Assembling ZnO with Bi₂₄Si₂O₄₀ via a n-n heterojunction mechanism: Boosted visible-light-driven photocatalytic removal of typical contaminants

In the present paper, Bi₂₄Si₂O₄₀ nanoparticles were assembled with ZnO by a simple hydrothermal procedure at 150 ºC for 24 h. The resultant binary ZnO/Bi₂₄Si₂O₄₀ nanocomposites were employed for detoxification of emerging pollutants including tetracycline hydrochloride (TCH), metronidazole (MET), cephalexin (CPX), and fuchsine (FS). The degradation rate constant of TCH, MET, CPX, and FS over the ZnO/Bi₂₄Si₂O₄₀ (30 %) nanocomposite, as an optimum photocatalyst, was 14.1, 2.25, 2.29, and 1.72 times better compared to ZnO, respectively. Furthermore, the activity of the optimal photocatalyst for TCH, MET, CPX, and FS degradation was respectively 6.34, 1.37, 1.63, and 1.36 times superior than the pristine Bi₂₄Si₂O₄₀. Hence, the synergism of ZnO and Bi₂₄Si₂O₄₀ components in promoting the photocatalytic activity is corroborated. The efficient charge production, segregation, and transfer were supported by DRS, PL, and EIS analyses, which confirmed the intimate heterojunction development between ZnO and Bi₂₄Si₂O₄₀ components. According to the trapping experiments and the obtained energy levels, the n-n junction mechanism was proposed for photocatalytic removal of the contaminants over ZnO/Bi₂₄Si₂O₄₀ nanocomposites. Finally, the biocompatibility of the treated sample was tested by growth of lentil seeds.