Degradation Of Pharmaceutical Organic Pollutants By Graphitic Carbon Nitride/metal Phthalocyanine Composite Catalytic Fibers

With the development of human economy and society,environmental pollution and energy shortage have become two major problems faced by human beings in today's world.Pharmaceutical and personal care products(PPCPs),which are widespread in human daily life and production processes,are harmful to the ecological environment and human health.Carbamazepine(CBZ)and sulfonamide antibiotics are the more typical PPCPs pollutants.CBZ is a refractory organic pollutant,which has a complex environment and exists in the form of low concentration.Traditional sewage treatment methods have low removal efficiency of such pollutants in the water environment,and it is difficult to achieve complete degradation.Therefore,from the perspective of sustainable development of human society,there is an urgent need to develop a green,efficient,and practical application prospect for the advanced treatment of PPCPs pollutants.Photocatalysis technology based on the solar light as driven force,with the advantages of mild reaction conditions and green environmental protection,is currently one of the effective ways to solve the problem of water environment pollution.The design of photocatalytic materials with high activity,high selectivity and high stability is the key to breaking through the bottleneck problem of photocatalytic technology in practical applications.Graphitic carbon nitride(g-C₃N₄)is a visible light-responsive polymer organic semiconductor photocatalyst with good thermal and chemical stability.However,the band gap of g-C₃N₄is 2.7 e V,resulting in a maximum absorption wavelength of 460 nm.The application of g-C₃N₄in photocatalysis is greatly limited due to the low utilization of visible light and the high recombination rate of photogenerated carriers.Metal phthalocyanines have attracted attention in the catalytic degradation of organic pollutants due to their good stability and excellent visible light response range.This thesis aims at solving the current problem of g-C₃N₄,such as low solar light utilization,high photo-generated charge recombination rate and easy sedimentation.We constructed three types of composite photocatalysts based on g-C₃N₄ and metal phthalocyanine,combining material design and preparation,structural analysis,mechanism research,and degradation pathway analysis.The utilization of visible light and the separation rate of photogenerated carriers of g-C₃N₄were improved by the combination of g-C₃N₄ and metal phthalocyanines.Meanwhile,the problem of agglomeration and deactivation of small molecular metal phthalocyanines was avoided,achieving the loading of composite catalysts on the surface of low-melting polyester fibers.By adjusting the type of metal phthalocyanines and combination method,the g-C₃N₄ composite catalytic system can achieve high-efficiency catalytic degradation of pharmaceutical organic pollutants under light irradiation.The main research results obtained in this paper are as follows:1.The g-C₃N₄/Zn Tc Pc/GQDs ternary composite photocatalyst was prepared by grafting method and solvothermal method.The performance of g-C₃N₄/Zn Tc Pc/GQDs ternary composite catalyst was studied by using Rhodamine B(Rh B),sulfaquinoxaline sodium(SQXNa)and carbamazepine(CBZ)as the model pollutants under solar light irradiation.Zn Tc Pc bonding on the g-C₃N₄ broadened the visible-light spectral response,and the introduction of GQDs promoted the photogenerated electron-hole-pair separation efficiency because of its efficient electrons-transfer property.The g-C₃N₄/Zn Tc Pc/GQDs ternary composite catalyst exhibited excellent photocatalytic performance,p H application range and good recycling performance.O₂·^-,¹O₂ and h⁺were identified as the main active species.During the reaction progresses,the chemical bonds of target substrates were gradually broken by the attack of the active species,resulting in the generation of biodegradable small molecule acids.2.In order to achieve a high-efficiency removal of recalcitrant contaminants in water,potassium peroxymonosulfate(PMS)was introduced as the oxidant.The g-C₃N₄-CoPc composite catalyst was synthesized by the interaction of the two planar structure materials.The results showed that the visible light response range of g-C₃N₄ could be expanded by the introduction of CoPc.On the other hand,the loading of CoPc on g-C₃N₄ effectively avoided the aggregation of phthalocyanine molecules into dimers.Compared with the g-C₃N₄/Zn Tc Pc/GQDs catalytic system,CBZ could be removed quickly and effectively by the g-C₃N₄-CoPc composite catalyst through activating PMS under solar light irradiation.Since CoPc was easily inactivated by the attacked of active species,the recycling performance of the catalytic system needed to be improved.·OH,SO₄·^-,O₂·^-and h⁺were the active species in the g-C₃N₄-CoPc catalytic system,which played an important role in the degradation of CBZ.The chemical bonds of CBZ molecule were gradually broken under the attack of various active species to generate different hydroxylated intermediate products,which are further oxidized.3.In order to further improve the recycling performance of the catalyst,iron hexadecachlorophthalocyanine(FePcCl₁₆)with more excellent chemical stability and environmently friendly was introduced.The g-C₃N₄-IMA-FePcCl₁₆ composite catalyst was prepared by connecting g-C₃N₄ and FePcCl₁₆ through the axial coordination of the imidazole group(1-methyl-1H-imidazole-5-carboxylic acid,IMA).The maximum absorption wavelength of pure g-C₃N₄ was only about 450 nm,but the introduction of FePcCl₁₆ made the composite catalyst have a good visible light response in the range of 600-800 nm.The g-C₃N₄-IMA-FePcCl₁₆ composite catalyst had excellent catalytic activity and recycling performance in the presence of PMS under visible light.g-C₃N₄-IMA-FePcCl₁₆ showed a wonderful degradation ability for different sulfonamide antibiotics.The catalytic system was suitable for the catalytic degradation of organic pollutants in the presence of a large number of inorganic ions.SO₄·^?,·OH,O₂·^?,¹O₂and Fe(IV)=O were the active species.O₂·^-and ¹O₂ were the main active species.The degradation pathway of CBZ was also analyzed according to ultra-performance liquid chromatography and high-definition mass spectrometry.The catalytic degradation process of the target substrate was different due to the active species in the catalytic system.4.Three types of catalytic fibers were prepared by loaded different composite catalysts onto low melting point fiber(LMPET)through hot-melt adhesive process to overcome the difficult recovery and limited light-receiving area of powder catalysts in actual wastewater applications.The results showed that powder catalyst could be firmly supported on the surface of the fiber,and the loaded catalytic fibers maintained the excellent visible light response of the powder catalyst.Through activity comparison,it was found that the g-C₃N₄-IMA-FePcCl₁₆/LMPET catalytic fiber showed the best photocatalytic activity for the degradation of CBZ and other recalcitrant contaminants.The catalytic fiber had excellent recycling performance.A series of hydroxyl addition compounds of CBZ were formed,and would be further deep oxidized.The high-efficiency photocatalytic degradation performance for different sulfonamide antibiotics was achieved,and the catalytic mechanism of the g-C₃N₄-IMA-FePcCl₁₆ powder catalyst would not be changed after loading.