Flocculation behavior and kinetics of hematite regulated by corn starch with different molecular structures

Fine iron mineral recovery through flotation and magnetic separation increasingly relies on starch-based flocculation technologies; however, the relationship between starch molecular structure and flocculation dynamics remains insufficiently understood. Herein, the effects of corn starches with distinct molecular structures on hematite flocculation were systematically investigated through static characterization and dynamic in situ analysis of bridging aggregation behavior. The results demonstrated that branched and cross-linked starches generated larger, denser, and more shear-resistant hematite aggregates than amylose starch, exhibiting higher aggregation efficiency and superior re-flocculation performance under hydrodynamic conditions. These enhanced flocculation behaviors were primarily attributed to their larger molecular weight, larger hydrodynamic size, and stronger intermolecular association capability, which promoted polymer chain extension and interparticle bridging. Adsorption and electrokinetic analyses revealed that branched and cross-linked starches formed denser adsorption layers on hematite surfaces and induced greater negative shifts in zeta potential than amylose starch. FTIR results further confirmed that starch adsorption onto hematite was predominantly governed by hydrogen bonding and specific interfacial interactions. Importantly, starch molecular structure was found to regulate not only aggregate formation, but also the dynamic evolution, compactness, and shear stability of flocs. These findings provide mechanistic insights into starch-mediated mineral aggregation and offer guidance for the rational design of starch-based flocculants in fine mineral processing.