A novel visible light controllable adsorption-desorption system with a magnetic recyclable adsorbent

Convenient and energy-efficient desorption or regeneration processes are prerequisites for the development of an ideal adsorbent. For this work, a novel magnetic adsorbent (citric acid/Bi₂O₂CO₃/Fe₃O₄) was controllably synthesized via a facile hydrothermal method. The as-prepared materials demonstrated the excellent adsorption of methylene blue (MB), where ~70% of the MB was absorbed within 10 min. Interestingly, the desorption process could be triggered by visible light irradiation, and 99% of the absorbed MB was released into solution within 4 h. Further, the magnetic materials could be conveniently recovered using a magnet and regenerated via a model hydrothermal process. Even after two regeneration cycles, approximately 60% adsorption and 63% desorption abilities were retained, which suggested strong potential for the recyclability of these materials.