Study On The Efficiency And Mechanism Of PPCPs Degradation By PBA Derived Metal Oxides Activated Persulfate

In recent years,advanced oxidation technology based on activating persulfate to produce free radicals has attracted extensive attention.Persulfate activation by transition metal oxides presents the advantages of little external energy cost and simple experiment conditions,which make it one of the most commonly used activation methods at present.In order to further improve the activation efficiency of metal oxides,increasing the active sites of catalysts and improving the electron transfer ability between metals are considered to be effective strategies.In this paper,metal oxides derived from Prussian blue analogues（PBA）were used as heterogeneous catalysts to activate persulfate（PMS）to degrade sulfamethoxazole（SMX）,one kind of Pharmaceutical and Personal Care Products（PPCPs）in water.The results are expected to provide a new idea for the preparation of heterogeneous catalysts.In this paper,the single metal oxide 0.2-Co₃O₄ was prepared by a coprecipitation-etching-calcination procedure,and the tri-metallic oxide Ni_1.5Co_1.5HCF-600 was prepared by a coprecipitation-calcination procedure.The materials were characterized by SEM,TEM,XRD,XPS,nitrogen adsorption and desorption test,FTIR and zeta potential test.The efficiency of SMX degradation by PMS activation,the factors that affected the degradation,the stability of the catalyst,the degradation mechanism and possible degradation pathway of SMX were studied based on the characterization results.The characterization results of 0.2-Co₃O₄ material showed that it was pure Co₃O₄ with rough and porous surface,and retained the typical cubic shape of PBA material,with specific surface area of 27.547 m²/g.The degradation efficiency experiment indicated that the k_obs of0.2-Co₃O₄/PMS system was 4.5 times as that of commercial SP-Co₃O₄.The degradation reaction was influenced by the initial concentration of PMS,catalyst dosage,initial p H,temperature of reaction system,inorganic anions and so on.After the reaction,the leaching cobalt of 0.2-Co₃O₄/PMS system was determined to be 13.3μg/L,meeting relevant national standards.After five cycle experiments,the catalytic performance of 0.2-Co₃O₄ decreased by14.4%.And it should be noted that no significant changes were observed in the morphology of the catalyst before and after use,indicating that 0.2-Co₃O₄ was stable.The study of degradation mechanism revealed that the main active species in 0.2-Co₃O₄/PMS system was SO₄^·-,with a contribution of 83.1%.There were two degradation pathways of SMX in 0.2-Co₃O₄/PMS system,including four degradation products.The characterization results of Ni_1.5Co_1.5HCF-600 material showed that it was a hybrid material which was mainly composed of Ni Fe₂O₄,Co Fe₂O₄,Ni O and Co O.It also had rough and porous surface,and retained the typical cubic shape of PBA material,with specific surface area of 109.71 m²/g.The degradation efficiency experiment indicated that the k_obs of tri-metallic oxide Ni_1.5Co_1.5HCF-600/PMS system were 6.1 times,2.3 times and 3.0 times as that of single metal oxide SP-Co₃O₄,bimetallic oxide Ni HCF-600 and Co HCF-600,respectively.The degradation reaction was influenced by the initial concentration of PMS,catalyst dosage,initial p H,temperature of reaction system,inorganic anions and so on.After the reaction,the leaching iron was 64.0μg/L,the leaching cobalt was 13.1μg/L,and the leaching nickel was 15.4μg/L,all meeting relevant national standards.After five cycle experiments,the catalytic performance of Ni_1.5Co_1.5HCF-600 still maintained high catalytic activity.Besides,no significant changes were observed in the morphology of the catalyst before and after use,indicating that Ni_1.5Co_1.5HCF-600 was stable.The study of degradation mechanism revealed that the main active species in Ni_1.5Co_1.5HCF-600/PMS system were SO₄^·-and ¹O₂,with contributions of59.5%and 40.5%respectively.The degradation mechanism involves the synergistic effects of tri-metal.There were four degradation pathways of SMX in Ni_1.5Co_1.5HCF-600/PMS system,including seven degradation products.In conclusion,these two materials derived from PBA could achieve high efficiency when used as heterogeneous catalysts activating PMS.The trimetallic oxide Ni_1.5Co_1.5HCF-600showed higher catalytic activity and good stability,which would broaden the idea of heterogeneous catalyst preparation in the future.