Fabrication of the new p-Co₃O₄/n-AgI hetero-junction and its solar photo-degradation of the fast green FCF

This work examines the heterogeneous advanced oxidation for the photodegradation of fast green FCF a recalcitrant dye on the novel hetero-junction Co3O4/AgI. The spinel Co3O4 synthesized by sol-gel route was characterized by thermal analysis (TG), FTIR, XRD, SEM, BET, diffuse reflectance and photo-electrochemically; AgI was synthesized by precipitation. Electrons in Co3O4-CB (-1.06 V-SCE) excited by sunlight are injected into AgI-CB (-0.90 V-SCE). The hetero-junction p-Co3O4/n-AgI brings important changes in the photo-catalytic properties, thus facilitating the rapid transfer of electron-hole (e(-)/h(+)) pairs and significantly improving the photoactivity. Some physical parameters like the pH, photocatalyst dose, CFC concentration as a function of illumination time have been studied. After 90 min, 20 mg/L of fast green FCF disappeared under optimal conditions (pH similar to 8, 25 degrees C, p-Co3O4/n-AgI (Wt. %: 1/1) at a dose of 1 mg/mL) upon natural sunlight. The photodegradation kinetic of fast green FCF, measured spectrophotometrically and by total organic carbon (TOC) showed that the oxidation follows a first-order model with a half catalytic life of 41 min.