Degradation Of Hydrochlorothiazide By Dielectric Barrier Discharge Plasma Combined With MnFe₂O₄

The treatment of pharmaceutical and personal care products（PPCPs）pollution is the research hotspot of experts and scholars.Dielectric barrier discharge（DBD）plasma,as a new advanced oxidation technology,produces O₃,H₂O₂,·OH,·O and other active substances which can decompose complex pollutants,but the utilization rate is not ideal.Therefore,in this study,DBD was combined with the commonly used heterogeneous Fenton catalyst MnFe₂O₄ to study the degradation performance of hydrochlorothiazide,which is considered as a typical pollutant,in order to explore a more efficient and energy-saving water pollution treatment technology.MnFe₂O₄ was successfully prepared by solvothermal method and its structure was characterized.The results of XRD,XPS and SEM indicated that all the elements in this material showed good absorbance.It was also observed that the material was mostly spherical particles with a diameter of about 200 nm.Meanwhile,there were many tiny crystal structures distributed on the surface of this spheres,representing the properties of loose and porous.The experimental results of adsorption and cyclicity illustrated that the adsorption of HCTZ by MnFe₂O₄ was limited,which indicated that the degradation process was induced by the composite system.At the same time,the catalytic performance of MnFe₂O₄ still maintained near the initial level after five cycles.The factors influencing the degradation of HCTZ in DBD system were discussed.When the initial concentration of HCTZ increased from 10 mg/L to 100 mg/L,the degradation efficiency and first-order constant showed a slow decline trend,indicating that the degradation performance would decline with the increase of the concentration of HCTZ.While the degradation efficiency and first-order constant would be improved when the power supply increased from 32.7 W to 58.7 W.Meanwhile,increasing the initial pH of the solution would inhibit the degradation performance of the system,and the effect of air flow rate on the degradation performance of the system was not obvious.The factors affecting the degradation of HCTZ in water by DBD/MnFe₂O₄composite system were analyzed.When the input power was increased to 58.7 W,the degradation efficiency and first-order constant of the system showed a high level,and HCTZ was removed within 20 min;When the initial pH of the solution was 11.3,the degradation process was greatly inhibited,and 39.5%of HCTZ remained in the solution after 60-min treatment;At the same time,it was verified that the most suitable dosage of catalyst in this system was 50 mg.The mineralization of HCTZ in the two degradation systems was compared,and the mechanism,degradation pathway and intermediate products of HCTZ degradation by DBD/MnFe₂O₄ were analyzed.After adding MnFe₂O₄,the mineralization performance was significantly improved,and the mineralization rate was nearly twice as high as that of DBD system at 60 min.By measuring the concentration of H₂O₂ at each time in the discharge system,it was found that the accumulation process of H₂O₂ in the system,and the strong oxidizing·OH produced by catalytic decomposition was the main reason for the removal of HCTZ.Meanwhile,the main degradation pathways and intermediates of HCTZ in water were deduced by LC-MS mass spectrometry analysis and the related literature review.