A comparative study of peroxydisulfate and peroxymonosulfate activation by a transition metal-H₂O₂ system

In this study, the impacts of common activation methods, namely heating, the addition of zero-valent metals (Cu, Fe, Al, Co, and Ni) and the addition of H₂O₂, on peroxydisulfate (PS) and peroxymonsulfate (PMS) activation were investigated. Rhodamine B (Rhb, 50 mg/L) was chosen as the substrate to be tested. Results showed that the efficiency of PMS was higher than that of PS under the same heat activation conditions. Cu, Fe, and Ni activated PS, while Co exhibited detrimental effects; Among them, Cu was the best. Co was the best activator among the investigated metals for PMS. Additionally, the use of H₂O₂ achieved a higher removal of Rhb in the PS/Cu system but inhibited the PMS/Co system. Three common anions (SO₄^2-, Cl^-, NO₃^-) that exist in the Yellow River were investigated. Cl^- was found to accelerate Rhb degradation, while SO₄^2- and NO₃^- slowed Rhb degradation. Toxicity experiment results showed that the addition of H₂O₂ promoted the transformation of Cu (0) to Cu²⁺ and Co (0) to Co²⁺, which was dangerous for seed germination. Graphical abstract.