Degradation Of Organic Pollutants In Water By Activation Of Persulfate Using Transition Metal Based Single Atom Catalysts

Advanced oxidation processes（AOPs）with persulfate as oxidant is an effective way to remove refractory organic pollutants in water,and the key point to expanding the application range of persulfate-based AOPs is to develop highly efficient catalysts.Single-atom catalysts（SACs）is a new type of catalyst in which metal elements are supported on the surface of carrier in the form of a single atom.Compared with metal-based catalysts,SACs shows significantly enhanced activity and huge application potential in various catalytic reactions.In recent years,studies have shown that SACs can efficiently activate persulfate to degrade organic pollutants,but there are still some shortcomings:（1）the metal loading of SACs is insufficient,（2）SACs is poor in stability and reusability,（3）the efficiency of pollutant degradation needs to be further improved.In this study,single Cu atom catalyst and single Fe atom catalyst were synthesized using metal organic framework（MOF）as the precursor and g-C₃N₄ as supportor respectively.Bisphenol A（BPA）and tetracycline（TC）were chosen as target pollutants to evaluate their performance in activating peroxydisulfate（PDS）to degrade organic pollutants.The activation mechanism of PDS was clarified by means of catalyst characterization,active species detection and active site exploration.In addition,we explored the catalytic degradation performance of single Cu atom catalyst in actual water and the stability of single Fe atom catalyst under extreme pH.This research provides new perspective for the development of SACs that can activate persulfate to degrade organic pollutants under extreme conditions and complex water.The main results are as follows:（1）A single Cu atom catalyst with metal loading of 10 wt%was synthesized by using Cu based MOF as precursor.The existence of single Cu is in the form of Cu-N₄ and Cu-N₂,and they activated PDS via electron transfer pathway.The abundant active sites greatly improved the catalytic efficiency,and the 0.1 m M BPA was completely degraded within 3min with the turnover frequency as high as 11.85 g^-1 min^-1.The Cu-SAC/PDS system can selectively degrade organic pollutants and not affected by anions and natural organic matters in water.The Cu-SAC maintains a high catalytic degradation efficiency in the pH range of 1-11.（2）A single Fe atom catalyst was prepared by C₃N₄ loading combined with modification of reduced graphene oxide（r GO）.Compared with C₃N₄-Fe,the addition of r GO improves the catalytic activity and pH adaptability of C₃N₄-Fe-r GO.In the pH range of 0-14,C₃N₄-Fe-r GO can activate PDS to degrade TC under the condition of light radiation.C₃N₄-Fe-r GO maintain good catalytic efficiency after 10 cycle use,and C₃N₄-Fe-r GO show extremely high stability and reusability under the condition of variable pH.