Electro-Catalytic Oxidation Of Paranitrophenol By Fe-Doped Sb-SnO₂/Ti Electrodes

In recent years,electro-catalytic oxidation is an effective method for organic compounds degradation.In this thesis,we have performed a fundamental study on the electrocatalytic oxidation technology for the organics waste water treatment.P-nitrophenol is selected as the simulation pollutant of toxic and biorefractory organics.The Fe doped Sb-SnO₂/Ti electrodes were prepared by a sol-gel process.The electro-catalytic performances of the electrodes were evaluated based on the disposal efficiency.And the results showed that the electrodes which prepared by the turnplate method were better than the one prepared by impregnation method.The effects of the calcination temperature and doping amount of Fe on the performances of the electrodes were also investigated.The results showed that the suitable calcination temperature was 600℃and the best doping amount of Fe was determined with the molar ratio of Sn:Sb:Fe being 1:0.02:0.0001. Then the surface morphology,chemical compostion and the crystal structure of the electrodes were analyzed by SEM,EDS and XRD.Those electrodes were also evaluated through the anode polarization curve and voltammetry curve.The results indicated that the Fe doped Sb-SnO₂/Ti electrodes was better than Fe undoped Sb-SnO₂/Ti electrodes.We use the Fe doped Sb-SnO₂/Ti electrode as anode and the titanium plate as cathode to degrade stimulant p-nitrophenol waste water in a glass trough.The effects of reaction time,initial concentration of p-NP,current density,electrolyte concentration and pH on degradation were systematically investigated.The results indicated that the degradation efficiency increased with the reation time and the tends became smooth when the raction time reached to certain degree.The degradation efficiency reached 97.2%when the reaction time was 90 min. The higher initial concetration of p-NP,the lower degradation efficiency. And the degradation efficiency also increased with the increasing of incurrent density.But after the current density reached 20 mA/cm²,the degradation efficiency would lower with the occurrence of negative effect. The higher electrolyte concentration of p-NP,the higher degradation efficiency.And after the electrolyte concentration reached 0.03 mol/L Na₂SO₄,the degradation efficiency would not increase.The degradation efficiency of p-NP was higher in the acidic conditions when compared to alkaline and neutral conditions.The results indicated that the optimum time was 90min,the optimum electrolyte concentration was 0.03 mol/L Na₂SO₄,and the optimum current density was 20 mA/cm².It also showed that the degradation of the p-NP conformed to the first order kinetics.From the HPLC and ion chromatograph(IC) results,we presumed that in the reaction process,with the·OH attacking,the-NO₂ could removed from p-NP,which result in the hydroquinone produced.Further oxidation of hydroquinone produced intermediates.As the reaction proceeded,these intermediates experienced several ring openings through further oxidization,and formed small molecule acids such as formic acid and acetic acid,which finally led to the production of CO₂ and H₂O.