Degradation Of Dimethyl Phthalate By PMS Activated With The Composite Of Magnetic Bi₂MoO₆ Doped With Cu

Dimethyl phthalate（DMP）is a widely used synthetic organic compound,which is often used as plasticizer in industrial production.It is an environmental hormone with biological toxicity and harm to human health,but it is difficult to remove in water by conventional water treatment process.In recent years,persulfate advanced oxidation method is often used to remove refractory organic compounds in water,and activated PMS is a potential method to degrade organic pollutants.Common persulfates include permonosulfate（PMS）and perbissulfate（PDS）.Activation of PMS to degrade organic pollutants has been widely studied.In this thesis,magnetic Bi₂MoO₆/Cu composite material was prepared by hydrothermal method for photocatalytic activation of PMS to degrade DMP.The preparation process conditions of magnetic Bi₂MoO₆/Cu composite material were optimized,and the microscopic morphology,crystal phase and optical absorption performance of magnetic Bi₂MoO₆/Cu composite material were analyzed by characterization.The effect of different photocatalytic reaction conditions on the degradation of DMP by activation of PMS with magnetic Bi₂MoO₆/Cu composite was studied,and the reaction kinetics of degradation of DMP by activation of PMS was studied,and the performance stability which magnetic Bi₂MoO₆/Cu activate PMS to degrade DMP was studied during the cycling use of magnetic Bi₂MoO₆/Cu photocatalyst.The active species and possible degradation pathway of DMP were investigated,and the degradation mechanism was analyzed.The performance of DMP degradation by photocatalytic activation of PMS with different catalysts was investigated.It is found that the magnetic Bi₂MoO₆/Cu composed of Fe₃O₄,Bi₂MoO₆ and Cu composite had the best photocatalytic activation of PMS to degrade DMP.The preparation process of magnetic Bi₂MoO₆/Cu composite was optimized by orthogonal experiment.The order of influence of various factors on magnetic Bi₂MoO₆/Cu photocatalytic activation of PMS to degrade DMP was hydrothermal temperature>hydrothermal time>content of Fe₃O₄>content of Cu.The optimal preparation conditions of magnetic Bi₂MoO₆/Cu composites are that,Hydrothermal temperature is 160℃,hydrothermal time is 12h,the content of Fe₃O₄ and Cu is 7%and 5%,respectively.Under the optimal preparation conditions,which the concentration of DMP solution is 20mg/L,the dosage of magnetic Bi₂MoO₆/Cu and PMS is 1g/L respectively,irradiating with 500W long arc xenon lamp,the degradation rate of DMP was 100%in 18min.After recycling,the efficiency of photocatalytic activation of PMS to degrade DMP decreased,but the magnetic Bi₂MoO₆/Cu composite still had a high effect of activation of PMS to degrade DMP.The analysis of field emission scanning electron microscopy（SEM）,X-ray energy spectroscopy（EDS）,field emission transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,specific surface area and aperture（BET）,UV-visible diffuse reflection（UV-VIS）DRS,magnetic properties（VSM）and other characterization showed that Fe₃O₄,Bi₂MoO₆ and Cu were successfully synthesized to form heterojunction.The saturation magnetization value of magnetic Bi₂MoO₆/Cu is5.95emu/g.Compared with magnetic Bi₂MoO₆ and magnetic Bi₂MoO₆,the absorption band edge of magnetic Bi₂MoO₆/Cu has a red shift and the band gap width has narrowed.The effects of different initial concentration of DMP,dosage of magnetic Bi₂MoO₆/Cu and DMP,pH value and disturbance in water on degradation efficiency of DMP by photocatalytic activation of PMS with magnetic Bi₂MoO₆/Cu were investigated.The results showed that the time needed for complete degradation of DMP by activation of PMS with magnetic Bi₂MoO₆/Cu composite lengthened with the increase of DMP concentration.The degradation efficiency of DMP increased first and then slowed down with the increase of the dosage of magnetic Bi₂MoO₆/Cu.The degradation rate of DMP was fast when the pH value was below 6 and was the fastest when the pH value was 3.When the pH value was above 6,the degradation rate of DMP decreased.When the concentration of PMS increased from0.25g/L to 0.5g/L,the degradation efficiency of DMP increased significantly,but when the concentration of PMS increased from 0.5g/L to 1g/L,the degradation efficiency of DMP increased slowly.With the increase of the concentration of CO₃^2-,the degradation effect of DMP decreased significantly.High concentration of Cl^-would hinder the degradation of DMP by photocatalytic activation of PMS with magnetic Bi₂MoO₆/Cu,and SO₄^2-would inhibit the degradation of DMP to a certain extent.Degradation of DMP by activation of PMS with magnetic Bi₂MoO₆/Cu composite conforms to the quasi-first-order reaction kinetic model.Kinetic studies showed that the reaction rate constants of magnetic Bi₂MoO₆/Cu,magnetic Bi₂MoO₆,Bi₂MoO₆/Cu and Bi₂MoO₆ were 0.1698,0.0201,0.0915 and 0.0197h^-1,respectively,indicating that magnetic Bi₂MoO₆/Cu had the strongest ability to degrade DMP.Radical quenching experiments showed that SO₄^-·and·OH were active species in photocatalytic activation of PMS to degrade DMP,in which SO₄^-·played a major role.The doped Cu ions enhanced the response range of magnetic Bi₂MoO₆ to visible light,and also provided active reaction sites for Cu²⁺/Cu⁺conversion in with Cu⁺could also activate PMS.DMP can be degraded through the ring opening reaction and ring fracture of benzene,and finally complete mineralization into CO₂and H₂O.