| The physical chemistry properties of ozone and its application in water treatmentare reviewed, and the emphasis of discussion lies in the O3/H2O2and the metalcatalytic ozonation technology, two popular research fields in ozonation of water atpresent. Based on the current research situation and shortages of O3/H2O2, thedegradation performance, kinetics and mechanism by Ti（Ⅳ）-catalyzed O3/H2O2process were studied.First of all, a kinetic model for Ti（Ⅳ）-catalyzed O3/H2O2process was establishedbased on the reaction mechanism, and its correctness was validated by theexperiments of acetic acid degradation in aqueous solution. The rate constant for thereaction of ozone with Ti2O52+obtained by this kinetic model （1.40×103L/（mol·sec））agreed well with the data （1.10×103L/（mol·sec）） analyzed by monitoring thedecomposition rate of dissolved ozone. Three key operating factors affecting organicdegradation in the Ti（Ⅳ）-catalyzed O3/H2O2process were studied, including Ti（Ⅳ）concentration, dissolved ozone concentration and initial H2O2concentration. Additionof Ti（Ⅳ） could effectively enhance the removal rate of acetic acid within a properconcentration of Ti（Ⅳ）. Besides, there also existed an optimal concentration range foreither H2O2or ozone in solution. In fact, a suitable concentration of H2O2could assurethe effective generation of Ti2O52+; however, too high concentration of H2O2wouldquench hydroxyl radicals generated in the solution. Secondly, acetophenone was degraded by Ti（Ⅳ）-catalyzed O3/H2O2process wasinvestigated under acidic condition. The experimental results indicated that addingTi（Ⅳ） to the solution of acetophenone could improve the oxidation efficiency ofozonation greatly at pH2.86. For example, the removal rate of acetophenone reached94.0%by Ti（Ⅳ）-catalyzed O3/H2O2process, but it was only28.0%by ozonationalone within20min. The apparent kinetics of Ti（Ⅳ）-catalyzed O3/H2O2process ofacetophenone could be divided into two stages. The values of apparent reaction rateconstant and Rctwere9.52×10-4s-1and6.57×10-10for the first stage; and3.82×10-3s-1and57.87×10-10for the second stage respectively, which indicates that more hydroxylradicals were generated in the second stage. The result might be attributed to thegeneration of hydrogen peroxide in the degradation process of acetophenone.Finally, acetophenone and nitrobenzene simulated wastewater as well as landfillleachate wastewater were chosen to be degraded by ozonation alone andTi（Ⅳ）-catalyzed O3/H2O2system in acidic conditions. Based on the data ofexperiment, the addition of Ti（Ⅳ） could greatly improve the CODcrremovalefficiencies for all three samles. The experimental results also indicated that UV254was significantly decreased, BOD5/CODcrwas greatly improved and the biochemicalproperty was also effectively improved in the Ti（Ⅳ）-catalyzed O3/H2O2system. Theeffect of pH value on the removal rate of acetopheone was also studied, demonstratingthat the pH range of this system was wide. However, it was more suitable for beapplicated in acidic condition compared with ozonation only. The results showed thatTi（Ⅳ）-catalyzed O3/H2O2process was more efficient and economical than ozonationonly. |
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