Research On The Electro-Fenton With Anthraquinone Modified Graphite Plate Electrode Applied In Degradation Of RhB

The ability of advanced oxidation to degrade the organic pollution effectively was well-known.The study on performance of cathode material on the electron-Fenton had attracted more attentions.Based on this,one of graphite plate cathode,which could produce hydrogen peroxide ultra-highly and degrade Rh B efficiently,had been prepared in this paper.The first part introduced the preparation and the electrochemical characteristics of modified electrode.The electro-chemical specialty of modified electrode and diffused anthraquinone-2-sulfonic acid had been compared.The results of cyclic voltammetry curve indicated that the modified electrode had good electrochemical activity.The reductive peak appeared at-0.4 V（vs Ag/Ag Cl）.The reductive peak current attained to-0.1266 A and the electron transfer charge had 4.80 C,which was 10.46 times and 5.7times of the bare graphite respectively,in the system of 0.1 mol·L^-1H₂SO₄ with oxygen saturated.Meanwhile,the electrochemical impedance spectroscopy diagram and fitting dates showed that the electron transfer internal resistance on the modified electrode surface was 0.169（?）,which was about half of the bare one and that results also indicated the reason of increasing electron transfer number.The electro-chemical behaviors of diffused anthraquinone-2-surfonic founded that the oxidation peak current and the reduction peak current were linearly related to the square of scan rate.Compared with the cyclic voltammetry curves of AQS,the redox peaks of the modified electrode trended to both sides and indicated that the reversibility of modified electrode decreased.After 20 cycles of continuous scanning in 0.5 mol·L^-1H₂SO₄solution,it was found that the modified electrode had good electrochemical stability.In the second part,different factors for degradation of Rh B had been investigated.The results of different cathode potential showed that the difference value of degradation rate between the modified and the bare one was maximum when the potential attained to-0.1 V（vs Ag/Ag Cl）.The results of different p H showed that the best p H was 3.0 in E-Fenton and the modified electrode displayed great degradation effect in acid solution.The ferrous ion was one of the Fenton reagents.It was found that the final degradation efficiency of Rh B reached 70.45%within 60 min when the concentration of ferrous ion was 0.2 mmol·L^-1.Finally,the modified electrode was proved to have high stability and repetitive operation feasibility by long time operation.The average degradation rate of the modified electrode was more than 80%seven times.In the third part,subsistent free-radicals and possible reaction mechanism had been investigated.After the determination of hydrogen peroxide content,the final accumulation of hydrogen peroxide of modified electrode was 92.90μmol·L^-1 within 60min,which was 4.56 times than that of the bare electrode.The detection result of superoxide free radicals was found that existence of that radicals were few in modified electrode system.But the inhibitory effect of BQ would be more obvious in the same free radical scavenger concentration,which demonstrated the superoxide free radicals were the precursor of hydroxyl radical.Besides,the process of degradation had been inferred.It was concluded that AQS were catalysts in the system and had the conversion of quinone/hydroquinone.The main source of hydrogen peroxide in the system was that the formation of superoxide radical by reduction of molecular oxygen with anthraquinone-catalyzed and then superoxide radicals combined with hydrogen ion under acidic conditions to form hydrogen peroxide.The degradation of the system was the result of the highly efficient oxidation of hydroxyl radicals produced by Fenton reaction.