Research On Treatment Of Phenolic Wastewater By Catalyzed Peroxydisulfate Activation With Isolated Diatomic Co-Fe Metal-Nitrogen Sites

Phenol and its derivatives will enter the environment in large quantities through the discharged waste water,which have caused serious environmental pollution.Considering the stability of its molecular structure,advanced oxidation technology based on peroxydisulfate（PDS）oxidation is one of the main technologies for the treatment of phenolic wastewater.Herein,we report an efficient polynary single-atom dual-metal catalyst featuring diatomic metal-nitrogen sites（Co/Fe-N-C）for PDS activation on phenolic compound degradation.In this paper,Co/Fe-N-C is characterized and analyzed by a variety of technical methods,and Co/Fe-N-C+PDS system is used for phenol and BPA degradation.The effects of different influencing factors on the degradation performance of the system and the catalytic mechanism of Co/Fe-N-C are explored.Main conclusions are listed as follows:（1）Co/Fe-N-C is prepared by an ion-exchange strategy based on the pyrolysis of a Zn/Co/Fe zeolitic imidazolate framework.Co/Fe-N-C is a rhombic dodecahedron shape with distinct edges,and the size of which is uniform in 50-100 nm.The specific surface area of the material is 723.36 m²/g,the pore volume is 0.65 cc/g,the average pore diameter is 2.09 nm,and the supported cobalt and iron exist in the form of single atoms.（2）When concentration of phenol and BPA in wastewater is 100 mg/L,Co/Fe-N-C dosage is 0.5 g/L,PDS concentration is 10 mmol/L,and initial p H is 6,Co/Fe-N-C+PDS system can completely degrade phenol and BPA in 20 minutes,and mineralization rate of which are 79.2%and 76.3%after 120 minutes,respectively.（3）The degradation of phenol by Co/Fe-N-C+PDS system follows pseudo-first-order,and its reaction rate constant is 0.2051 min^-1.The system can be utilized in a wide range of initial p H（3-9）for complete degradation of phenol.Moreover,the optimal p H range for the reaction is 2.8-3.（4）The stability of Co/Fe-N-C is relatively high.After 9 recycling experiments,the mineralization rate of phenol was still higher than 50%within 120 minutes,and the leaching amount of Co and Fe ions after the reaction were 0.0005 mg/L and0.0007 mg/L,respectively.The leaching amount is far less than the China Surface Water Environmental Quality Standard（GB 3838-2002）.（5）According to the results of reactive oxidation species（ROS）quenching experiments and oxidant substitution experiments,it can be concluded that free radical and non-free radical pathways are coexist in Co/Fe-N-C+PDS system,and ROS as·OH,SO₄^●-,O₂^●-and ¹O₂were identified.。（6）Combining the experimental results of H₂-TPD and reaction rate constant of the phenol degradation,the turn-over frequency（TOF）of the Co/Fe-N-C catalyst is calculated to be 27.17 min^-1,which is higher than many reported nano metal catalysts and homogeneous catalysts.