Facile Synthesis Of Coal Fly Ash-based Metal Oxide Fenton Catalyst For The Degradation Of Organic Matter By Hydrogen Peroxide

China produces a significant amount of fly ash（CFA）every year due to coal-fired power generation.At present,CFA has become the largest industrial solid waste in China and caused a series of environmental problems.Finding a high value-added method of CFA has become a research focus.Although CFA has been used to some extent in sewage treatment,such as the preparation of adsorbent and flocculant by CFA.However,there are still few researches on the preparation of Fenton-like catalysts using CFA as raw material.How to realize the high value-added use of CFA is the research direction of this paper.Therefore,three kinds of catalysts,modified fly ash supported copper oxide（CuO-FAZ）,modified fly ash supported copper aluminum bimetallic oxide（Cu-Al/FAZ）and modified fly ash supported N-doped copper aluminum bimetallic oxide（Cu-Al-N/FAZ）,were synthesized using modified CFA as the support.With bisphenol A（BPA）as the target pollutant,the performance of these three catalysts for H₂O₂degradation of BPA was investigated and the catalytic mechanism was discussed.The main contents are as follows:（1）CFA molecular sieve（FAZ）was prepared through an alkaline melting method,followed by loading of nano CuO particles onto FAZ to prepare a heterogeneous Fenton catalyst（CuO-FAZ）.The removal experiment results showed that more than 85%of BPA was degraded within 60 minutes,and after five consecutive cycles,BPA removal remained over 70%,the leaching amount of copper ion is 0.23 mg/L.Indicating that the CuO-FAZ not only has superior catalytic performance,but also demonstrated excellent stability.Radical quenching experiment showed that the·OH_（sur）radicals played a primary role in BPA removal.In addition,through the characterization of FTIR,XPS and electrochemistry,it is found that a ligand complex could be formed between the catalyst and BPA,enhancing the generation of·OH_（sur）radicals as well as the reduction of≡Cu²⁺_{（surface）}to≡Cu⁺_{（surface）}.Finally,it is proved that CuO-FAZ has certain application potential in the treatment of industrial wastewater through the treatment of actual coking wastewater.（2）The Cu-Al/FAZ was synthesized based on CuO-FAZ by introducing Al₂O₃.The removal experimental results showed that Cu-Al/FAZ achieved 90%BPA removal under the condition of only adding 40 m M H₂O₂,requiring less than one third of that of CuO-FAZ.Additionally,Cu-Al/FAZ displayed good catalytic efficiency in the initial p H range of 3 to 9.Through XPS,fluorescence and electrochemical characterization,it was discovered that the introduction of Al₂O₃generated a substantial amout of oxygen vacancy（Ov）in Cu-Al/FAZ,which facilitated the interaction between BPA and H₂O₂,ultimately enhancing the BPA removal rate.Moreover,the electron-rich Cu site in the Cu-Al/FAZ aided in the selective conversion of H₂O₂to·OH radicals,thereby improving the utilization efficiency of H₂O₂.（3）In order to further improve the catalytic performance of Cu-Al/FAZ,N-doped Cu-Al-N/FAZ was prepared.The experimental results show that the Cu-Al-N/FAZ can achieve more than 85%BPA removal efficiency after 30 min reaction,with a kinetic constant of 0.063 min^-1,which is 1.7 times that of the Cu-Al/FAZ.Compared with the Cu-Al/FAZ,the Cu-Al-N/FAZ exhibits superior catalytic activity and broader p H applicability,maintaining more than 80%removal at an initial p H of 11.Through XPS,fluorescence and electrochemical characterization,it has been found that the the doping of N element leads to the formation of electron-rich N sites and electron-poor Cu sites in Cu-Al-N/FAZ.Among them,the electron-poor Cu site can promote the formation of the ligand complex between Cu-Al-N/FAZ and BPA,which not only avoids the ineffective decomposition of H₂O₂,but also promotes the reduction from≡Cu²⁺_{（surface）}to≡Cu⁺_{（surface）}in the system.In addition,the pyrrole N doped in Cu-Al-N/FAZ can cooperate with Cu to form Cu-Nx site,which can form charge transfer intermediate after reacting with H₂O₂,thus greatly improving the reaction rate of Fenton process.