From pollutants to non-toxic products: an Ov-rich S-scheme heterojunction for photocatalytic antibiotic degradation and toxicity assessment

Abstract

Photocatalytic technology based on a heterojunction structure has been demonstrated as an effective approach to address environmental pollution and energy issues. In this study, an oxygen-vacancy (Ov)-rich S-scheme BiVO₄/Bi-TCPP heterojunction was fabricated via a facile hydrothermal method for the degradation of tetracycline (TC) and oxytetracycline (OTC), and innovatively applied to wheat seed germination experiments to evaluate the ecological safety of treated water samples. A series of characterization results indicate that the one-step strategy enables the in situ introduction of oxygen vacancies and simultaneous heterojunction construction, avoiding complex post-treatment processes. The oxygen vacancies generate defect sites and electron trapping centers, effectively narrowing the band gap, enhancing visible light absorption capacity, and promoting the separation of photogenerated carriers. The S-scheme heterojunction formed by BiVO₄/Bi-TCPP coupling effectively facilitates charge transfer, further promotes carrier separation, and improves photocatalytic activity. Under visible light irradiation, the optimized system achieved a TC degradation rate of 90.15% within 90 min and an OTC degradation rate of 85.30% within 120 min, with excellent stability. In addition, the photocatalytic degradation mechanism and dominant active species of the Ov-rich S-scheme BiVO₄/Bi-TCPP heterojunction were investigated. Wheat seed germination experiments confirmed that the phototreated antibiotic wastewater significantly reduced the inhibitory effects on the wheat seed germination rate and root elongation, demonstrating that this system not only efficiently removes antibiotics but also effectively eliminates their ecological toxicity, ensuring the environmental safety of the effluent. This study provides new insights into the O_v-regulated S-scheme photocatalytic degradation of TC and OTC and broadens its potential application in wastewater remediation.