Visible-Light-Driven Degradation of Rhodamine B in Aqueous Solution Using Co/g-C₃N₄: Activity, Pathways, and Mechanism

Rhodamine B (RhB) is a widely used cationic organic dye due to its bright color and fluorescence characteristics. Because of high stability, non-biodegradability, and carcinogenesis, the effective degradation of RhB from wastewater is a persistent issue that demands attention and resolution. Herein, a highly active and recyclable photocatalyst, Co/g-C3N4, was successfully synthesized under a facile calcination route to efficiently degrade RhB in simulated wastewater. The photocatalyst was characterized, the conditions for degradation were optimized, and radical trapping experiments were used to probe the mechanism. Under optimal reaction conditions (i.e., Co, 2%; mass, 30 mg; pH, 3; initial concentration of RhB, 20 mg/L; V, 50 mL; t, 30 min; T, 25 °C; and L, 300 W Xe lamp), the resulting composite has a superior degradation efficiency of up to 97.65% at room temperature. Several active oxygen species (•OH, •O2–, and h+) were present during the degradation of RhB. More interestingly, the catalyst was stable and maintained efficiency after five cycles in RhB solution, indicating that the 2%Co/g-C3N4 has the potential to efficiently degrade RhB in wastewater treatment.