Hydrophilic, hollow Fe3O4@PDA spheres with a storage cavity for efficient removal of polycyclic structured tetracycline

Antibiotics are emerging pollutants in aquatic ecosystems and there is much recent interest in their removal from water systems. However, the development of efficient sorbents for handling this problem remains a challenge. Herein, we report biomimetic hydrophilic, hollow polydopamine (PDA)-based composites of Fe3O4@PDA that were synthesized by a facile oxidation polymerization route. In order to assess the feasibility of Fe3O4@PDA hollow spheres as a potential sorbent for antibiotic removal, a series of adsorption experiments were conducted using tetracycline (TC) as the model antibiotic molecule. In contrast to the non-hollow counterpart of PS@Fe3O4@PDA, the designed Fe3O4@PDA hollow spheres exhibited much enhanced adsorption in removing TC at pH values from 2 to 10. The adsorption of TC onto Fe3O4@PDA hollow spheres fit a pseudo-second-order kinetics model, and the maximum adsorption capacity was 151.7 mg g(-1) calculated from a Langmuir isotherm model at pH = 8. After adsorption, the Fe3O4@PDA hollow spheres could be quickly recovered from the TC solution due to the room-temperature paramagnetic property of Fe3O4 nanoparticles that were pre-loaded into the interior surface of hollow PDA shells. The combination of excellent adsorption capacity, good reusability and high stability, together with a mild preparation procedure enables these types of hollow composites to have potential applications in specific fields.