Modification Of Carbon Fiber Electrode Materials And Degradation Of Diclofenac By Electro-Fenton

The electro-Fenton?EF?technology is based on the continuous electrochemical generation of hydrogen peroxide through cathodic oxidation reduction reaction reaction?ORR?.It is considered as a clean electrochemical technology.However,the homogeneous EF system is limited by some conditions,such as narrow pH range and iron sludge.Therefore,in this study,we used the mixture of porous carbon and carbon black to modify activated carbon fiber to improve the hydrogen peroxide production capacity of the cathode.Then,pyrite?FeS₂?was prepared by hydrothermal synthesis method and used as heterogeneous catalyst.This system was called“FeS₂-EF”.To explore the treatment effect of diclofenac sodium.The main research contents are as follows:1)The surface and internal pore channels of activated carbon fiber were uniformly filled with porous carbon by ultrasonic impregnation method.When the mass of the loaded porous carbon was 0.01 g,the hydrogen peroxide production could be increased by 46 times(182.5 mg L^-1).Then carbon black was added and the total mass was maintained at 0.01 g.When 2:3 was the mass ratio of porous carbon to black carbon,concentration of H₂O₂ accumulated after 120 min was increased to 227.4 mg L^-1.A series of characterization analysis was carried out on the electrodes,and it was found that the surface morphology and electrochemical properties of the electrode were changed after the porous carbon was mixed with carbon black.These properties increased the ORR activity sites of modified electrode and enhanced the reactivity of EF.2)Graphit carbon nitride?g-C₃N₄?was used to modify the activated carbon fiber electrode,the in-situ yield of H₂O₂ was increased by more than 7times,and the yield of H₂O₂ was 33.54 mg L^-1 at 60 min.Through a series of characterization,it could be obtained that the micro-surface of g-C₃N₄/ACF electrode and electrochemical properties were changed.After applying a certain voltage,the photoinduced electron hole separation speed was accelerated and the electron transfer rate was accelerated,but it didn't change the ORR of the two electrons.The modified electrode was applied to degrade phenol in the photoelectro-Fenton system,and the degradation effect was 1.5times and 5 times higher than that of using electro-Fenton process and photo-Fenton process only.The characteristic peak of the hydroxyl radical was also the strongest.All of these confirmed the existence of photoelectric synergy.3)The optimal hydrothermal synthesis time of FeS₂ was 24 h,it was found that the prepared FeS₂ had high purity and large specific surface area.At the same time,the electrolyte could be adjusted to acidity,and the cycle between Fe²⁺and Fe³⁺could be completed by FeS₂ itself.Then,different currents?0.05A,0.1 A,0.15 A?and initial concentration(50,100,200 mg L^-1)were applied.Under neutral conditions,it was found that FeS₂ possessed good catalytic effect.Even when the concentration of diclofenac sodium was 200 mg L^-1,the removal rate could reach 82.03%after only 8 minutes of treatment,and TOC could be removed by 70%?3 h?.4)To investigate the advantages and mechanism of degradation of diclofenac sodium by FeS₂-EF system.It was found that FeS₂-EF system breaked the pH limit of the EF reaction,which has great advantages for practical engineering application.The results of control factors and capture experiments confirmed that·OH played a major role in the reaction process,and·O₂^-generated by molecular oxygen activation in FeS₂ surface played an auxiliary role,which jointly eliminated the toxicity of diclofenac sodium.The degradation pathway of diclofenac sodium was investigated by LC-MS.At the same time,the FeS₂ catalyst could be reused.