Activation Of Peroxymonosulfate By Fe₃O₄-CeO₂ For The Degradation Of Glyphosate

The broad-spectrum herbicide glyphosate is the most widely used and most widely productive pesticide variety in the world,the use of which in the past half a century has caused water and other environmental pollution.Therefore,the treatment of glyphosate in environmental media has attracted attention.Persulfate oxidants have the advantages of low cost,easy transportation and storage,high safety factor,and strong oxidative ability.The catalyst for efficiently activating persulfate is the focus of advanced oxidation technology research.In this study,the Fe₃O₄-CeO₂ composite catalyst was constructed to synergistically activate persulfate to achieve rapid catalytic degradation of glyphosate pollutants in water.In this paper,with glyphosate as the target pollutant,the catalysts were prepared by co-precipitation method,and the influence factors for catalyst preparation were investigated.Under the optimized preparation conditions like ion ratio Fe²⁺:Fe³⁺:Ce³⁺=2:4:1,calcination temperature 400℃,calcination time 5 h,the degradation rate of glyphosate reached 97%.The process parameters for the degradation of glyphosate were explored.The optimization results of the process parameters showed that with a catalyst dosage of 3 g/L,an oxidizer dosage of 0.5 m M,and a p H=5,the degradation rate of glyphosate reached 100%.The influence of various anions on the reaction was investigated.The results showed that Cl^-promoted the degradation of glyphosate,and HCO₃^-and H₂PO₃^2-inhibited the reaction.Through a series of characterizations,the reasons for the efficient activation of persulfate by the catalyst were discussed.XPS and H₂-TPR characterizations indicated that after the introduction of Fe,the reduction temperature of Fe₃O₄ increased due to the strong interaction between Fe³⁺/Fe²⁺and Ce⁴⁺/Ce²⁺through the Fe-O-Cebond.The strong interaction would not only promote the migration of lattice oxygen,enhancing the reduction performance of CeO₂,but also accelerate the conversion of Fe³⁺→Fe²⁺,significantly improving the activation efficiency of the catalyst.The catalyst with a specific surface area of 135.60 m²/g provided sufficient contact area for the reaction.The active oxygen species of the system were explored by a combination of quenching experiments and EPR characterization.The results demonstrated that the active oxygen species of the catalytic system were surface-bound SO₄^-·and OH·.