Research And Application Of Corn Stover Magnetic Biochar Activated Persulfate To Degrade Bisphenol A

The biochar loaded with CoFe₂O₄ nanoparticles（CoFe₂O₄/HPC）fabricated by pyrolysis exhibited strong magnetic property,hierarchical porous and graphitized structure.CoFe₂O₄/HPC showed much better bisphenol A degradation than CoFe₂O₄ in presence of peroxymonosulfate.The graphitized structure and the synergistic effect between graphitized structure and CoFe₂O₄ were found to be responsible for the superiority of CoFe₂O₄/HPC among all the other catalysts.The prominent role including radical way mainly contributed by SO4·– and non-radical way achieved by 1O2,and the secondary role of electron transfer way proceeded by graphitized structure were uncovered.The processes such as redox between Co（III）/Co（II）and Fe（III）/Fe（II）,the reduction of Fe（III）by O2·–,and the participation of C=O in 1O2 production were significant to the excellent catalytic performance of CoFe₂O₄/HPC.Considering its excellent separation,stability,adaptability and reusability,CoFe₂O₄/HPC opened up a novel way to develop green catalyst to activate PMS for organic pollutants degradation.（1）Using the pyrolysis method,using corn stalks as raw materials,adding potassium bicarbonate and CoFe₂O₄,successfully synthesized the heterogeneous catalyst CoFe₂O₄/HPC with rich graphitized porous structure.The uniform pores can be seen under the microscopic morphology observed by scanning and transmission electron microscopy,and they are successfully embedded/buried in the material surface/hole.The surface area of the material is 664.8 m2 g-1,and the loading amount of CoFe₂O₄ is10% by mass.（2）CoFe₂O₄/HPC has high efficiency activation performance.Under the neutral condition of pH=7.4（boric acid buffer）,add 0.5 g/L of persulfate and 0.05 g/L of catalyst CoFe₂O₄/HPC,10 mg/L of bisphenol A will be degraded within 8 minutes complete.In addition,the reaction efficiency can be further improved when the dosage of peroxymonosulfate,the dosage of catalyst,the reaction temperature or the pH value of the solution is slightly decreased.The degradation effect of the system in the presence of anions and humic acid is not too much affected,and the reaction system has a wider pH acceptance range.（3）Through EPR and quencher experiments,it is concluded that the main oxidative active species in this system are SO4·– and 1O2,as well as an electron conduction mechanism.Other ROS such as ·OH and O2·– also make a certain contribution to the degradation reaction.In CoFe₂O₄/HPC and PMS systems,the graphitized structure and the presence of Fe and Co elements can improve the catalytic performance of the catalyst.The redox,graphitized structure between Co（III）/Co（II）and Fe（III）/Fe（II）and the synergistic effect between CoFe₂O₄ nanoparticles,C=O participation in the generation of free radicals and other processes are an important part of the excellent catalytic performance of CoFe₂O₄/HPC.（4）The reaction path of CoFe₂O₄/HPC and PMS system to degrade bisphenol A was measured by GC-MS experiment.The attack of SO4·– and 1O2 breaks the C=C bond in the middle of the biphenyl ring and degrades bisphenol A to form phenolic substances.Some intermediates are further degraded by dehydrogenation to generate anthraquinones and cyclic ketones.Another part of the intermediates is converted into products with a molecular weight greater than BPA due to the oxidative coupling reaction.These large molecular mass intermediates continue to degrade through the ring-opening reaction.These intermediates are finally cracked into easily degradable small molecular alkanes,which are less toxic than bisphenol A.Finally,these alkanes are gradually mineralized into CO2 and H2 O in the presence of active oxygen.（5）It is concluded that CoFe₂O₄/HPC has good stability and reusability through 5consecutive cycles of degradation test and measurement of metal ion leakage.Moreover,CoFe₂O₄/HPC has good activation performance for PMS.It can degrade a variety of organic pollutants such as BPA,tartrazine,sulfadiazine,phenol and p-hydroxybenzoic acid,and contains many complex components of tap water,Jialu River,Yellow River,Longhu and in different actual water environments such as Xianghu,it still shows excellent activation performance.Therefore,CoFe₂O₄/HPC is considered to be a very promising and persistent green catalyst with lower cost,turning corn stalks into valuables,and replacing pure CoFe₂O₄ for activating peroxymonosulfate,which is a very promising and persistent green catalyst for the restoration of organic matter.