Polyimide Surface Double Reaction Center Construction And Activation Of Peroxide To Remove Organic Pollutants In Water

In this paper,aiming at the problem of the refractory organic pollutants removal and engineering application bottlenecks of Fenton catalysis,the“metal”and“nonmetal”modified organic polymer materials-polyimide?PI?were used to induce the electronic polarization distribution on the surface of PI,constructing the dual reaction center?DRC?,and synthesis the new types of graphitization“metal-organic”and“nonmetal”DRC catalyst.Based on a new catalyst,a Fenton-like water treatment system is constructed,which removes typical refractory organic pollutants in water by activating hydrogen peroxide?H₂O₂?and persulfate?PMS?and other peroxides.The degradation process was revealed,and the electronic effect of pollutants was realized,which significantly improved the problems of high energy consumption and low efficiency in water treatment.Meanwhile,a solidified bed small test device was built based on metal-organic DRC catalyst,which was used to treat the actual pharmaceutical wastewater,providing a theoretical basis for the engineering application of the DRC catalyst.This paper focuses on the feasibility of practical application,and studies the surface DRC construction,structural characterization and performance evaluation of the catalyst.First,the PI precursor was modified by copper species,and a new DRC catalyst of surface-modified carbon nitrogen oxide polymer?RSC-CNOP?with reduced copper species was synthesized through high temperature annealing reduction treatment and graphitization.The combination of the reductive metal species?Cu⁰/Cu⁺?and the organic polymer causes abnormal phase transfer of electrons?Cu?O?C????,leading to the formation of enhanced O electron-rich microcenter and C???electron-poor microcenter.Based on RSC-CNOP,a heterogenous Fenton-like reaction system was established to activate H₂O₂ under normal temperature and pressure conditions to degrade typical refractory organic pollutants in water,such as bisphenol A?BPA?and 2-chlorophenol?2-CP?,Ciprofloxacin?CIP?and Rhodamine B?RhB?,etc.It was found that H₂O₂ was quickly reduced to hydroxyl radicals?·OH?in the enhanced O electron-rich center and also oxidized pollutants;while pollutants and their intermediate products could replace H₂O₂ as the main electron-donor and decomposed in the C???electron-poor center.The electrons obtained from the pollutants are quickly transferred to the O center through the Cu-O-C???bond bridge,which realizes the efficient cycle operation of the system.The results show that the catalytic system has good activity of degrading pollutants and high reaction efficiency in a wide range of pH 3-11.The above research found that metallic copper only participated in the construction of the surface DCR,and did not mainly participate in the Fenton-like reaction.However,the existence of metal species is still the root cause of a series of bottlenecks in the practical application of Fenton-like technology.Based on this,the PI precursor was modified by oxygen-rich substance L-ascorbic acid instead of metal species,and L-ascorbic acid O(O_Vc)doped nano-flower polymer with DRC was synthesized through molecular doping and graphitization(O_Vc-CNOP Nfs).The doping of O_Vc causes the accumulate bidirectionally of?electrons on the aromatic ring through the C-O-C bond bridge[C????O?C???],thereby forming electron-rich/poor centers on the catalyst surface.A heterogenous Fenton-like reaction system was established based on O_Vc-CNOP Nfs,and PMS was activated under normal temperature and pressure conditions to degrade typical refractory organic pollutants in water.It was found that the O_Vc-CNOP Nfs/PMS system used the electrons of the pollutant itself adsorbed on the electron-poor C???center to oxidize it directly,and inhibited the ineffective decomposition of PMS,and promoted the reduction of PMS in the electron-rich O center to generate a large number of hydroxyl?·OH?and sulfate(SO₄^·-)radicals.Therefore,the system shows more excellent performance in the removal of various refractory organic pollutants,and even completely degrades BPA and other substances within 1 minute.Finally,based on the engineering practice,the Cu-organic DRC catalyst was immobilized,and a small solidified bed reactor was built for the treatment of pharmaceutical wastewater.It was found that the COD could be degraded to 57-67 mg/L at the residence time of 20 min after the optimization of synthesis of catalysts and reaction conditions.After the continuous operation of the reaction unit for 4 months,the performance of the catalyst remains stable,which provides a conditional reference and theoretical basis for the practical application of DCR catalyst.