Elemental mercury removal from flue gas by CoFe₂O₄ catalyzed peroxymonosulfate

Highlights: • A magnetic CoFe₂O₄ catalyst was firstly used in air pollutant control. • A new method of removing Hg⁰ was developed based the catalytic oxidation process. • Removal mechanism was proposed according to the characterizations and literatures. - Abstract: A magnetic cobalt ferrite (CoFe₂O₄) catalyst was prepared by sol-gel method, and characterized by a X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET) and hysteresis loop method. The chemical states on surface of the fresh and spent catalysts were analyzed by a X-ray photoelectron spectroscopy (XPS). The experiments of elemental mercury (Hg⁰) removal from flue gas were conducted in a laboratory scale using activated peroxymonosulfate (PMS) catalyzed by CoFe₂O₄, and the effects of the dosage of catalyst, the concentration of PMS, initial solution pH and reaction temperature on mercury removal efficiency were investigated. The average removal efficiency of Hg⁰ could maintain steady at 85% in 45 min when the concentrations of CoFe₂O₄ and PMS were 0.288 g/L and 3.5 mmol/l respectively, solution pH was 7 and reaction temperature was 55 °C. In order to speculate the reaction mechanism, ethyl alcohol and isopropyl alcohol were used as the quenching agents to indirectly prove the existence of SO₄·⁻ and ·OH.