Co and S co-doped graphitic carbon nitride synergistically degrades carbamazepine in water with peroxymonosulfate

Abstract

Transition metals are frequently used to create catalysts that activate peroxymonosulfate (PMS) to degrade water contaminants. However, the degradation efficiency may be decreased if metal ions are released into the solution. In this work, a one-step calcination method was used to modify graphitic carbon nitride (CN) in the presence of Co and S. The synthesis of CoS₂ was notably aided by the doping of S, which also improved the degradation efficiency of CBZ by penetrating the tri-s-triazine ring of CN, which alters the electron distribution and speeds up the electron transfer efficiency between Co²⁺ and Co³⁺. The Fenton-like reaction mechanism degrades carbamazepine (CBZ, C = 20 mg/L) by 98 % within 40 min when paired with PMS. When the pH value ranges between 5 and 9, the degradation efficiency of CBZ remains above 90 % even in the presence of humic acid and other anions. Sulphate radicals (SO₄⁻·) and superoxide radicals (O₂⁻·) were identified as the primary reactive oxygen species (ROS) involved in the reaction process. A believable CBZ degradation route was suggested. Additionally, the entire reaction process is environmentally safe due to the toxicity calculation.