| Summary: | 碩士 === 國立高雄科技大學 === 化學工程與材料工程系 === 107 === The purpose of this study was to investigate the removal efficiency and mineralization efficiency of Sulfathiazole (STZ) by advanced oxidation processes included O3, UV/O3, O3/H2O2, O3/Na2S2O8, UV/H2O2, UV/Na2S2O8, UV/O3/H2O2 and UV/O3/Na2S2O8. The effects of pH on the removal efficiency and mineralization efficiency of STZ were investigated, and the changes of residual ozone concentration and residual hydrogen peroxide concentration were analyzed. Besides, 1 wt% and 3.5 wt% salinity were set up in UV/O3, UV/Na2S2O8 and UV/O3/Na2S2O8 processes at pH 7 and pH 9 to simulate as seawater condition.
The UV/O3/Na2S2O8 process at pH 7 showed the best STZ removal efficiency and mineralization efficiency both 99%. The pseudo-first-order rate constant of STZ in the UV/O3/Na2S2O8 system at pH 5 was 0.0835 min-1. Residual ozone concentration was lower in alkaline conditions which ozone was less stable in alkaline conditions than in acidic and neutral conditions. Residual hydrogen peroxide concentration was lower in alkaline conditions while the hydrogen peroxide could be decomposed easily in alkaline conditions than in acidic and neutral conditions. 3.5 wt% salinity in UV/Na2S2O8 process at pH 9 decreased STZ mineralization efficiency from 85% to 51%. The effects of hydrogen peroxide concentration at pH 5 were performed in the O3/H2O2 and UV/O3/H2O2 systems. The best mineralization efficiency of STZ in O3/H2O2 process was 69% with 5 mM hydrogen peroxide concentration. The best removal efficiency and mineralization efficiency of STZ in UV/O3/H2O2 process ware 99% and 87% with 2.5 mM hydrogen peroxide concentration.
The experimental results of active species trapping revealed that hydroxyl radicals (HO•) played a major role in the UV/O3 process and the major active species were hydroxyl radicals and sulfate radicals (SO4－•) in the UV/O3/Na2S2O8 system. Moreover, the concentration of hydroxyl radicals and sulfate radicals was higher at pH 9 than at pH 5 and pH 7.
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