Preparation, Characterization Of Novel Electrode Materials For Packed-bed Electrode Reactor And The Electro-catalytic Degradation Of Acid Orange Ⅱ

To improve the catalytic activity and stability of anode and particle electrode inthe packed-bed electrode reactor, in present work, the novel PbO2anode and γ-Al2O3particle electrode were prepared, optimized, characterized and applied for theelectro-catalytic oxidation of acid orange II (AOII), and the possible degradationpathways and electro-catalytic oxidation mechanisms of AOII were investigated. Themain research contents and results are summarized as follows:(1) The PbO2electrodes doped with different concentration of fluoride wereprepared by electrodeposition. The results of scanning electron microscopy (SEM)and X-ray diffraction (XRD) show that F-doping on the electrode can form tetragonalcrystal structure of β-PbO2, decrease the crystal size, and improve its catalytic activityand stability. Linear-sweep voltammetry (LSV), accelerated lifetime (ALT),fluorospectrophotometry(FP), cyclic voltammetry (CV), electrochemical impedancespectroscopy(EIS), AOIItreatment and UV-Vis analysis reveals that theoptimumconditionofthe concentrationoffluoride doping on the electrode is0.04mol/L.(2)Three different intermediate layers (SnO2-Sb2O5, IrO2-Ta2O5and RuO2-IrO2)were coated on Ti-substrate, and then PbO2was electrodeposited to prepareTi/SnO2-Sb2O5/PbO2, Ti/IrO2-Ta2O5/PbO2and Ti/RuO2-IrO2/PbO2, respectively.SEM, XRD and X-ray photoelectron spectroscopy (XPS) tests show that theintermediate layers are all covered by β-PbO2with tetragonal crystal structure and themain chemical valence of Pb is4+. LSV, ALT, FP, CV, EIS, AOII treatment and UV-Visanalysis reveal that the presence of intermediate layers can increase the stability ofPbO2electrode, and SnO2-Sb2O5is more suitable to be intermediate layer according tothe higher electro-catalytic activity.(3)Ti/SnO2-Sb2O5/PbO2electrodes doped with different metallic elements,including Bi, Ce, Co and Nd, were prepared by anodic codeposition. SEM, XRD andXPS analysis reveal that the Nd-PbO2electrode is covered by β-PbO2with tetragonalcrystal structure and the main chemical valence of Nd is3+, and doping with Nd canuniform the crystal particle size and distribution. The results of LSV, ALT, FP, CV, EIS,AOII treatment and UV-Vis show that the Nd-PbO2electrode exhibits the bestperformance for electro-catalytic oxidation and stability, the optimum condition of Nddoping on the electrode is at the ratio of50:1.(4) Various catalysts with different active single metallic oxides, i.e. Cu,Mn, Pb, Sn and Sn-Ce-Sb complex metal oxides supported over γ-Al2O3used as particleelectrodes were prepared by the incipient wetness impregnation. SEM,energy-dispersive X-ray spectroscopy (EDS), AOIItreatment and UV-Vis testsshowthatSn/γ-Al2O3has excellent electro-catalytic activity and stability for AOII treatment.Doping with Ce can improve the catalytic activity and stability of Sn/γ-Al2O3. Moreover, the results of tests also reveal that the optimum ratio of Sn to Ce is10:1and theSn-Ce-Sb/γ-Al2O3particle electrode is covered with finer and more crystal particles.(5) AOII was treated by a packed-bed electrode reactor with the novelTi/SnO2-Sb2O5/PbO2electrode doped with Nd as anode and Sn-Ce-Sb/γ-Al2O3asparticle electrode. A possible pathway for AOII degradation was proposed bymonitroring the temporal evolution of intermediates in the solution, with the use ofsome techniques including UV-Vis, FTIR and GC/MS. Meanwhile, the possiblemechanism of electro-catalytic oxidation of AOII has also been proposed. By meansof electro-catalytic oxidation, AOII can be completely degraded by hydroxylradicalswhich are generated on anode, particle electrodes, and by the interaction ofanode and particle electrodes.