Regenerable urchin-like Fe3O4@PDA-Ag hollow microspheres as catalyst and adsorbent for enhanced removal of organic dyes

[Display omitted] •Urchin-like Fe3O4@PDA-Ag hollow microspheres have been successfully synthesized.•Organic dyes could be catalytically reduced by the urchin-like hollow microspheres.•Urchin-like hollow structure greatly enhances adsorption and catalytic performance.•Fe3O4@PDA-Ag show high reusability, easy separability, and fast regeneration ability. In this work, novel urchin-like Fe3O4@polydopamine (PDA)-Ag hollow microspheres have been prepared via a facile synthesis method by in situ reduction and growth of Ag nanoparticles on mussel-inspired PDA layers coated on Fe3O4 hollow cores. The catalytic reduction efficiency and adsorption performance of the as-prepared urchin-like Fe3O4@polydopamine (PDA)-Ag hollow microspheres for model organic dyes (i.e., methylene blue and rhodamine B) under varying pH condition have been systematically investigated, which are demonstrated to be significantly enhanced as compared to that of spherical (relatively smooth) solid Fe3O4@PDA-Ag microspheres. The as-prepared urchin-like Fe3O4@PDA-Ag hollow microspheres show high reusability, easy separability, and fast regeneration ability, with no obvious drop in the catalytic and adsorption efficiency after cyclic reuse. The versatile PDA coatings on the urchin-like microspheres allow further surface functionalization for development of multifunctional catalyst and adsorbent materials. This work provides a very useful and facile methodology for synthesizing and tuning the urchin-like morphology of Fe3O4@PDA-Ag microspheres, with great potential applications in catalysis and wastewater treatment.