Research Of Citric Acid Buffer System To Enhance Bi/Fe~0 Oxidative Degradation Of Atrazine

With the rapid development of agriculture,water pollution caused by atrazine（ATR）as a commonly used herbicide is becoming increasingly serious.Fe⁰ has been widely studied due to its advantages such as strong reducing ability,low toxicity and low cost.However,since the degradation of pollutants in the system with Fe⁰ alone is mainly dominated by the reduction mechanism and the reaction rate is slow,it needs to be modified to reduce the activation energy of the system and enhance its oxidative degradation ability.In this paper,sodium borohydride（Na BH₄）reduction method was used to synthesize Fe⁰ and bimetallic Bi/Fe⁰ nanoparticles,combined with citric acid（CA）/sodium citrate（Na CA）to form Fe⁰+Na CA+CA and Bi/Fe⁰+Na CA+CA buffer systems to oxidatively degrade ATR.In addition,the degradation rates of ATR by Fe⁰+Na CA+CA and Bi/Fe⁰+Na CA+CA buffer systems in the cyclic degradation experiment were also discussed.The important factors and intermediate products in the reaction process of Bi/Fe⁰+Na CA+CA buffer system were analyzed,and the possible degradation pathway of ATR was explored.The main conclusions of this article are as follows:（1）Fe⁰ nanoparticles was synthesized by Na BH₄ reduction method,and the oxidative degradation of ATR by Fe⁰+Na CA+CA buffer system was studied.The experiment found that after 3 hours of reaction,52%of the ATR in the Fe⁰+Na CA+CA buffer system was removed.EPR analysis showed that the yield of active species in the Fe⁰+Na CA+CA buffer system was also higher than that of the Fe⁰+Na CA and Fe⁰+CA systems.The cyclic degradation experiment found that the Fe⁰+Na CA+CA buffer system had a good cycle degradation effect on ATR,indicating that the buffer system effectively allexiated the corrosion efficiency of Fe⁰ and prolonged its service life.（2）Bimetallic Bi/Fe⁰ nanomaterials was synthesized with different ratios,and when the molar ratio of Bi and Fe is 4%,the Bi/Fe⁰+Na CA+CA buffer system has the best degradation effect on ATR,and 73%of ATR can be removed after 3 hours of reaction,which is 21%higher than the Fe⁰+Na CA+CA buffer system,indicating that Bi/Fe⁰ bimetallic modification effectively enhances the oxidative degradation ability of Bi/Fe⁰+Na CA+CA buffer system to ATR.In the Bi/Fe⁰+Na CA+CA buffer system,the degradation efficiency of ATR in three cycles of degradation experiments can reach about 73%,and the XRD pattern of the Bi/Fe⁰before and after used did not change significantly,proving that Bi/Fe⁰ was in the Bi/Fe⁰+Na CA+CA buffer system has good stability.（3）Compared with Bi/Fe⁰+CA system,the Bi/Fe⁰+Na CA+CA buffer system reduces the impact on the acidity of the environment and reduces the release of iron ions,making the additional impact on the environment lower.As the reaction progresses,the p H value of the Bi/Fe⁰+Na CA+CA buffer system is weakly alkaline,and Fe（II）[Cit]^-can further react with H₂O₂ to form·OH,which can continue to degrade ATR.The content of Fe（Ⅲ）increases with the number of cycles,indicating that Bi/Fe⁰ was oxidized during the reaction.But at the same time,the Fenton reaction continues,generating active species continuously to promote degradation.