Catalytic Degradation Of Organic Pollutants By Pyridine Bridged Metal Phthalocyanine And Its Supported Fiber

In recent years,the problem of water pollution caused by industrial wastewater has become increasingly prominent around the world,posing a threat to the ecological environment and human health.Advanced oxidation techniques（AOPs）have been widely used to treat refractory organic pollutants,among them,the advanced oxidation technology based on peroxymonosulfate（PMS）has attracted extensive attention due to its low price and high redox potential,and has great potential for application in the degradation of organic pollutants.In the activated persulfate oxidation technology,transition metal ions are commonly used to activate PMS.However,transition metal ions are difficult to recover and cause environmental pollution,which is limited in practical applications.Metal phthalocyanine is a macrocyclic compound composed of 18πelectrons.The central metal and nitrogen atom are fixed between four pyrrole rings in the form of coordination bonds,which can effectively prevent the metal from overflowing in the form of ions,making it widely used in the field of catalysis.However,metal phthalocyanines are easy to form aπ-πconjugated stacking structure,and most of them exist in the form of aggregation in water,which makes them less active.In addition,in addition to the coordination of four surrounding nitrogen atoms,metal phthalocyanines can also regulate the active site in the form of axial coordination,thereby affecting the catalytic oxidation ability of phthalocyanine derivatives.In this paper,the catalytic performance of metallophthalocyanine derivatives is regulated by designing different types of pyridine axial ligands,exposing more active sites,thereby improving the catalytic activity.The electrospinning technology was used to load the catalyst on polyacrylonitrile（PAN）to obtain nanofiber;The PAN molecular chain can isolate and effectively disperse the metal phthalocyanine molecules from each other,avoid the aggregation of the phthalocyanine molecules,and improve the recycling performance.In this paper,the catalytic performance,catalytic mechanism,degradation products and degradation pathways of the catalysts and supported fibers were studied.The content mainly consists of the following three aspects:1.First,4-aminopyridine was reacted with isonicotinyl chloride hydrochloride（INA）,and a bipyridine structure with an amide group was obtained through amide bonding,and the two ends were then axially coordinated with iron phthalocyanine（Fe Pc）.A single amide group pyridine bridged metal phthalocyanine catalyst（Fe Pc-Py-INA）was prepared by the method of the site.The samples were characterized by scanning electron microscope（SEM）,Fourier infrared spectroscopy（FTIR）,two-dimensional X-ray diffraction（XRD）and other instruments.The results showed that the central metal atom of Fe Pc was successfully coordinated with the nitrogen atom on the pyridine group.Using carbamazepine（CBZ）as the target pollutant,the performance of Fe Pc-Py-INA in the catalytic activation of PMS under dark reaction conditions was investigated.Fe Pc-Py-INA could completely degrade CBZ in 10 min.In comparison,the removal rate of Fe Pc to CBZ was only 65%,indicating that the catalytic performance of metal phthalocyanine can be significantly improved by axial coordination.The catalytic mechanism of the system was investigated by trapping agent quenching experiments and electron paramagnetic resonance（EPR）methods,and it was found that ¹O₂and O₂·^-were the main active species for the catalytic degradation of CBZ.2.In order to further study the effect of the bridge structure with bipyridine functional groups on the catalytic performance,pyridine bridged metal phthalocyanine was obtained by different bonding methods,The symmetrical structure containing bisamide was introduced by oxalyl chloride（COCl）,and then the bisamide group pyridine bridged metal phthalocyanine catalyst（Fe Pc-Py-COCl）was prepared by axial coordination between Fe Pc and its two ends,catalytic nanofibers were prepared by loading Fe Pc-Py-COCl and Fe Pc-Py-INA onto PAN,respectively.Through FTIR,XRD and UV-vis diffuse reflectance spectroscopy（DRS）studies,it was found that the pyridine bridged metal phthalocyanine powder catalyst has been uniformly supported on PAN.In comparison,Fe Pc-Py-COCl/PAN could remove CBZ more quickly and efficiently under dark reaction conditions,and the removal rate was as high as 99.1%within 30 min.The trapping agent quenching and EPR experiments showed that ¹O₂and O₂·^-played a major role in the degradation of CBZ,and·OH and SO₄·^-played a secondary role.The degradation process of CBZ and SQX catalyzed by PMS activated by Fe Pc-Py-COCl/PAN nanofibers was studied by ultra high performance liquid chromatography-mass spectrometry（UPLC-HDMS）.Eight intermediates of CBZ and seven intermediates of SQX were detected.As the reaction progresses,CBZ and SQX undergo ring opening and chemical bond cleavage,and were eventually oxidized to small acid compounds.3.In order to further optimize the interaction between the coordinating group of the axial pyridine and the metal phthalocyanine,the metal phthalocyanine derivatives with their own pyridine group were also studied in this paper.Iron phthalocyanine with amino group（Fe MATNPc）was prepared first,and the acyl group on INA was amide-bonded with the amino group in Fe MATNPc,and the nitrogen atom of the pyridine group on INA was axially coordinated with the metal ion in Fe MATNPc to prepare The exocyclic pyridine bridged metal phthalocyanine derivatives（Fe MATNPc-INA）were obtained and successfully supported on PAN to form Fe MATNPc-INA/PAN catalytic fibers.Through FTIR,XRD,SEM and X-ray photoelectron spectroscopy（XPS）studies,it was found that the relationship between Fe MATNPc and INA depends on the covalent bond of axial coordination and amide bond.The catalytic fibers could effectively activate PMS under dark reaction condition,effectively degraded various organic pollutants such as CBZ,and still had good catalytic performance in the presence of a large number of inorganic anions.Through dimethyl sulfoxide（DMSO）oxidation,trapping agent,and EPR experiments,it was shown that the catalytic fiber forms O-O bonds by activating PMS,the axial coordination structure could promote the homolytic and heterolytic of the O-O bond to form Fe（IV）=O active species and SO₄·^?,which reacted with H₂O to generate·OH,which together promoted the degradation of CBZ.Finally,the degradation process of CBZ was studied by UPLC-HDMS,and the possible degradation paths of CBZ were obtained.The results showed that the different active species made the degradation pathways of the target pollutants different.The effect of chloride ions on the degradation products of CBZ was also studied.Chlorinated by-products were found in the reaction,but with the progress of the reaction,the generated chlorinated by-products and other intermediate products can be further deeply degraded.This paper provides a new idea for developing axially coordinated metallophthalocyanine catalysts with excellent activity and recyclability.