The Formation Mechanism Of Hydroxyl Radicals And Decolorization Kinetic Model Of Orange ? In Poly-Silicate-Ferric Heterogeneous UV-Fenton Sy Stem

The iron leaching process was usually inhibited by the high stability of iron oxides in heterogeneous UV-Fenton system.The key to solving this problem was that the catalyst can effectively release iron ions.Therefore,it was a good choice to developed a new type of catalyst with high iron ion releasing ability,and the new catalyst has re-adsorption ability to iron ions after the catalytic reaction ends.In this study,poly-silicate-ferric(PSF)was developed as a catalyst in a heterogeneous UV-Fenton system.The catalytic performance of PSF was examined in terms of the degradation and mineralization of Orange ?.The release and re-adsorption of iron ions as well as the·OH radical generation was studied in detail.In the Fenton system,the concentration of Fe? was played an important role in the catalytic oxidation system.The ability of different organic acids to complex Fe? and its complexation complex to reduce Fe? was studied.At the same time,the catalytic process of PSF and the mechanism of·OH formation under the oxalate enhanced system were studied.Based on the analysis of Orange ? degradation in the heterogeneous UV-Fenton system with PSF as catalyst,the accuracy between full-process linear fitting method and piecewise linear fitting method in calculating kinetic constant were compared.A kinetic model of Orange ? decoloration was established and verified in terms of catalyst amount and hydrogen peroxide concentration.The conclusion was as follows:(1)In the heterogeneous UV-Fenton system,PSF has higher catalytic activity than iron oxides.The scavenging experiment proved that hydroxyl radical was the main active species for Orange ? decolouration in this system.Which indicating that the heterogeneous UV-Fenton system was followed the-OH oxidation mechanism.During catalytic process,the effective release of iron ions from PSF could promote hydroxyl radical generation and Orange ? degradation.After treatment,the re-adsorption of iron ions on PSF could avoid the additional pollution caused by iron ions.The results confirmed that PSF was a high activity catalyst for UV-Fenton system.(2)In the organic acid enhanced heterogeneous UV-Fenton system,the order of Fe? complexing ability in PSF under different systems was:EDTA>Citrate>Oxalate>Malonate>Basic>Acetate;The ability of different carboxylate-Fe?combinations to convert to Fe?:Oxalate>EDTA>Citrate>Base>Malonate>Acetate.And the catalytic process of PSF and the formation mechanism of·OH under the oxalate enhanced system were proposed.(3)The degradation process of Orange ? in heterogeneous UV-Fenton system using PSF as a catalyst was studied.In heterogeneous UV-Fenton system,the decolorization process of Orange ? can be divided into two stages:rapid and slow decolorization stages using 15 min as the dividing line.The rapid decolorization stage was mainly dominated by nitrogen double bonds breaking,and chromophore degradation as a supplement.While the slow decolorization stage was mainly dominated by chromophore mineralization,and nitrogen double bonds breaking as a supplement.The kinetic model based on two-stage linear fitting method had higher accuracy and smaller error in simulation,which can successfully predict Orange ?degradation in this heterogeneous UV-Fenton system through theoretical calculation.