| 摘要: | 研究探討觸媒加氫脫氯技術對於溶解相OCDD/F之去除與降解，以具高化學還原特性之鈀活性碳(Pd/AC)觸媒進行加氫脫氯程序之效率測試。加氫脫氯反應乃利用鈀觸媒催化產生之氫原子取代含氯有機物之氯原子並脫氯成無毒性之產物。然而此技術較少應用於液相PCDD/Fs之去除且影響因子也尚未釐清，因此本研究以受高濃度OCDD/F污染之廢水作為研究標的，透過實驗室試驗探討各操作參數包括溶劑、溫度之影響並計算反應速率常數。實驗結果顯示於特定OCDD/F濃度，Pd/AC觸媒加氫脫氯反應以異丙醇為溶劑之去除及破壞效率較以甲醇為溶劑佳，於反應時間300分鐘對OCDD質量去除及破壞效率分別為99.8及95.3%，對OCDF質量去除及破壞效率分別為99.8及97.7%，使用高比率溶劑量對OCDD/F之去除效率又稍高於使用低比率溶劑量，就破壞效率而言，則是使用低比率醇類對OCDD/F破壞效率較佳，並且也進行PCDDs及PCDFs間之總體效率探討，而物種分布方面以OCDD/F佔主要，2,3,4,7,8-PeCDF為主要之毒性貢獻物種。此外反應速率常數計算結果顯示以異丙醇為溶劑之反應速率常數較甲醇大，又以50%異丙醇之OCDD及OCDF反應速率常數最高，分別為0.0048及0.0057 min-1。不同溫度下進行OCDD/F之加氫脫氯實驗結果顯示去除及破壞效率均隨反應溫度上升而增加，並藉由Arrhenius equation計算之OCDD及OCDF活化能分別為24.8與23.1 kJ/mole。觸媒重複性測試實驗結果顯示對OCDD/F之去除效率雖有些微下降，然仍可達91%以上，顯示此觸媒具有相當高之反應活性及穩定性。;Removal/destruction efficiency of liquid-phase OCDD and OCDF achieved with hydrodechlorination process (HDC) was experimentally evaluated over palladium activated carbon (Pd/AC) catalyst in liquid phase. Palladium catalyst is applied to catalyze dechlorination reaction and to replace chlorine atom of chlorine-containing organic pollutants with hydrogen atom to form nontoxic products. However, the literature on the removal PCDD/Fs of HDC reaction in liquid phase is limited and the influencing factors have not been clarified. Therefore, high-concentration OCDD/F are selected as targets, the effects of solvents and temperature on dechlorination efficiency were investigated via experimental tests. The experimental results showed that the highest hydrodechlorination efficiency is achieved with isopropanol as solvent. OCDD removal and destruction efficiencies were 99.7 and 95.3%, respectively, within 300 minutes. On the other hand, the removal and destruction efficiencies of OCDF were up to 99.8 and 97.7%, respectively. In addition, the OCDD/F removal efficiency achieved with the high volume content of 80% alcohols is higher than that of 50% alcohols, whereas the destruction efficiency of OCDD/F reveals the opposite trend. OCDD/F are the dominant species while 2,3,4,7,8-PeCDF is the major toxicity contributing species in both solid and liquid phases. Moreover, it is shown that the reaction rate constant of isopropanol as solvent is higher than that of methanol toward OCDD/F removal. The highest rate constants of OCDD and OCDF with 50% as solvent isopropanol are 0.0048 and 0.0057 min-1, respectively. The activation energies of OCDD and OCDF calculated with the Arrhenius equation were 24.8 and 23.1 kJ/mole, respectively. The result of long-term experimental tests, indicate that the Pd/AC catalyst has good potential for removing PCDD/Fs from wastewater. |
