Study On The Oxidation System Of Ozone Or Ozone/Hydrogen Peroxide Promoted By Lewis Acids Containing Titanium

The physical chemistry properties of ozone and its application in water treatment are reviewed, and the emphasis of discussion is put on O₃/H₂O₂ system. On the basis of the research fact of ozonation and the disadvantage of O₃/H₂O₂ system, an advanced oxidative system of ozone or ozone/hydrogen peroxide promoted by Lewis acid containing titanium was proposed. The contents of the dissertation include three parts: honeycomb-like ceramic containing titanium (Fw) catalytic ozonation of acetophenone; oxidation of acetic aicd by O₃/H₂O₂ promoted by honeycomb-like ceramic containing titanium; oxidation of acetic acid by O₃/H₂O₂ promoted by molecular sieve TS-1.In chapter III,honeycomb-like ceramic containing titanium catalytic ozonation of acetophenone were investigated. The results showed that honeycomb-like ceramic containing titanium could increase the degradation efficiency of acetophenone, which was more significantly in acidic solution. This oxidative system followed the mechanism of·OH oxidation by the test of adding tert-butanol. The kinetics of honeycomb-like ceramic containing titanium catalytic ozonation of acetophenone could be divided into two stages. The values of apparent reaction rate constant and Rct were 8.77×10^-4 s^-1 and 10.34×10^-10 for the first stage; 4.63×10^-3 s^-1 and 172.34×10^-10 for the second stage, respectively. On the basis of the change of water color, analytic result of sample by atomic absorption spectrometry, and the kinetic of acetophenone degradation, it could be speculated that Ti(IV) leaching from honeycomb-like ceramic containing titanium was the main factor for the improvement of degradation rate of acetophenone.In chapter IV,the oxidative efficiency of O₃/H₂O₂ promoted by honeycomb-like ceramic containing titanium for acetic acid degradation were investigated. The results showed that the coexistence of honeycomb-like ceramic containing titanium and hydrogen peroxide were the necessary conditions for effective degradation of acetic acid by ozonation. The higher concentrations of honeycomb-like ceramic containing titanium and hydrogen peroxide , the better degradation efficiency of acetic acid. According to the experimental results of acetic acid degradation and kinetic analysis of ozone decomposition in its saturated solution at different pH, O₃/H₂O₂/Fw system can effectively produce hydroxyl free radicals in acidic solution. We speculated a yellow complex (Ti2O52+) that formed from the reaction Ti(IV) with H₂O₂ could cause initiate the decomposition of ozone to produce hydroxyl radicals , which led to effective degradation of acetic acid.In chapter V, O₃/H₂O₂ promoted by molecular sieve TS-1 was used to degrade acetic acid, and its mechanism was also discussed. The results indicated that the oxidative system could degrade acetic acid effectively, and that the coexistence of TS-1 and H₂O₂ was a necessary condition for this oxidative system. A test of adding tert-butanol revealed the oxidative system followed a mechanism of·OH oxidation. The Rcts of O₃/H₂O₂ and O₃/H₂O₂/TS-1 were 1.62×10^-8 and 8.67×10^-7, respectively, indicating that O₃/H₂O₂/TS-1 system could generate more hydroxyl radicals. However, it was found that the coexistence of TiO₂ and H₂O₂ could not improve the efficiency of ozonation of acetic acid, indicating that different titanium phases of Lewis acids containing titanium might play an important role in this system. According to the experiment results and apparent phenomenon, the mechanism of ozone/hydrogen peroxide promoted by TS-1 might be similar to the mechanism of ozone/hydrogen peroxide promoted by honeycomb-like ceramic containing titanium oxidation system.In summary, the coexistence of some Lewis acids containing titanium and hydrogen peroxide in acidic solution can obviously improve the efficiency of ozonation of organics. The experimental results are highly significant to broaden the application of ozone in wastewater treatment.