Activation Of Peroxodisulfate By Erbium Ion-Doped Bismuth Ferrite For Degradation Of 2,4-Dichlorophenol

2,4-Dichlorophenol（2,4-DCP）is a typical refractory and highly toxic chlorophenol organic pollutant.It is discharged into the water environment with industrial production and human activities,and its lower concentration may seriously threaten humans health and the growth of animals and plants.A series of problems derived from 2,4-DCP have been highly valued by relevant environmental protection agencies at domestic and international,and they are regarded as one of the priority pollutants for control.At present,it is difficult to remove 2,4-DCP with traditional water treatment technology,so it is urgent to find and develop new green and efficient methods to degrade it.Among them,the advanced oxidation technology（AOPs）based on the activation of persulfate to generate sulfate radicals（·SO₄^–）has received widespread attention due to its rapid reaction and strong oxidizing ability.In this research,a new type of visible light/bismuth ferrite/peroxodisulfate catalytic oxidation system was established.To achieve the purpose of enhancing the degradation effect of 2,4-DCP,with the help of visible light irradiation,the peroxodisulfate（PDS）was activated by the bismuth ferrite photocatalyst modified with rare earth metal ions.In this research,the erbium ion-doped bismuth ferrite((Bi_1-xEr_xFe O₃;x=0、0.02、0.04、0.06)visible light catalyst was mainly prepared by the sol-gel method.And the internal structure,microscopic morphology,element composition and optical properties of the Bi_1-xEr_xFe O₃ photocatalyst were explored with the participation of various materials characterization methods,such as XRD,SEM,UV-vis DRS,XPS,etc.Characterization results shows that Er³⁺is successfully doped into Bi Fe O₃lattice,and the catalyst has certain visible light absorption characteristics.The degradation efficiency of the organic pollutant 2,4-DCP by the visible light/bismuth ferrite/peroxodisulfate catalytic oxidation system under different experimental conditions was systematically studied.The results showed that the Bi Fe O₃ photocatalyst with an Er³⁺doping concentration of 6%has the best activation performance for PDS;in addition,the photocatalytic activity for 2,4-DCP by it was the highest.Under the conditions that the dosage of BEFO₆,the PDS concentration and the initial p H of the solution are 1.0g/L,3m M and 7,respectively,the 2,4-DCP solution of 20 m L and 20 mg/L can be degraded by about 90%within 60minutes.At the same time,after three recycling experiments,the catalytic activity of BEFO₆ photocatalyst was maintained above 80%.The research also found that the degradation of 2,4-DCP by the visible light/bismuth ferrite/peroxodisulfate catalytic oxidation system conforms to the pseudo first-order reaction kinetics,the reaction rate constant increases with the increase of the photocatalyst dosage,and as the concentration of PDS and the initial p H value of the solution increase,it first increases and then decreases.From the degradation effect of 2,4-DCP by six different reaction systems including BEFO₆,PDS,Vis/BEFO₆/PDS,etc.it can be concluded that a good synergistic effect has been constructed between the BEFO₆ visible light catalyst and PDS,which can significantly increase 2,4-DCP rate of degradation.Through the free radical quenching experiment of adding methanol and tert-butanol,the active oxide species（ROS）produced in the Vis/BEFO₆/PDS system are analyzed as·SO₄^–and·OH.Among them,the oxidation of organic pollutants is dominant by·SO₄^–.In view of the physical and chemical properties of the BEFO₆ visible light catalyst and the degradation efficiency of 2,4-DCP,the possible mechanism of degradation of 2,4-DCP by visible light/bismuth ferrite/peroxodisulfate catalytic oxidation system was described.