Integrating magnetized bentonite and pinecone-like BiOBr/BiOI Step-scheme heterojunctions as novel recyclable photocatalyst for efficient antibiotic degradation

Abstract

Utilizing the cost-effective natural clay and surface heterojunction engineering to synergistically construct an efficient heterojunction system and promote the separation of photogenerated charges is an appealing strategy for achieving superior photocatalytic activity. In this study, BiOBr/BiOI step-scheme (S-scheme) heterojunction in-suit grown on magnetized bentonite (MBT) was first engineered via facile and mild coprecipitation coupling microwave solvothermal process. The optimized magnetic bentonite/BiOBr/BiOI (MBT25/BiOBr/BiOI, the mass ratio of MBT to BiOBr/BiOI was 25%) attained the largest reaction rate constant (k = 0.021 min−1) in tetracycline (TC) photocatalytic degradation within 80 min visible-light irradiation. In addition, the reaction rate constant k of MBT25/BiOBr/BiOI for TC degradation was 10.51 folds higher than that of pristine BiOI. Significantly, the characterization results demonstrated that MBT effectively assisted the pinecone-like morphology formation of BiOBr/BiOI and endowed the wonderful magnetic-separation ability for MBT25/BiOBr/BiOI. Additionally, MBT ingeniously introduced at the interface could couple with S-scheme heterojunction between BiOBr and BiOI to synergistically boost the separation and transfer of photogenerated charges. As expected, superior photochemical properties and efficient production of active species over MBT25/BiOBr/BiOI were confirmed. Notably, recycling experiments verified the wonderful photocatalytic stability and high recovery efficiency of MBT25/BiOBr/BiOI. Furthermore, the abundant O2− and OH active species led to hydroxylation, dealkylation, deamidation and ring opening of TC molecules. A synergistically enhanced mechanism over S-scheme MBT25/BiOBr/BiOI was clarified based on band structure calculations. This study offers an innovative perspective to design multifunctional photocatalysts with superior activity by integrating properties of magnetized clay and S-scheme heterojunction.