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Removal of Microplastics from Water by Etherification-Modified Starch Composite with Titanium Polysilicate
Summary
Researchers developed a starch-based composite coagulant using etherified corn starch and titanium polysilicate that achieved 95.51% microplastic removal efficiency at 4 mg/L dosage through electrostatic interaction and mesh-trapping mechanisms. This bio-based coagulant is significant because it avoids residual aluminum or iron ions from conventional coagulants, offering a safer water treatment approach that reduces microplastic load in drinking water without introducing additional metal contaminants.
Traditional aluminum and iron salt coagulants are widely used, but the residual metal ions affect the safety of water quality. In this study, a new starch-based composite coagulant, etherified starch composite titanium polysilicate (PSFZ), was prepared by etherification and thermal polymerization reaction using natural corn starch as raw material. In the optimization of the preparation process, four parameters, namely, the synthesis pH of polysilicic acid, the ratio of starch to titanium polysilicate, the reaction temperature and time, were focused on, and after determining the optimal ranges of the factors through one-way experiments, the process was optimized by using orthogonal tests, and the microplastic removal rate was taken as the core evaluation index. Characterization results showed that PSFZ is a polycrystalline phase/amorphous composite polymer, and its three-dimensional mesh structure has a large specific surface area, which endows it with excellent sweeping net trapping and adsorption bridging performance. The experiments showed that the removal rate of humic acid (NaHA) reached 84.57% when the dosage of PSFZ was 3.5 mg/L, and the microplastic removal efficiency peaked at 4 mg/L (95.51%). The mechanism study showed that the hydrolysis of titanium polysilicate generated polynuclear hydroxyl complexes, while the quaternary ammonium group (N+) in starch neutralized the negative charge on the surface of microplastics through electrostatic interaction; in addition, the three-dimensional network of polysilicate and the long-chain of starch synergistically interacted with each other, and efficiently removed the pollutants through the adsorption and bridging and the net-trapping and sweeping mechanisms.