Construction of a visible-light-driven magnetic dual Z-scheme BiVO4/g-C3N4/NiFe2O4 photocatalyst for effective removal of ofloxacin: Mechanisms and degradation pathway

Inefficient utilization of photo-induced charge carriers and low recyclability are limitations for photocatalyst to get access to the practical application. A novel ternary BiVO4/g-C3N4/NiFe2O4 composite with dual Z-scheme heterojunction was successfully developed and constructed to enhance the separation of photo-induced charge carriers and the absorption range of visible light. The structure, composition, morphology, magnetic, and optical properties of this photocatalyst were investigated comprehensively. The photocatalytic performance, mechanism, and pathway of ofloxacin degradation under visible light were studied. Results indicated that the internal interaction between different semiconductors presented the successful fabrication of ternary composite, and its red shift of adsorption range of visible light contributed to an enhancement of photocatalytic ability. The as-prepared ternary composite exhibited highest photocatalytic removal rate constant for ofloxacin, which was 3.8, 16.3 and 71.2 times as much as that of the pure BiVO4, pure g-C3N4 and pure NiFe2O4, respectively. The five successive recycling experiments exhibited the high photocatalytic stability of the as-prepared catalyst, with simple recovery operation due to its magnetic property. The holes and superoxide radicals dominated the photocatalytic degradation process of pollutants. A dual Z-scheme heterojunction other than conventional heterojunction was responsible for the enhancement on redox capacity and the separation of charge carriers. Different transformation products during ofloxacin photocatalytic degradation were identified and transformation pathway was put forward. This study provides a promising strategy on the application of visible-light-driven photocatalysts in water treatment.