Preparation And Catalytic Performance Of Attapulgite Based Catalysts Supported By Bimetallic Oxides

In this paper,two kinds of composite catalysts were prepared by hydrothermal method using attapulgite（ATP）modified by graphene oxide（GO）as support and various metal oxides as active substances:Fe₂O₃-Cu O/r GO-ATP and Fe₂O₃-Co₃O₄/r GO-ATP,with methylene blue（MB）and tetracycline（TC）as target pollutants.The catalytic properties of these two catalysts were studied.The research content mainly includes the following three aspects:（1）GO was prepared by an improved Hummers method and mixed with attapulgite to obtain composite support.The composite catalyst Fe₂O₃-Cu O/r GO-ATP was prepared by hydrothermal method.The composition,structure and morphology of the composite material were characterized by SEM,FT-IR,XRD,XPS and Raman.The single factor control variable method was used to study the catalytic performance of the catalyst,the reusability and the change of solution absorption spectrum during the treatment process were investigated,and the kinetic model was determined.The experimental results showed that the optimal reaction conditions for TC degradation with this catalyst were temperature 60℃,catalyst dosage 1 g/L,p H 8,rotation speed10 r/min,aeration intensity 1 L/min and initial solution concentration 50 mg/L.Under these conditions,the TC degradation rate reached 94.51%.The optimum reaction conditions for the degradation of MB with this catalyst are as follows:temperature60℃,catalyst dosage 1 g/L,p H 10,rotation speed 20 r/min,aeration intensity 1L/min and initial solution concentration 50 mg/L.Under these conditions,the degradation rate of MB is as high as 99.87%.the reuse experiment results show that the catalyst has good recycling applicability.The absorption spectrum changes of the two organic compounds at different times of degradation were investigated.It was found that the characteristic peaks of the two organic compounds gradually weakened with the progress of the reaction,and no new peaks appeared,indicating that the macromolecular structure had been destroyed.The kinetic study showed that the degradation of both pollutants was more consistent with the second-order kinetic model.（2）The composite catalyst Fe₂O₃-Co₃O₄/r GO-ATP was prepared by one-step hydrothermal method by loading bimetallic oxides Fe₂O₃and Co₃O₄on r GO-ATP support.The composite catalyst Fe₂O₃-Co₃O₄/r GO-ATP was characterized by SEM,FT-IR,XRD and XPS.The results showed that the metal oxides were successfully loaded on the surface of the support.The single factor control variable method was used to study the catalytic performance of the catalyst,analyze its recyclability,investigate the change of absorption spectrum at different time during the degradation process,and determine the degradation kinetics model.The results showed that the optimal reaction conditions for TC degradation were temperature 60℃,catalyst dosage 0.8 g/L,p H 7,rotation speed 10 r/min,aeration intensity 1 L/min and initial solution concentration 50 mg/L.Under these conditions,the TC degradation rate was94.06%.The optimum reaction conditions for the degradation of MB with this catalyst were as follows:temperature 60℃,catalyst dosage 1 g/L,p H 8,rotation speed 20r/min,aeration intensity 0.6 L/min,initial solution concentration 100 mg/L.Under these conditions,the degradation rate of MB reached 98.38%.It is found that the catalyst has good reusability through repeated use.The absorption spectra of the two kinds of organic matter were measured at different time of degradation.The characteristic peaks of the two kinds of organic matter were weakened and no new peaks appeared,indicating that the catalyst had a good degradation effect on the two kinds of pollutants.The kinetic study showed that the degradation of the two pollutants was more consistent with the second-order kinetic model.（3）The degradation mechanism of Fe₂O₃-Co₃O₄/r GO-ATP on two kinds of pollutants was investigated.It was found that hole electrons played a leading role in the system,and superoxide radicals were secondary species.Based on the determination results of LC-MS,the degradation intermediates of TC and MB and their possible paths were speculated.