Efficient visible-light-responsive novel P/BiOIO3/Co-TCPP Z-scheme heterojunction photocatalyst for oxytetracycline hydrochloride removal: synergistic effects of P doping and organic complexes

In this paper, Co²⁺ was successfully assembled into a complex by solvothermal method with meso-tetra (4-carboxyphenyl) porphyrin (TCPP), and then a novel P/BiOIO₃/Co-TCPP inorganic-organic composite photocatalytic material was prepared by one-pot solvothermal method. It was found that after 60 min of reaction under visible light, the degradation rate of the preferred P/BiOIO₃/Co-TCPP composite material for 20 mg/L oxytetracycline hydrochloride (OTC) reached 88.15 %, with its pseudo-first-order kinetic model fitting constant measured at 0.03852 min⁻¹. It was 5.12 and 1.52 times that of BiOIO₃ and P-doped BiOIO₃ respectively, and there was no significant decrease in activity after three consecutive uses. Meanwhile, the noxiousness of the OTC solution after photocatalytic degradation by this catalyst was significantly reduced. The characterization results indicate that the primary factor contributing to the improved activity is the P/BiOIO₃/Co-TCPP catalyst can be attributed to the doping of BiOIO₃ by P and the coupling of Co-TCPP to BiOIO₃, which significantly improves the catalyst's response ability to visible light. Meanwhile, P/BiOIO₃ and Co-TCPP form a Z-scheme heterojunction, which greatly facilitates the separation of photogenerated carriers. Finally, the electron transfer mechanism and possible degradation pathways of the photocatalytic degradation of OTC by P/BiOIO₃/Co-TCPP were proposed. This study provides a feasible and effective method for the modification of BiOIO₃-based heterojunction photocatalysts and the treatment of antibiotics in water bodies.