Peroxymonosulfate catalyzed by rGO assisted CoFe₂O₄ catalyst for removing Hg⁰ from flue gas in heterogeneous system

The cobalt ferrite-reduced oxidized graphene (CoFe₂O₄/rGO) catalyst was synthesized by hydrothermal method and characterized by Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Brunauere Emmette Teller (BET) and Hysteresis loop. For developing a new method of removing elemental mercury (Hg⁰) from flue gas, the effects of catalyst dosage, PMS concentration, solution pH and reaction temperature on the removal efficiency were investigated experimentally by using peroxymonosulfate (PMS) catalyzed by CoFe₂O₄/rGO at a self-made bubbling reactor. The average removal efficiency of Hg⁰ in a 30-min period reached 95.56%, when CoFe₂O₄/rGO dosage was 0.288 g/L, PMS concentration was 3.5 mmol/L, solution pH was 5.5 and reaction temperature was 55 °C. Meanwhile, based on the free radical quenching experiments, in which, ethyl alcohol and tert butyl alcohol were used as quenchers to prove indirectly the presence of ^•OH and SO₄^•-, the characterizations of catalysts and reaction products, and the existing results from other scholars. The reaction mechanism was proposed.