Synthesis Of CD/Fe₃O₄ Composite Material And The Study On Promoting Photocatalytic Degradation Of Hexaconazole

The unscientific use of pesticides lead to increasingly serious contamination.Therefore,the degradation of organic pollutants such as pesticides has attracted widespread attention from researchers.Photocatalytic degradation technology has the advantages of green,low energy,and environmental protection,and can effectively degrade organic pollutants into carbon dioxide and water,attracting much attention in the field of catalytic research.Nano-metal oxides such as ZnO and TiO₂,play an important role in photocatalytic systems and are widely used in the field of photocatalytic degradation of pesticides.However,most of them have good degradation effects under ultraviolet light.CD is characterized by low toxicity,friendly environment,photo induced electron transfer,and two-photon absorption.It has been reported that CD can catalyze the degradation of organic pollutants under visible light,but the study on CD in terms of photocatalysis is not perfect,catalysis efficiency of single CD structure is low.CD composite material has obvious effect on improving the photocatalytic performance.In this thesis,hydrothermal synthesis method was used to prepare nano-Fe₃O₄ and CD to obtain CD/Fe₃O₄ composites,and the morphology of the composites were characterized.The photocatalytic degradation efficiency of hexaconazole was explored to improve the photocatalytic performance of the composites.Finally,a simple prediction of the safety of the composites on plants was made.The main research contents and results are as follows:（1）Citrate as carbon source,which was prepared by hydrothermal synthesis method with nano-Fe₃O₄ was prepared by co-precipitation method,on the basis of preparation of CD method,to join the nano-Fe₃O₄,preparation of the CD/Fe₃O₄composite material.The structure,morphology,optical properties and main components were detected by transmission electron microscopy,fluorescence spectrophotometer and X-ray diffraction,and the results were as follows:CD/Fe₃O₄ composite materials,through the projection electron microscope we can see that the preparation of composite materials is that many globular structure,these carbon spheres and Fe₃O₄ package together;By X-ray diffraction,we can know that the composite material is composed of nano-Fe₃O₄.From the measurement results of the fluorescence spectrophotometer,it is found that the best excitation wavelength is red-shifted and the excitation wavelength range is increased,which is favorable for energy absorption and electron transition under visible light,and better functions as a photocatalytic degradation pesticide.（2）Study on the photocatalytic effect of CD/Fe₃O₄ composite material,and the results are as follows:The degradation of hexaconazole was obviously promoted by composite materials.Compared with the dark treatment,it can be known that the degradation of the compound materials to hexaconazole is photocatalytic degradation.According to the kinetics analysis of the degradation process of hexaconazole,the degradation of hexaconazole was in accordance with the first order kinetics of the photocatalytic degradation of CD/Fe₃O₄ composite material.（3）To analyze the degradation factors of hexaconazole,the results are as follows:In composite material concentration is 0.75 g/L before,with the increase of concentration of composite material,has listed in the solution of the degradation effect is gradually increasing,when the solution has listed in point CD/Fe₃O₄ composite material concentration is greater than 0.75 g/L,after the solution has listed the photocatalytic degradation of effect becomes not obvious,considering the factors such as dosage,so we choose 0.75 g/L for the best CD/Fe₃O₄ composite material.The study on the addition of Fe₃O₄ in the preparation of composite materials shows that the content of Fe₃O₄ in the composite was higher than 0.01 g,the content of Fe₃O₄ was increased again has no obvious effect on the catalytic degradation.Therefore,In the 10 g citric acid,we prepare composite materials with the addition of0.01 g.By analyzing the solution pH to neutral,weak acid and weak base for CD/Fe₃O₄composite material photocatalytic degradation has effects of hexaconazole in the solution,we found that in the condition of neutral effect is best.（4）To study the toxicity of composite materials,the results are as follows:The root treatment of cowpea was carried out by the composite material,and the plant height and fresh weight were analyzed directly.It was found that the composite material had no significant effect on the seedlings of cowpea.The results of chlorophyll,SOD and POD in leaves and the root vitality showed that the low-concentration treatment at the concentration of 0.25 g/L was no significant change in activity compared to the clear water control.This shows that the composite material is not toxic to cowpea seedlings at this concentration.At a concentration of0.5 g/L,a stress response occurred in addition to a marked increase in POD activity.The remaining indicators did not change significantly compared with the clear water control.The results showed that when the concentration was 0.5 g/L,the composite material had no obvious inhibition and damage to cowpea seedlings.However,when the concentration was higher than 0.5 g/L,the chlorophyll content,root activity,SOD activity,and POD activity of cowpea seedlings decreased under high-concentration nanomaterials stress,indicating that the composites produced damage to cowpea seedlings,and the concentration was higher.The more obvious the damage to cowpea seedlings.Therefore,it is recommended that the composite material be used at a concentration of less than 0.5 g/L to protect plants from damage.