Tetracycline Degradation Under Visible Light Using a New SiNW/CeO2/NiO Composite as a High-Efficiency Photocatalyst

Abstract

Recently, extensive research has focused on the purification of antibiotic-contaminated wastewater via photocatalysis techniques. In this context, many types of photocatalysts have been studied. In this work, silicon nanowires (SiNWs) were synthesized and coated with nickel oxide (NiO) and cerium oxide (CeO2) via a hydrothermal technique and used as new photocatalysts to degrade a recalcitrant antibiotic, namely, tetracycline (TC), under visible light irradiation. The prepared samples were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–Vis spectrophotometry (UV–Vis). These characterizations revealed that SiNWs are well coated over their entire length with NiO and CeO2. A 96% degradation rate of TC was achieved within 120 min under visible light irradiation. This enhanced performance is attributed to improved visible light absorption, efficient charge generation, and better charge separation and transfer enabled by the synergistic effects among SiNWs, CeO2, and NiO. The primary species involved in TC degradation were determined by radical scavenging tests to be e⁻, ⋅OH, O2⋅-, and h⁺, which allowed to suggest a reaction mechanism. Finally, this work proposes a new approach to synthesize a powerful photocatalyst that is able to eliminate emerging contaminants from the aquatic environment