Degradation of sulfamethoxazole in water by AgNbO3 photocatalyst mediated by persulfate

Abstract

In this paper, silver niobate (AgNbO₃) material was synthesized by a solid-state reaction. AgNbO₃ was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller (BET) measurement. The photocatalytic activity of AgNbO₃ was investigated in degradation of sulfamethoxazole (SMX) under visible light, which is a widely used antibiotic with significant threats towards health and aquatic organisms. Persulfate (PS) oxidant was found to improve the efficiency of the proposed photocatalytic removal of SMX by AgNbO₃. The different operational parameters in the AgNbO₃/PS/Vis system were investigated. The best photocatalytic performance was achieved with 0.5 g L⁻¹ AgNbO₃, 1.0 mM PS, and pH = 5.0 as the optimal conditions, achieving 98% of SMX degradation after 8 h of visible-light irradiation. Scavenger and electron spin resonance (ESR) experiments were carried out to identify the major reactive species in the SMX degradation and to propose the photocatalytic mechanism by the AgNbO₃/PS/Vis system. The photodecomposition was found to be majorly caused by holes and ˙O₂⁻ species, with ˙OH and SO₄˙⁻ radicals contributing to improve the photocatalytic process. The AgNbO₃ catalyst was stable and reusable with efficient photocatalytic activity in three successive recycling experiments and its XRD patterns remained virtually unchanged. The reported process of PS activation by the AgNbO₃ photocatalyst is promising for visible-light application in remediation of antibiotic-contaminated water.