Study On Ultrafast Degradation Of Organic Pollutants By Free Radical And Non Free Radical Mediated Flow Through Electrocatalytic System

Advanced oxidation processes（AOPs）based on transition metal activated persulfate（PS）have attracted much attention due to their strong oxidation ability and wide application.However,the process is still faced with the problems of difficult recovery of powder catalyst and slow reaction kinetics.Based on this,we designed and developed a flow-through electrocatalytic system based on carbon nanotubes（CNT）films modified by nanoscale zero valent copper（n ZVC）or nanoscale palladium particles,which can realize the synergistic enhancement of degradation efficiency of typical organic pollutants by free radicals and non free radicals,In this paper,the optimized preparation,characterization analysis,performance test and mechanism research of nanocomposite membrane were systematically studied.（1）n ZVC-CNT/PMS system.The electroactive n ZVC-CNT composite films were prepared by in-situ reduction technology.The morphology,composition and other physical and chemical properties of the materials were characterized by a variety of advanced characterization methods.The results show that the size of nzvc is 2±1 nm and it is uniformly distributed on the wall of CNT.Congo red was used as a model organic compound to further investigate the degradation efficiency of the system.The results show that the system can completely degrade Congo red（?<2 s）in a single flow condition,and maintain this high-efficiency degradation performance in a wide p H range.Electron paramagnetic resonance spectroscopy and control experiments confirmed that·OH and¹O₂ played an important role in the degradation of Congo red.The carbonyl group and electrophilic oxygen of CNT act as electron donor and electron acceptor respectively,and activate PMS to generate·OH and ¹O₂ through single electron transfer.However,the electron deficient Cu atom can easily react with PMS via surface hydroxyl groups to form the reaction intermediate(Cu²⁺-O-O-SO₃^-),and then destroy the coordination bond of metastable intermediate to form ¹O₂.In the presence of Cl^-,NO₃^-,SO₄^2-and other interfering ions,or in different background substrates（lake water and tap water）,the degradation of Congo red was not significantly inhibited.In addition,the degradation experiments of other different kinds of new organic pollutants（such as methylene blue,methyl orange,tetracycline,and bisphenol A）by the system also showed that the above organic pollutants could be effectively degraded under the single filtration condition,indicating that the system can be applied to the effective treatment of a variety of different organic pollutants.（2）Pd-CNT/PMS system.The proper loading of Pd nanoparticles on CNT was realized by electrochemical deposition.The microstructure and chemical composition of the materials were characterized by advanced methods.The"structure-activity"relationship between the preparation parameters of the composite membrane and the degradation performance of organic compounds was studied with Congo red as the target.The results showed that the system could completely degrade Congo red in single flow mode,and the degradation efficiency remained unchanged for 24 hours.The formation of atomic hydrogen（H*）was confirmed by EPR.The H*produced by the auxiliary electric field can be used as a single electron reductant of PMS,and then it can be decomposed into·OH and SO₄^·-.Using 2,4-dichlorophenol as H*quencher,the key H*species were identified by cyclic voltammetry and linear scanning techniques,and the potential effects of H₂ and H*_abs were excluded.The results of spectroscopic characterization before and after degradation showed that the crystal plane and valence state of Pd did not change significantly.In addition,the system can also show excellent degradation performance for other typical organic pollutants.The two activated PMS systems proposed in this study provide an efficient,green,and rapid technical means for the treatment of organic pollutants in water.