Mechanism Study On The Degradation Of Tetracycline In Water By Fe²⁺/Ni-Fe PBA Based Heterogeneous Photo-Fenton Process

With the improvement of human quality of life and the development of industry,antibiotics have been used more and more in all aspects,and the consequent pollution has become more and more serious.In recent years,photo-Fenton technology has been widely used in the degradation of tetracycline due to its ability to rapidly and efficiently decompose and even mineralize organic pollutants.Prussian blue and its analogs（PBAs）are simple cubic-structured metal-organic frameworks（MOFs）that have attracted the attention of researchers due to their special thermal properties and unique reactivity.In this study,low-cost and non-toxic Ni-Fe PBA was selected as the research object,and Ni-Fe PBA was modified by doping with ferrous ions to improve its photo-Fenton catalytic degradation performance of tetracycline.X-ray diffraction（XRD）and Fourier Transform infrared spectroscopy（FI-IR）confirmed the successful synthesis of Ni-Fe PBA.The XRD results showed that the doping of ferrous ions did not change the crystal structure of Ni-Fe PBA.FI-IR confirmed the formation of Ni-C≡N-Fe bond and Fe（II）-C≡N-Fe（III）bond in Fe²⁺/Ni-Fe PBA.Fe²⁺/Ni-Fe PBA was observed by scanning electron microscopy（SEM）to be composed of many fine particles,and energy dispersive X-ray spectrometer（EDX）results showed that the elements in the catalytic material were uniformly distributed.The N₂ adsorption-desorption curves confirmed the mesoporous structure of Fe²⁺/Ni-Fe PBA.The analysis of specific surface area and pore size distribution shows that Fe²⁺doping can obtain catalytic materials with higher specific surface area and larger pore size.X-ray photoelectron spectroscopy（XPS）analysis results show that both Ni³⁺/Ni²⁺and Fe³⁺/Fe²⁺valence states exist in Fe²⁺/Ni-Fe PBA.In this study,Fe²⁺/Ni-Fe PBA has a good degradation effect on tetracycline（TC）.Under the experimental conditions of TC concentration of 20 mg/L,H₂O₂concentration of 20 m M,catalyst dosage of 0.2 g/L,and temperature of 25°C,Ni-Fe PBA can only degrade 71%of TC during 60 min,while Fe²⁺/Ni-Fe PBA can degrade91%of TC during 60 min.Further,radical quenching experiments and electron paramagnetic resonance（EPR）experiments showed that the oxidation process mediated by free radicals and non-radical pathways jointly promoted the degradation of TC.The·OH mediated radical pathway plays a dominant role,while ¹O₂ and O₂·^-play a relatively minor role.The performance of Fe²⁺/Ni-Fe PBA photo-Fenton degradation of TC has little change in a wide p H range（p H=4～10）,and the interference test of inorganic ions shows that various inorganic ions(Cl^-,SO₄^2-,CO₃^2-)have different effects on the catalytic effect.The recycling experiments proved that Fe²⁺/Ni-Fe PBA had good reusability.Meanwhile,the catalytic performance of Fe²⁺/Ni-Fe PBA catalytic material applied to actual water is also investigated.In this study,Fe²⁺-doped Ni-Fe PBA was prepared by simple co-precipitation method,and the heterogeneous catalytic mechanism of Fe²⁺/Ni-Fe PBA in the photo-Fenton system was elucidated.