Efficiency And Mechanism Of Organic Chelant-modified Iron-based Nanoparticles In Activation Of Peroxymonosulfate

For relieving agglomeration and improving limited catalytic degradation ability of iron-based microspheres,Fe₃O₄ nanoparticles were prepared by coprecipitation and further modified by different chelants,including Epigallocatechin gallate（EGCG）,L-ascorbic acid（VC）,β-alaninediacetic acid（β-ADA）,to prepare EGCG@Fe₃O₄,VC@Fe₃O₄ andβ-ADA@Fe₃O₄ nanoparticles.Various characterization techniques were applied to reveal that the three chelants respectively chelated on the surface of Fe₃O₄ and did not change its crystal structure,and the modified Fe₃O₄possess smaller particle sizes and better dispersion.Three modified Fe₃O₄-activated peroxymonosulfate（PMS）systems were constructed for sulfadiazine（SD）removal to evaluate catalytic degradation efficiency of different catalysts.The results show that the PMS utilization rate and the SD removal rate were significantly elevated in the three chelant-modified Fe₃O₄/PMS systems,the SD removal rate increased from 37.9%to 68.3%,56.6%,54.0%after modification.EGCG@Fe₃O₄/PMS system presented a steady SD removal pattern,and the system possesses the highest SD removal rate when oxidant dosage is 0.3 mmol/L and catalyst dosage is 0.8 g/L.While VC@Fe₃O₄/PMS andβ-ADA@Fe₃O₄/PMS system showed rapid degradation at the initial stage and almost constant removal rate at the later stage.The three chelant-modified Fe₃O₄/PMS systems can effectively remove SD at neutral initial pH.Results of quenching experiments and electron spin resonance tests further confirm that·OH and SO₄^-·were both generated in the three modified system,and SD removal in the catalytic system mainly depends on the generation of radicals.TOC determinations imply that a part of the SD removed in the catalytic system was converted into intermediate products.It is proposed that chelants strengthen the activation of PMS and promote the reduction reaction of Fe³⁺on the surface of Fe₃O₄,which further realize the efficient degradation of SD.