Study On The Performance And Mechanism Of Carbon-based Single-atom Cobalt Catalyst For The Activation Of Peroxymonosulfate For The Degradation Of Norfloxaci

Antibiotics have been widely used for human health,animal husbandry,agricultural control and so on.However,the water pollution caused by antibiotics has attracted increasing attention all over the world.Norfloxacin（NOR）is a typical fluoroquinolone antibiotic,and its concentration in water environment has reached ng/L～μg/L.Due to the antibacterial activity,traditional biochemical treatment processes have limitations in the treatment of antibiotic wastewater.Advanced oxidation technology based on peroxymonosulfate（PMS）has been proved to be an effective method for the treatment of antibiotic wastewater.In addition to the strong oxidizing free radicals such as hydroxyl radical（^·OH）and sulfate radical(SO4^·-),the activation of PMS can also generate singlet oxygen（¹O2）,metastable PMS/catalyst complexes and hypervalent metals.Compared with free radicals,nonradical oxidation of pollutants shows higher selectivity and practical application potential.Carbon-based single-atom catalysts（SACs）have demonstrated their potential to degrade pollutants via nonradical pathways.Single-atom cobalt（Co）catalysts are considered to be desirable for PMS activation to degrade pollutant because of the maximum atomic utilization efficiency and the highest reactivity of Co atom.However,previous researches mostly underlined the degradation performance of pollutants.The nonradical pathway and mechanism of the activation of PMS at carbon-based single-atom Co sites are still ambiguous,and the actual active species involved in pollutant degradation have not been explored deeply enough.Therefore,this study investigated deeply the nonradical pathway and mechanism of NOR degradation by activated PMS with carbon-based single-atom Co catalyst,and the actual active species involved in NOR degradation.The main research contents are as follows:（1）Co _SA-N₃-C efficiently activates peroxymonosulfate for norfloxacin degradation and mechanism study.Firstly,a carbon-based single-atom Co catalyst with Co-N3 coordination（Co SA-N3-C）was synthesized by simple one-step pyrolysis using sustainable sodium alginate as a precursor,and was used to activate PMS for NOR degradation.The low-coordination Co-N3 configuration in Co SA-N3-C has excellent electronic structure,which can enhance the electronic interaction between single-atom Co and PMS molecules,thus promoting the activation of PMS.Nonradical Co（IV）=O and electron transfer pathway in Co SA-N3-C/PMS/NOR system were the main active species and pathways that induced the degradation of NOR.In practical application,Co SA-N3-C/PMS system showed a wide range p H adaptability and good cycling stability,which could achieve complete degradation of other pollutants,and possessed higher degradation performance in a variety of actual water substrates.（2）Co _SA-N₃/B-C efficiently activates peroxymonosulfate for norfloxacin degradation and mechanism study.Based on the excellent catalytic activity of single-atom Co sites in Co SA-N3-C,a biheteroatom-doped Co SA-N3/B-C catalyst was successfully prepared by introducing B atoms and used to activate PMS for NOR degradation.Further doping of B atoms effectively optimized the electronic structure of Co-N3 site and promoted the activation of PMS.Compared with the above Co SA-N3-C,Co SA-N3/B-C achieved the completed degradation of NOR within 20 min,showing higher catalytic activity.Similarly,the nonradical Co（IV）=O and electron transfer play a dominant role in NOR degradation.Co SA-N3/B-C/PMS system showed better practical application potential,better wide range applicability and excellent cycling stability.In this paper,for the first time,the active species produced during PMS activation and involved in pollutant degradation at the carbon-based Co-N3 site were clearly explored.Based on the excellent electronic structure of low coordination Co-N3 configuration,the biheteroatom-doped Co SA-N3/B-C was further applied in activating PMS to degradate of pollutants,which expaned its catalytic application range.This study offers new insights for rational design of carbon-based single atom catalysts with appropriate coordination structure and has significant implications for the persulfate-mediated pollutant elimination processes.