Rapid Detection Of Mecury Ions And Kanamycin And Efficient Removal Of Tetracycline Antibiotics In Aqueous Solution

With the continuous development of human society,people are polluting the environment while creating a better life,among which water pollution seriously threatens the survival and development of human beings.As typical pollutants,heavy metals and antibiotics pose a great threat to human health and ecological environment in aqueous solution.Therefore,it is a very important task to seek simple,rapid and low-cost detection methods,and efficient and green removal methods.In recent years,the colorimetric method with fast and simple,and the advanced oxidation technology with high efficiency and environmentally friendly have gradually become a research hotspot.Gold nanoparticle（AuNPs）,as a metal nanomaterial,has excellent optical properties and easy surface modification,which makes it a promising application in rapid colorimetric detection.In addition,when the size of metal particles is reduced to the atomic level,the surface free energy increases dramatically and the surface activity increases accordingly,which can achieve 100%atomic utilization efficiency.Therefore,single^-atom catalyst（SAC）has received extensive attention in the field of catalysis.In this paper,by using AuNPs and SAC,firstly,AuNPs was systematically used to construct a series of colorimetric detection methods,further single^-atom Co catalyst was creative applied to the efficiently persulfate activation catalytically degrades pollutants.We hope this work can provides new methods and techniques for controlling heavy metals and antibiotic in water pollution.Specific as follows:The first section developed and constructed a series of sensitive and efficient Hg²⁺ colorimetric methods based on AuNPs in aqueous solution.Firstly,the selective Hg²⁺ detection method was constructed based on the antiaggregation of AuNPs in the presence of dithiothreitol.When dithiothreitol which pre^-added with Hg²⁺ added to the AuNPs solution,the addition of Hg²⁺inhibited AuNPs aggregation induced by dithiothreitol due to the formation of Hg²⁺-S bonds,so as to achieve the detection purpose.The change of absorbance ratio(A₆₅₀/A₅₂₅)was linearly correlated with Hg²⁺ concentration.Under the optimal conditions,the detection range of the visual detection method is 0.10.5 μM and 0.5-5 μM,and the lower limit of detection（LOD）is 24 nM.Secondly,in order to further improve the detection performance of AuNP-based visual method for Hg²⁺,a visual detection method the anti-aggregation of AuNPs in the presence of thiobarbituric acid was constructed.Under the optimal conditions,the detection range of the colorimetric detection method is 0.01-2μM and 2-30 μM,and the lower LOD is 2.4 nM.The above visual detection methods show good selectivity,which does not affect the detection method in the detection system containing other metal ions.The detection results of Hg²⁺in tap water,pond water and lake water are consistent with the results of AAS.Compared with other detection methods,the visual detection methods constructed in this experiment has the advantages of simple pretreatment,low cost,facile detection,simple operation and good selectivity,which provides a new method for the detection of Hg²⁺ in actual water.The second section detailedly described the construction of a series of rapid and efficient kanamycin colorimetric methods based on the hydrogen-bonding recognization of functionalized AuNPs.Firstly,the chitosan functionalization AuNPs（chitosan-AuNPs）probe was prepared by electrostatic adsorption.When kanamycin was added to the chitosan-AuNPs probe,the hydrogen-bonding interaction between kanamycin and chitosan caused the aggregation of AuNPs.The absorption peak was red-shifted and the color changed,and the concentration of kanamycin was linearly correlated with the absorbance ratio(A₆₅₀/A₅₂₀).Under the optimal conditions,the detection range of the visual detection method is 0.001-40 μM,and the lower LOD is 8 nM.Secondly,in order to further improve and study the AuNP-based colorimetric method for detecting kanamycin.Different from the above method,in this method,6Thioguanine functionalization AuNPs（6-Thioguanine^-AuNPs）probe was prepared by Au-S covalent bond.When kanamycin was added to the 6Thioguanine^-AuNPs probe,the hydrogen-bonding interaction between kanamycin and 6-Thioguanine caused the aggregation of AuNPs.The concentration of kanamycin was linearly correlated with the absorbance ratio(A₆₂₀/A₅₂₀).Under the optimal conditions,the detection range of the visual detection method is 0.005-0.2 μM and 0.2-18 μM,and the lower LOD is 1.8 nM.The above methods detection of kanamycin in tap water,drinking water,lake water,pond water,milk and urine was consistent with HPLC.In this study,the hydrogen bond recognition of functionalized AuNPs was used to detect kanamycin in water with the advantages of simple,rapid,cheap and reliable,providing a new method for AuNPs-based colorimetric detection of antibiotics or other organic compounds.In the third section,the single^-atom catalyst（CoN/O-pCN）was successfully prepared by anchorng cobalt atoms on polymeric carbon nitride（pCN）via simple in-situ thermal polymerization method,and applied it for persulfate activation catalytic degration of tetracycline（TC）for the first time.The X-ray absorption spectroscopy（XAS）and high-angle annular dark fieldscanning transmission electron microscopy（HAADF-STEM）prove the single cobalt atoms is successfully anchored on pCN.Moreover,extended X-ray absorption fine structure（EXAFS）and X-ray absorption near-edge structure（XANES）analysis demonstrates that the embedded cobalt atoms are constructed by covalently forming the Co-N and Co-O bond.Experiment results indicated that the prepared single^-atom cobalt catalyst can be used for efficient persulfate activation catalytic degradation of TC.Results showed that with the increase of the dosage of catalyst and PMS,the catalytic activity was enhanced.In addition,pH value and anions showed little influence on the catalytic degradation of TC.The active species quenching and EPR trapping experiments indicated that SO₄^·-,·OH,and ¹O₂ are conducive to the TC degradation in which the 102 was the dominating active species.The single^-atom cobalt sites of the CoN/O-pCN catalyst as active sites are responsible for the activation PMS for the generation of ¹O₂.And CoN/O-pCN will release a small amount of Co²⁺ during the reaction,the Co²⁺ activates PMS to produce SO₄^·-and ·OH.These active species reacted with TC,thus leading to the degradation of TC.It can provide a new way for antibiotic treatment in aqueous solution.In the fourth section,the degradation of oxytetracycline（OTC）by CoN/OpCN activation PMS under visible light was further discussed on the basis of previous study.As a new semiconductor material,pCN has been widely used in the field of photocatalysis.And the single^-atom metal doping provides a new strategy to change electronic structure and properties of pCN.UV-vis diffuse reflectance spectra（DRS）,photoelectric current（PC）,and electrochemical impedance spectroscopy（EIS）proved that cobalt doping is beneficial to improve the photocatalytic performance of pCN,including visible light absorption ability,photoelectron-hole separation and migration ability,electron conduction rate.Catalytic degradation of OTC experiments displayed that the OTC degradation efficiency in CoN/O-pCN/PMS/Vis system was significantly enhanced compared with CoN/O-pCN/Vis and CoN/O-pCN/PMS systems.Further,according to the active species quenching and capture experiments,it was found that the reactive species in CoN/O-pCN/PMS system including ·O₂^-、¹O₂、h⁺、·OH and SO₄^·-,among which ·O₂^-was the dominating active species,followed by ¹O₂.Finally,the degradation mechanism of OTC by CoN/OpCN/PMS system was deduced.First,the CoN/O-pCN is activated to produce electrons（e^-）and holes（h⁺）under visible light irradiation.The photo-generated e^-can capture O2 to generate ·O₂^-,meanwhile the photogenerated e^-can also activate PMS to generate SO₄^·-.In addition,the photo-generated h⁺ generated by valence band（VB）can also directly act on pollutants.Secondly,a small amount of Co²⁺ activated PMS extracted from CoN/O-pCN produced ·OH and SO₄^·-.Finally,the single^-atom cobalt sites of the CoN/O-pCN catalyst as active sites are responsible for the activation PMS for the generation of ¹O₂.These reactive species(·O₂^-、¹O₂、h⁺、·OH and SO₄^·-)act together on OTC to effectively catalyze the degradation of OTC.In this study,a new SAC for persulfate activation catalytic degradation of antibiotics was developed,providing a new way for SACs to be used in advanced oxidation technology to degrade organic pollutants.