Degradation Of Tetracycline By Iron-based Organic Frameworks Derivatives And Complexes With Activated PMS

Recently,with the improvement of living standards,the increasing demand for animal protein has led to the extensive use of antibiotics as drugs and growth promoters.Incomplete absorption by animals and inadequate sewage treatment systems makes tetracycline widely available in surface and ground water.Long-term exposure to residual tetracycline can induce a variety of human diseases.Non-homogeneous advanced oxidation based on sulfate radicals is an effective method for treating organic pollutants in water,but traditional iron-based catalysts are challenged by low efficiency,susceptibility to oxidation and agglomeration.Based on these challenges,this paper using iron-based metal-organic frameworks derivative as the target to investigate the enhancement of peroxymonosulfate activation by temperature modulation of the derivatives’surface groups and doping non-metallic atoms to enhance electron transport.In addition,theoretical calculations and experimental results were combined to reveal the catalytic mechanism of peroxymonosulfate and estimating the environmental risks in the degradation of tetracycline.Provides a theoretical basis for the practical application of iron-based metal-organic frameworks derivative.The main points of the study are as follows,（1）MIL-100（Fe）precursors were prepared by three different iron salts as iron sources,which were used as a template to prepare Fe⁰ encapsulated with carbonyl modified carbon by a one-step pyrolysis method under high temperature Ar atmosphere.Fe⁰ as a slow-release source of Fe²⁺enhances the efficiency of peroxymonosulfate.The unique encapsulation structure slows down the oxidation of Fe⁰.The functional groups on the surface of catalysis obtained by temperature modulation as active sites for ¹O₂contributed significantly to the non-radical degradation of tetracycline in the catalytic system.Rich pore structure and large specific surface area of the carbon layer provide a substrate for the dispersion of Fe⁰,which effectively avoids the agglomeration of Fe⁰.In addition,the excellent electron transport properties of the carbon layer improve the activation efficiency of peroxymonosulfate.The Fe⁰ derived from iron-based metal-organic frameworks is less affected by inorganic ions and organic matter,even in natural water.In addition,the performance of the recovered catalysts still remained at a high level after high temperature regeneration,which provides a basis for the practical application of iron-based metal-organic frameworks derivative.Combining density flooding theory and experimental results to propose a degradation pathway for tetracycline,and the toxicity evolution of the intermediate products was evaluated by ECOSAR（Ecological structure activity relationship）.The results show that this system can significantly reduce the environmental risk and provide a guarantee for water safety.（2）The N atoms were doped into the derivatives in the form of endogenous by one-step pyrolysis with MIL-101（Fe）and NH₂-MIL-101（Fe）as precursors.In addition,N atom doping was achieved by co-pyrolysis using g-C₃N₄ as the exogenous N source.On the one hand,the introduction of the N atom improves the stability of iron-based metal-organic frameworks,so that it retains its original structure after pyrolysis;on the other hand,it enhances the electron transfer properties.The doped N atom forms an Fe-N-C electron bond bridge between Fe and C,due to the difference in electronegativity,the local polarization on the Fe-N-C electron bond bridge forms a local electric field,which promotes the electron transfer from C to Fe.The catalyst bonds to peroxymonosulfate through electrostatic interactions and breaks its O-O bond,then coordinating with iron species,which leading to the formation of Fe IV=O,thus significantly improving the activation performance.Compared to the previous work,the degradation efficiency of tetracycline still remained at a high level under conditions where the amount of peroxymonosulfate was halved.ECOSAR assessed that tetracycline and its intermediates have significantly reduced in acute toxicity,developmental toxicity and mutagenicity.It is a promising environmentally friendly catalyst for application in practical wastewater treatment.