Iron-Based Nanocomposites For Antibiotic Degradation In The Water Environment

Antibiotics such as ciprofloxacin（CIP）and Sulfamethazine（SMT）have become serious emerging pollutants in water environment.Because the continuous discharge of antibiotics produces sustainable ecotoxicological effects on animals,plants and microorganisms in the environment,and seriously threatens human health,degradation of antibiotics is of great significance to protect the environment.In this paper,the transition metal element iron and carbon materials are compounded,and the magnetic spherical iron-based nano materials and hollow tubular iron-based monatomic catalysts are synthesized respectively through the synthesis scheme design,so as to realize the efficient degradation of antibiotics.At the same time,we conducted a series of studies on the properties of the synthesized catalysts,and found that they have good enzyme-like activity and catalytic degradation performance.The specific work contents are as follows:（1）Firstly,we synthesized magnetic Fe₃O₄ by solvothermal method.Then a layer of polydopamine is wrapped to protect the magnetic core and the carbon layer of the shell is modified by iron source and nitrogen source.Finally,the composite catalyst Fe₃C/Fe₃O₄@NC was obtained by calcination:Taking magnetic Fe₃O₄ as the core and the nitrogen doped carbon supported by Fe₃C is used as the shell layer.The catalyst not only has good peroxidase and oxidase performance,but also has good Fenton-like degradation performance.In the presence of 1 mM potassium persulfate and 0.1g L^-1 Fe₃C/Fe₃O₄@NC,the removal rate of ciprofloxacin can reach about 87.0%after 20 min,and the kinetic rate constant is 0.0532 min^-1,w which is about three and seven times that of Fe₃O₄ and Fe₃O₄@NC,respectively.After five cycles,the removal rate of ciprofloxacin still reached 67.1%.Through quenching experiment,it was found that sulfate radical and hydroxyl free were the main active oxygen components involved in Fenton-like reaction.At the same time,we simulated the actual water quality and evaluated the practical application performance of Fe₃C/Fe₃O₄@NC composite catalyst.In wastewater,common organic compounds reduce the degradation rate to some extent,but inorganic ions have a much smaller effect.These results indicate that the Fe₃C/Fe₃O₄@NC composites have good stability and reusability.The excellent magnetic response ensures that Fe₃C/Fe₃O₄@NC catalyst can achieve efficient heterogeneous separation by applying magnetic field,which is a promising technology for the degradation of CIP by oxidizing PMS.（2）To sum up the problems and experience of the first system,We use carboxylated carbon nanotubes as the carbon carrier,and the nitrogen source decomposes and attacks the carboxylated carbon nanotubes under high temperature.Nitrogen atoms replaced part of the carbon atoms or carboxyl functional groups in the carbon network,and the metal source was anchored and the aggregate growth was restricted.Finally,a catalyst with more stable structure and excellent performance was synthesized.A series of metal-supported nitrogen-doped carbon nanotubes（M-NCNTs）single atom catalysts（Cr,Mn,Fe,Co and Ni）were successfully synthesized by a simple method.Spherical aberration-corrected high-angle annular dark-field scanning transmission microscopy and extended X-ray absorption fine structure spectroscopy confirmed the atomic dispersion of Cr,Mn,Fe,Co and Ni in nitrogen-doped carbon nanotube carriers,and that all(M-NCNTs contained Porphyrin-like MN4 sites.The results of inductively coupled plasma emission spectroscopy show that the method can be used to produce high metal-loaded monatomic catalysts with a small number of metal sources to a large extent,and all metals can easily reach 2.00 wt.%.Fe-NCNTs with 2.23 wt.%metal loading not only had good activities of oxidase like,peroxidase and glucose oxidase,but also had good electrochemical catalytic performance.Among all M-NCNTs,Fe-NCNTs had the best catalytic degradation performance of Sulfamethazine.Fe-NCNTs/PDS system was suitable for acidic and neutral environments and had higher PDS utilization rate,and its kinetic rate constants were about 13 times of CNTs and 2 times of NCNTs.The influence of anions and different water samples on the removal of sulfamethazine and the degradation path of pollutants were investigated.The results proved that Fe-NCNTs/PDS system can be used for reference in practical wastewater treatment.