Experimental and Molecular Dynamics Study of Flocculation Mechanisms for Sustainable Phosphate Tailings Management

ABSTRACT Efficient flocculation of dolomite‐rich phosphate tailings is crucial for safe disposal and water recovery. In this study, four representative polymeric flocculants—non‐ionic polyacrylamide (PAM), anionic poly(acrylic acid) (PAA), cationic poly(2‐(methacryloyloxy)ethyl trimethylammonium chloride) (PDMC) and zwitterionic poly(acrylic acid‐ co ‐(3‐acrylamidopropyl)trimethylammonium chloride) (PAA–APTAC)—were systematically evaluated through sedimentation tests and molecular dynamics (MD) simulations. The sedimentation experiments showed distinct performance among the four flocculants. PAA exhibited the most efficient clarification through electrostatic neutralisation and bridging. PAM produced the densest flocs via hydrogen bonding. PDMC demonstrated rapid but less compact flocculation, whereas PAA–APTAC showed poor performance as intramolecular charge pairing limited surface anchoring. MD simulations further revealed distinct adsorption modes and chain conformations: PAA and PDMC formed extended conformations mediated by counter‐ions. PAM exhibited a single‐layer hydrogen‐bonded adsorption, while PAA–APTAC maintained a stretched conformation without effective surface binding. These results highlight that effective flocculation depends on balancing polymer chain extension for bridging with strong surface affinity, and they provide a mechanistic framework for selecting flocculants tailored to carbonate‐dominated tailings.