Preparation Of CeO₂-based Composites By High Temperature Micro-explosion Method And Their Photo-Fenton Properties

Hydrothermal method,precipitation method and sol-gel method are often used to prepare CeO₂-based photo-Fenton materials,but the particles of nanomaterials prepared by the above methods are relatively large.In this paper,a new preparation method-high temperature micro-explosion method is used to obtain CeO₂-based photo-Fenton materials with finer nanoparticles,larger pore size and porous morphology.As a photo-fenton material with excellent oxygen storage capacity,chemical stability and stable Ce³⁺/Ce⁴⁺redox properties,Cerium dioxide（CeO₂）,which are conducive to the formation of abundant oxygen vacancies,has been widely studied.However,the photo-fenton effect of CeO₂ is still not ideal due to the wide band gap.Therefore,doping,semiconductor coupling and load are often used to overcome these shortcomings to improve the performance of photo-fenton.However,these existing modification methods are often complicated,so this paper attempts to adopt a new preparation method to modify CeO₂.（1）Using pectin as carbon source,cerium nitrate as cerium source and sodium tungstate as tungsten source to prepare the gel precursor in one step by High temperature microburst method.After high temperature calcination,CDs-W/CeO₂ heterojunction photo-fenton material was constructed in situ and used for tetracycline degradation（20 mg/L）.It was characterized by XRD,XPS,SEM,UV-vis DRS,EIS and ESR.Among all the CDs-W/CeO₂ composite photo-fenton materials,the CDs-W/CeO₂ composite（CWC-3）with 7%W doping has the highest degradation rate of tetracycline.When the concentration of catalyst in solution reaches20 mg,the degradation rate of substrate is 85%in 30 min.The degradation rate constant of CDs and W is 62 times that of CeO₂,indicating that the doping of CDS and W successfully improves the photo-fenton activity of semiconductor materials.The optimum concentration of catalyst material is 20 mg,the concentration of H₂O₂ is 4 m M,and the solution p H is 3.After three cycles,the degradation rate of CWC-3 can still reach 84%,which indicates that CWC-3composite can be used for repeated degradation and has strong stability.The active groups in the catalytic system were evaluated by adding quench agents.Hydroxyl radical（·OH）were the main active groups in the system.Finally,the possible degradation mechanism was proposed.（2）Using a similar method,a series of CDs-Fe/CeO₂ composite photo-Fenton materials were constructed with iron nitrate as the iron source and other experimental conditions unchanged,and used for the degradation of tetracycline（20 mg/L）.Among all the CDs-Fe/CeO₂composite photo-Fenton materials,the CDs-Fe/CeO₂ composite material（CFC-2）with 4%Fe doping has the highest degradation rate for tetracycline.When the catalyst concentration in the solution reaches 20 mg,the H₂O₂ concentration is 6 m M,and the p H of the solution is 2,the photo-Fenton effect of the system is the best.The degradation rate of the substrate is 87%in30 min,which indicates that the doping of CDs and Fe successfully improves the photo-Fenton activity of the semiconductor material.After three cycles of use,the degradation rate of CFC-2can still reach 85%,indicating that CFC-2 has strong stability.The active groups in the catalytic system were evaluated by adding quenchers,and s hydroxyl radicals（·OH）were the main active groups in the system.Finally,the possible degradation mechanism was proposed.