An eco-safety g-C3N4/Nb2O5/Ag ternary nanocomposite for photocatalytic degradation of pharmaceutical wastes and dyes in wastewater and zebrafish embryonic assessment

•We develop a simple ultrasonic-assisted assembly strategy for preparing photocatalysts.•Doped Ag can optimize the nanocomposite bandgap for visible-light photocatalysis.•The optimal photocatalyst can remove dual organic pollutants.•The eco-safety and photocatalytic activity of g-C3N4/Nb2O5/Ag are demonstrated by zebrafish embryonic assessment. In this work, we developed a ternary g-C3N4/Nb2O5/Ag photocatalyst through a simple hydrothermal process with ultrasonic-assisted assembly for the photocatalytic degradation of Norfloxacin (NRF) and Methylene Blue (MB) in wastewater. The bandgap of the prepared nanocomposite was tuned to 2.81 eV, which is favorable for visible light photocatalytic reaction. The photocatalytic process involved the generation of reactive species such as hydroxyl radicals (·OH), photo-generated holes (h+), and superoxide radical (·O2−), with the reactivity following the order: ·OH > h+ > ·O2−. With the comprehensive characterizations, the g-C3N4/Nb2O5/Ag nanocomposite exhibited optimal degradation efficiency, achieving 83 % for NRF and 92 % for MB (pH 9) under visible light irradiation within 70 and 80 min, respectively. The intermediate products formed during the photocatalytic degradation were identified with gas chromatography-mass spectrometry (GCMS–). In addition, the biocompatibility and photocatalytic efficacy of g-C3N4/Nb2O5/Ag were examined through zebrafish embryo development studies in the degraded wastewater. The results indicated that treated wastewater did not adversely affect the zebrafish growth. This comprehensive study not only demonstrates the effectiveness of the ternary g-C3N4/Nb2O5/Ag photocatalysts in degrading complex organic pollutants under visible light but also underscores their potential environmental safety as evaluated through biological assays. [Display omitted]