Activation Of Persulfate By Modified Chitosan Utilized For Degrading Sulfonamide Antibiotics In Soil

At present,the wide detection of antibiotics in the soil environment poses great challenges to the stability of the ecological environment and the health of human life.Seeking an oxidation treatment technology with less limited reaction conditions,a green economy,and no secondary pollution is the key to soil antibiotic pollution remediation.In this study,modified chitosan granules（CA-CS）were successfully prepared and the feasibility of sulfamethazine（SM2）in CA-CS activated persulfate removal systems was verified.The effect characteristics of different impact factors on the ability of the system to remove SM2 were discussed,and the activation efficiency of CA-CS on sulfates in different sulfonamide antibiotics and oxidation dose systems was explored.Through the degradation of SM2 by different reaction systems,free radical quenching experiments,electrochemical and intermediate product analysis,the possible mechanisms of action and specific oxidation mechanisms of different components on SM2 degradation in the oxidation system were explored.The main contents were as follows:CA-CS was successfully introduced into the carboxyl group by chitosan granules modified by citric acid acylation,showing a regular spherical shape.CA-CS can efficiently activate SM2 in the persulfate removal system,and different citric acid to chitosan mass ratio and chitosan mass fraction preparation conditions will have a greater impact on the sphere and dispersion state of the modified products.CA-CS activated the persulfate oxidation system under the conditions of SM2concentration of 20mg/L,the soil-water ratio of 1:10,and the persulfate concentration of 15mmol/L was added to CA-CS,and the removal rate of SM2 within 180 minutes of the system reaction could be as high as 96.8%.The increase in persulfate concentration and CA-CS dosing has a certain effect on the removal of SM2 in the system.The CA-CS activated persulfate system enables efficient removal of SM2 over a wide p H range,and the advantages of lower system p H for SM2 removal are more prominent.At the same time,CA-CS has good reusability.The activation efficiency of CA-CS on persulfates has strong adaptability and extensiveness to different oxidant concentrations and pollutant types.In the CA-CS activated persulfate oxidation system,each component plays a different role in the degradation of SM2.The soil’s ability to activate persulfate is weak and has a certain inhibitory effect on CA-CS’s ability to activate persulfate to degrade antibiotics.CA-CS can rapidly enrich SM2 and persulfate on the surface,activate persulfate at its surface or solid/liquid interface to produce active oxidizing substances to degrade SM2,and a small amount of CA-CS can significantly improve the oxidation degradation rate and oxidative degradation capacity of low-dose persulfate systems.The solubility of sulfonamide antibiotics has a more significant effect on the degradation of CA-CS-activated persulfate slow oxidation systems.Non-free radical pathways such as ¹O₂ oxidation and electron transfer in CA-CS activated persulfate systems have a more prominent contribution to the degradation of SM2,which is mainly degraded to generate intermediate products,CO₂ and H₂O through hydroxylation,cyclic cracking,smiles-type rearrangement,and sulfonamide bond rupture.