Spartina alterniflora biochar coupled BiOBr with dominant exposed facet and oxygen vacancies for efficiently photocatalytic degradation of ciprofloxacin

Addressing water pollution caused from the misuse of ciprofloxacin (CIP) is an urgent issue. In this study, Spartina alterniflora biochar coupled BiOBr (BC@BiOBr) composites were hydrothermally synthesized to achieve a synergistic effect of adsorption-coupled photocatalytic oxidation. In the BC@BiOBr composites, BiOBr microspheres grew in-situ on the surface of Spartina alterniflora biochar, forming the layered structure assembled by many nanosheets. Among the obtained products, when the mass fraction of BC was 20%, BC@BiOBr-2 exhibited the best photocatalytic performance and superior stability towards the degradation of CIP, achieving a 100% degradation efficiency within 90 min. The introduction of BC not only elevated the adsorption ability and increased the active reaction sites, but also narrowed the band gap and enhanced the visible light response range of BiOBr, accompanied by the rich oxygen vacancies and dominant exposed (102) facet of BiOBr, synergistically improving the photocatalytic activity greatly. The photocatalytic mechanism was speculated according to the tests of electron paramagnetic resonance and radical quenching experiments, proving the predominant roles of ·O₂^- and ·OH during the photocatalytic process. Overall, this work provides a feasible strategy for enhancing the photocatalytic performance of BiOBr while promoting the high-value reuse of the invasive species Spartina alterniflora.