Characteristics And Mechanism Of Of Ibuprofen Degradation In Water Catalyzed By Ozone With Modified Biochar

In recent years,heterogeneous catalytic ozonation,as one of the advanced oxidation technologies,has been widely used in the advanced treatment of wastewater due to its advantages of strong oxidation capacity,simple process and low treatment cost.The core of its technology is the preparation of efficient,economic and environmental protection new ozone catalytic materials.As a common low-cost and easily prepared catalyst,biochar material can catalyze the degradation of organic pollutants by ozone,and has great potential in practical application.However,the catalytic performance of biochar catalysts remains to be improved and the specific mechanism of catalytic ozone needs to be further clarified.In this paper,the biochar was optimized and modified by simple doping and loading to improve its catalytic performance,and the feasibility of the above method was verified by combining the characterization of catalysts and degradation efficiency of target pollutants.Furthermore,the influencing factors,active substances composition and action mechanism of the two catalytic ozone systems were analyzed and compared.The specific research results are as follows:（1）Nonmetallic nitrogen-doped biochar（N-C）was prepared by hydrothermal method using wood chips as carbon source and dicyandiamide as nitrogen source.The N-C and pure biochar were characterized by XRD,SEM,Raman and XPS,and the catalysts were screened based on their catalytic performance.On this basis,the catalytic system of N-C catalytic ozone removal of organic pollutants was constructed,and the oxidative degradation efficiency of the catalytic system was systematically studied,and the effects of initial pH,ozone dosage and catalyst dosage on IBP degradation efficiency were deeply explored.The results showed that compared with some common carbon based catalysts（g-C₃N₄,biochar,granular activated carbon）and metallic oxide（Mn O₂,Fe₃O₄）,N-C catalytic ozone system had very outstanding oxidation degradation performance of organic pollutants,and the removal rate of IBP was up to 100%after 5 min reaction.In addition,the analysis of influencing factors shows that the treatment efficiency of the system increases with the increase of pH and ozone dosage,but compared with the increase of ozone dosage,the increase of catalyst concentration can significantly improve the treatment capacity of the system.（2）Fe-Mn bimetallic supported biochar（Fe-Mn-C）was successfully prepared by one-step hydrothermal method with wood chips,ferric chloride and manganese chloride as raw materials.The physicochemical properties of catalysts prepared with different Fe/Mn ratios were comprehensively characterized and screened.On this basis,the catalytic performance of the catalyst was systematically studied.The results showed that Fe-Mn-C showed good catalytic performance compared with metal oxides and single-metal supported biochar.IBP in the system could be completely degraded in about 10 min,and the removal rate of total organic carbon was 44.2%.It is found that Fe-Mn-C has a positive correlation with pH,ozone dosage and catalyst dosage,and it can play a good catalytic capacity under different anions and different water conditions.（3）The reaction mechanism of N-C/O₃ system and Fe-Mn-C/O₃ system was studied.Through EPR analysis and quenching experiments,it was found that N-C could effectively catalyzed ozone to produce more reactive oxygen species,such as superoxide radical（·O₂^-）and H₂O₂,·O₂^-is the main active substance in the reaction system.The results showed that chemical surface groups（C=O and C-O=C）,pyridine N and delocalizedπelectrons were the active sites of nitrogen-doped biochar.The active oxidants in Fe-Mn-C/O₃ system are hydroxyl radicals（·OH）and superoxide radicals（·O₂^-）belonging to the free radical pathway and part of H₂O₂,among which the main active substances are hydroxyl radicals（·OH）and superoxide radicals（·O₂^-）of the free radical pathway.C=O is considered to be the active site of ozone catalyzed by carbon materials,and the cyclic transformation between Fe（Ⅱ）/Fe（Ⅲ）and Mn（Ⅱ）/Mn（Ⅲ）is also the main reason for promoting catalytic ozone reaction.