Development Of Cucurbitacin-based Ternary Catalyst And Its Application In Photodegradation Of Pesticide

Organic pesticides play an important role in agricultural production.Compared with inorganic pesticides,organic pesticides have stronger effect,wider range of action,wide variety and stable chemical structure,which cause serious harm to the environment after polluting water.How to quickly and effectively remove the pollution of organic pesticides remaining in water has always been a concern of people.The photocatalytic technology driven by sunlight has the characteristics of good adaptability,energy saving and environmental protection,no harm to the human body and the environment,and has a wide range of application prospects.In recent years,it has been widely used in removing pesticide residues,pharmaceutical residues and printing and dyeing pollutants.cucurbituril（Q[n]s）,is a new supramolecular main compound.Due to the characteristics of the cavity structure with hydrophilic on the outside and hydrophobic on the inside of cucurbituril,and have the ability to selectively complex metal ions and neutral molecules,it has attracted wide attention.However,cucurbituril do not respond to visible light,and their potential in photocatalytic removal of organic pesticide pollution remains unknown.To solve these problems,this study proposed for the first time the introduction of cucurbituril-coordinated inorganic nanomaterials composite organic semiconductor,and constructed two kinds of cucurbituril-based ternary catalysts for the removal of pesticide residues in water environment.1.A novel supramolecular photocatalyst with the macrocyclic compound of cucurbit[7]uril（Q[7]）block,g-C₃N₄/Ag₃PO₄@Q[7]composite,is successfully prepared by ternary organic-inorganic hybridization.The morphology,structure and optical properties of the composites were characterized by FT-IR,XRD,Raman,SEM,TGA,UV-DRS,BET and PL spectra,the degradation products were detected by LC-MS.The prepared g-C₃N₄/Ag₃PO₄@Q[7]ternary catalyst was applied to remove organic pesticides pyroquilon and admire under visible light,the degradation path and reaction mechanism of the photocatalyst for the degradation of pesticides pyroquilon and admire were revealed.The experimental results showed that under the drive of 35 W LED lamp,the reaction temperature was 25℃,the substrate concentration was 7.4×10^-5mol/L for pyroquilon and 3.8×10^-5mol/L for admire,the dosage of catalyst was 0.4 g/L,and the reaction time was 300 min.The g-C₃N₄/Ag₃PO₄@Q[7]ternary catalyst showed a removal efficiency of 93.9%for pyroquilon and a degradation efficiency of 96.8%for admire in water environment,with the reaction rates of 9.3×10^-3min^-1 and 1.2×10^-2min^-1,respectively.The photocatalyst exhibits a high stability and reusability,the degradation efficiencies are afforded as 74%for pyroquilon and 86%for admire in five catalytic cycles.Comparing with the reported photocatalysts,the developed material offered performance advantages of low energy consumption and fast reaction rates in the degradation of pyroquilon and admire pesticides.2.A ternary composite（CdS@PANI/Q[7]）,including the inorganic CdS semiconductor,organic semiconductor polyaniline（PANI）,and the macrocyclic compound cucurbit[7]uril（Q[7]）,is reached with the coordination of Q[7]to the metal cations and supramolecular encapsulation of PANI within the cavity of the macrocycle.The morphology,structure and optical properties of the ternary catalyst were characterized by FT-IR,XRD,Raman,SEM,TGA,UV-DRS and BET.The catalyst was applied to the removal of organic pesticide thiamethoxam under visible light.The kinds of free radicals causing degradation of thiamethoxam were evaluated and the reaction mechanism of thiamethoxam degradation by this photocatalyst was revealed.The experimental results showed that:Driven by a 35 W LED lamp,the reaction temperature was 25℃,the substrate concentration was 4×10^-5 mol/L,and the catalyst dosage was 0.2 g/L.The degradation efficiency of the pesticide thiamethoxam in water environment by CdS@PANI/Q[7]ternary composite material was 85%.The catalytic kinetic constant was 0.003 min^-1.After 3 cycles,the removal efficiency of the catalyst still reached 79%.The proposed catalytic mechanism involved the restrained recombination of photoinduced hole-electron pairs and enhanced contact between the photocatalyst with the thiamethoxam substrate on the surface of CdS@PANI/Q[7].The material developed in this study demonstrates potential applications for the rapid degradation of pesticides.