Design Of Hierarchical Co-Based Spinel Nano-Hollow Polyhedron Towards Light Activation Of PMS Species And Their Catalytic Degradation Of Enfloxacin

In recent years,under the social background of the rapid development of the pharmaceutical industry,it has been found that water sources are rich in antibiotics in many places.After containing antibiotics in water,it will cause a serious impact on the normal growth of aquatic organisms,and will induce drug-resistant bacteria,which has high toxicity,and they are all difficult to treatment.Because the trace antibiotics in water are not conducive to people's health,which has aroused widespread concern.However,it is difficult to obtain the ideal treatment effect,due to the high cost and pollution of the traditional technology to the treatment of antibiotic wastewater.In recent years,advanced oxidation technology?AOPs?based on activated peroxy-monosulfate?PMS?to generate sulfate radicals has become an Research hotspot.The sulfate radicals generated in the process that have a higher oxidation Capability?E⁰=2.5-3.1 V?,longer free radical lifetime?30-40?s?,and wider pH range.Compared with the homogeneous catalytic system,the use of heterogeneous spinel metal oxide as a catalyst can overcome the problems of secondary pollution of metal ions in the homogeneous catalytic system and difficulty in reuse.In order to improve the catalytic activity of spinel oxide-activated PMS,a light-assisted cobalt-based spinel oxide-activated PMS coupling system was established in this study.A typical fluoroquinolone antibiotic was used as the target pollutant.The micro/nano morphology of the catalyst and its metal ion ratio and type effectively improve the catalytic activity of cobalt-based spinel catalysts to activate PMS.The main research contents are as follows:?1?Using bimetallic organic frame Zn-Co ZIF-67 as the template,Zn_xCo_3-xO₄?0<x?1?were successfully synthesized by calcination at a high temperature.The physicochemical properties of the synthesized catalysts were studied by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.The reaction mechanism of the composite system was studied by transient absorption spectroscopy?TAS?.The results show that the prepared Zn_xCo_3-xO₄ had the monodisperse polyhedral structure,the unique mesoporous structure and the strong visible light absorption.Different ratios of Zn-Co will affect the catalytic activity of Zn_xCo_3-xO₄ Photoelectric properties and catalytic activity.Compared with ZnCo₂O₄??=102.06 ns?and Zn_0.3Co_2.7O₄??=119 ns?,Zn_0.6Co_2.4O₄ has a longer life span of photo-generated carriers??=145.83 ns?.In the composite system of visible light catalysis and PMS oxidation,Zn_0.6Co_2.4O₄ showed the best catalytic activity for 1 hour.The Enrofloxacin?ENR?,a typical fluoroquinolone antibiotic,degradation efficiency of reached81.3%.Electron paramagnetic resonance spectroscopy effectively confirmed the production of SO₄·-and·OH active species in the coupled system.?2?In order to further investigate the effect of element doping on the catalytic activity of cobalt-based spinels,in this section,a ternary metal cobalt-based spinel nano-hollow polyhedron structure was prepared.Prepared with Mg-Zn-Co trimetal ZIF-67 as template.The results showed that the prepared multicomponent spinel MgxZn_1-xCo₂O₄?x=0,x=0.5,x=1?was similar to Zn_xCo_3-xO₄ and had the hollow Nano-Hollow polyhedron structure with unique mesoporous structure and strong visible light absorption.This makes the construction of multi-element spinel under visible light irradiation,Mg_xZn_1-xCo₂O₄ has a higher PMS activation ability,the coupling system to ENR makes ENR in the visible light catalysis and PMS oxidation composite system,the reaction efficiency reached 88.31%in 1 hour.It was shown that the catalytic activity of the ternary metal Mg_0.5Zn_0.5Co₂O₄ with visible light was better than that of the corresponding binary metals ZnCo₂O₄ and MgCo₂O₄.In addition,although metallic cobalt ions have certain biological toxicity,due to the very stable structure of spinel materials,it was difficult for metal ions to enter the water body.When the reaction was detected by ICP instrument for 1 h,the cobalt in the system was only 0.02 mg/l,and the leakage was extremely low,which would not cause secondary pollution to the environment.In this dissertation,the catalytic activity of binary metal and ternary metal cobalt-based spinels to degrade ENR by activating PMS under the visible light irradiation was investigated.The study found that the type of metal and the ratio of metal,and the microstructure of the material have a significant effect on the catalytic activity of cobalt-based spinel.The theoretical mechanism of the structure-activity relationship was studied by means of characterization such as transient absorption spectroscopy.Under the premise of ensuring a high cobalt content,the life of the photogenerated carrier of the cobalt-based spinel can be effectively extended by changing the metal type and proportion,thus enhance the catalytic activity of activated PMS.This study can provide a new idea for the application of visible light-assisted multi-spinel activated PMS to solve the problem of antibiotic contamination.