Heterogeneous Cobalt Activate Peroxymonosulfate To Degrade Organic Wastewater

Dye wastewater has drawn extensive attention because of its high chroma,complex components,and difficulty in biodegradation.Traditional treatment methods can no longer meet the growing demand for environmental protection.Compared to traditional oxidation techniques using hydroxyl radicals?·OH?,sulfate radicals?·SO₄^-?have attracted widespread attention for their advantages such as simplicity,high efficiency,and low secondary pollution,and they have shown a wide application prospects to organic wastewaters.The use of transition metal cobalt catalyst is considered to be a highly efficient method of catalyzing peroxymonosulfate?PMS?to the production of·SO₄^-.The homogeneous Co/PMS system has fast reaction speed and simple operation,but the leaching cobalt ions may cause secondary pollution to the environment and the catalyst is difficult to be collected and used again.The heterogeneous system can effectively solve the defects in the homogeneous system.In this paper,methylene blue?MB?was selected as a model pollutant to study the degradation efficiency in Co₃O₄/PMS?Co⁰-Fe⁰/PMS?Co⁰-Fe⁰/g-C₃N₄/PMS and CoFe₂O₄/g-C₃N₄/PMS four different heterogeneous systems.?1?Co₃O₄ was prepared by hydrothermal method and was characterized by X-ray Diffraction and Scanning Electronic Microscopy,and the particle size of Co₃O₄ was about 50nm.At 20?,the dosage of Co₃O₄ was 50 mg/L,PMS was 400 mg/L,and pH=7,the initial concentration of methylene blue was 50 mg/L.After 30min,the degradation rate reached to98.5%,and increased the temperature and decreased the solution concentration could help increase the degradation rate of methylene blue.?2?Nano-scale iron and cobalt bimetal was prepared by liquid-phase reduction method and characterized by XRD and SEM.The prepared catalyst was about 40 to 100 nm in size,and the bimetallic particles aggregated with each other.Under 30?,the mass fraction of 2%bimetallic dosage was 50 mg/L,PMS dosage was 700 mg/L,pH=7,the initial concentration of 50 mg/L methylene blue solution,after treated 30 min,its degradation rate can reach to93.2%.Higher temperature and lower concentration of the solution can speed up the reaction rate.?3?g-C₃N₄ supported iron-cobalt bimetallics were prepared by liquid-phase reduction and characterized by XRD,SEM,etc.Metal particles were attached to the pores of g-C₃N₄and entered the crystal lattice.At 25?,the mass fraction of cobalt was 10%.When the addition of Co⁰-Fe⁰/g-C₃N₄ was 50 mg/L,the dosage of PMS was 600 mg/L,at pH=7,the degradation rate was 88.4%after the initial concentration of 50 mg/L methylene blue solution was treated for 30 min.Increasing the temperature and decreasing the concentration of the solution can increase the degradation efficiency of methylene blue.?4?The preparation of g-C₃N₄ supported CoFe₂O₄ was used hydrothermal method.The prepared catalyst was characterized by XRD and SEM.CoFe₂O₄ was adhered in the pore of g-C₃N₄.At 20?,the mass fraction of CoFe₂O₄ was 60%.When the addition of catalyst was50 mg/L,the dosage of PMS was 600 mg/L,and pH=7,the degradation rate reached 87.5%after 30 min with the methylene blue solution with an initial concentration of 25 mg/L.Increasing the temperature and decreasing the concentration of the solution can increase the degradation efficiency.?5?The free radical verification experiments of above four systems show that·OH and·SO₄^-exist in the degradation process.