Interfacial engineering of CQDs sensitized NiFe2O4 spheres anchored CoCr2O4/MoO3-x NSs for boosted visible light driven photodegradation of antibiotic, mechanistic insights, and its toxicity assessment

High demand of an efficient photocatalyst to degrade the antibiotics is one of the major challenges for industrial applications. Herein, the CQDs sensitized NiFe2O4 spheres anchored CoCr2O4/MoO3-x NSs with high doxycycline (DOXY) photodegradation efficiency were successfully prepared via co-precipitation, hydrothermal-calcination assisted methods. The abundant oxygen defects and synergistic effect of the photocatalyst contributed to its excellent photodegradation efficiency (99.70 % at pH 6) with a rate constant of 0.0388 min-1 under visible light irradiation. The kinetic study revealed that the interfacial engineered NFO/CQDs co-decorated MoO3-x/CCO composite have 13.30, 5.87, and 7.05 times greater efficiency than the pristine MoO3, CCO, and NFO respec-tively. The n-p-n heterojunction formed under the action of internal electric field at the interface have greatly suppressed the charge carrier recombination. Meanwhile, the enlarged specific surface area (342.70 m2/g) provided more active sites to improve the reaction. The superoxide radical (center dot O2-), and hydroxyl radical (center dot OH) played crucial role in the DOXY degradation process, as affirmed by radical trapping experiment and ESR analysis. Moreover, the crystalline structure, bonding energy and photodegradation ability remained unchanged after six consecutive cycles indicating excellent recyclability, and stability for practical applications. The toxicity of the end products was investigated against E. coli and S. epidermis, revealing the complete mineralization of the antibiotics, and further confirmed by ecotoxicity analysis. The dual vacancy enriched (surface decorated and intrinsic O-vacancies) NFO/CQDs co-decorated MoO3-x/CCO composite exhibited remarkable stability, structural and catalytic properties providing an insight into the efficient photocatalytic degradation of pharmaceutical pollutants.

Automated summary

In this study, CQDs sensitized NiFe2O4 spheres anchored CoCr2O4/MoO3-x NSs were successfully prepared and exhibited high doxycycline photodegradation efficiency under visible light irradiation. The abundant oxygen defects and synergistic effect of the photocatalyst contributed to its excellent performance. The composite material also showed remarkable stability and recyclability.