Preparation Of Modified Prussian Blue Analogues And Their Performance In Adsorption And Degradation Of Methylene Blue

As an advanced oxidation technique（AOPs）,Fenton method mainly relies on the degradation of organic pollutants by strong oxidizing radicals,so the design and synthesis of catalysts with high catalytic activity,good stability,energy saving and environmental protection is the key to solve water pollution.In this paper,the cobalt-iron Prussian blue analogs（PBAs）were subjected to H₂O₂ modification and heat treatment with different atmospheres as a starting point,focusing on the adsorption capacity of each material for methylene blue（MB）and the degradation of MB in each Fenton catalytic system.The main studies are as follows:1)The cobalt-iron Prussian blue analogs were prepared by hydrothermal synthesis,and the contents of sodium citrate（TSCD）,polyvinylpyrrolidone（PVP）addition,hydrothermal temperature and hydrothermal time were regulated.The optimum preparation conditions were determined by XRD,TEM characterization and performance testing,and Co-PBA-0was successfully prepared with TSCD=0.1250 mmol·L^-1 and hydrothermal reaction at 120℃for 24 h.The dominant crystalline surface of Co-PBA-0 was（2 2 0）with polyhedral morphology,and 68%MB decolorization rate could be achieved within 50 min.2)Co-PBA-0 was used as a precursor and Co-PBA-30 was obtained by using 30%H₂O₂ modification for 30 min.99%MB decolorization was achieved in 20 min with an activation energy of 30.23 k J·mol^-1.The changes in the physicochemical properties of the material before and after H₂O₂ modification were compared by various characterization methods.The results showed that the percentage of Co（II）increased after H₂O₂ treatment.In addition,the factors influencing the performance test were also investigated.Finally,the electron paramagnetic resonance（EPR）radical detection and radical burst experiments were conducted to verify that the main active species of Co-PBA-30 catalyzed H₂O₂oxidation is·OH,and the degradation pathway of MB was postulated.3)Co-PBA-0 was subjected to heat treatment in air,N₂ and Ar atmospheres using a self-sacrificing template,and the changes in physicochemical properties and performance of the products at different temperatures were investigated.Among them,the air calcination produced metal oxides,but the sintering phenomenon affected the material properties.In contrast,both N₂ and Ar calcinations at 610°C successfully produced nitrogen-doped carbon-coated Co Fe alloys with a core-shell structure,which showed high adsorption and catalytic properties.In particular,the calcination product N₂-610 at 610°C under N2atmosphere could achieve 95%decolorization of MB within 30 min and still maintain 90%decolorization after four cycles.The EPR assay and free radical burst experiments demonstrated that the main active species catalyzing the oxidation of H₂O₂ is·OH,and the degradation pathway of MB was postulated.