Study On The Catalytic Performance Of Cu-doped Fe@Fe₂O₃ In Heterogeneous Electro-Fenton Process For Tetracycline Degradation

As one of the most widely used antibiotics,tetracycline（TC）has brought residual contaminants to the environment,which has caused huge threatens to human health.Electro-Fenton process（EF）,one of the Advanced oxidation processes in wide use,is a hot research subject due to its efficient oxidation and low risk of second pollution.Heterogeneous electro-Fenton process（HEEF）can help avoid the cost and decreased activity problem in the transportation,storage and application of activated catalysts and H₂O₂.In this work,Cu-doped Fe@Fe₂O₃（CFF）core-shell nanoparticles was synthesized via a two-step reduction method and a two-hour aging process.CFF was characterized by scanning electron microscope（SEM）,transmission electron microscopy（TEM）,scanning transmission electron microscopy mapping（STEM-mapping）,X-ray diffractometer（XRD）and X-ray photoelectron spectroscopy（XPS）.From the results of characterization,the CFF nanoparticles are composed of abundant spherical nanoparticles with the diameter around 20–100 nm,the core-shell structure of which was also proved（the CFF nanoparticle containing a Fe/Cu nanoparticle core and a layer of iron and copper oxide shell（Fe₂O₃,Cu₂O and Cu O））.CFF was combined with carbon nano-tube（CNT）and coated on Ni foam in order to fabricate the CFF/CNT composite cathode.The composite cathode was applied in the HEEF system for TC degradation.Different systems were conducted for comparison and the HEEF system with CFF/CNT cathode showed higher TC degradation efficiency,more thoroughly mineralization and greater·OH yields.Influence factors were optimized,and under the optimized operation,98.1%TC degradation efficiency within 2 h were achieved.Combining the XPS and radical trapping experimental results,it was proved that the HEEF system was an electro-chemical advanced oxidation process containing heterogeneous electro-Fenton and Fenton-like process,anode oxidation and homogeneous electro-Fenton reactions.Additionally,based on the identification of main representative by-products,plausible pathways for the mineralization of TC in aqueous solution by·OH was speculated.·OH radicals,as the major active species,attacked TC molecules,leading to their gradual degradation and complete mineralization to H₂O,CO₂ and inorganic ions.This work presented an overall assessment of the application potential of CFF/CNT composite cathode in the HEEF process on TC removal.This assessment was supported by mineralization capacity,recyclability and the application in actual pharmaceutical wastewater degradation.89.8%mineralization ratio within 6 h was achieved.Good recyclability and stability of CFF were proved for the nearly 100%TC removal efficiency in the first 6 recycles,low Fe（II）concentration in the system and free risk of secondary pollution of heavy metals.Lastly,actual wastewater application experiment was conducted with the pharmaceutical wastewater sample from Liuyang Bio-medicine Garden,in Hunan Province,China.