Bio-synthesized ZnO nanoparticles and sunlight-driven photocatalysis for environmentally-friendly and sustainable route of synthetic petroleum refinery wastewater treatment

Characterization of the synthesized NPs

UV visible absorption

The UV–vis absorption spectra of ZnO materials are depicted in Fig. 2(a). Both samples exhibited UV–vis absorption spectra, with a wide intense absorption from about 350 nm, which may be linked to the intrinsic absorption of the BG of ZnO NPs caused by electron (e−) transfer out from VB towards the CB^{34,43,44,45,46}.

Since ZnO is a direct band gap Semicond., its ABS coefficient (α) is correlated to the…