A Study On The Oxidation Efficiency Of Different Phases Titanium Dioxide Catalytic Ozone(/hydrogen Peroxide)

The physical chemistry properties of ozone and its application in water treatment are reviewed, and the emphasis of discussion lies in the H2O2/O3 and the catalytic ozonation technology, which becomes hotspots recently. Based on the current research situation and shortages of H2O2/O3, and the photocatalytic efficiency of different phases titanium dioxide(Ti O2), a focus on the oxidation efficiency of different phases of Ti O2 catalytic H2O2/O3, was investigated. The contents of the dissertation include three parts: The oxidation efficiency of different phases Ti O2 catalytic H2O2/O3 for acetic acid(HAc, a probe compound for hydroxyl radical) degradation; Effect of different common anions on the oxidative efficiency of Ti O2/H2O2/O3; The removal of sulfosalicylic acid by rutile Ti O2/O3In chapter III, the oxidation efficiency of titanium dioxide(Ti O2) catalytic H2O2/O3 for acetic acid(HAc, a probe compound for hydroxyl radical) degradation, was investigated, with a focus on the effect of different phases of Ti O2. Adding rutile of Ti O2 could significantly improve the oxidation efficiency of H2O2/O3 at initial p H 3.0, while the effect of anatase of Ti O2 was negligible. The mechanism study indicated that there were some relationships between the degradation rate of HAc and the decomposition rate of H2O2. Compared with rutile Ti O2, anatase Ti O2 enabled H2O2 a rapid decomposition, which was unfavorable for HAc degradation. The results showed that the addition of Ti O2 had a negative effect on the oxidation efficiency of H2O2/O3 at initial p H either 7.0 or 10.0, and that the anatase of Ti O2 had a more negative effect. Addition of Ti O2 could markedly accelerate the decomposition rate of H2O2 at p H 3.0, which was further confirmed the evolution of concentration of dissolved ozone in a batch test. The amounts of superoxide ion radical(·O2-) in H2O2/O3, anatase Ti O2/H2O2/O3 and rutile Ti O2/H2O2/O3 were determined as the following order: H2O2/O3< Ti O2(rutile)/H2O2/O3< Ti O2(anatase)/H2O2/O3, which was in accord with the results of the results of HAc degradation. There was an obvious competitive adsorption among acetic acid, H2O2 and O3. The decomposition of H2O2 and O3 on the Ti O2 surface was an key way to produce hydroxyl radicals. The Ti O2(rutile)/H2O2/O3, which was high catalytic activity, had a better oxidation efficiency than H2O2/O3 in p H<4. This broadened the application of H2O2/O3 in acidic conditions.In chapter IV, The effect of different common anions on the efficiency of Ti O2/H2O2/O3 was investigated under acidic conditions, and the target compound was acetic acid, a probe compound for hydroxyl radical. The results showed that sulfate(SO42-) and nitrate(NO3-) had no effect on the degradation efficiency of acetic acid. The presence of phosphates would reduce the decomposition rate of H2O2, thus lead to decreasing the degradation rate of acetic acid. The result might attribute to the adsorption of phosphate on the surface of Ti O2. At the initial p H of 3.0, the presence of chloride ion would greatly reduce the oxidative efficiency of Ti O2/H2O2/O3, and the higher the concentration of chloride ion, the more significant reduce in acetic acid degradation. However, chloride ion almost had no effect on the degradation efficiency of acetic acid when the p H of solution was higher than p H 4.4. The existence of fluorinion greatly improved free hydroxyl radicals in the solution, which improved the the oxidation efficiency.The above results are of significance for the application of Ti O2/H2O2/O3 in the treatment of acidic wastewater.In chapter V, the influence of rutile Ti O2 was researched in degradating aromatic compounds sulfosalicyl acid. Adding Ti O2 had a slight improve on the degradation of sulfosalicylic acid. The oxidation efficiency was more reflected on the removal of COD(Chemical Oxygen Demand). A removal of COD was increased by 15 %by the presence of Ti O2 in 20 minutes, which revealed a good mineralization. The result was meaningful in the degradation of refractory wastewater.In summary, the coexistence of rutile and hydrogen peroxide in acidic solution can obviously improve the efficiency of ozonation of organics. Anatase could quickly decomposed H2O2, which lead to a low catalytic efficiency in the pathway of radicals. Common anions in water also had important effects on the oxidation efficiency of the system, which depended the existance of anions. Rutile Ti O2/H2O2/O3 greatly improved the biodegradability of sulfosalicyl acid.The experimental results are highly significant to broaden the application of ozone in wastewater treatment.