Tetracycline hydrochloride degradation over manganese cobaltate (MnCo2O4) modified ultrathin graphitic carbon nitride (g-C3N4) nanosheet through the highly efficient activation of peroxymonosulfate under visible light irradiation.

Peroxymonosulfate (PMS) activation by heterogeneous transition metal oxides is an effective approach for treating emerging pollutants in water. However, the low PMS activation efficiency associated with the valency conversion rate of transition metals has been a major challenge to sulfate radical-based oxidation. In this work, manganese cobaltate (MnCo2O4) nanoparticles anchored on graphitic carbon nitride (g-C3N4) flakes (MnCo2O4/g-C3N4) were successfully prepared and showed high PMS activation efficiency under visible (Vis) light. The obtained catalysts degraded 96.1% of the tetracycline hydrochloride (TCH) through the synergistic effect of PMS and photocatalysis. The reaction rate constant (0.2505 min-1) was 5.3 and 1.8 times higher in the MnCo2O4/g-C3N4/PMS/Vis system than in the pristine g-C3N4 (0.0471 min-1) and MnCo2O4 (0.1435 min-1) systems, respectively. The characterization results verified that g-C3N4, which functions as the electron donor in the photocatalytic heterojunction system, could transmit numerous photogenerated electrons to MnCo2O4, thereby increasing the cyclability of divalent-trivalent metal ions. The composites also showed good stability, cycling capability, and cation/anion tolerance. Tentative degradation mechanism and reaction pathways were proposed based on the reactive species and degradation products.