Activation Of Peroxysulfate By Carbon-based Composite For Degradation Of Organic Pollutants

Environmental Endocrine Disruptors,as micropollutants widely existing in the water environment in recent years,pose a potential threat to organisms and the environment.Advanced oxidation technology based on persulfate has the advantages of strong oxidation capacity,wide application range and high selectivity,becoming a new and efficient treatment technology of organic pollutants.Among many activation methods,transition metal catalysts are favored by researchers because of their simple activation conditions and no extra energy consumption.However,they also have disadvantages such as easy leaching of metal ions and secondary pollution.Carbon-based materials represented by graphitic carbon nitride（g-C₃N₄）have the advantages of large specific surface area,controllable structure,and good stability,and are favored by researchers.However,the catalytic activity of carbon-based materials is limited.Combining them with transition metals can effectively improve the catalyst’s ability to activate persulfate.In this paper,a typical endocrine disruptor bisphenol A was used as the target pollutant,and a cobalt-supported carbon composite catalyst was prepared by different methods to activate PMS and degrade bisphenol A.The main research results of this paper are as follows:（1）Using ZIF-67 and melamine as precursors,Co₃O₄/g-C₃N₄ composite catalyst was prepared by one-step pyrolysis.Modification of g-C₃N₄ with ZIF-67 as precursor can significantly improve its catalytic activity.Different loading ratios of ZIF-67 in the composite catalyst showed different catalytic performance.The degradation experiment results showed that when the mass ratio of ZIF-67 to melamine reached 15%,the Co₃O₄/g-C₃N₄ composite catalyst had the highest degradation efficiency of bisphenol A,and bisphenol A could be completely degraded within 15 min.Compared with g-C₃N₄,the catalytic performance is greatly improved.（2）Physicochemical characterization of Co₃O₄/g-C₃N₄ catalyst prepared by one-step pyrolysis and study on the reaction mechanism of activated PMS to degrade BPA.It was found that Co₃O₄/g-C₃N₄ presented an irregular block structure with Co₃O₄ particles about 10 nm attached to the surface of g-C₃N₄ material.XRD and XPS characterization confirmed the successful recombination of the catalysts.Through GC-MS detection of possible intermediates in Co₃O₄/g-C₃N₄/PMS/BPA system,radical quenching experiment and EPR characterization analysis,it is concluded that non-radical（¹O₂）plays a dominant role and radical pathway(SO₄^·-、·OH、·O₂^-)synergistic catalytic degradation mechanism.（3）The preparation method of Co₃O₄/g-C₃N₄ composite catalyst was improved by freeze-drying method with ZIF-67 and urea precursor.It was found that when the mass ratio of ZIF-67 to urea was 3%,the degradation efficiency of bisphenol A reached 100%within 4 min.The improved preparation method of Co₃O₄/g-C₃N₄composite catalyst is more conducive to the dispersion of metal active sites,and the degradation performance of the catalyst for bisphenol A is obviously improved.At the same time,the improved Co₃O₄/g-C₃N₄ composite catalyst also showed excellent catalytic performance for rhodamine B and tetracycline,demonstrating the wide applicability of this material.