Isonicotinic Acid Bridged Cobalt Tetra-Aminophthalocyanine To Catalytic Degradation On Organic Pollutants

With the development of agriculture and industry water pollution is becoming increasingly serious.Advanced oxidation process（AOPs）is widely used in organic wastewater treatment due to its high efficiency and thorough degradation.Activation of peroxymonosulfate（PMS）to produce sulfate radical（SO4·^-）and hydroxyl radical（·OH）is one of the effective methods to remove refractory organic pollutants from water.Among the many activation techniques for PMS,transition metal ions have gained a lot of attention because of their high activation efficiency,the simplicity of the reaction device,low cost and the possibility of large-scale use.However,transition metal ions are difficult to recycle during use and can cause secondary pollution.Metal phthalocyanines are macrocyclic compounds with four isoindole groups connected by hetero-bridging groups,which can hold the metal ions inside the macrocyclic cavities through covalent bonding,effectively avoiding the overflow of metal ions.Due to the highly planar conjugated structure of metal phthalocyanines,they are prone toπ-πplanar stacking leading to a decrease in activity.The introduction of a ligand can axially coordinate with the central metal ion of the metal phthalocyanine to disrupt the stacking structure of the phthalocyanine and expose more active sites,and can modulate the electron transport capacity of the central metal ion to improve the catalytic performance of the metal phthalocyanine.In this thesis,isonicotinic acid was introduced as a ligand to axially coordinate with cobalt tetra-aminophthalocyanine（CoTAPc）,and two catalysts,composite and self-linked,were formed by different linkage methods to improve their catalytic performance.The two catalysts were characterised and tested,and the catalytic mechanism and pollutant degradation history were investigated.Details of the study are as follows:1.The reaction of 4-pyridinecarbonyl chloride hydrochloride（INA）with four amino groups outside the CoTAPc ring,followed by the axial coordination linkage of INA with other CoTAPc molecules,resulted in pyridine-bridged tetraaminocobalt phthalocyanine（CoTAPc-TINA）.The successful synthesis of CoTAPc-TINA by Fourier infrared spectroscopy（FTIR）,ultraviolet-visible spectrophotometry（DRS）,X-ray diffraction（XRD）and X-ray electron energy spectroscopy（XPS）showed that CoTAPc and INA were successfully synthesized through amide and coordination bonds.The introduction of INA avoided the stacking of CoTAPc,exposed more active sites,and CoTAPc-TINA was effective in activating PMS under dark reaction,with 98.8%removal of carbamazepine（CBZ）in 10 min with 0.4 m M PMS,and still had good catalytic performance under different inorganic ions and p H conditions.Inductively coupled plasma（ICP）and cycle tests show that the activity of CoTAPc-TINA is basically unchanged after 5 cycles of use,and there is almost no spillover of core metal ions.Electron paramagnetic resonance（ERP）and radical quenching experiments showed that superoxide radicals（O₂·^-）,singlet oxygen（¹O₂）,·OH and SO₄·^-were the main oxidising active species in the CoTAPc-TINA/PMS,and the reaction mechanism of PMS activation by CoTAPc-TINA was proposed.The degradation intermediates and final products of CBZ were detected by ultra-high liquid chromatography-mass spectrometry（UPLC-HDMS）.The results indicated that CBZ was finally converted to non-toxic small molecule fatty acids in the CoTAPc-TINA/PMS system,and the degradation course of CBZ was postulated.2.In order to further improve the application range of the catalyst and reduce the amount of CoTAPc used,CoTAPc was compounded with graphitic phase carbon nitride（g-C₃N₄）,a semiconductor photocatalyst,via INA.The INA was first reacted with the terminal amino group of g-C₃N₄ to form g-C₃N₄-INA with pyridine ligands.g-C₃N₄-INA was connected to CoTAPc by N→Cocoordination bonds to obtain the composite catalyst g-C₃N₄-INA-CoTAPc.g-C₃N₄-INA-CoTAPc was obtained by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,thermogravimetric analysis（TG）,ICP,XPS,DRS,FTIR and XRD.The results showed that the best catalytic performance was achieved at a CoTAPc mass fraction of 2.77%.The successful connection of g-C₃N₄ and CoTAPc via INA effectively broadened the visible response range of g-C₃N₄ and the separation of photogenerated electron-hole pairs,and avoided the stacking of CoTAPc and promoted the conversion rate of Co^III to Co^II.The catalytic performance of g-C₃N₄-INA-CoTAPc was tested using CBZ as a typical pollutant model.The removal rate of CBZ was 99.9%within 50 min under visible light irradiation,and it still had good catalytic performance under different inorganic ions and p H conditions.In addition,the catalytic activity remained essentially unchanged after 10 repetitions.Through free radical quenching experiments,EPR and photocurrent response tests,it was determined that the g-C₃N₄-INA-CoTAPc/PMS/visible light system in the removal of CBZ O₂·^-,¹O₂ and SO₄·^-were the main oxidation.By density functional theory（DFT）calculation,it is proved that INA promotes the homolysis of O-O bond in PMS,thus improving the activation rate of PMS.Using UPLC-HDMS,the intermediate and final products of CBZ degradation were detected and the degradation pathway of CBZ was inferred,and the results indicated that CBZ was finally converted into non-toxic small molecule acids.