A magnetically separable α-NiMoO4/ZnFe2O4/coffee biochar heterojunction photocatalyst for efficient ketoprofen degradation

Abstract

In this study, a novel heterostructure i.e., ZnFe2O4 nanosphere-decorated α-NiMoO4 nanorods on coffee biochar (BC), was fabricated via a hydrothermal method. The magnetically separable α-NiMoO4/ZnFe2O4/BC composite demonstrated 98.65 % degradation of ketoprofen (KP) in 180 min under visible light irradiation. Analysis of cyclic tests, total organic carbon, and fluorescence excitation-emission matrices revealed the excellent stability and mineralization abilities of photocatalysts, respectively. The effects of influencing factors (pH, anions, and different concentrations of KP/photocatalysts) on degradation of KP by the photocatalysts were suggested as promising prospects in water/wastewater treatment. BC acts as a conductor and an electron mediator in heterostructure. The enhanced photocatalytic performance of the heterostructure was ascribed to increased visible light absorption and efficient photoinduced charge carrier separation. Furthermore, photoluminescence spectral and electrochemical investigations indicated the efficient separation of photoinduced charge carriers. Electron spin resonance spectroscopy and scavenger experiments demonstrated that •OH played a major role in KP degradation. According to the liquid chromatography-tandem mass spectroscopy analysis, KP was degraded via three degradation pathways by 24 degraded intermediates. This study provides a new perspective on fabrication of efficient heterojunction photocatalysts exhibiting good recovery and insight on mechanisms and pathways underlying KP degradation.