The Fabrication Of Three-dimensional Porous Transition Metal/Nitrogen Doped Carbon Fiber Nanocomposite Catalyst And Its Activated Persulfate Properties

With the rapid development of industry,water shortage and pollution become serious.In particular,water pollution caused by various organic pollutants becomes one of the most prevalent and serious threats to human health and ecosystems.Due to its chemical stability,p-nitrophenol（PNP）is difficult to degrade in wastewater.Advanced oxidation methods（AOPs）are widely used for the degradation of organic pollutants due to their high efficiency,green and easy operation.Among them,activation of peroxymonosulfate（PMS）to generate efficient reactive oxygen species(·OH,¹O₂,SO₄^·-etc.)has good catalytic activity for pollutant degradation and is considered as a promising strategy for treating the water pollution.In order to activate PMS,transition metals activated PMS are widely studied for their low energy consumption and ease of operation in practical applications.Although the catalytic performance of homogeneous metal catalysts is good,the secondary pollution caused by metal ions poses a potential threat to human health and also increases the operating cost.Heterogeneous metal catalysts show great potential,but still have disadvantages such as insufficient catalytic performance,poor dispersion,easy agglomeration,limited surface active sites,and poor structural stability.Carbon materials are widely used to activate PMS due to their advantages of environmental friendliness,large specific surface area,and high adsorption capability,but they still have the disadvantage of low catalytic efficiency.In order to overcome the above disadvantages of advanced oxidation techniques,transition metal nanoparticles were immokilied on 3D support for the efficient degradation of PNP.（1）A cobalt oxide nanoparticles（Co O_x NPs）/cobalt-nitrogen co-doped（cobalt single atom）carbon fiber composite catalyst（Co O_x-Co SA@N-C）was constructed by a facile strategy of pyrolysis of three-dimensional metal-polysaccharide corrdination precursors and applied to the activated PMS degradation of PNP.The Co O_x-Co SA@N-C catalyst has large specific surface area as well as a porous structure,which can increase the active sites.the Co O_x-Co SA@N-C catalyst exhibited excellent catalytic ability in PMS activation and could efficiently degrade PNP in a wide p H range（3.0～9.0）with a total organic mineralization rate of 70.1%.It showed good catalytic activity for a wide range of organic pollutants.Compared with N-C（49.05%）and Co SA@N-C（79.5%）,the Co O_x-Co SA@N-C catalyst showed the highest degradation efficiency（97.1%）for PNP,indicating that the synergistic effect of Co O_x NPs and Co-N_xpromoted the excellent PMS activation and pollutant degradation performance of the Co O_x-Co SA@N-C catalyst.The presence of·OH,¹O₂,SO₄^·–and O₂^·–species in the reaction system was found by radical trapping experiments,suggesting the existence of both radical and non-radical processes in this catalytic system,where ¹O₂ and SO₄^·–play a major role in the catalytic reaction.（2）A novel cobalt-iron bimetallic oxide quantum dots/nitrogen-doped carbon fibers（NCFs）composite catalyst（Co Fe₂O₄ QDs/NCFs）was successfully prepared by a simple method.The catalyst has a three-dimensional porous structure and its bimetallic oxide quantum dots are uniformly distributed,which is conducive to exposing more active sites for efficient activation of PMS for the degradation of PNP.Compared with Fe₃O₄ QDs/NCFs（64.6%）,NCFs（10.4%）and commercial Co Fe₂O₄（10.4%）,the Co Fe₂O₄ QDs/NCFs catalyst showed the best PNP degradation rate（95.0%）,indicating that the coupling between Co Fe₂O₄ QDs and NCFs and the synergy between Co and Fe could significantly improve the activation of PMS.Similarly,the radical capture experiments verified the presence of·OH,¹O₂,SO₄^·–and O₂^·–species in the reaction system.The mechanism of Fenton-like degradation of PNP by Co Fe₂O₄ QDs/NCFs catalysts was proposed.The Co Fe₂O₄ QDs/NCFs catalysts have high catalytic activity,good structural stability and recyclability.