99.5 % and 81.6 %, respectively, outperforming conventional PFS and PZr coagulants by 12–15 % in turbidity removal and reducing residual iron below WHO limits (0.3 mg·L −1 ). Mechanistic insights from zeta potential analysis confirmed its dual neutralization–bridging action. PFZS-CS's superior performance, low residual metal, and biodegradable nature highlight its potential for sustainable drinking water treatment. • A novel eco-friendly starch-based inorganic–organic coagulant was successfully developed. • Aqueous-phase synthesis method conditions were optimized for maximum water purification efficiency. • The composite coagulant achieved excellent turbidity and organic pollutant removal. • SEM, XRD, and FTIR analyses confirmed structure and effective functionalization. • Real water treatment validated high performance with minimal metal residue.