Photocatalytic Degradation Of Atrazine In Water By Ag₃PO₄ Based Composites

As a widely used herbicide in the world,atrazine can effectively prevent the growth of weeds in farmland to improve the economic benefits of agricultural production.But the pesticide residues of atrazine can drain into the soil,rivers and lakes,causing pollution to groundwater,surface water,and with the food chain enrichment caused varying degrees of damage to the plant,animal and human.In recent years,with the development of photocatalytic technology,simple,cheap and efficient photocatalytic degradation of atrazine has become the focus of research.As a new high activity and visible^-light responsive catalyst,Ag₃PO₄ has been widely studied in the field of splitting water to release O2,reduction of CO₂,degradation of NO_x compounds and degradation of organic pollutants.However,the application of Ag₃PO₄ in photocatalytic degradation of atrazine was less.In this work,we prepared two Ag₃PO₄ based photocatalysts?Au NRs/Ag₃PO₄ and Mo-Ag₃PO₄?by different methods.We tested the physical properties and chemical structure of photocatalysts through a series of characterization methods,such as SEM,XRD,XPS and so on.We studied the photocatalytic performances of degrading atrazine in water by Ag₃PO₄ based photocatalysts under visible light irradiation.Photocatalytic degradation of atrazine showed that the photocatalytic activity was the best when the initial pH of reaction system was six,and with the photocatalytic process,the pH value of the system decreased gradually.It was found that the main active species in the catalytic reaction were h⁺ and ·OH radical.We have determined the intermediates of degrading atrazine by liquid chromatography-mass spectrometry?LC-MS?and ion chromatograph.The intermediate products included 2-hydroxy-4-ethylamin-6-isopropylamino-s-triazine,2-chloro-4-amino-6-isopropylamino-s-triazine,2-hydroxy-4-amino-6-isopropylamino-striazine,2,4-hydroxy-6-isopropylamino-s-triazine and so on.The possible mechanism of photocatalytic degradation of atrazine by Ag₃PO₄ based photocatalysts was studied.Ag₃PO₄ was stimulated by light to produce e^-and h⁺,and the presence of Au NRs and Mo element in the composite system was helpful to promote the transfer of e^-in order to improve the catalytic activity.The h⁺ could react with H₂O in the reaction system to produce ·OH radical and H+,which made the pH value of the system decrease with the reaction.At the same time,the generated ·OH radicals could attack the C-Cl bond of the atrazine molecule,the secondary carbon atom of the side chain and the central carbon atom of the side chain.It could get the final product for cyanuric acid by a series of chemical reactions,such as dechlorination reaction,hydroxylation and alkylation reaction.The cyanuric acid will be further mineralized into H₂O,CO₂ and NO₃^-.This dissertation not only enriches the application of Ag₃PO₄ based photocatalysts in the field of photocatalytic degradation of pesticide organic pollution,but also provides a theoretical basis for the practical application to photocatalytic degradation of atrazine.