Simultaneous Enhancement of Mechanical Properties, Crystallization, and Oil–Water Separation of Polylactic Acid via Morphology‐Controlled Hydroxyapatite and Tannic Acid Modification

ABSTRACT Hydroxyapatite (HA) with particulate and whisker morphologies was synthesized via chemical co‐precipitation, followed by surface modification with tannic acid (TA). The TA‐modified HA was then incorporated into polylactic acid (PLA) as a nanofiller. The morphology of HA was found to significantly influence the crystallization behavior, mechanical properties, and thermal stability of PLA. The whisker‐shaped HA improved both the tensile strength and elongation at break of PLA, reaching 32.6 ± 1.3 MPa and 153.5 ± 13.4%, respectively. The HA acted as a heterogeneous nucleating agent, inducing PLA crystallization and notably enhancing its thermal stability. Furthermore, when porous PLA membranes were immersed in HA suspensions, HA adsorbed onto the membrane surface via hydrogen bonding, significantly increasing hydrophilicity. The rejection rate of oil‐in‐water emulsions exceeds 99%, with a flux recovery rate exceeding 90% after 10 separation cycles. This study provides a new strategy to simultaneously address the “strengthening and toughening” and “long‐term durability” challenges in bio‐based membranes, advancing the development of sustainable water treatment technologies.