Hydrochar-mediated photocatalyst Fe3O4/BiOBr@HC for highly efficient carbamazepine degradation under visible LED light irradiation

Construction of composite photocatalysts with high charge transfer efficiency and fast surface catalytic reaction has recently gained huge interest. In this work, a hydrochar microsphere-mediated photocatalyst Fe3O4/BiO-Br@HC with rapid surface catalytic reaction and electron transfer was fabricated. Under visible-LED-light irradiation, removal of refractory analgesic carbamazepine (CBZ) and total organic carbon (TOC) reached 100% and 67.41%, respectively, by Fe3O4/BiOBr@HC20% within 40 min, demonstrating the excellent photocatalytic activity compared to other photocatalysts. The narrower band gap (2.02 eV) of Fe3O4/BiOBr@HC obviously improved the visible light absorption. The hydrochar with abundant surface oxygen functional groups provided more active oxygen species .O-2(-) (4.05 mu M) and .OH (107.8 nM), and acted as an electron bridge to promote the electron transfer of BiOBr and Fe3O4. Eleven main CBZ intermediates were identified and three degradation pathways were proposed to illustrate the contribution of superoxide radicals, hydroxyl radicals, and photo generated holes to the photodegradation of CBZ. Furthermore, five-cycle reusing experiments revealed that Fe3O4/BiOBr@HC composite catalysts have excellent reusability and stability, indicating that they have a promising application future.