利用熱、紫外線、零價鐵和亞鐵離子活化過硫酸鹽處理NMMO廢水

N-甲基嗎林-N-氧化物（NMMO)是一種有機化合物，在萊賽爾工藝中用作溶解纖維素的溶劑，用於生產萊賽爾纖維。只有少數研究調查使用生物程序和臭氧化程序去除 NMMO 廢水，顯示出降解 NMMO 廢水的困難。本論文以高級氧化程序（AOPs）處理含 NMMO 的廢水，以過硫酸鹽為氧化劑，探討各種活化方法，包括加熱、紫外線、添加零價鐵（ZVI）及亞鐵離子（Fe2+）對 NMMO 降解去除的影響，並研究反應時間、溫度、PS 劑量及各種變因對去除效率的影響。此外，本論文中也比較過硫酸鹽 AOPs與 H2O2 AOPs 對 NMMO 去除的效率。在 UV/PS/ZVI 程序中，使用 100％的PS 理論劑量並添加 1g/L 的 ZVI，反應 3 小時後，其 TOC 去除效率僅為 4 ％。然而，在 Fe(II）/PS 的程序中，使用 100％的 PS 理論劑量並添加1g/L 的 Fe(II），反應 4 小時後，COD 和 TOC 去除效率僅分別達到 15％和 50％。在 UV/H2O2 程序中，使用 50％的理論 H2O2 劑量，反應 4 小時後， COD 和 TOC 的去除效率也僅分別達到 17.3％和 40.4％。而在本研究之預處理程序中，熱/PS 程序具有最佳的 COD 和 TOC 去除效率，在加熱溫度為 80°C 時，使用 100％的 PS 理論劑量，反應 3 小時後，其 COD 和 TOC去除效率分別達到 62.5％和 78.1％，並且在程序中添加的 PS 已被消耗99％，此結果表明大多數的 PS 都已經被活化來氧化有機污染物。經由上述熱/PS 前處理程序處理後，未處理 NMMO 廢水的 BOD5/COD 比值從 0.1 （該比值被認為對生物降解具有頑固性）增加至 0.3，結果表明藉由熱 /PS 處理程序能提升此水體的生物降解性，因此能採用熱/PS 程序作為後續生物降解處理程序之前處理。在熱/PS 程序處理 NMMO 廢水的成本方面，此熱/PS 系統需要 0.064 kWh/L 的能量，其能源成本約為 0.004 美元/升，而化學藥劑成本為 0.34 美元/升，所以處理的總成本為 0.344美元/升。

關鍵字

過硫酸鹽； NMMO 廢水；高級氧化程序；紫外光；熱

並列摘要

N-methylmorpholine-N-oxide (NMMO), an organic compound, is used in the Lyocell process as a solvent to dissolve cellulose for the production of Lyocell fibers. Only a few studies investigated the removal of NMMO-wastewater using biological process and ozonation processes, showing the difficulties of degrading NMMO-wastewater. In this study, NMMO-containing wastewater was treated using AOPs, i.e., oxidation process using persulfate, in order to produce an effluent suitable for biological treatment. Various combination of PS activation methods were investigated including heating process, UV, addition of zero valent iron (ZVI), ferrous ion (Fe2+) and hydrogen peroxide (H2O2). Various effects were studied such as reaction time, temperature and PS dosage. In the UV/PS/ZVI system, the TOC removal efficiency was only 40% after 3 hours using the theoretical PS dosage of 100% with the ZVI dosage of 1 g/L. On the opposite, the COD and TOC removal efficiency only reached the value of 15% and 50% after 4 hours, respectively in the Fe(II)/PS process at the Fe(II) dosage of 1 g/L and the theoretical PS dosage of 100%. Using the the UV/H2O2 process, the COD and TOC removal efficiencies only reached the value of 17.3% and 40.4%, respectively, with the theoretical H2O2 dosage of 50% and the reaction time of 4 hours. Compare to the other processes, the heat/PS system had the best COD and TOC removal efficiencies with the theoretical PS dosage of 100% at 80 °C and the reaction time of 3 hours. The COD and TOC removal efficiencies reached 62.5% and 78.1%, respectively. 99% of PS concentration was consumed after 3 hours, showing its activation. The degradation of organic matters was more efficient at higher temperatures with 36.74% and 78.1% of TOC removal at 60°C and 80°C, respectively, after 2 hours of reaction using the heat/PS system. The COD and TOC removal efficiencies increased with increasing PS dosage, showing that the heat/PS system was PS dosage dependent. The BOD5/COD ratio in the raw NMMO wastewater was 0.1 and this value is considered recalcitrant for biodegradability. After treatment with the heat/PS system, the BOD5/COD ratio increased to the value of 0.3 at the theoretical PS of 100%, the temperature of 80°C and the reaction time of 3 hours, indicating the effluent to be suitable for biodegradability. The activation of theoretical PS dosage of 100%, which was almost complete to oxidize the organic pollutants, required the energy of 0.192 kWh/L in the heat/PS system. The energy cost is about 0.011 USD/L and the chemical cost is 0.34 USD/L, increasing the total cost of the process to 0.351 USD/L of treated wastewater.